JPH09263494A - Thin stabilized zirconia film/single-crystalline silicon substrate laminated structure and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a stabilized zirconia film/c-Si laminated structure free from ion drift. SOLUTION: A thin stabilized zirconia (ZrO2 ) film 2 is grown on a single- crystalline silicon semiconductor substrate 1 to obtain the objective laminated structure. The zirconia film 2 contains about equal amts. of a stabilizer made of oxide of a metal whose valence is lower than 4 as the valence of Zr and an oxygen ion hole vanishing agent made of oxide of a metal whose valence is higher than 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a good stabilized zirconia thin film / single crystal silicon composite structure free from ion drift and a method for manufacturing the same.

[0002]

Zirconia: ZrO ₂ has a melting point of 2700.
Not only is it as high as ℃, it is mechanically tough, but it also has strong corrosion resistance to chemicals, has excellent insulating properties, and has a high dielectric constant, so it is applied in various industrial fields. It is known that pure zirconia has three kinds of polymorphs, that is, cubic crystal, tetragonal crystal, and monoclinic crystal from high temperature. However, since the temperature lowers, a phase transition occurs in a crystal system with low symmetry. However, a cubic single crystal useful for application cannot be obtained at room temperature. However, when a divalent or trivalent metal oxide is solid-dissolved in this, the crystal is stabilized, and the cubic crystal region, which is a high temperature phase, can be lowered to around room temperature. Hereinafter, such cubic zirconia is collectively referred to as "stabilized zirconia".

Yttria: Y as a stabilized zirconia
Yttrium-stabilized zirconia stabilized with ₂ O ₃ : YS
Z (Yttria-Stabilized Zirconia) and Samaria: S
Samaria stabilized zirconia stabilized with m ₂ O ₃ (SS
Z), or calcium-stabilized zirconia (CSZ) stabilized with calcium oxide has been reported.

The lattice constant a ₀ = of stabilized zirconia
0.51 to 0.52 nm is single crystal silicon (cubic crystal): c
Since the lattice constant of —Si is close to a ₀ = 0.54 nm, researches on epitaxial growth on a c-Si substrate have been studied by researchers in Japan and abroad recently, and electron beam evaporation method, ion beam sputtering method, laser ablation method have already been performed. Have succeeded in film forming means such as. To give an example, “Fukumoto et al.“ Japanese Journal of Applied ”
Physics, "27, 1988, L1404." Reported that the electron beam evaporation method succeeded in forming a c-axis oriented YSZ epitaxial film on a Si (100) substrate.

Since Si is generally liable to undergo solid phase reaction with other materials and mutual diffusion, and amorphous SiO ₂ is relatively easily generated on the surface in an oxidizing atmosphere, heteroepitaxial growth is not possible. It's not easy. Therefore, the research results that stabilized zirconia can be epitaxially grown on Si have been extremely useful for the development of new Si semiconductor technology.

Also noteworthy in the crystallographic relationship between the stabilized zirconia and a certain group of crystals is one-half of the <110> axial length of the stabilized zirconia (~).
(0.36 nm) or a-axis length is almost equal to the a- and b-axis lengths of the following cubic or tetragonal crystal. Here, the group of crystals is platinum: Pt.
(A ₀ = 0.39 nm) and iridium: Ir (a ₀ = 0.3
8 nm), lead titanate: PbTiO ₃ (a ₀ =
0.39 nm) and lead titanium zirconate: Pb (Zr _x Ti
Tetragonal perovskite ferroelectrics such as _1-x ) O ₃ (abbreviation PZT, a ₀ = about 0.39 nm), tetragonal high temperature superconductivity such as yttrium barium copper oxide: YBa ₃ Cu ₃ O _7-x (abbreviation YBCO) Body, (normal) dielectric such as SrTiO ₃ and BaF ₂ , semiconductor such as Si and Ge.

The above facts suggest the possibility of epitaxial growth of these various materials on stabilized zirconia single crystal substrates. In fact, on a single crystal (100) YSZ substrate, c-axis oriented YBa ₃ Cu ₃ O _7-x (eg GA
Samara, Journal of Applied Physics, 68, 1990, 421
4.) and Si (eg HM Masasevit et al., Journalo
f the Electrochemical Society, 130, 1983, 1752.)
The epitaxial film of is obtained. In addition, the inventor of the present application has found that in a recent experiment, the single crystal YSZ (10
0) The Pb (Zr _x Ti _1-x ) O ₃ film and the Pt film (both have c-axis orientation) epitaxially grown on the substrate or the single crystal SSZ (100) substrate have been successfully obtained.

In addition, the fact that various films such as those mentioned above can be epitaxially grown on a single crystal stabilized zirconia substrate means that even on a single crystal stabilized zirconia film.
It means that the film can be epitaxially grown. Thus, it has become possible to epitaxially form a wide variety of single crystal thin film materials on a single crystal Si substrate through an oxide epitaxial film called stabilized zirconia.

Attention is paid most to this new technology in the field of functional integrated circuits described below. recent years,
An active attempt has been made to mount functional materials such as a ferroelectric thin film, a high temperature superconductor thin film, and a semiconductor thin film on a Si semiconductor integrated circuit substrate.
This is a high value-added functionality that combines special functions such as polarization inversion characteristics, pyroelectricity, piezoelectricity, superconductivity, and optical / high temperature semiconductor characteristics that cannot be achieved with conventional circuit configurations and high-speed arithmetic processing of Si integrated circuits. It is intended to be an integrated circuit.

In many cases, the functional thin film, when it becomes a crystal, exhibits the above-mentioned interesting physical properties. Therefore, in a functional integrated circuit, the performance is most efficiently
In order to use it with the highest sensitivity, a technique for producing a single crystallized film is strongly desired. Further, the ferroelectric substance has strong polarization reversal characteristics, pyroelectricity, and piezoelectricity and exhibits crystal anisotropy, so that it is necessary to devise the orientation in a specific direction in which the characteristics appear. Generally speaking, it is difficult to form a single crystal film on an amorphous substrate or a polycrystalline substrate. In order to solve this problem, a method is known in which a substrate having a crystal structure similar to the crystal structure (or lattice constant) of a single crystal film to be grown is used and heteroepitaxial growth is performed on the base. To apply this method to a functional integrated circuit, the Si substrate, which is the only single crystal body, is partially exposed, and the functional device is constructed by using this as a substrate.

Although the structure of the functional device is various, there are many application examples and a practically important structure is that a functional thin film or other film is formed on the Si substrate (IS structure) on which the insulating film (I) is formed. It is of structure. For example, an MFIS type in which a metal (M) -insulating film (I) -semiconductor (S) transistor is replaced by a laminated thin film body including at least one ferroelectric film (F = functional thin film) on the "I" portion of the transistor. , Or MFMI
S-type non-volatile memory, pyroelectric sensor, piezoelectric sensor, etc. are good examples. A high-temperature superconductor (F) wiring integrated circuit aiming at low power consumption and high-speed calculation is another example. Here, the high-temperature superconductor wiring is arranged on the insulator film / Si substrate (IS structure) except for the contact portion. In addition to this, a so-called SOI type MOS device in which a single crystal semiconductor film (F = S) is formed on a single crystal Si substrate through an insulator film may be added as an example. This device is extremely important for realizing an integrated circuit with high speed, high integration, and high radiation resistance, and its structure is MOF (= S) IS. As described above, the IS composite structure is one of the basic structures for constructing the functional thin film or the functional device on the Si integrated circuit substrate.

In order to construct a functional device including a single-crystal functional thin film on the IS structure substrate, it is necessary to transfer the crystallinity of the Si substrate up to the functional thin film formed on the upper part by heteroepitaxy. For this purpose, at least the I layer must be an epitaxially grown insulating film. The above-mentioned stabilized zirconia film (in particular, YS
(Z film) satisfies the above functions,
It is attracting attention.

As mentioned above, stabilized zirconia / c-S
The i composite structure is extremely useful because it has a requirement as a substrate for realizing a functional integrated circuit or the like. However, in order to actually use it, the "ion drift" problem, which will be described in detail below, must be solved.

FIG. 5 shows the results of measuring the CV characteristics of an MIS capacitor composed of an Al electrode film / single crystal stabilized zirconia film / c-Si for various sweep rates SR (= 1 to 0.001 V / sec). FIG. The characteristic of FIG. 5 is that after sweeping the gate bias voltage at 5V for 30 minutes,
This is the result of performing the step-down direction in steps of 0.1 V, maintaining the voltage again for 30 minutes when reaching -5 V, then reversing the sweep direction and stepping up toward 5 V. The measurement frequency is a 1 MHz sine wave.

From the results shown in FIG. 5, it can be seen that the hysteresis in the clockwise direction is generated in the characteristic in the step-down direction and the characteristic in the step-up direction. This hysteresis indicates that ions that can be moved by an electric field are present in the single crystal stabilized zirconia film and that they are drifting. The C-V characteristic (not shown) for SR> 1 V / sec is SR =
It is no different from that of 1V / sec. Also, the hysteresis is S
Since it disappears at R = 0.005 V / sec or less,
It is understood that the response of mobile ions is distributed in the range of several seconds to several hundreds of seconds. Hereinafter, as a measure for measuring the degree of ion drift of the composite structure, the degree of ion drift: ΔV
The amount of [V] is defined. ΔV is SR as shown in FIG.
Is the maximum width of the hysteresis observed in the C-V characteristics obtained by changing

According to recent research on zirconia, such ion drift is caused by the movement of oxygen ion vacancies, which are inevitably generated in a zirconia crystal by the introduction of a stabilizer, by being attracted to an external electric field. It has been known. To explain this in more detail, in the stabilized zirconia: ASZ (A is a metal element of the stabilizer), the divalent or trivalent metal ions A ²⁺ and A ^{3+ of} the stabilizer are ZrO.
Oxygen ion vacancy: Vo is formed depending on the added amount and the valence of the replaced ion in order to enter the cation lattice position by substituting the tetravalent Zr ⁴⁺ ion of the ₂ crystal and maintain electrical neutrality. To be done. The reaction of generating such a lattice defect for YSZ and CSZ is represented by the following formula (Formula 1).

[0017]

Embedded image

However, Y (Zr): Y replacing Zr is displayed Ca (Zr): Ca replacing Zr is displayed "+": number of positive effective charges "-": number of negative effective charges As is clear from the formula (1), when a trivalent metal ion such as Y substitutes two tetravalent Zr ions, one oxygen ion vacancy is generated, and a divalent metal ion such as Ca becomes Zr. When one ion is replaced, one oxygen ion vacancy is generated. When an electric field is applied, the oxygen ion vacancies behave like positive mobile ions and move in the direction of the electric field.

6 (a) to 6 (c) are two-dimensional schematic views of cubic CSZ-stabilized zirconia single crystals. In this, “□” represents oxygen ion vacancies. Now, when a positive electric field: E is applied from the bottom to the top of the paper, the oxygen ions closest to the bottom of the electric field as viewed from the oxygen ion vacancy can move toward the vacancy. When actually moved, the oxygen ion vacancy moves to the original position of the oxygen ion as shown in (b). The nearest oxygen ion on the lower side moves to the hole moved to the new position again as shown in (c). In this way, the oxygen ion vacancies move in the direction of the electric field. When there is an electric field, negatively charged oxygen ions move in the direction opposite to the electric field through the holes, and positively charged holes drift relatively toward the electric field. This is the ion drift.

[0020]

The ion drift (presence and slow response) of such a stabilized zirconia film depends on the surface potential of the underlying Si semiconductor substrate and the characteristics of the functional device formed above for a long time. (0.1 seconds to 1000
This makes it unstable over a second period of time, which is extremely harmful and greatly hinders the realization of a functional integrated circuit based on a single crystal-stabilized zirconia film / c-Si composite structure.

The present invention has been made to solve the above-mentioned problems of the prior art, and provides a single crystal-stabilized zirconia film / c-Si composite structure without ion drift and a method for manufacturing the same. It is an object.

[0022]

Means for Solving the Problems In order to achieve the above object, the present invention is configured as described in the claims. That is, in the invention described in claim 1, as a structure of the composite structure, a novel oxide containing a metal oxide having a valence higher than Zr on c-Si (hereinafter referred to as a vacancy quencher) is added. A single crystal-stabilized zirconia having a different composition is arranged. The invention described in claims 2 to 7 shows a configuration example of each component of claim 1.

In addition, claims 8 to 11 are examples of a method for manufacturing the above composite structure, in which a natural oxide film on the surface of a Si semiconductor substrate is removed, and then an electron beam vapor deposition method or an ion method is applied to this. A stabilized zirconia thin film is formed by beam sputtering, laser ablation, or chemical vapor deposition.

In the stabilized zirconia film / c-Si composite structure of the present invention, the oxygen ion vacancy quenching agent newly added to the stabilized zirconia has a function of removing oxygen ion vacancies in the stabilized zirconia film. . Therefore, the ion vacancy to be drifted disappears from the stabilized zirconia crystal body, and the present invention can solve the ion drift problem, which is a problem of the conventional technique. Furthermore, since the stabilized zirconia film still maintains the cubic crystal structure and quality even if a vacancy quencher is added, it functions as a substrate for forming an epitaxial film of various materials including functional materials. Is not harmed at all.

[0025]

According to the present invention, in a composite structure in which a cubic stabilized zirconia thin film is grown on a single crystal silicon semiconductor substrate, the stabilized zirconia thin film is made of an oxide of a valence metal lower than 4 valences. Owing to the constitution in which the stabilizer and the oxygen ion vacancy quencher composed of an oxide of a valence metal higher than tetravalent are contained in equal amounts, the oxygen ion vacancies are removed from the stabilized zirconia thin film, As a result, an excellent effect that the ion drift problem can be solved is obtained.

Further, in the method using the electron beam evaporation apparatus described in the first embodiment (Example 3) of the manufacturing method, the stabilized zirconia is formed by an inexpensive film forming means called the electron beam evaporation apparatus. Therefore, there is an advantage that the composite structure can be manufactured at a lower cost than other film forming methods.

In addition, the method described in the second embodiment of the manufacturing method (Example 4) is 45 compared with other examples.
Since the film can be formed at a low temperature of 0 ° C., it is extremely effective when a non-heat resistant material or structure is formed on the Si substrate before film formation.

The method described in the third embodiment (Example 5) of the manufacturing method has the characteristic that the composition of the metal element of the stabilized zirconia film becomes equal to the composition of the target metal element. Therefore, it is possible to use the optimum condition obtained by a certain laser ablation film forming apparatus as that of another laser ablation film forming apparatus. This has the advantage that the time required for optimization can be saved when starting up a large-scale film forming apparatus for production.

Further, the fourth embodiment of the manufacturing method (Example 6) has an excellent feature that it can provide a stabilized zirconia film having high coverage even on a Si single crystal substrate having fine irregularities.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION The structure of a composite structure of a stabilized zirconia thin film and a substrate according to the present invention and an example of a method for producing the structure will be described in detail below with reference to the drawings. In addition,
In the following figures, objects with the same numbers are all the same objects, and once described in detail, the objects will be briefly described in later figures.

(1) First Embodiment of Composite Structure <
Example 1> FIG. 1 is a schematic cross-sectional view of essential parts showing a first embodiment of a composite structure according to the present invention. In FIG. 1, reference numeral 1 is a single crystal Si (100) substrate. 2 is a cubic epitaxially stabilized zirconia thin film, in which trivalent metal oxide Y ₂ O ₃ or Sm ₂ O ₃ or a stabilizer composed of a mixture thereof and a pentavalent metal oxide are contained. Ta ₂ O ₅ ,
Nb ₂ O ₅ , V ₂ O ₅ , or a annihilation agent composed of a mixture thereof is added. The concentrations of the stabilizer and the annihilation agent are approximately equal and are between 5 mol% and 25 mol%. The stabilizer and the annihilation agent are added in situ during the epitaxial growth. This cubic epitaxially stabilized zirconia thin film 2 is epitaxially formed by one method arbitrarily selected from an electron beam evaporation method, an ion beam sputtering method, a laser ablation method and a chemical vapor deposition method. A detailed description will be given in Examples of the manufacturing method described later.

(2) Second Embodiment of Composite Structure <
Example 2> FIG. 2 is a schematic cross-sectional view of essential parts showing a second embodiment of the composite structure according to the present invention. In FIG. 2, reference numeral 1 is a single crystal Si (100) substrate. Reference numeral 2'denotes a cubic epitaxially stabilized zirconia thin film, in which a stabilizer composed of a divalent metal oxide CaO and a vacancy disappearant composed of a hexavalent metal oxide WO ₃ or MoO ₃ are contained. Has been added. The concentrations of the stabilizer and the annihilation agent are almost equal,
It is between 8 mol% and 30 mol%. The stabilizer and the annihilation agent are added in situ during the epitaxial growth. The cubic epitaxially stabilized zirconia thin film 2'is epitaxially formed by one method selected from electron beam evaporation method, ion beam sputtering method, laser ablation method, and chemical vapor deposition method. The description will be given in the embodiment of the manufacturing method described later.

(3) First Embodiment of Manufacturing Method of Composite Structure <Example 3> Here, a manufacturing method for realizing the composite structure shown in FIG. 1 by an electron beam evaporation method will be described. First, RCA cleaning (a traditional Si substrate cleaning method consisting of cleaning SC1 with a mixed solution of ammonia water and hydrogen peroxide solution and cleaning SC2 with a mixed solution of hydrochloric acid and hydrogen peroxide solution) and diluted hydrofluoric acid cleaning (5% concentration) The cleaning method of immersing the substrate in the HF aqueous solution for several tens of seconds, followed by rinsing with pure water and drying) to remove contaminants and natural oxides on the surface of the Si substrate 1.

Subsequently, a stabilized zirconia film 2 (hereinafter abbreviated as YSZ: Ta) stabilized on yttrium oxide Y ₂ O ₃ and vacancy-erased on tantalum oxide Ta ₂ O ₅ is formed on the Si substrate 1. It is formed by the electron beam evaporation method. The target for vapor deposition was a mixture of Y ₂ O ₃ powder, ZrO ₂ powder and Ta ₂ O ₅ powder in a molar ratio of x: (1-x-y): y, and hot-pressed into a disc shape (diameter 15 mm, thickness 7 mm). It is a tablet shaped into. Here, x = about 9% and y = about 15%. The reason that the molar concentration of Ta ₂ O _{5 in} the tablet is higher than that of Y ₂ O ₃ is that the evaporation of Ta ₂ O ₅ is relatively slower than that of Y ₂ O ₃ or ZrO ₂ .

The film forming procedure will be described. First, a hearth (= tablet filling place) is filled with tablets, and immediately the cleaned Si substrate 1 is placed on a substrate holder in the vapor deposition tank, and the interior of the vapor deposition tank is evacuated. To do. This holder has the ability to heat the substrate from room temperature to 1000 ° C., and opposes it with a sufficient distance to the vapor deposition tablet housed in the hearth in the vapor deposition tank. Exhaust of the deposition apparatus is powerful, internal pressure can be reduced to below 10 ~ ⁹ Torr. When the pressure in the vapor deposition tank reaches 10 to ⁶ Torr, the substrate temperature is heated to a predetermined film forming temperature. When the temperature is stable and the pressure in the vapor deposition tank falls to 10 to ⁹ Torr or less, the output of the vapor deposition power supply is turned on and the electron beam is projected onto the tablet to start vapor deposition. After the vapor deposition is started, when the YSZ film thickness becomes approximately 3 nm, high-purity dry oxygen is externally introduced to adjust the pressure to 2 × 10 ⁶ torr and the filament current is increased to continue film formation. The film thickness is determined by the film formation time, and the film formation rate is determined by the filament current.

The typical epitaxial YSZ: Ta film forming conditions are as follows. YSZ film forming conditions Film forming pressure 1 × 10 to ⁸ Torr (up to 3 nm film thickness) 2 × 10 to ⁶ Torr (introducing O ₂ from film thickness 3 nm) Film forming temperature 800 ° C. (substrate temperature) Target Y ₂ O ₃ : ZrO ₂ : Ta ₂ O ₅ = 9: 81: 8 Input power 200 W Filament current 20 mA (initial) 50 mA (from film thickness 3 nm) Electron beam accelerating voltage 8 kV Film formation was performed as described above, and the film thickness reached the desired value. By the way, the output of the vapor deposition power supply is turned off to complete the film formation. After that, the substrate is gradually cooled while being placed in the vapor deposition tank, and the substrate is taken out of the vapor deposition tank after the temperature of the substrate is sufficiently low.

The concentrations of the stabilizer and the annihilation agent of the YSZ: Ta film thus deposited were the same (= 11%) within the range of experimental accuracy. Also, the crystal structure of the film was a single crystal epitaxial film having a fluorite structure (cubic crystal) (details are described in the section of effects described later). Since this manufacturing method uses an electron beam evaporation apparatus, which is an extremely common and inexpensive film forming means, it has an advantage that a large-area epitaxial YSZ film can be formed at a lower cost than other film forming methods described later. . Further, the structure of the second embodiment (Example 2) of the composite structure can be realized by using the above manufacturing method (however, the conditions are slightly different).

(4) Second Embodiment of Manufacturing Method of Composite Structure <Example 4> Here, a manufacturing method for realizing the composite structure shown in FIG. 2 by an ion beam sputtering method will be described. First, as in the third embodiment, contaminants and natural oxides on the surface of the Si substrate 1 are removed by RCA cleaning and diluted hydrofluoric acid cleaning.

Subsequently, calcium oxide C was deposited on the Si substrate 1.
stabilized with aO-, oxide Tagusuten WO ₃ in an oxygen-ion vacancies stabilized zirconia film was quenched of 2 '(hereinafter CS
Z: W) is formed on the Si substrate 1 by the ion beam sputtering method. The sputtering target is CaO powder, ZrO ₂ powder, and WO ₃ powder in a molar ratio of x: (1-x-
y): It is mixed with y and shaped into a disk shape by hot pressing. Here, x = about 11% and y = about 11%.

Explaining the procedure of film formation, first, the target is set on the target holder, the Si substrate 1 immediately after the cleaning is set on the substrate holder in the vapor deposition tank, and the inside of the vapor deposition tank is evacuated. This holder has the ability to heat the substrate from room temperature to 600 ° C, and about 60c from the target.
They are facing each other with a distance of m. Exhaust of the deposition apparatus is powerful, internal pressure can be reduced to below 10 ~ ⁹ Torr. When the pressure in the vapor deposition tank reaches 10 to ⁶ Torr, the substrate temperature is heated to a predetermined film forming temperature. When the temperature is stable and the pressure in the vapor deposition tank falls below 10 to ⁹ Torr, the output of the power source of the ion source is turned on, and the ion beam is projected onto the tablet to start vapor deposition. After vapor deposition, at least 10 until the CSZ film thickness reaches 3 nm.
The film is formed while maintaining a high vacuum of about ⁸ Torr level, but when the thickness exceeds 3 nm, high-purity oxygen containing 10 mol% ozone is injected from the outside toward the substrate. After that, the pressure is 5 × 10 ~ ⁶ To
Adjust to rr. Then, the ion beam current is increased to continue film formation. The film thickness is adjusted by the film forming time, and the film forming rate is adjusted by the ion beam current or the ion beam accelerating voltage.

The optimum film forming conditions for the apparatus used by the present inventor are as follows. CSZ: W film forming conditions film forming pressure 1 × 10 to ⁷ Torr or less (up to film thickness 3 nm) 5 × 10 to ⁶ Torr (introducing O ₂ + O ₃ (10 mol%) from film thickness 3 nm) film forming temperature 450 ° C. (substrate Temperature) Target CaO: ZrO ₂ : WO ₃ = 11: 80: 9 Ion species Xe Ion source voltage 1500 V Ion current 9 mA (up to 3 nm film thickness) 14 mA (from 3 nm film thickness) When the value reaches a desired value, the output of the vapor deposition power source is turned off, the introduction of O ₂ + O ₃ is cut off, and the substrate is gradually cooled. After the substrate temperature is sufficiently low, the substrate is taken out of the vapor deposition tank.

The concentrations of the stabilizer and the annihilation agent of the CSZ: W film thus deposited were the same (= 15%) within the range of experimental accuracy. Also, the crystal structure of the film was a single crystal epitaxial film having a fluorite structure (cubic crystal) (details are described in the section of effects described later). The manufacturing method of the fourth embodiment can form a film at a low temperature of 450 ° C., as compared with the manufacturing method of the third embodiment and the examples described later. This is extremely effective when another material that cannot withstand high heat is formed on the Si substrate, which is an advantage that other manufacturing methods do not have. Although not described in detail, the structure of the composite structure shown in the first embodiment (Example 1) can be realized by using this manufacturing method (however, the conditions are slightly different).

(5) Third Embodiment of Method for Producing Composite Structure <Example 5> Next, an example of a method for producing the composite structure shown in FIG. 1 by a laser ablation method will be described. First, similar to the manufacturing method of the first embodiment, contaminants and natural oxides on the surface of the Si substrate 1 are removed by RCA cleaning and diluted hydrofluoric acid cleaning.

Subsequently, samarium oxide S is formed on the Si substrate 1.
Stabilized with m ₂ O ₃ (Samaria), niobium oxide Nb
A stabilized zirconia film 2 (hereinafter SSZ: Nb) in which oxygen ion vacancies are eliminated by ₂ O ₅ is formed on the Si substrate 1 by a laser ablation method. Target is Sm ₂ O ₃ powder and Z
A mixture of rO ₂ powder and Nb ₂ O ₅ powder (which has a purity of 99.999% or more) in a molar ratio of x: (1-x-y): y and hot-pressed into a disc shape (diameter 10 mm, Thickness 10mm)
It has been shaped into. Where x = about 18%, y = about 1
8%.

Explaining the procedure of film formation, first, the target is set in the target holder in the vacuum tank of the film forming apparatus, the Si substrate 1 immediately after the cleaning is set in the substrate holder in the evaporation tank, and the inside of the evaporation tank is set. Exhaust. This holder has the ability to heat the substrate from room temperature to 600 ° C., and opposes it with a distance of about 5 cm from the target. Exhaust of the vapor deposition apparatus is strong, and the back pressure can be lowered to 10 to ⁹ Torr or less. Deposition tank pressure is 1
When it reaches 0 to ⁶ Torr, the substrate temperature is heated to a predetermined film forming temperature. The temperature is stable, and the pressure in the vapor deposition tank is 10 to ⁸
When the temperature falls below Torr, the output of the laser light source is turned on and high-density laser light is projected onto the tablet to start vapor deposition. The laser light source of this embodiment is a KrF (wavelength 248n
m, pulse width 20 ns) excimer laser. The repetition frequency was 10 Hz and the energy density was 1.3 J / m ³ . After the start of vapor deposition, a high vacuum of at least 10 to ⁸ Torr is maintained until the film thickness of SSZ reaches 3 nm.
Then, when exceeding 3 nm, high-purity oxygen is introduced from the outside to adjust the pressure to 5 × 10 to ⁵ Torr. The standard deposition rate was 0.025 nm per pulse. The film thickness is adjusted by the film formation time (equivalent to the number of pulses).

The optimum film forming conditions in the apparatus used by the present inventor are as follows. SSZ: Nb film formation conditions Film formation pressure 1 × 10 to ⁷ Torr or less (up to film thickness 3 nm) 5 × 10 to ⁴ Torr (film thickness 3 nm to introduce O ₂ ) Film formation temperature 775 ° C. (substrate temperature) Target Sm ₂ O ₃ : ZrO ₂ : Nb ₂ O ₅ = 18: 64: 18 Target / Substrate distance 5 cm Laser light source KrF excimer laser (energy 130 mJ) Excitation pulse width 20 ns, repetition frequency 10 Hz When the value reaches 0, the laser light source is stopped, the introduction of O ₂ is stopped, and the substrate is gradually cooled. After the substrate temperature is sufficiently low, the substrate is taken out of the vapor deposition tank.

The concentrations of the stabilizer and the annihilation agent of the SSZ: Nb film thus deposited were both the same (= 18%) within the range of experimental accuracy. The crystal structure of the film was a single crystal epitaxial film having a fluorite structure (cubic crystal). The composition of the metal element of the stabilized zirconia film formed by this manufacturing method is characterized in that it is almost equal to the composition of the target even if the vapor deposition conditions are changed. This means that the composition of the stabilized zirconia film is uniquely determined by the composition of the target without depending on the film forming apparatus. Such a feature is useful because it has an effect that the time required for optimization can be shortened when a large-scale production film forming apparatus is started up based on the optimum conditions obtained by the experimental film formation. Although not described in detail, the structure of the composite structure shown in the second embodiment (Example 2) can be realized by using this manufacturing method (however, the conditions are slightly different).

(6) Fourth Embodiment of Method for Producing Composite Structure <Example 6> Next, the composite structure shown in FIG. 1 was subjected to chemical vapor deposition (CV).
An example of the manufacturing method realized in D) will be described. First, similarly to the manufacturing method of the third embodiment, contaminants and natural oxides on the surface of the Si substrate 1 are removed by RCA cleaning and diluted hydrofluoric acid cleaning.

Then, samarium oxide Y was deposited on the Si substrate 1.
Stabilized with ₂ O ₃ (yttria), tantalum oxide Ta ₂
A stabilized zirconia film 2 (hereinafter YSZ: Ta) in which oxygen ion vacancies are eliminated by O ₅ is formed on the Si substrate 1 by the low pressure CVD method. The raw materials were yttrium tridipivaloyl methane: Y (DPM) ₃ , zirconium tetradipivaloyl methane: Zr (DPM) ₄ , tantalum pentaethoxide: Ta (OC ₂ H ₅ ) ₅ , and O _2. Is. Where D
PM means C ₁₁ H ₁₉ O ₂ .

The apparatus used is a conventional cold wall type low pressure CVD apparatus as shown in FIG. This device is more complicated in structure and operating method than the physical vapor deposition devices shown in Examples 3 to 5, and will be described in detail with reference to FIG. In FIG. 3, 10 is a reactor. The reactor 10 includes a susceptor 12 that mechanically supports the single crystal Si substrate 11 and holds it at a predetermined temperature, a shower head 13 that mixes vapors, and sprays the mixed vapors uniformly toward the susceptor 12, An exhaust port 14 for the generated gas generated by the deposition reaction and excess source vapor is provided. 15, 16,
17 is Y (DPM) ₃ raw material, Zr (DPM) ₄ raw material,
It is a vaporization container for Ta (OC ₂ H ₅ ) ₅ raw material and has a temperature control function. A carrier gas of which flow rate is controlled: Ar is introduced into the vaporization vessels 15, 16 and 17, and the vaporized raw material vapor is transported by the Ar gas and guided to the shower head 13.

To the shower head 13, O ₂ whose flow rate is controlled is also connected as shown in the figure. Vaporization container 1
The transport pipes connecting 5, 16 and 17 and the shower head 13 are kept at a temperature higher by about 10 ° C. than the temperature of each raw material vaporization container. Further, 18 to 21 are supply valves for the respective raw material vapors. The gas produced in the reactor and the excess raw material vapor are discharged to the outside of the reactor by the vacuum exhaust device 23 via the exhaust main valve 22. Reference numeral 24 is a pressure controller for keeping the pressure in the reactor constant during film formation.

The film forming procedure is as follows. The Si single crystal substrate 1 that has been cleaned is placed on the susceptor 12, all the raw material vapor supply valves 18 to 21 are closed, and the exhaust main valve 22 is opened to temporarily evacuate the inside of the reactor 10. The temperature of the susceptor 12 is set to a predetermined substrate temperature, and the pressure of the reactor 10 is reduced to 10 to ⁶ Torr. Subsequently, the pressure regulator 24 is operated and the supply valves 18 to 21 are operated.
Open, and each material is jetted from the shower head to start film formation.

Typical film forming conditions in this example are shown below. YSZ: Ta film forming conditions film forming pressure 2 Torr film forming temperature 650 ° C. (substrate temperature) material, material temperature, flow rate Y (DPM) ₃ , 140 ° C., 15 sccm Zr (DPM) ₄ , 165 ° C., 17 sccm Ta (OC ₂ H) ₅ ) ₅ , 130 ° C., 20 sccm O ₂ 200 sccm Distance between shower head and substrate 3 cm After film formation was performed as described above, when the film thickness reached the desired value, the raw material vapor supply valves 18-21 were closed and pressure was adjusted. The controller 24 is stopped, and the substrate 11 is gradually cooled while the reactor 10 is evacuated. The substrate 11 is taken out of the reactor 10 after the substrate temperature becomes sufficiently low.

What is important in film formation is the generated YSZ: T.
a film composition, that is, a stabilizer Y ₂ O ₃ and a vacancy quencher T
a ₂ O ₅ concentration is almost equal, and the predetermined value is 5 mol% to 25 mol
% (Y (DPM) ₃ raw material and Ta (OC)
_This means controlling the temperature and flow rate of the ₂ H ₅ ) ₅ raw material.
It has been confirmed that, under the above conditions, the concentration of the stabilizer and the pore eliminator is about 11%.

The stabilized zirconia film formed by the present manufacturing method has extremely good coverage even at the geometrical stepped portion on the substrate surface as compared with the film formed by the physical vapor deposition method. For example, aspect ratio (ratio of base length to wall length)
When a film is formed on a vertical groove structure substrate of 1: 2, a good coverage (ratio of the thinnest film thickness inside the groove to the film thickness value on the substrate surface) of 0.9 or more is obtained. Such a feature is very advantageous when a stabilized zirconia film is uniformly formed on a single crystal Si substrate having irregularities. Although not described in detail, the structure of the composite structure shown in the second embodiment (Example 2) can be realized by using this manufacturing method (however, the conditions are slightly different).

Next, FIG. 4 is a table showing the characteristics of the composite structures manufactured on the Si (100) substrate by the manufacturing method of Examples 3 to 6 described above. The stabilized zirconia films all have the same thickness. In FIG. 4, indicates the crystallinity of the stabilized zirconia film, and indicates the degree of ion drift extracted from the high frequency C-V characteristic of MIS capacitance (Hilteresis): Δ
Indicates V [V]. The method of measuring the CV characteristics has been described in the above-mentioned section of the prior art. Also, for comparison,
The characteristics of the composite structure based on the conventional technique described with reference to FIG. 5 are also shown.

As shown in FIG. 4, the crystal system of the stabilized zirconia of the composite structure according to the present invention is a cubic system in all the examples, and is completely c-axis oriented. And the lattice constant is almost equal to that of the stabilized zirconia of the conventional example. Further, the crystal relationship with the single crystal Si (100) substrate is Si
(001) ‖XSZ: Y (001), Si [110] ‖
XSZ: Y [110]. However, ‖ means parallel. Further, XSZ: Y represents an arbitrary stabilized zirconia film produced by the manufacturing method of Examples 3 to 6.

From the above crystallographic facts, all the stabilized zirconia films formed by the manufacturing methods of Examples 3 to 6 are epitaxially grown on the single crystal Si substrate, and the crystal quality of the film is stabilized by the conventional technique. It can be seen that the film is comparable to the zirconia film.

Next, MIS, which is a measure of ion drift,
Focusing on ΔV of the capacity, ΔV> 5V is extremely large in the conventional example, and as described above, it has been a serious obstacle in device application. On the other hand, in each of the examples of FIG. 4, ΔV <0.05 V, which is suppressed by two digits or more. The mobile oxygen ion concentration estimated from this ΔV is Nm = 2.9.
It becomes x10 ¹⁰ / cm ² , and it is understood that the concentration of mobile ions (such as sodium) in the gate oxide film of the MOS integrated circuit is reduced to the allowable 10 ¹⁰ / cm ² .

Thus, in the composite structures of Examples 1 and 2, and the manufacturing methods of Examples 3 to 6, while maintaining the crystallinity of the stabilized zirconia film at high quality, the problems of the prior art were encountered. The ion drift problem caused by the oxygen ion vacancies, which was the point, can be solved.

Next, the mechanism by which the present invention solves the ion drift problem will be described. Ion drift is caused by the movement of oxygen ion vacancies in stabilized zirconia in the electric field. Oxygen ion vacancies are formed because the tetravalent Zr ion of zirconia is replaced by the divalent or trivalent metal ion contained in the stabilizer, as described in the section of the description of the prior art. This is because the electrically neutral condition must be satisfied. However, in the present invention, the oxygen ion vacancy quenching agent containing a pentavalent or hexavalent metal ion is added at the same time as the addition of the stabilizer, so that oxygen neutral vacancy is not generated and the electrical neutral condition is satisfied. Can be made. For example, YSZ: T
In the example of a (the structure of Example 1 and the manufacturing method of Example 3),
The chemical formula of the addition is as shown in the following (formula 3).

[0062]

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In the formula (3) below, Ta ₂ O ₅ is 1
When mol addition, excess interstitial oxygen ions Io of 1 mol ^-
However, since the interstitial oxygen ions and the vacancies Vo ⁺⁺ of Y ₂ O ₃ cancel each other out by the addition of an equal amount, they are represented by the following (Formula 4) as a whole. And the vacancies disappear.

[0064]

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Similarly, in the case of CSZ: W, the overall formula (Chem. 5) is obtained, and oxygen ion vacancies do not occur.

[0066]

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As described above, in the present invention, since oxygen ion vacancies as movable charge carriers do not exist in the stabilized zirconia film, ion drift does not occur even when an electric field is applied to the composite structure. The problem can be solved.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing a first embodiment (Example 1) of a composite structure of the present invention.

FIG. 2 is a sectional view of an essential part showing a second embodiment (Example 2) of the composite structure of the present invention.

FIG. 3 is a configuration diagram of a chemical vapor deposition apparatus used in a fourth embodiment (Example 6) of the manufacturing method of the present invention.

FIG. 4 is a chart showing a comparison between each example of the present invention and a conventional example.

FIG. 5 is a diagram showing an experimental result for explaining an ion drift phenomenon of a stabilized zirconia / single crystal silicon composite structure according to a conventional technique.

FIG. 6 is a diagram for explaining the mechanism of ion drift.

[Explanation of symbols]

1 ... Single crystal Si substrate. 2 ... Single crystal stabilized zirconia thin film containing a stabilizer composed of trivalent metal oxide and oxygen ion quencher composed of pentavalent metal oxide 2 '... Stabilizer composed of divalent metal oxide Single-crystal stabilized zirconia thin film containing oxygen ion quencher composed of hexavalent metal oxide 10 ... Reactor 11 ... Single-crystal Si
Substrate 12 ... Susceptor 13 ... Shower Head 14 ... Exhaust Ports 15, 16, 17
Material vaporizer 18 to 21 Supply valve 22 Exhaust main valve 23 Vacuum exhaust device 24 Pressure regulator

Claims (11)

[Claims] 1. A composite structure in which a stabilized zirconia thin film (ZrO ₂ ) is grown on a single crystal silicon semiconductor substrate, wherein the stabilized zirconia thin film is made of an oxide of a valence metal having a valence of 4 or less than Zr. Stabilized zirconia thin film and single crystal silicon, containing substantially the same amount of a stabilizer and an oxygen ion vacancy annihilation agent composed of an oxide of a valence metal having a valence higher than tetravalence of Zr. Composite structure with substrate. 2. The oxide metal of the oxygen ion vacancy quencher has a valence of 5, when the oxide metal of the stabilizer has a valence of 3. A composite structure of the stabilized zirconia thin film according to 1 and a single crystal silicon substrate. 3. The stabilizer is Y ₂ O ₃ or Sm ₂ O ₃ , or a mixture of Y ₂ O ₃ and Sm ₂ O ₃ , and the oxygen ion vacancy quencher is Ta ₂ O. ₅ or Nb ₂ O ₅ or V ₂ O ₅ , or Ta ₂ O ₅ and Nb ₂ O ₅ and V ₂
The composite structure of a stabilized zirconia thin film and a single crystal silicon substrate according to claim 2, which is a mixture containing two or more kinds of O ₅ . 4. The valence of the oxide metal of the oxygen ion vacancy quencher is 6 when the valence of the oxide metal of the stabilizer is divalent. A composite structure of the stabilized zirconia thin film according to 1 and a single crystal silicon substrate. 5. The stabilized zirconia thin film and single crystal silicon according to claim 4, wherein the stabilizer is CaO and the oxygen ion vacancy quencher is WO ₃ or MoO _3. Composite structure with substrate. 6. The stabilized zirconia according to any one of claims 1 to 5, wherein the concentrations of the stabilizer and the oxygen ion quencher are in the range of 5 mol% to 30 mol%. A composite structure of a thin film and a single crystal silicon substrate. 7. A composite structure in which a stabilized zirconia thin film is grown on a single crystal silicon semiconductor substrate, wherein the stabilized zirconia thin film is a single crystal film heteroepitaxially grown on the single crystal silicon semiconductor substrate. A composite structure of the stabilized zirconia thin film according to any one of claims 1 to 6 and a single crystal silicon substrate. 8. A method for producing a composite structure of the stabilized zirconia thin film according to any one of claims 1 to 7 and a single crystal silicon substrate, wherein the surface of the single crystal silicon semiconductor substrate is formed. A step of removing and washing the natural oxide film, a step of quickly mounting the substrate after the washing in a vacuum vapor deposition tank without generating a natural oxide film, and evacuating to 10 to ⁸ Torr or less; Forming a stabilized zirconia thin film on the single crystal silicon substrate by one film forming method selected from electron beam evaporation method, ion beam sputtering method and laser ablation method. A method for producing a characteristic composite structure. 9. A vapor deposition target used in the electron beam vapor deposition method, the ion beam sputtering method, and the laser ablation method mixes the stabilizer, the oxygen ion vacancy quenching agent, and zirconia powder in a predetermined ratio. 9. The method for producing a composite structure according to claim 8, wherein the composite structure is then pressed and shaped into a disc shape. 10. In the step of forming a stabilized zirconia thin film by each of the above film forming methods, film formation is performed in a high vacuum at the initial stage of vapor deposition, and when the film thickness reaches approximately 3 nm, oxygen is externally supplied to the vapor deposition tank. Alternatively, the method for producing a composite structure according to claim 8 or 9, wherein oxygen containing ozone is introduced and film formation is subsequently performed. 11. A method for producing a composite structure of the stabilized zirconia thin film according to any one of claims 1 to 7 and a single crystal silicon substrate, wherein the surface of the single crystal silicon semiconductor substrate is formed. A step of removing and washing the natural oxide film, a step of quickly mounting the substrate after washing on the reactor without generating a natural oxide film, and exhausting the substrate to 10 to ⁶ Torr or less; And a step of forming a stabilized zirconia thin film on the single crystal silicon substrate by a chemical vapor deposition method.