JP2008066668A - Semiconductor device and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve characteristics of an element using a single crystal having a perovskite structure by enabling formation of the single crystal having the perovskite structure of proper quality on a silicon substrate. <P>SOLUTION: A semiconductor device using a ferroelectric film having the perovskite structure includes: an a-axis orientation single-crystal buffer film 13 of Zr<SB>1-x</SB>Si<SB>x</SB>O<SB>2</SB>(0.08≤x≤0.10) formed on a single-crystal silicon substrate 11; a lower electrode 14 which is made of the single crystal of the perovskite structure or Pt and formed on the buffer film 13; the ferroelectric film 15, which is made of the single crystal of the perovskite structure and formed on the lower electrode 14; and an upper electrode 16, which is formed as a single crystal of the perovskite structure or Pt and formed on the ferroelectric film 15. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor device using a single crystal having a perovskite structure as a ferroelectric film, a resistance change film, or a magnetic film, and more particularly to a semiconductor device having an improved base material for producing a single crystal having a perovskite structure. And a manufacturing method thereof.

In recent years, a semiconductor device using a new material such as a ferroelectric memory (FRAM) using a ferroelectric film having a perovskite structure has been devised. In this type of apparatus, it is necessary to form a single crystal ferroelectric film with good characteristics on a single crystal silicon substrate. For this reason, various buffer films such as Pt, Ir, IrO _x , SrTiO ₃ , TiN, TiAlN, and YSZ have been studied. However, a substance having a good crystallinity and good as a buffer film that does not react with the silicon substrate even after heat treatment has not yet been discovered.

For example, the use of YSZ (Yttira Stabilized Zirconia) as the buffer layer has been studied (see, for example, Non-Patent Document 1). However, rare earth yttrium contained in YSZ is very likely to diffuse into the silicon substrate by heat treatment. If yttrium diffuses into the silicon substrate, there is a problem that the electrical characteristics of the substrate deteriorate. Since buffer films other than YSZ are difficult to be films with good crystallinity in the first place, there are more problems than YSZ.
Sung Kyun Lee, Dietrich Hesse, Ulrich Gosele, and No Nyung Lee, Applied Physics Letters 86, 142903 (2005).

  Thus, conventionally, in a ferroelectric memory using a ferroelectric film having a perovskite structure, it has been difficult to form a high-quality single crystal on a silicon substrate, which has been a factor of deteriorating device characteristics. The above problem is not limited to the ferroelectric memory, but can be similarly applied to a resistance change memory using a resistance change film having a perovskite structure, a magnetic head using a magnetic film having a perovskite structure, and the like.

  The present invention has been made in consideration of the above circumstances, and the object of the present invention is to form a high-quality perovskite single crystal on a silicon substrate, and to provide an element using a single crystal of a perovskite structure. It is an object of the present invention to provide a semiconductor device capable of improving characteristics and a manufacturing method thereof.

  In order to solve the above problems, the present invention adopts the following configuration.

That is, a semiconductor device according to one embodiment of the present invention includes a Zr _1-x Si _x O ₂ a-axis oriented single crystal buffer film formed over a single crystal silicon substrate, the Pt or A lower electrode formed of a single crystal having a perovskite structure, a ferroelectric film formed on the lower electrode and formed of a single crystal having a perovskite structure, and a Pt or perovskite structure formed on the ferroelectric film And an upper electrode formed of a single crystal.

Further, a semiconductor device according to another aspect of the present invention is formed on a Zr _1-x Si _x O ₂ a-axis oriented single crystal buffer film formed on a single crystal silicon substrate, the buffer film, It has a ferroelectric film formed of a single crystal of a perovskite structure and an electrode formed on the ferroelectric film and formed of a single crystal of a Pt or perovskite structure as a gate stack structure of a transistor. And

Further, a semiconductor device according to another aspect of the present invention is formed on a Zr _1-x Si _x O ₂ a-axis oriented single crystal buffer film formed on a single crystal silicon substrate, the buffer film, A lower electrode formed of a single crystal having a Pt or perovskite structure, a resistance change film formed on the lower electrode and formed of a single crystal having a perovskite structure, and a Pt or perovskite structure formed on the resistance change film. And an upper electrode formed of a single crystal.

Further, a semiconductor device according to another aspect of the present invention is formed on a Zr _1-x Si _x O ₂ a-axis oriented single crystal buffer film formed on a single crystal silicon substrate, the buffer film, A first magnetic film formed of a single crystal of a perovskite structure; a tunnel insulating film formed of the single crystal of a perovskite structure; and formed on the tunnel insulating film; And a second magnetic film formed of a single crystal having a perovskite structure, and an electrode formed on the second magnetic film and formed of a single crystal having a Pt or perovskite structure.

A method for manufacturing a semiconductor device according to another embodiment of the present invention includes a step of forming a non-single-crystal film of Zr _x Si _1-x O _2-y in an oxygen deficient state on a single crystal silicon substrate, Forming an a-axis oriented single crystal buffer film of Zr _x Si _1-x O ₂ by annealing the Zr _x Si _1-x O _2-y film in an atmosphere containing oxygen. Features.

According to the present invention, a single crystal having a good perovskite structure can be formed on a silicon substrate by using an a-axis oriented single crystal Zr _1-x Si _x O ₂ film as a buffer film. The characteristics of the device using a single crystal can be improved.

  The details of the present invention will be described below with reference to the illustrated embodiments.

(First embodiment)
FIG. 1 is a cross-sectional view showing a schematic configuration of a semiconductor device according to the first embodiment of the present invention, particularly a ferroelectric capacitor.

A SiO ₂ buffer film (interface layer) 12 is formed on a single crystal silicon substrate 11 having a plane orientation of (001), and a Zr _0.9 Si _0.1 O ₂ film (a-axis oriented single crystal buffer film) 13 is formed thereon. ing. A ferroelectric capacitor in which a ferroelectric film 15 is sandwiched between electrodes 14 and 16 is formed on the buffer film 13. That is, the SrRuO ₃ film is formed as the lower electrode 14 on the buffer film 13, the BaTiO ₃ film is formed as the ferroelectric film 15 thereon, and the SrRuO ₃ film is formed as the upper electrode 16 thereon.

Each of BaTiO ₃ as the ferroelectric film 15 and SrRuO ₃ as the electrodes 14 and 16 is a single crystal having a perovskite structure, and the crystal structure of the BaTiO ₃ is a cubic perovskite structure that is expanded to martensite in the c-axis direction. It is a tetragonal perovskite structure, and the <004> direction faces the film thickness direction.

  Next, a method for manufacturing the semiconductor device of this embodiment will be described.

First, the natural oxide film on the surface was peeled off by dilute hydrofluoric acid treatment on the substrate 11 where the (001) plane of the silicon single crystal was exposed. Next, an oxygen deficient film made of Zr _0.91 Si _0.09 O _1.95 was formed on the substrate 11 to a thickness of about 100 nm by chemical co-sputtering using zirconium and a silicon target. In this film formation, it is not always necessary to use a sputtering method, and various film formation methods such as a CVD method, an ALD method, an MBE method, and an EB vapor deposition method can be used.

Next, the Zr _0.91 Si _0.09 O _1.95 film on the silicon substrate 11 is annealed at 750 ° C. for 30 seconds in an atmosphere of [O ₂ ] / ([Ar] + [O ₂ ]) = 3% to eliminate oxygen deficiency. In addition, a Zr _0.91 Si _0.09 O ₂ film was obtained. The annealing conditions may be from 750 ° C. to 1050 ° C., the atmospheric oxygen may be from 100 ppm to 100%, and the annealing time may be from 30 seconds to 8 minutes. By the above annealing, the Zr _0.91 Si _0.09 O ₂ film 13 is changed to an epitaxial single crystal film with respect to the silicon substrate 11.

FIG. 2 is a cross-sectional TEM (transmission electron microscope) photograph showing that the Zr _0.91 Si _0.09 O ₂ film is an epitaxial single crystal film. Depending on the printing situation of the photograph, a pattern that may be misunderstood as a grain boundary may appear, but when we examined the connection state of atomic point sequences and the results of micro area composition analysis in detail, Such a pattern is judged not to be a grain boundary. The epitaxial single crystal Zr _0.91 Si _0.09 O ₂ film had a tetragonal fluorite structure, and the a-axis direction was in the film thickness direction. The X-ray diffraction result by the thin film method showing this is shown in FIG.

Thus, after forming a Zr _0.91 Si _0.09 O _2-y film in an oxygen deficient state, annealing in an atmosphere containing oxygen can form a high-quality single crystal Zr _0.91 Si _0.09 O ₂ film. it can. Here, the oxygen deficiency _y in the Zr _0.91 Si _0.09 O _2-y film formed by sputtering is preferably in the vicinity of y = 0.05. According to the experiments by the present inventors, it was confirmed that if the oxygen deficiency y is 0.043 or more and 0.116 or less, a good quality single crystal can be obtained by subsequent annealing.

Specifically, it is 0.047, 0.057, 0.059, 0.061, 0.062, 0.116, 0.043 as _y in Zr _0.91 Si _0.09 O _2-y by chemical co _- sputtering. , 0.000, 0.053, 0.056, and 0.046 were prepared, but y = 0.000, that is, after passing through all the oxygen-deficient films other than the sample in which no oxygen-deficiency was observed. A tetragonal single crystal Zr (Si) O ₂ film as described in this embodiment was successfully produced. Samples with various film thicknesses of 5, 10, 20, 50, 100, and 450 nm were prepared as the film thickness of the Zr _0.91 Si _0.09 O ₂ film, and tetragonal single crystal Zr (Si) O was formed at any film thickness. Succeeded in creating _two films.

  FIG. 4 shows X-ray photoelectron spectroscopy results derived from the 3d orbitals of zirconium atoms. In a ZrSiO sample having oxygen vacancies, there are peaks derived from Zr—Zr bonds in addition to peaks derived from Zr—O bonds. In a ZrSiO sample having no oxygen vacancies, there are peaks derived from Zr—O bonds, but there are no peaks derived from Zr—Zr bonds.

The amount of oxygen deficiency in the ZrSiO sample can be estimated by comparing the area of the peak derived from the Zr—O bond with the area of the peak derived from the Zr—Zr bond. This is because if oxygen is deficient more than the stoichiometric ratio, an amount of Zr-Zr bonds proportional to the amount of oxygen deficiency must be generated. However, since it is necessary to multiply each peak by a known inherent conversion factor, the oxygen deficiency amount does not match the simple peak area intensity ratio in FIG. In FIG. 4, a value of 0.053 was estimated as the oxygen deficiency _y in Zr _0.91 Si _0.09 O _2-y .

Further, when the buffer film 13 is described as Zr _1-x Si _x O ₂ by a general formula, the Si composition ratio x is preferably in the vicinity of x = 0.09. According to the experiments by the present inventors shown below, it was confirmed that when x is in the range of 0.08 or more and 0.10 or less, a large dielectric constant can be obtained and it is a single crystal.

FIG. 5 is a diagram showing a change in dielectric constant composition in a Zr _1-x Si _x O ₂ sample in which oxygen vacancies are not present by annealing. It can be seen that the dielectric constant is increased at x = 8%, 9%, and 10%, and that Zr _1-x Si _x O ₂ becomes a single crystal in the range of 0.08 ≦ x ≦ 0.10. Since the dielectric constant of SiO ₂ is as low as about 3.9, the dielectric constant increases within the above range of x despite the basic tendency that the dielectric constant decreases as x increases. it makes sense.

  FIG. 6 is a diagram showing that only 200 diffraction peaks appear in the film thickness direction, that is, the a-axis direction, in the range of x from 0.08 to 0.10. In particular, in the range of x from 0.08 to 0.09, the 200 peak is sharp, indicating a very good a-axis orientation state.

Further, as shown in FIG. 7A, when the crystal direction with a small dielectric constant is oriented in the film thickness direction, the a-axis orientation hardly occurs because the oxygen diffusion barrier in the film thickness direction is large. On the other hand, when the crystal direction with a large dielectric constant is oriented in the film thickness direction as shown in FIG. 7B, the a-axis orientation is likely to occur because the oxygen diffusion barrier in the film thickness direction is large. In the present embodiment, the range of x is set from 0.08 to 0.10, and a high dielectric constant of Zr _1-x Si _x O ₂ is obtained. Therefore, a-axis orientation is likely to occur.

Further, an interface layer (buffer layer) 12 mainly composed of SiO ₂ is interposed between the single crystal Zr _0.91 Si _0.09 O ₂ buffer film 13 and the silicon substrate 11 as shown in FIGS. However, the interface layer 12 containing SiO ₂ as a main component is not necessarily present, and it is possible to adjust the annealing conditions so that it does not exist. When the interface layer 12 containing SiO ₂ as a main component was observed closely, it was found to be a crystal. The crystal structure of the interface layer 12 containing SiO ₂ as a main component is consistent with the pseudo-cristobalite. The pseudo-cristobalite of the interface layer 12 mainly composed of SiO ₂ is continuous with the atomic arrangement in the tetragonal fluorite-type Zr _0.91 Si _0.09 O ₂ single crystal film layer and the atomic arrangement in the single crystal Si substrate. It was in such a joined state. Since such an atomic arrangement has few transitions at the interface, good electrical characteristics can be obtained due to few electrical defects.

Next, an SrRuO ₃ film serving as the lower electrode 14 was epitaxially formed on the single crystal Zr _0.91 Si _0.09 O ₂ buffer film 13 by sputtering using an SrRuO ₃ target. In this epitaxial film formation, it is possible to use an ALD method, an MBE method or the like in addition to the sputtering method. The crystal structure of the SrRuO ₃ film 14 thus formed is a cubic perovskite structure, and the <004> direction is the film thickness direction.

Next, a BaTiO ₃ film as a ferroelectric film 15 was epitaxially deposited on the SrRuO ₃ lower electrode 14 by sputtering using a BaTiO ₃ target to a thickness of about 500 nm. In this epitaxial film formation, it is possible to use an ALD method, an MBE method or the like in addition to the sputtering method. The crystal structure of the BaTiO ₃ film thus formed is a tetragonal perovskite structure obtained by extending a cubic perovskite structure to martensite in the c-axis direction, and the <004> direction faces the film thickness direction.

Here, for example, a Ba _0.7 Sr _0.3 TiO ₃ film may be used instead of the BaTiO ₃ film. Although there is an advantage that epitaxial growth is facilitated by increasing the content of Sr instead of Ba, there is a problem that the dielectric characteristics deteriorate. The practically acceptable Sr mixing amount is up to 0.3. That is, Ba _1-s Sr _s TiO ₃ (0 ≦ s ≦ 0.3) can be used.

Further, in the Ba _1-x Sr _x TiO ₃ film, the [Ti] / ([Ba] + [Sr]) ratio is not necessarily 1 and can be 0.7 or more and 1.1 or less. When the above [Ti] / ([Ba] + [Sr]) ratio is greater than 1, it has a perovskite structure in which the Ti site is partially lost, but even if the Ba (or Sr) site is partially lost, ferroelectricity is obtained. The property does not deteriorate rapidly. Alternatively, there may be a structure in which the TiO ₂ anatase crystal is epitaxially penetrated into the grain boundary of the Ba _1-x Sr _x TiO ₃ crystal, but even in that case, the ferroelectric characteristics do not deteriorate rapidly. . When the above [Ti] / ([Ba] + [Sr]) ratio is smaller than 1, for example, a layered perovskite structure such as a K ₂ NiF ₄ structure is formed, but Ba _1-x Sr which is a part of the layered perovskite structure. _{Even if the x} O layer crystal structure portion increases, the ferroelectric characteristics do not deteriorate rapidly. The layered perovskite crystal such as the K ₂ NiF ₄ structure can also be regarded as a structure in which a Rudersden-Popper type defect penetrates a simple perovskite crystal such as SrTiO ₃ . In either view, the actual structure is exactly the same.

Therefore, it is desirable that the [Ti] / ([Ba] + [Sr]) ratio is 1, but it can be used even if it is deviated from 1, and it is not essential to deviate from 1. The range of the composition deviation is a value experimentally obtained as an allowable range of deterioration of the ferroelectric characteristics, and further composition deviation is theoretically possible. The situation of such a composition shift is the same for the SrRuO ₃ film having a perovskite structure.

Next, an SrRuO ₃ film as the upper electrode 16 was epitaxially deposited on the BaTiO ₃ ferroelectric film 15 by an sputtering method using an SrRuO ₃ target to a thickness of about 300 nm. In this epitaxial film formation, it is possible to use an ALD method, an MBE method or the like in addition to the sputtering method. The crystal structure of the SrRuO ₃ film thus formed is a cubic perovskite structure, and the <004> direction is the film thickness direction.

Next, a Pt electrode having a thickness of about 500 nm was formed on the SrRuO ₃ upper electrode 16 by sputtering. In film formation of the Pt electrode, various film formation techniques such as CVD, ALD, EB vapor deposition, and sol-gel can be used. Any electrode material may be used as long as it has a low chemical reactivity with SrRuO ₃ such as Au, TiN, and highly doped Si instead of Pt.

FIG. 8 shows the PV characteristics of a ferroelectric capacitor composed of SrRuO ₃ (upper electrode) 16 / BaTiO ₃ (ferroelectric) 15 / SrRuO ₃ (lower electrode) 13. Polarization depicts hysteresis with respect to voltage. Since the remanent polarization is kept sufficiently large at 0 V, it can be used as a nonvolatile memory, for example.

  In order to obtain the ferroelectric characteristics as shown in this embodiment, the ferroelectric must have good crystallinity. FIG. 9 shows the PV characteristics of the capacitor having the above structure in which the ferroelectricity is inferior in crystallinity. Although hysteresis exists, it is inferior in the square characteristic, has a small amount of remanent polarization at 0 V, and is not practical.

When a ferroelectric capacitor as shown in this embodiment is used as a non-volatile memory, it is easiest to make a cross-point type memory arrangement and the degree of integration can be increased, but it is compatible with individual manufacturing apparatuses. Depending on the details of the process technology, it is not always possible to manufacture a product having good characteristics as described in this embodiment. Therefore, in order to obtain robustness that can withstand practical use, it is preferable to produce a selection transistor and connect the SrRuO ₃ lower electrode 14 or the SrRuO ₃ upper electrode 16 of this embodiment to the source or drain of the selection transistor.

  FIG. 10 is a cross-sectional view showing a schematic configuration of a nonvolatile memory using the ferroelectric capacitor of the present embodiment. In addition, the same code | symbol is attached | subjected to FIG. 1 and an identical part, and the detailed description is abbreviate | omitted.

  A gate electrode 103 is formed on a Si substrate 101 (11) through a gate insulating film 102, and impurities are ion-implanted into the substrate surface using the gate electrode 103 as a mask to form source / drain regions 104 and 105. Thus, a selection transistor is configured. A ferroelectric capacitor as shown in FIG. 1 is formed on the drain region 105 of the selection transistor.

That is, by laminating the SiO ₂ buffer film 12, the Zr _0.91 Si _0.09 O ₂ buffer film 13, the SrRuO ₃ lower electrode 14, the BaTiO ₃ ferroelectric film 15, and the SrRuO ₃ upper electrode 16 in this order on the drain region 105. A ferroelectric capacitor is formed. A plug 106 for electrically connecting the lower electrode 14 and the drain region 105 is formed on the side surface of the ferroelectric capacitor.

Since the Zr _0.91 Si _0.09 O ₂ buffer film 13 described in this embodiment has no conductivity, a plug 106 for electrically connecting the SrRuO ₃ lower electrode 14 and the source or drain of the selection transistor is provided. There is a disadvantage that it becomes necessary and the process is slightly complicated. However, the crystallinity of the ferroelectric material is better than anything else, because it leads to improvements in square-shaped characteristics, charge retention characteristics, long-term reliability, and other characteristics of various ferroelectric memories. large.

The mechanism by which the Zr _0.91 Si _0.09 O ₂ film becomes a single crystal can be understood by considering the microscopic internal energy state inside the crystal. As a result of such consideration, for example, Zr _0.9 Nb _0.1 O _The authors' research has revealed that a _{2 + y} film or the like is likely to be a single crystal on the Si substrate by using the manufacturing method described in this embodiment. In this case, since the Zr _0.9 Nb _0.1 O _{2 + y} film is conductive, the plug 106 can be omitted.

As described above, according to the present embodiment, by forming the a-axis-oriented single crystal Zr _0.91 Si _0.09 O ₂ film 13 on the silicon substrate 11, it does not contain a component that easily reacts with the silicon substrate 11 and is 1000 ° C. The single crystal buffer film 13 having no structural change at all by the heat treatment up to and having extremely good crystallinity and a coherence length of 100 nm or more can be obtained. Since the SrRuO ₃ electrodes 14 and 16 and the BaTiO ₃ ferroelectric film 15 are epitaxially grown on the Zr _0.91 Si _0.09 O ₂ buffer film 13, the crystallinity of the ferroelectric film 15 and the electrodes 14 and 16 is increased. Therefore, it is possible to obtain a laminated film having excellent ferroelectric characteristics. That is, a high-quality perovskite single crystal can be formed on the silicon substrate 11, thereby improving the device characteristics of a ferroelectric capacitor or a ferroelectric memory using the single crystal of the perovskite structure.

(Second Embodiment)
FIG. 11 is a sectional view showing a schematic configuration of a semiconductor device according to the second embodiment of the present invention, particularly a ferroelectric memory. In this embodiment, a ferroelectric film is used for the gate insulating film.

A Zr _0.91 Si _0.09 O ₂ film (a-axis oriented single crystal buffer film) 23 having a thickness of 5 nm is formed on a part of the (001) single crystal silicon substrate 21 with a very thin SiO ₂ buffer film 22 _interposed therebetween. Is formed. A 200 nm thick Ba _0.8 Sr _0.2 TiO ₃ film (ferroelectric film) 25 is formed on the buffer film 23, and a 300 nm thick SrRuO ₃ film (gate electrode) 26 is formed thereon. Source / drain regions 27 and 28 are formed on both sides of the gate portion.

  Next, a method for manufacturing the semiconductor device of this embodiment will be described.

A film having a composition of Zr _0.91 Si _0.09 O _1.97 in an oxygen-deficient state is formed on the silicon substrate 21 treated with dilute hydrofluoric acid as in the first embodiment by a method similar to that in the first embodiment. did. Subsequently, the Zr _0.91 Si _0.09 O _1.97 film was subjected to spike annealing at 700 ° C. for 1 second or less in an atmosphere of [O 2] / ([Ar] + [O 2]) = 0.3% to compensate for oxygen vacancies. Thus, an a-axis oriented single crystal Zr _0.91 Si _0.09 O ₂ buffer film 23 was formed in the film thickness direction. As in the first embodiment, there may or may not be an interface layer 22 mainly composed of SiO ₂ between the Zr _0.91 Si _0.09 O ₂ buffer film 23 and the Si substrate 21.

Next, a Ba _0.8 Sr _0.2 TiO ₃ film (ferroelectric film) 25 was formed about 200 nm epitaxially on the single crystal Zr _0.91 Si _0.09 O ₂ buffer film 23 by the same method as in the first embodiment.

Next, an SrRuO ₃ film (gate electrode) 26 was formed on the Ba _0.8 Sr _0.2 TiO ₃ ferroelectric film 25 epitaxially by the same method as in the first embodiment to a thickness of about 300 nm. Since the electrical resistance of the SrRuO ₃ gate electrode 26 increases as the crystallinity deteriorates, it is desirable to be epitaxial.

Next, a mask (not shown) having a transistor gate pattern is formed on the stacked film, and dry etching is performed in an atmosphere containing Ar and CF ₄ to form a gate portion. The drain regions 27 and 28 were exposed.

  A general semiconductor process can be applied to the subsequent processes. For example, the source / drain regions 27 and 28 may be activated by doping impurities in the source / drain regions 27 and 28 on the pattern by an ion implantation method and performing spike annealing at 1050 ° C. for 1 second, for example. These processes do not deteriorate the ferroelectric properties so as to be a problem.

With such a configuration, it is possible to operate as a ferroelectric memory using a ferroelectric film as a gate insulating film. In this case, similarly to the first embodiment, a single crystal Zr _0.91 Si _0.09 O ₂ film 23 a-axis oriented is formed on the silicon substrate 21, so that a single crystal having a high-quality perovskite structure is formed on the silicon substrate 21. As a result, the device characteristics of a ferroelectric memory using a single crystal having a perovskite structure can be improved.

In this embodiment, unlike the first embodiment, the ferroelectric characteristics of the device are affected by the electric field applied to the laminated film of the Zr _0.91 Si _0.09 O ₂ buffer film 23 and the Ba _0.8 Sr _0.2 TiO ₃ ferroelectric film 25. _Therefore , it is desirable that the Zr _0.91 Si _0.09 O ₂ film 23 is thin. However, if the Zr _0.91 Si _0.09 O ₂ film 23 is too thin, there is a problem that the barrier function for reducing the leakage of the Ba _0.8 Sr _0.2 TiO ₃ ferroelectric film 25 is lowered. The limit of thinning that can maintain the barrier function of the Zr _0.91 Si _0.09 O ₂ film 25 is 0.6 nm as the equivalent oxide thickness (EOT) including the interface SiO ₂ layer 22.

(Third embodiment)
In the first embodiment, instead of the BaTiO ₃ film as a single crystal ferroelectric material (A. Beck, JG Bednorz, Ch. Gerber, C. Rossel, and D. Widmer, Applied Physics Letters 77, (2000 ), 139) can be used as a resistance change memory, that is, an RRAM, by using a SrZr _0.998 Cr _0.002 O ₃ film (resistance change film). As a method for forming the resistance change film, a sputtering method may be used as in the first embodiment.

When the SrZr _0.998 Cr _0.002 O ₃ film is used as a resistance change memory, desired characteristics may not be obtained if the electrodes sandwiching the insulating film are different, but this structure is common in that the SrRuO ₃ electrode is used. There is almost no doubt about reproducibility. When the resistance change film is described as SrZr _1-t Cr _t O ₃ by a general formula, if the Cr composition ratio t is in the range of 0.001 or more and 0.003 or less, the resistance is determined by the sign of the applied voltage. It was confirmed that this was a good single crystal having a resistance change characteristic that changed greatly.

When forming a resistance change memory, in addition to the SrRuO ₃ / SrZr _0.998 Cr _0.002 O ₃ / SrRuO ₃ film, for example, a Pt / Pr _0.7 Ca _0.3 MnO ₃ / Pt film, an Ag / Pr _0.7 Ca _0.3 MnO ₃ / YBa film, or the like. ₂ Cu ₃ O ₇ film, Ag / LaCoO ₃ / LaAlO ₃ film (resistance change is obtained between upper Ag electrodes), Ag / BiSr ₂ CaCu ₂ O ₈ / LaAlO ₃ film, Ag / La _0.75 Sr _0.25 MnO _{A 3} / LaAlO ₃ film, an Ag / La _0.80 Ca _0.20 MnO ₃ / LaAlO ₃ film, and the like are possible. In particular, the present inventors have confirmed by experiments that Pt has almost the same lattice constant as those of these crystals, and that it is actually epitaxially grown almost interchangeably with perovskite. Therefore, perovskite Zr _0.91 Si _0.09 O ₂ film on the above epitaxial growth, since Pt is also believed to epitaxially grow Zr _0.9 Si _0.1 O ₂ film, Pt / Pr _0.7 Ca _0.3 MnO in Zr _0.91 Si _0.09 O ₂ film _{The 3} / Pt film can be produced epitaxially.

Thus, according to the present embodiment, a resistance change memory can be manufactured by using a resistance change film whose resistance changes depending on the polarity of voltage application, such as a SrZr _0.998 Cr _0.002 O ₃ film. In this case, similarly to the first embodiment, a single crystal Zr _0.91 Si _0.09 O ₂ film 23 a-axis oriented is formed on the silicon substrate 21, so that a single crystal having a high-quality perovskite structure is formed on the silicon substrate 21. As a result, the device characteristics of the resistance change memory using a single crystal having a perovskite structure can be improved.

  Note that the RRAM described in this embodiment can also be formed and used so as to be in electrical contact with the source or drain of the selection transistor in the same manner as that described in the first embodiment.

(Fourth embodiment)
FIG. 12 is a sectional view showing a schematic configuration of a semiconductor device according to the fourth embodiment of the present invention. This example can be used privately as a magnetic memory (MRAM) using the TMR (Tunnel Magneto-Resistance) effect or GMR (Giant Magneto Resistance) effect, and further as a magnetic head.

A Zr _0.91 Si _0.09 O ₂ buffer film 43 is formed on the single crystal silicon substrate 41 via an SiO ₂ buffer film (interface layer) 42, and a La _0.7 Sr _0.3 MnO ₃ film (first magnetic film) is formed thereon. 44, a Zr _0.9 Si _0.1 O _1.93 film (tunnel insulating film) 45 having a thickness of 3.5 nm is formed thereon, and a La _0.7 Sr _0.3 MnO ₃ film (second magnetic film) 46 is formed thereon. Is formed.

A part of the second magnetic film 46, the tunnel insulating film 45, and the first magnetic film 44 is etched in a mesa shape, and an insulating film 47 such as SiO ₂ is embedded in a side portion of the mesa. A Pt electrode 48 is formed on the second magnetic film 46 and the insulating film 47.

In this semiconductor device, a La _0.7 Sr _0.3 MnO ₃ magnetic film 44 is formed on a Zr _0.91 Si _0.09 O ₂ buffer film 43 as shown in the first embodiment by a sputtering method. A thick Zr _0.9 Si _0.1 O _1.93 tunnel insulating film 45 is formed again, is subjected to the same heat treatment as in the first embodiment, is single-crystallized, and a La _0.7 Sr _0.3 MnO ₃ magnetic film 46 is formed again. It can be operated as a resistance change film. Here, the heat treatment can be performed after depositing all the laminated structures.

In the case described with La _1-u Sr _u MnO ₃ the magnetic film 44, 46 in the general formula, so long as the composition ratio u of 0.3 or less 0.2 or more Sr, good with magnetic properties Single crystal was confirmed. Further, as the tunnel insulating film 45, SrTiO ₃ can be used instead of Zr _x Si _1-x O ₂ .

Such a laminated film can be used, for example, as a part for detecting a change in magnetic memory in an MRAM, or as a component for detecting magnetic memory on a disk such as a hard disk head. In this case, an a-axis oriented single crystal Zr _0.9 Si _0.1 O ₂ film 43 is formed on the silicon substrate 41 to form a high-quality perovskite single crystal as the magnetic films 44 and 46 on the silicon substrate 41. Thus, the characteristics of the device using a single crystal having a perovskite structure can be improved.

(Modification)
In addition, this invention is not limited to each embodiment mentioned above. In the embodiment, the Zr _0.91 Si _0.09 O ₂ buffer film is formed on the single crystal silicon substrate via the SiO ₂ film, but the SiO ₂ film may be omitted. Further, the Si composition x in the Zr _1-x Si _x O ₂ buffer film is not limited to 0.09, and may be in the range of 0.08 ≦ x ≦ 0.10.

The ferroelectric film in the first and second embodiments is not limited to Ba _1-s Sr _s TiO ₃ (0 ≦ s ≦ 0.3), and may be a ferroelectric single crystal having a perovskite structure. Further, the resistance change film in the third embodiment is not limited to SrZr _1-t Cr _t O ₃ (0.001 ≦ t ≦ 0.003), and the various films described above can be used, and a simple perovskite structure. Any crystal may be used. Further, the magnetic film in the fourth embodiment is not limited to _{La 1-u Sr u MnO 3} (0.2 ≦ u ≦ 0.3), may be a magnetic single crystal of a perovskite structure.

  In addition, various modifications can be made without departing from the scope of the present invention.

1 is a cross-sectional view showing a schematic configuration of a ferroelectric capacitor according to a first embodiment. FIG. 3 is a cross-sectional TEM photograph (micrograph) showing the crystal state of the buffer film in the first embodiment. The figure which shows the X-ray-diffraction result by the thin film method of the ferroelectric capacitor in 1st Embodiment. The figure which shows the X-ray photoelectron spectroscopy result derived from the 3d orbit of a zirconium atom. Shows the change in composition of the dielectric constant at Zr _1-x Si _x O ₂ samples as there are no oxygen vacancy by annealing. The figure which shows that only the diffraction peak of an a-axis direction comes out in the film thickness direction in the range whose composition ratio x of Si is 0.08 to 0.10. The figure which shows the example when the crystal direction with a small dielectric constant orientates in the film thickness direction, and when the crystal direction with a large dielectric constant orients. The figure which shows the polarization with respect to the electric field of the ferroelectric substance in 1st Embodiment. The figure which shows the polarization with respect to the electric field of the ferroelectric substance inferior to crystallinity than 1st Embodiment. 1 is a cross-sectional view showing a schematic configuration of a ferroelectric memory according to a first embodiment. Sectional drawing which shows schematic structure of the ferroelectric memory concerning 2nd Embodiment. Sectional drawing which shows schematic structure of the semiconductor device concerning 4th Embodiment.

Explanation of symbols

11, 21, 41, 101 ... single crystal silicon substrate 12, 22, 42 ... SiO ₂ buffer film (interface layer)
13, 23, 43 ... ZrSiO ₂ buffer film 14 ... SrRuO ₃ film (lower electrode)
15, 25 ... BaTiO ₃ film (ferroelectric film)
16 ... SrRuO ₃ film (upper electrode)
26 ... SrRuO ₃ film (gate electrode)
27, 104 ... Source region 28, 105 ... Drain region 44 ... LaSrMnO ₃ film (first magnetic film)
45 ... ZrSiO ₂ film (tunnel insulating film)
46 ... LaSrMnO ₃ film (second magnetic film)
47 ... Embedded insulating film 48 ... Pt electrode 102 ... Gate insulating film 103 ... Gate electrode 106 ... Plug

Claims (10)

An a-axis oriented single crystal buffer film of Zr _1-x Si _x O ₂ formed on a single crystal silicon substrate;
A lower electrode formed on the buffer film and formed of a single crystal having a Pt or perovskite structure;
A ferroelectric film formed on the lower electrode and formed of a single crystal having a perovskite structure;
An upper electrode formed on the ferroelectric film and formed of a single crystal having a Pt or perovskite structure;
A semiconductor device comprising: An a-axis oriented single crystal buffer film of Zr _1-x Si _x O ₂ formed on a single crystal silicon substrate;
A ferroelectric film formed on the buffer film and formed of a single crystal having a perovskite structure;
An electrode formed on the ferroelectric film and formed of a single crystal having a Pt or perovskite structure;
As a gate stack structure of a transistor. An a-axis oriented single crystal buffer film of Zr _1-x Si _x O ₂ formed on a single crystal silicon substrate;
A lower electrode formed on the buffer film and formed of a single crystal having a Pt or perovskite structure;
A resistance change film formed on the lower electrode and formed of a single crystal having a perovskite structure;
An upper electrode formed on the variable resistance film and formed of a single crystal having a Pt or perovskite structure;
A semiconductor device comprising: An a-axis oriented single crystal buffer film of Zr _1-x Si _x O ₂ formed on a single crystal silicon substrate;
A first magnetic film formed on the buffer film and formed of a single crystal having a perovskite structure;
A tunnel insulating film formed on the first magnetic film and formed of a single crystal having a perovskite structure;
A second magnetic film formed on the tunnel insulating film and formed of a single crystal having a perovskite structure;
An electrode formed on the second magnetic film and formed of a single crystal having a Pt or perovskite structure;
A semiconductor device comprising:   5. The semiconductor device according to claim 1, wherein an Si composition ratio x of the buffer film is in a range of 0.08 ≦ x ≦ 0.10. The semiconductor device according to claim 1, wherein the electrode is SrRuO ₃ , and the ferroelectric film is Ba _1-s Sr _s TiO ₃ (0 ≦ s ≦ 0.3). 4. The semiconductor device according to claim ₃ , wherein the electrode is SrRuO ₃ , and the variable resistance film is SrZr _1-t Cr _t O ₃ (0.001 ≦ t ≦ 0.003). The electrode is Pt, the magnetic layer is _{La 1-u Sr u MnO 3} (0.2 ≦ u ≦ 0.3), the tunnel insulating film in SrTiO ₃ or Zr _x Si _1-x O ₂ The semiconductor device according to claim 4, wherein the semiconductor device is provided. Forming a non-single crystalline film of Zr _x Si _1-x O _2-y in an oxygen deficient state on a single crystal silicon substrate;
Annealing the Zr _x Si _1-x O _2-y film in an atmosphere containing oxygen to form an a-axis oriented single crystal buffer film of Zr _x Si _1-x O ₂ ;
A method for manufacturing a semiconductor device, comprising: The Zr _x Si _1-x O _2-y film is formed by sputtering, and the Si composition x in the Zr _x Si _1-x O _2-y film is in the range of 0.08 ≦ x ≦ 0.10. 10. The method of manufacturing a semiconductor device according to claim 9, wherein the method is set.

Images