JPH05243525A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To furnish an oxide buffer film being used preferably when various oxide ceramic thin films of a high-permittivity and ferroelectric material, a superconductor material and a nonlinear optical material, a magnetooptical material, an electrooptical material and an acoustooptical material being abundant in optical characteristics, and the like are formed on a silicon substrate, and an insulating film being used preferably for a capacitor of DRAM. CONSTITUTION:A bismuth silicate layer 3 is formed by supplying a gas containing a bismuth component onto the surface of a silicon substrate or silicon layers 1 and 2 of a silicon oxide or the like at an ambient temperature of 760 to 800 deg.C. On the bismuth silicate layer 3 having a semiconductive property, a ferroelectric layer, an oxide optical material layer and an oxide superconductor layer are formed. The bismuth silicate layer of high permittivity is used as a capacitor of DRAM. A crystal structure of silicon of the ground layer and a perovskite structure of a ferroelectric and others formed on the surface are matched in a lattice with the crystal structure of bismuth silicate and thus the bismuth silicate layer and the ferroelectric layer are to grow epitaxially.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a method for manufacturing the same, and more particularly to a high dielectric constant / ferroelectric material, a superconductor material, a nonlinear optical material / magneto-optical material having a high optical property on a silicon substrate. Materials, electro-optic materials, acousto-optic materials, and various oxide ceramic thin films that are preferable for forming oxide ceramic thin films, and DRAM (dynamic
The present invention relates to an insulating film preferably used for a capacitor of random access memory).

[0002]

2. Description of the Related Art PZT (Pb _1-x Zr _x TiO ₃ ) P
LZT [(Pb _{1-x / 100} La _{x / 100} ) (Zr _{y / 100} Ti
_{z / 100} ) _{1-x / 400} O ₃ ], PT (PbTiO ₃ ), SrTiO _{3 and} other high dielectric constant / ferroelectric materials are mainly applied to semiconductor memories. Non-volatile memory that uses GaN and DRA that uses high dielectric constant
In recent years, the M capacitor insulating film has attracted attention.

The reason why a ferroelectric thin film is applied to a non-volatile memory can be determined by forming one memory cell with an FET transistor switch of the same type as an ultra-highly integrated DRAM and a ferroelectric thin film capacitor. This is because the value, voltage value, operating speed, reliability, etc. are extremely improved. Ferroelectrics are materials that have spontaneous polarization and can be inverted by an external electric field. Many oxide ferroelectrics belong to the perovskite type, lithium niobate type, and tungsten bronze type.

The principle of a non-volatile memory using a ferroelectric thin film will be described by taking barium titanate as an example. That is, above the Curie temperature of about 120 ° C., which belongs to the cubic system and the centers of gravity of positive and negative electrification coincide with each other, but at room temperature, the ions are relatively displaced and the arrangement of valence electrons is changed to change the unit cell. A permanent electron dipole moment Σq _i l _i (C · m) is generated inside. When the same direction and magnitude of displacement occur throughout the crystal, the spontaneous polarization P _S is defined as the permanent electric dipole moment per unit volume, so that P _s = Σq, where V is the volume of the unit square lattice. The size is _i l _i N (C / m ³ ). The direction of this spontaneous polarization can be aligned with the electric field direction by an externally applied electric field.

In the as-produced single crystal, or in microcrystals in ceramics or thin films, the directions of spontaneous polarization are not aligned and are divided into domains like domains in magnetic materials. However, when an electric field is applied to the virgin sample in such a state, the polarization P and the electric field E draw a hysteresis curve as shown in FIG. After applying a high voltage once, it is in the state of A or C when the electric field is 0, and the remanent polarization −P _r or + P _r is retained, respectively.
If these states are defined as “0” or “1” respectively, writing of “0” information or “1” information can be selected depending on the direction of application of the electric field. Note that P _r is 10 μC
A value of about / cm ² is obtained. The read pulse voltage direction (+ direction) and the written direction are the same, that is, C → B in the C state (P _MAX −P _r ) ×
When the area charge flows in the opposite direction, that is, in the A state, A →
An electric charge of (P _MAX + P _r ) × area corresponding to B flows.
This difference, that is, 2P _r × area is the polarization inversion charge,
Information can be read by discriminating and measuring this charge amount.

A structure shown in FIG. 14 has been proposed as a nonvolatile memory (FRAM) using such a ferroelectric thin film, and the lower electrode 3 of the capacitor 30 (ferroelectric) is proposed.
1 becomes a drive line (DL), and the upper electrode 32
Is connected to a transistor, which is different from the structure of a normal DRAM. This is because a good PZT thin film element 30 cannot be formed on silicon or polysilicon, and thus it is necessary to form the PZT thin film 30 on the platinum thin film 31. Such a ferroelectric nonvolatile memory (F
RAM) is the high speed of SRAM and DRAM and EEPRO
Since it has the nonvolatility of M and the cell size is the same as that of DRAM in principle, it can be an ideal memory.

[0007]

However, regarding the number of rewritings (the number of polarization switchings), the cycle time is 100 ns and the guarantee period is 10 as in the DRAM.
In terms of a year, the conventional ferroelectric non-volatile memory has a rewrite life of 10 ¹⁰ although it needs to be rewritten at least 10 ¹⁵ times. This is because there is an oxygen-deficient region (low oxygen concentration region, see FIG. 15) in the ferroelectric thin film near the interface with the platinum electrode, and this region becomes n-type and space charge is generated. It is considered that the cause is that an abnormal electric field is generated in the ferroelectric thin film by the electric charge and the polarization is fixed (for example, Nikkei Microdevice, June 1991, p. 83). As a result, when the polarization direction is repeatedly inverted, there is a problem that the ferroelectric thin film becomes fatigued, the size of the residual polarization becomes small, and the leak current increases. Therefore, in order to effectively utilize the advantages of the ferroelectric substance, it is necessary to remove the oxygen-deficient region from the ferroelectric thin film during the film formation to improve the rewriting life.

On the other hand, a high quality silicon oxide SiO ₂ thin film (dielectric constant ε _r ˜3.8) obtained by thermal oxidation of Si has been used for the cell capacitor of the conventional DRAM. 1M DRAM due to reduction of area
The film thickness of SiO ₂ required for the required capacitance is about 1
It became less than 00 angstroms and approached the limit of thinness. Therefore, the nitride Si ₃ N ₄ (dielectric constant ε _r ~
In addition to adopting 7), the above problem has been solved by increasing the area as a capacitor, although the used area of the flat surface of the silicon substrate is small by structural improvement of the trench type capacitor or the stack type capacitor.

However, even if such a nitride Si ₃ N ₄ having a high dielectric constant is adopted, it is necessary to improve a complicated manufacturing process such as a trench type capacitor or a stack type capacitor. Further, although the development of a high dielectric constant thin film is desired due to the demand for further improvement in the degree of integration, even if a high dielectric constant material is directly deposited on a silicon oxide layer, the silicon oxide and the high dielectric constant material are electrically conductive. Since it is a serial junction, the dielectric constant of the entire circuit is dominated by silicon oxide having a low dielectric constant. Therefore, there is a demand for the development of a new technology that simplifies the manufacturing process while increasing the capacitance.

Therefore, in order to obtain a semiconductor device in which the advantages of ferroelectrics and the like are fully exhibited, the inventors of the present invention need to epitaxially grow a film of ferroelectrics or the like satisfactorily. In order to achieve epitaxial growth, the substrate on which the thin film such as a ferroelectric material is formed is a good-quality single crystal, and the unit cell size of the substrate and the thin film such as a ferroelectric material is at least two-dimensional. Based on the knowledge that it is necessary to do, we conducted diligent research. As a result, the unit cell constant of silicon (0.542n
unit cell constant of bismuth silicate (1.04
nm) is almost an integral multiple, and this bismuth silicate exhibits good crystallinity under predetermined conditions. Furthermore, a perovskite structure, which is a basic structure of a ferroelectric substance formed on the bismuth silicate layer, etc. Lattice constant (about 0.4 nm)
On the other hand, it was found that the lattice constant of bismuth silicate was lattice-matched, and the present invention was completed.

The present invention has been made in view of the above problems of the prior art, and has a high dielectric constant / ferroelectric material, a superconductor material, and a non-linear optical material rich in optical characteristics on a silicon substrate. An object is to provide an oxide buffer film that is preferable for forming various oxide ceramic thin films such as magneto-optical materials, electro-optical materials, and acousto-optical materials, and an insulating film that is preferable for capacitors of DRAMs. To do.

[0012]

In order to achieve the above object, the semiconductor device of the present invention is characterized in that a bismuth silicate layer is formed on the surface of a silicon substrate or a silicon-based layer such as silicon oxide. This bismuth silicate layer can be configured as a capacitor of a dynamic random access memory.

Further, the bismuth silicate layer can be made semiconductive. It is preferable to form a ferroelectric layer, an oxide optical material layer, or a superconductor layer on this semiconductive bismuth silicate layer.

In order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention is characterized in that a bismuth component is formed on the surface of a silicon substrate or a silicon-based layer such as silicon oxide under an ambient temperature of 760 ° C to 800 ° C. The gas containing gas is supplied to form a bismuth silicate layer.

[0015]

[Function] Various oxide ceramics such as high dielectric constant / ferroelectric material, superconductor material, nonlinear optical material, magneto-optical material, electro-optical material, acousto-optical material rich in optical characteristics on a silicon substrate of a semiconductor device In order to form a thin film and bring out the advantages peculiar to these oxide ceramic thin films, good epitaxial growth of the oxide ceramic thin film is essential. In order to achieve this good epitaxial growth, the substrate on which the oxide ceramic thin film is formed is a good single crystal, and the size of the unit cell of the substrate and the oxide ceramic thin film are at least two-dimensionally matched. It is necessary to have

In the present invention, the ambient temperature is 760 on the surface of the silicon substrate or the silicon-based layer such as silicon oxide.
A gas containing a bismuth component is supplied at a temperature of from 800 to 800 ° C. to form a bismuth silicate layer. The bismuth silicate layer obtained by this manufacturing method has the same cubic crystal structure as silicon, and moreover, the unit lattice constant of bismuth silicate (0.542 nm) with respect to the unit lattice constant of silicon (0.542 nm). 1.04 nm) is almost an integral multiple, so that it is possible to regularly arrange the bismuth silicate crystals on the silicon crystals (see FIG. 16A). From 760 ℃ to 8
If the temperature is 00 ° C., good crystallinity is exhibited (see FIGS. 3 to 5). Therefore, a requirement for favorable epitaxial growth of the oxide ceramic thin film formed on the surface of the bismuth silicate layer, that is, the substrate on which the oxide ceramic thin film is formed is a good single crystal, and It can be satisfied that the size of the unit cell of the ceramic thin film is at least two-dimensionally matched.

Further, the lattice constant of bismuth silicate is lattice-matched with the lattice constant (0.37 to 0.4 nm) of the perovskite structure which is a basic structure of a ferroelectric substance or the like formed on the bismuth silicate layer. That is, since the crystals of the ferroelectric substance can be regularly arranged on the crystal of the bismuth silicate, the crystals of the ferroelectric substance can be epitaxially grown well (FIG. 16 (B)).
reference). Further, this bismuth silicate layer is an insulator in a normal state, but since it has a property that it can be made into a semiconductor by doping impurities, it does not need to be a film requiring insulation or semiconductivity. It can also be used as a film.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a semiconductor device according to an embodiment of the present invention, in which a silicon oxide layer 2 is formed on the surface of a silicon wafer 1 which constitutes a silicon substrate. The silicon wafer 1 of this embodiment may be either a p-type silicon single crystal or an n-type silicon single crystal, and the method of growing the silicon single crystal to produce it may be either the CZ method or the FZ method. The silicon oxide layer 2 formed on the single crystal silicon substrate 1 may be formed by oxidizing silicon of the single crystal silicon substrate by thermal oxidation, anodic oxidation, or the like, or by vapor phase growth (CVD) or sputtering. For example, the oxide film may be deposited on the surface of the silicon substrate without oxidizing the silicon of the silicon substrate. In short, since the bismuth silicate layer 3 according to the present invention is formed by reacting silicon contained in the underlayer forming the formation surface with the bismuth component, the underlayer contains the metallic silicon component. I wish I had it. This requirement can be applied to the semiconductor devices of the respective embodiments (FIGS. 7 to 12) described later.

Next, a bismuth silicate layer 3 is formed on the silicon oxide layer 2 formed on the silicon substrate 1. The bismuth silicate layer 3 is represented by the chemical formula Bi ₁₂ SiO ₂₀ or Bi ₄ Si ₃ O ₁₂ , and has a lattice constant of 1.04n.
It is composed of bismuth silicate having a cubic crystal structure of m. As described above, bismuth silicate is an insulator that has a simple chemical composition, has the same cubic crystal structure as silicon, and has a relatively low generation temperature, and can be made into a semiconductor by doping impurities. It has the property. Further, it is not toxic and film formation is easy, and it is advantageous in terms of raw material cost.

In order to form such a bismuth silicate layer 3 on the silicon oxide layer 2, bismuth oxide or metal bismuth is formed by a chemical vapor deposition method, a molecular beam epitaxy method, a sol-gel method, a sputtering method or a vapor deposition method. The bismuth oxide or the metal bismuth thus deposited is reacted with the metal silicon contained in the underlayer (silicon oxide layer 2) by depositing it on the layer 2 and subjecting it to a separate heat treatment or a heat treatment simultaneously with the deposition. .. As a result, the bismuth silicate layer 3 is formed on the silicon substrate 1.
Is formed. At this time, all of the silicon oxide layer 2 as the underlayer disappears, but this can be verified by surface analysis such as XPS (X-ray photoelectron spectroscopy) or Auger electron spectroscopy.

A specific example of the method for producing the bismuth silicate layer 3 is as follows. For example, the film thickness is about 500n
When a bismuth silicate layer is formed on a silicon substrate on which a silicon oxide layer of m is formed by a chemical vapor deposition method (MOCVD method), triphenylbismuth containing a bismuth component (Bi (C ₆ H ₅ ) ₃ ) Using a gas as a raw material, a carrier gas made of nitrogen and oxygen for oxidizing the raw material gas are simultaneously supplied onto a silicon substrate at a flow rate of 70 cc / min. The pressure around the silicon substrate during film formation is about 10
The temperature of the evaporation chamber is 80 ° C., and the temperature of the silicon substrate is 760 ° C. to 800 ° C. At this time, the silicon component forming the bismuth silicate is supplied from the silicon oxide layer formed on the silicon substrate.

Whether or not the product produced by such a production method is bismuth silicate is verified by comparing with an X-ray diffraction diagram of a separately synthesized bismuth silicate powder (Bi ₄ Si ₃ O ₁₂ ). FIG. 2 is an X-ray diffraction pattern of the separately synthesized bismuth silicate powder (Bi ₄ Si ₃ O ₁₂ ), and FIGS. 3 to 6 are X-ray diffraction patterns of the thin film obtained by the above-described manufacturing method. 3 to 6, the substrate temperature is 760 ° C. to 8 ° C., respectively.
The X-ray-diffraction figure of the produced | generated film at the time of changing to 20 degreeC is shown. This X-ray diffraction measurement was performed using a powder X-ray diffractometer manufactured by Mac Science Co., Ltd. (the target of the X-ray tube is copper, the voltage applied to the tube at the time of measurement is 40 kV, and the current is 20 mA). The horizontal axis represents the Bragg angle, and the vertical axis represents the strength.

Comparing FIG. 2 and FIG. 6 among the diffraction results, the X-ray diffraction pattern of the film formed on the silicon substrate and the X-ray diffraction pattern of the bismuth silicate powder are completely in agreement. It is understood that the film is bismuth silicate (Bi ₄ Si ₃ O ₁₂ ), and it is also understood that the film prepared at 820 ° C. is polycrystalline. Further, as is clear from the X-ray diffraction diagrams of FIGS. 3 to 5, in the bismuth silicate layer produced under the substrate temperature condition of 760 ° C. to 800 ° C., the intensity of the diffraction line in the specific orientation is extremely strong. From this, it is understood that the generated bismuth silicate layer is epitaxially grown on the silicon substrate with the crystal orientations aligned. Further, among 760 ° C. to 800 ° C., the sharpest diffraction line in a specific direction appears at 780 ° C. shown in FIG.
It is also in the vicinity, and it can be seen that the crystallinity of bismuth silicate becomes the best when the bismuth silicate layer is grown under the substrate temperature condition. The above-described method for producing the bismuth silicate layer is a specific example, and the method for producing the bismuth silicate layer of the present invention is not limited to this specific example.

As described above, the bismuth silicate layer according to the present invention has various characteristics preferable for application to various semiconductor devices described below. For example, since it has the same cubic crystal structure as silicon, and the unit lattice constant of bismuth silicate (1.04 nm) is almost an integral multiple of the unit lattice constant of silicon (0.542 nm). As shown in FIG. 16A, bismuth silicate crystals can be regularly arranged on the silicon crystals. Further, this bismuth silicate exhibits good crystallinity under predetermined conditions, that is, when the substrate temperature is 780 ° C to 800 ° C. Therefore, the requirements for epitaxial growth (that is, the substrate on which the thin film such as a ferroelectric is formed is a good-quality single crystal, and the unit cell size of the substrate and the thin film such as a ferroelectric is at least two-dimensionally Can be satisfied).

Further, with respect to the lattice constant (0.37 to 0.4 nm) of the perovskite structure, which is a basic structure of a ferroelectric substance or the like formed on the bismuth silicate layer, the lattice constant of bismuth silicate (1.04 nm) ) Is 0.4 × 2√2 = 1.13≈1.04 as shown in FIG. 16 (B), and crystals of ferroelectric substance or the like should be regularly arranged on top of bismuth silicate crystals. As a result, crystals such as ferroelectrics can be epitaxially grown well.
Further, although it is an insulator in a normal state, it has a property that it can be made into a semiconductor by doping an impurity (for example, phosphorus), so that it can be used also as a layer that requires insulation, and has semiconductivity. It can also be used as a required layer. Furthermore, since the chemical composition is simple and the generation temperature is relatively low, there is no toxicity and film formation is easy,
The handling of materials in the manufacturing process is simple, no special management is required, and the raw material cost is also advantageous.

FIG. 7 is a sectional view showing a ferroelectric memory using the above-described bismuth silicate layer of the present invention. P-type silicon is used for the silicon substrate 1, and n and n are used for the source and drain by ion implantation. Formed diffusion layers 4 and 5 are formed. The bismuth silicate layer 3 according to the present invention is formed on the upper surface of the channel 6 located between the diffusion layers, and the ferroelectric layer 7 is formed on the upper surface of the bismuth silicate layer 3. Since the ferroelectric layer 7 constitutes an insulating layer in the conventional MOS structure, the bismuth silicate layer 3 of this embodiment is made a semiconductor by doping phosphorus or the like. The gate electrode 8 formed on the upper surface of the ferroelectric layer 7 is made of aluminum or polysilicon,
The source electrode 9 and the drain electrode 10 are also made of aluminum or polysilicon. Reference numeral "11" in the figure is a field silicon oxide layer SiO ₂ . Ferroelectric materials forming the ferroelectric layer 7 of this embodiment include PZT, PLZT, PT (PbTiO ₃ ), Bi.
The ₄ Ti ₃ O ₁₂ and the like can be exemplified.

To manufacture such a ferroelectric memory, first, the field silicon oxide film 11 is formed on the surface of the silicon substrate 1 by the local oxidation method (LOCOS). This field to form a silicon oxide film SiO ₂ is an underlying oxide film SiO ₂ and Naitonaido film Si ₃ N ₄ was deposited on the silicon substrate 1 by photoetching, after part nitride film forming the transistor Si _While leaving ₃ N ₄ , B is ion-implanted using the photoresist film as a mask. This B functions as a channel stopper that electrically separates adjacent elements. Then, when wet oxidation is performed using water vapor, the silicon substrate in the portion where the nitride film is not present is oxidized to form the field silicon oxide film 11.

Next, the underlying silicon oxide film and the nitride film used for the local oxidation method (LOCOS) are removed, and a gate silicon oxide film is newly formed by dry or hydrochloric acid oxidation. The bismuth silicate layer 3 according to the present invention
Since it can be directly deposited on the silicon substrate 1, this gate silicon oxide film may be omitted. On the gate silicon oxide film thus formed (or directly on the silicon substrate), the bismuth silicate layer 3 is formed by the method described above or the like. Further, after forming a desired ferroelectric film 7 on the bismuth silicate layer 3 having good crystallinity, polysilicon is deposited by thermal decomposition of SiH ₄ gas or the like, and phosphorus or the like is added to impart conductivity. Is added.
Then, the polysilicon gate electrode 8 is processed by photoetching and dry etching using CF ₄ gas or the like. Then, As ions are implanted using the polysilicon gate electrode 8 as a mask to form diffusion layers 4 and 5, and
Although not shown, an SiO ₂ film (phosphosilicate glass, PSG) containing P as an interlayer insulating film is formed by the CVD method. Finally, a hole for connecting an electrode is opened in the interlayer insulating film by dry etching, and aluminum Al containing Si is deposited by sputter deposition to form the source electrode 9 and the drain electrode 10. The aluminum electrodes 9 and 10
Can be processed by photoetching and dry etching using BCl ₃ system gas.

According to the ferroelectric memory having such a structure, the bismuth silicate layer 3 forming the underlayer is a good quality single crystal, and the two-dimensional match well with the lattice constant of the silicon substrate 1. Therefore, the ferroelectric substance is formed by epitaxial growth, and various characteristics of the ferroelectric substance layer 7 such as the determination threshold value, the voltage value, the operating speed, and the reliability can be fully exhibited. The method for manufacturing the ferroelectric memory described above is a specific example, and the semiconductor device of the present invention is not limited to this.

FIG. 8 is a sectional view showing a memory using a ferroelectric substance as in the above-mentioned embodiment. In this case, the ferroelectric substance is used as a capacitor, and the bismuth silicate layer according to the present invention is used for this capacitor. It is configured as a lower electrode. That is, p-type silicon is used for the silicon substrate 1, and n-type diffusion layers 4 and 5 are formed in the source and the drain by ion implantation. One diffusion layer 4 is a bit of the ferroelectric memory of this embodiment. Connected to the wire. The gate silicon oxide layer 12 is formed on the upper surface of the channel 6 located between these diffusion layers.
And a gate electrode 13 made of polysilicon or the like is formed on the upper surface of the gate silicon oxide layer 12. The gate electrode 13 is connected to the word line of the ferroelectric memory of this embodiment. On the upper surface of the other diffusion layer 5, the bismuth silicate layer 3 of the present invention formed directly on the silicon substrate or via the silicon oxide film is formed, and further on the bismuth silicate layer 3. A ferroelectric layer 7 is formed on the. Since the ferroelectric layer 7 constitutes a capacitor in the conventional DRAM structure, the bismuth silicate layer 3 of this embodiment is made semiconductor by doping phosphorus or the like. The upper electrode 14 of the capacitor formed on the upper surface of the ferroelectric layer 7 is made of an oxide conductor such as polysilicon. In addition, reference numeral "1" in the figure
“1” is a field silicon oxide layer SiO ₂ , and “15” is an interlayer insulating film.

Also in the ferroelectric memory having such a structure, the bismuth silicate layer 3 forming the lower electrode of the ferroelectric layer 7 (capacitor) is a good single crystal and has a lattice constant of the silicon substrate 1 and 2 Since the dimensions are well matched, the ferroelectric is epitaxially grown to form a film, and various characteristics such as a discrimination threshold value, a voltage value, an operating speed, and reliability of the ferroelectric layer 7 are regretted. Can be demonstrated without. Further, since the upper electrode 14 also uses an oxide conductor, the oxygen-deficient region generated near the interface between the ferroelectric layer 7 and the upper and lower electrodes 3, 14 can be removed, and as a result, this oxygen-deficient region is removed. It is possible to improve the life of the number of times of rewriting (the number of times of polarization switching) which is considered to be caused by the presence of.

The bismuth silicate layer according to the present invention is used as a base layer of an optical integrated circuit using various oxide optical materials such as nonlinear optical materials, magneto-optical materials, electro-optical materials, and acousto-optical materials having excellent optical characteristics. Can be used. An optical integrated circuit is made by forming a portion with a slightly higher refractive index on the surface of one substrate to form an optical waveguide, and based on this, a laser diode that is a light source and a switch / modulator that is a functional element. It is an optical circuit that has a certain function as a whole by integrating a diode which is a detection element. As such an optical integrated circuit, a waveguide is formed by using a substrate having a material having electro-optic, acousto-optic, magneto-optic, and non-linear optical effects as a substrate, and the guided light is guided by an external input signal while the light is confined in the waveguide. By controlling, various guided wave optical devices having new functions different from the conventional bulk type devices can be constructed.

FIG. 9 is a cross-sectional view showing an application example of the bismuth silicate layer according to the present invention in an optical integrated circuit using the above-mentioned oxide optical material, which is formed on the silicon substrate 1 by the method described above. The bismuth acid layer 3 is formed.
The bismuth silicate layer 3 is made into a semiconductor by adding phosphorus or the like, and an oxide optical material layer 16 made of an oxide optical material having desired optical characteristics is formed thereon to form an optical waveguide. is doing. In the figure, reference numeral "17" is an electrode for taking in an external input signal, and "18" is a semiconductor laser layer which is a light source. Although not shown, a photodetection element is arranged on the right side in the figure.

As the oxide optical material used in this embodiment, Ti-diffused LiNbO ₃ , LiTaO ₃ , As ₂ S are used.
_Three films, a YIG film / GGG, a paramagnetic glass, a ZnO film and the like can be exemplified, and it is preferable to use them properly depending on the interaction with light by an external input signal. For example, when the external input signal is electric, the refractive index is changed by the electro-optic effect (Pockels effect), and the amplitude / phase modulation /
In order to control the functions of optical path switching, deflection, diffraction, mode conversion, etc., Ti-diffused LiNbO ₃ , L as a waveguide material
It is preferable to use iTaO ₃ , PZT, PLZT, and PT. When the external input signal is a sound wave, the waveguide is used to control the functions such as deflection, diffraction, mode conversion, and single sideband generation by changing the refractive index by the acousto-optic effect (photoelastic effect). Ti diffusion LiNbO ₃ , A as material
It is preferable to use an s ₂ S ₃ film. When the external input signal is a magnetic field, the plane of polarization is rotated by the magneto-optical effect (Faraday effect), and the functions such as non-reciprocity and mode conversion are controlled. Therefore, YIG film / GGG as a waveguide material,
It is preferable to use paramagnetic glass. Further, when the external input signal is light, Ti diffusion L is used as a waveguide material in order to induce polarization induction by a non-linear optical effect and control functions such as second harmonic generation and parametric amplification.
It is preferable to use iNbO ₃ , ZnO film, PZT, PLZT, and PT.

According to the optical integrated circuit configured as described above,
Since the oxide optical material can be epitaxially grown well, the excellent optical characteristics of the oxide optical material can be fully exhibited, and the optical modulator, the optical switch (using the electro-optical effect), the optical Isolator (an element that uses magneto-optical effect to pass light in only one direction and is used to prevent back light), Wavelength converter (conversion of semiconductor laser light to blue laser light by wavelength conversion using nonlinear optical effect) ), An optical modulator (the direction in which light travels is controlled by an electric signal using an acousto-optic effect), an optical sensor, a magneto-optical sensor, a piezoelectric element, and the like, which are preferable.

FIG. 10 is a sectional view showing an application example of the bismuth silicate layer according to the present invention in a Josephson junction device using an oxide superconductor. The Josephson junction element is a circuit element utilizing the Josephson effect in which an electron pair passes through the insulating film by a tunnel effect when two superconductors are separated by a thin insulating film. It can be applied to high-speed electronic computers.
In this specific example, the bismuth silicate layer 3 is formed on the silicon substrate 1 by the above-described method, etc., and after being made into a semiconductor by adding phosphorus or the like, a layer 19 made of an oxide superconductor is formed thereon. Is forming. In addition, reference numeral "2" in the figure
"0" is the channel of the Josephson junction device. The oxide superconductor used in this example is YBa ₂ Cu.
₃ O ₇ , Bi ₂ Sr ₂ Ca ₂ Cu ₃ O ₁₀ , Tl ₂ Ba ₂
Such as Ca ₂ Cu ₃ O ₁₀ and the like.

It is known that the superconducting transition temperature and the critical current density of the oxide superconductor described above are closely related to the crystallinity of the superconductor, and the superconducting property is not exhibited unless the crystallinity is increased. ing. However, according to this example, the bismuth silicate layer 3 forming the underlayer of the superconductor is a high-quality single crystal as described above, and the lattice constant of the silicon substrate 1 and the two-dimensional satisfactorily improved. Because they match, superconductor 1
9 is epitaxially grown to form a film, and exhibits excellent superconducting properties.

The above oxide superconductor can be used as a wiring material for a semiconductor device, for example, in addition to the Josephson element. FIG. 11 is a sectional view showing an application example of a bismuth silicate layer when an oxide superconductor is used as a semiconductor device electrode or wiring material. In this embodiment, a MOS type semiconductor is illustrated as a semiconductor device, p-type silicon is used for the silicon substrate 1, and n-type diffusion layers 4 and 5 are formed in the source and the drain by ion implantation. On the upper surface of the channel 6 located between these diffusion layers,
The bismuth silicate layer 3 according to the present invention is formed, and the gate electrode 21 made of an oxide superconductor is formed on the upper surface of the bismuth silicate layer 3. In this case, since the bismuth silicate layer 3 constitutes the gate insulating layer in the conventional MOS structure, the bismuth silicate layer 3 above the channel is formed as an insulator without being made into a semiconductor. On the other hand, the bismuth silicate layer 3 is also formed on the upper surfaces of the diffusion layers 4 and 5 serving as the source and the drain, and the source electrode 22 and the drain electrode 23 made of an oxide superconductor are formed on the bismuth silicate layer. Has been formed. The bismuth silicate layer 3 formed on this diffusion layer is made into a semiconductor by adding phosphorus or the like. Reference numeral "11" in the figure is a field silicon oxide layer SiO ₂ .

In the semiconductor device configured as described above, the electrodes made of a superconductor and the underlying layers of the wirings 21, 22 and 23 are
As described above, since the bismuth silicate layer 3 is a good-quality single crystal and two-dimensionally matches well with the lattice constant of the silicon substrate 1, the superconductors 21, 22 and 23 grow epitaxially. The film is formed as a film and exhibits excellent superconducting properties. Therefore, the electric resistance is extremely smaller than that of conventional electrodes and wiring materials such as aluminum and polysilicon, and the power consumption of the semiconductor device can be reduced.

Further, the bismuth silicate layer according to the present invention is
It can be used as a capacitor of DRAM by utilizing its high dielectric constant. FIG. 12 is a cross-sectional view showing a specific example in which the bismuth silicate layer according to the present invention is applied to a capacitor dielectric film of DRAM. P-type silicon is used for the silicon substrate 1, and n-type diffusion layers 4 and 5 are formed in the source and the drain by ion implantation, and one diffusion layer 4 is connected to the bit line of the integrated circuit. A silicon oxide layer 24 forming a gate insulating layer is formed on the upper surface of the channel 6 located between these diffusion layers, and a gate electrode made of an oxide conductor such as polysilicon is formed on the upper surface of the gate silicon oxide layer 24. 25 are formed. The gate electrode 25 is connected to the word line of the integrated circuit.

On the upper surface of the other diffusion layer 5, there is formed a bismuth silicate layer 3 of the present invention formed directly on a silicon substrate or through a silicon oxide film, and further, this bismuth silicate. An electrode 26 made of an oxide conductor such as polysilicon is formed on the layer 3. This electrode 26 is connected to a fixed potential in the DRAM. In the bismuth silicate layer 3 of this embodiment, since the bismuth silicate layer 3 itself constitutes the capacitor in the DRAM structure,
The film is formed as an insulator without being made into a semiconductor. Reference numeral "11" in the figure is a field silicon oxide layer SiO ₂ .

The DRAM according to this embodiment can be manufactured as follows. That is, first, a field silicon oxide layer 11 for isolation between element regions is formed on the p-type silicon substrate 1 by a selective oxidation method using, for example, SiN. The bismuth silicate layer 3 is formed on the field silicon oxide layer 11 by the method described above, and the electrode 26 made of a conductor such as polysilicon is formed on the bismuth silicate layer 3. As a result, a DRAM capacitor is formed.
Next, a silicon oxide layer 24 (gate insulating layer) is formed to form a gate electrode 25 and a word line of the transistor integrated circuit, and then an oxide conductor such as polysilicon is deposited to form the gate electrode 25. .. Using the gate electrode 25 as a mask, n-type ions such as As are implanted to form diffusion layers 4 and 5, and a silicon oxide layer 15 which is an interlayer insulating layer is formed thereon. Although not shown, the electrode connected to the bit line of the transistor integrated circuit is formed by opening the interlayer insulating layer 15 and depositing aluminum containing Si by sputter deposition. D like this
The manufacturing method of the RAM is one specific example for obtaining the DRAM according to this embodiment, and is not particularly limited.

As described above, when the bismuth silicate layer according to the present invention is used as a capacitor of DRAM, a simple structure and a good manufacturing process can be performed without complicated manufacturing processes such as the conventional trench type or stack type. A high dielectric constant film (dielectric constant ε _r = 56) having excellent crystallinity can be formed. Therefore, the manufacturing process of the DRAM can be simplified, and at the same time, the conversion to the planar type, which is required for improving the degree of integration, can be performed, and a semiconductor device with low cost and high integration can be obtained.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0045]

As described above, according to the present invention, since the bismuth silicate layer is formed on the surface of the silicon substrate or the silicon-based layer such as silicon oxide, the oxide ceramic layer can be favorably epitaxially grown. , High dielectric constant / ferroelectric material, superconductor material, various optical ceramic thin films such as nonlinear optical material, magneto-optical material, electro-optical material, acousto-optical material, etc. A semiconductor device can be obtained. If the bismuth silicate layer is used as a DRAM capacitor, a planar type simple structure and high crystallinity can be obtained without a complicated manufacturing process such as a trench type or a stack type. A dielectric constant film can be formed. As a result, low cost and highly integrated DRA
M can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a semiconductor device according to an embodiment of the present invention, (A) shows a state before forming a bismuth oxide layer on a silicon substrate, and (B) shows a bismuth oxide layer formed. Shows the state of being done.

FIG. 2 is an X-ray diffraction pattern of bismuth silicate powder.

FIG. 3 is an X-ray diffraction diagram when a bismuth silicate layer according to an example of the present invention is formed under the condition that the substrate temperature is 760 ° C.

FIG. 4 is an X-ray diffraction diagram when a bismuth silicate layer according to an example of the present invention is formed under the condition that the substrate temperature is 780 ° C.

FIG. 5 is an X-ray diffraction diagram when a bismuth silicate layer according to an example of the present invention is formed under the condition that the substrate temperature is 800 ° C.

FIG. 6 is an X-ray diffraction diagram when a bismuth silicate layer according to an example of the present invention is formed under the condition that the substrate temperature is 820 ° C.

FIG. 7 is a sectional view showing a semiconductor device according to another embodiment of the present invention.

FIG. 8 is a sectional view showing a semiconductor device according to still another embodiment of the present invention.

FIG. 9 is a sectional view showing a semiconductor device according to still another embodiment of the present invention.

FIG. 10 is a sectional view showing a semiconductor device according to still another embodiment of the present invention.

FIG. 11 is a cross-sectional view showing a semiconductor device according to still another embodiment of the present invention.

FIG. 12 is a sectional view showing a semiconductor device according to still another embodiment of the present invention.

FIG. 13 is a hysteresis curve showing the relationship of the polarization P with respect to the electric field E of the ferroelectric substance.

FIG. 14 is a cross-sectional view showing a conventional nonvolatile RAM using a ferroelectric substance.

FIG. 15 is a diagram illustrating a cross-sectional structure and a composition ratio of a conventional ferroelectric substance and a metal electrode.

16A is a plan view showing a basic unit of a crystal structure of a silicon single crystal and a bismuth silicate crystal, and FIG. 16B is a plan view showing a basic unit of a crystal structure of a bismuth silicate crystal and a perovskite structure. ..

[Explanation of symbols]

 1 ... Silicon substrate (silicon-based layer) 2 ... Silicon oxide layer (silicon-based layer) 3 ... Bismuth silicate layer 7 ... Ferroelectric layer 16 ... Oxide optical material layer 19, 21, 22, 23 ... Oxide superconductivity Body layer

Claims (7)

[Claims] 1. A semiconductor device comprising a bismuth silicate layer formed on the surface of a silicon substrate or a silicon-based layer such as silicon oxide. 2. The semiconductor device according to claim 1, wherein the bismuth silicate layer is semiconducting. 3. The semiconductor device according to claim 2, wherein a ferroelectric layer is formed on the bismuth silicate layer. 4. The semiconductor device according to claim 2, wherein an oxide optical material layer is formed on the bismuth silicate layer. 5. The semiconductor device according to claim 2, wherein an oxide superconductor layer is formed on the bismuth silicate layer. 6. The semiconductor device according to claim 1, wherein the bismuth silicate layer is a capacitor of a dynamic random access memory. 7. An atmosphere temperature of 760 ° C. to 800 ° C. on the surface of a silicon substrate or a silicon-based layer such as silicon oxide.
A method of manufacturing a semiconductor device, comprising supplying a gas containing a bismuth component at a temperature of 0 ° C. to form a bismuth silicate layer.