JP6999106B2 - Semiconductor device - Google Patents

Description

The present invention relates to a semiconductor device useful as a power device or the like and a semiconductor system including the same.

Conventionally, a semiconductor device in which a Schottky barrier electrode is provided on a semiconductor substrate is known, and various Schottky barrier electrodes are used for the purpose of increasing the reverse withstand voltage and further reducing the forward rising voltage. It is being considered.
In Patent Document 1, a metal having a small barrier height is arranged in the central portion on the semiconductor, and a Schottky contact between the metal having a large barrier height and the semiconductor is formed in the peripheral portion on the semiconductor to obtain a reverse withstand voltage. It is described that the voltage is increased and the forward rising voltage is decreased.

Further, a combination of a shotkey electrode and an ohmic electrode has also been studied. For example, in Patent Document 2, a wide bandgap semiconductor in which a shotkey electrode and an ohmic electrode made of the same metal are formed on a substrate. The device is described, and it is described that such a configuration can improve the thermal breakdown resistance when a high current such as a surge current flows in the forward direction. However, there are problems in the adhesion of each interface between Schottky junction and ohmic junction and the adhesion between each junction, it is necessary to limit the electrode material, and the barrier height changes depending on the temperature. I wasn't always satisfied because of some problems. Therefore, a semiconductor device having a low rising voltage and excellent temperature stability has been desired.

In addition, Patent Document 3 describes a semiconductor device in which a conductive guard ring and a main joint portion bonded to a Schottky electrode are connected via a short-circuit portion, and such a semiconductor device is described. It is stated that it alleviates electric field concentration and contributes to improving withstand voltage. However, even if a large number of guard rings are installed, they are short-circuited with the main joint, so that there is a problem that the withstand voltage deteriorates.

Japanese Unexamined Patent Publication No. 52-10970 Japanese Unexamined Patent Publication No. 2014-78660 Japanese Unexamined Patent Publication No. 2014-107408

An object of the present invention is to provide a semiconductor device having excellent Schottky characteristics and semiconductor characteristics.

As a result of diligent studies to achieve the above object, the present inventors have found that the semiconductor region and the barrier electrode are included in a semiconductor device having at least a semiconductor region and a barrier electrode provided on the semiconductor region. By providing a plurality of barrier height adjusting regions on the semiconductor region in which the barrier height with the barrier electrode is smaller than the barrier height at the interface between the semiconductor region and the barrier electrode, the rising voltage is lowered and the temperature is stable. It was found that the properties can be made excellent and the withstand voltage can be made even better, and it was found that such a semiconductor device can solve the above-mentioned conventional problems at once.
In addition, after obtaining the above findings, the present inventors have further studied and completed the present invention.

That is, the present invention relates to the following invention.
[1] A semiconductor device including at least a semiconductor region and a barrier electrode provided on the semiconductor region, and the semiconductor region and the barrier electrode are placed between the semiconductor region and the barrier electrode. A semiconductor device characterized in that a barrier height adjusting region in which the barrier height with the barrier electrode is smaller than the barrier height at the interface thereof is provided, and a plurality of the barrier height adjusting regions are provided on the semiconductor region.
[2] The semiconductor device according to the above [1], wherein a plurality of the barrier height adjusting regions are provided between the inside of the barrier electrode and the semiconductor region.
[3] The semiconductor device according to the above [1] or [2], wherein a guard ring is provided on the outer peripheral portion of the barrier electrode.
[4] The semiconductor device according to the above [3], wherein a part or all of the guard ring is embedded in the surface of the semiconductor region.
[5] The semiconductor device according to any one of [1] to [4], wherein the barrier height at the interface between the barrier electrode and the barrier height adjusting region is less than 1 eV.
[6] The semiconductor device according to any one of the above [1] to [5], wherein the electrode material of the barrier electrode is metal.
[7] The semiconductor device according to any one of [1] to [6], wherein the semiconductor region contains a crystalline oxide semiconductor as a main component.
[8] The semiconductor device according to any one of the above [1] to [7], wherein the semiconductor region contains a gallium compound as a main component.
[9] The semiconductor device according to any one of the above [1] to [8], wherein the semiconductor region contains α-Ga ₂ O ₃ or a mixed crystal thereof as a main component.
[10] The semiconductor device according to any one of the above [1] to [9], which is a diode.
[11] The semiconductor device according to the above [10], which is a junction barrier Schottky diode.
[12] The semiconductor device according to any one of the above [1] to [11], which is a power device.
[13] A semiconductor system including a semiconductor device, wherein the semiconductor device is the semiconductor device according to any one of [1] to [12].

The semiconductor device of the present invention is excellent in Schottky characteristics and semiconductor characteristics.

It is a figure which shows typically one preferable aspect of the junction barrier Schottky diode (JBS) of this invention. It is a figure explaining the suitable manufacturing method of the junction barrier Schottky diode (JBS) of FIG. It is a figure which shows typically one preferable aspect of the junction barrier Schottky diode (JBS) of this invention. It is a figure explaining the suitable manufacturing method of the junction barrier Schottky diode (JBS) of FIG. It is a figure explaining the suitable manufacturing method of the junction barrier Schottky diode (JBS) of FIG. It is a figure which shows typically a suitable example of a power-source system. It is a figure which shows typically a suitable example of a system apparatus. It is a figure which shows typically a preferable example of the power supply circuit diagram of a power supply device. It is a schematic block diagram of the film forming apparatus (mist CVD apparatus) used in the reference example. It is a figure which shows the IV measurement result in a reference example, (a) shows the forward measurement result, (b) shows the reverse direction measurement result.

The semiconductor device of the present invention is a semiconductor device including at least a semiconductor region and a barrier electrode provided on the semiconductor region, and the semiconductor region is located between the semiconductor region and the barrier electrode. A barrier height adjusting region is provided in which the barrier height with the barrier electrode is smaller than the barrier height at the interface with the barrier electrode, and a plurality of the barrier height adjusting regions are provided on the semiconductor region.

The barrier electrode is not particularly limited as long as it forms a Schottky barrier having a predetermined barrier height at the interface with the semiconductor region. The electrode material of the barrier electrode is not particularly limited as long as it can be used as a barrier electrode, and may be a conductive inorganic material or a conductive organic material. In the present invention, it is preferable that the electrode material is metal. The metal is not particularly limited, but preferably, for example, at least one metal selected from the 4th to 11th groups of the periodic table can be mentioned. Examples of the metal of Group 4 of the periodic table include titanium (Ti), zirconium (Zr), hafnium (Hf), and the like, with Ti being preferable. Examples of the metal of Group 5 of the Periodic Table include vanadium (V), niobium (Nb), and tantalum (Ta). Examples of the metal of Group 6 of the Periodic Table include one or more metals selected from chromium (Cr), molybdenum (Mo), tungsten (W) and the like. Cr is preferable because the semiconductor characteristics such as switching characteristics become better. Examples of the metal of Group 7 of the periodic table include manganese (Mn), technetium (Tc), and rhenium (Re). Examples of the metal of Group 8 of the periodic table include iron (Fe), ruthenium (Ru), and osmium (Os). Examples of the metal of Group 9 of the Periodic Table include cobalt (Co), rhodium (Rh), and iridium (Ir). Examples of the metal of Group 10 of the periodic table include nickel (Ni), palladium (Pd), platinum (Pt), and the like, and Pt is preferable. Examples of the metal of Group 11 of the periodic table include copper (Cu), silver (Ag), and gold (Au). Examples of the means for forming the barrier electrode include known means, and more specifically, examples thereof include a dry method and a wet method. Examples of the dry method include known means such as sputtering, vacuum deposition, and CVD. Examples of the wet method include screen printing and die coating.

The semiconductor region is not particularly limited as long as it contains a semiconductor as a main component, but in the present invention, it is preferable that the semiconductor region contains a crystalline oxide semiconductor as a main component. The crystalline oxide semiconductor preferably has a β-gallia structure or a corundum structure, and more preferably has a corundum structure. Further, the semiconductor region preferably contains a gallium compound as a main component, more preferably contains an InAlGaO-based semiconductor as a main component, and most preferably contains α-Ga ₂ O ₃ or a mixed crystal thereof as a main component. .. The "main component" is, for example, when the crystalline oxide semiconductor is α-Ga ₂ O ₃ , the atomic ratio of gallium in the metal element in the semiconductor region is 0.5 or more, and α-Ga. It is sufficient if ₂ O ₃ is included. In the present invention, the atomic ratio of gallium in the metal element in the semiconductor region is preferably 0.7 or more, more preferably 0.8 or more. Further, the semiconductor region is usually a single-phase region, but may have a second semiconductor region or another phase composed of a different semiconductor phase as long as the object of the present invention is not impaired. Further, the semiconductor region is usually in the form of a film, and may be a semiconductor film. The thickness of the semiconductor film in the semiconductor region is not particularly limited and may be 1 μm or less or 1 μm or more, but in the present invention, it is preferably 1 μm to 40 μm, and 1 μm to 1 μm. It is more preferably 25 μm. The surface area of the semiconductor film is not particularly limited, but may be 1 mm ² or more, or may be 1 mm ² or less. The crystalline oxide semiconductor is usually a single crystal, but may be a polycrystal. Further, the semiconductor film may be a single-layer film or a multilayer film. When the semiconductor film is a multilayer film, the multilayer film preferably has a thickness of 40 μm or less, and is a multilayer film including at least a first semiconductor layer and a second semiconductor layer. When the Schottky electrode is provided on the first semiconductor layer, it is also preferable that the carrier concentration of the first semiconductor layer is smaller than the carrier concentration of the second semiconductor layer. In this case, the second semiconductor layer usually contains a dopant, and the carrier concentration of the semiconductor layer can be appropriately set by adjusting the doping amount.

The semiconductor film preferably contains a dopant. The dopant is not particularly limited and may be a known one. Examples of the dopant include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium and niobium, and p-type dopants. In the present invention, the dopant is preferably Sn, Ge or Si. The content of the dopant is preferably 0.00001 atomic% or more, more preferably 0.00001 atomic% to 20 atomic%, and 0.00001 atomic% to 10 atomic% in the composition of the semiconductor film. Is most preferable. In the present invention, the dopant used for the first semiconductor layer is germanium, silicon, titanium, zirconium, vanadium or niobium, and the dopant used for the second semiconductor layer is tin, which provides adhesion. It is preferable because the semiconductor characteristics are further improved without impairing.

The semiconductor film is formed, for example, by means such as a mist CVD method, and more specifically, for example, the raw material solution is atomized or dropleted (atomization / droplet atomization step), and the obtained mist or liquid is obtained. The droplets are transported onto the substrate with a carrier gas (transportation step), and then the mist or droplets are thermally reacted in the film forming chamber to form a semiconductor film containing a crystalline oxide semiconductor as a main component on the substrate. It is suitably formed by laminating (depositioning step).

(Atomization / droplet formation process)
The atomization / droplet atomization step atomizes or atomizes the raw material solution. The means for atomizing or dropletizing the raw material solution is not particularly limited as long as the raw material solution can be atomized or atomized, and may be known means, but in the present invention, ultrasonic waves are used. The atomizing means or droplet forming means used is preferable. Mists or droplets obtained using ultrasonic waves are preferable because they have a zero initial velocity and float in the air. For example, instead of spraying like a spray, they may float in space and be transported as gas. Since it is a possible mist, it is not damaged by collision energy, so it is very suitable. The droplet size is not particularly limited and may be a droplet of about several mm, but is preferably 50 μm or less, and more preferably 100 nm to 10 μm.

(Raw material solution)
The raw material solution is not particularly limited as long as it contains a raw material that can be atomized or atomized and can form a semiconductor region, and may be an inorganic material or an organic material. In the invention, the raw material is preferably a metal or a metal compound, preferably gallium, iron, indium, aluminum, vanadium, titanium, chromium, rhodium, nickel, cobalt, zinc, magnesium, calcium, silicon, yttrium, strontium and More preferably, it contains one or more metals selected from gallium.

In the present invention, as the raw material solution, a solution in which the metal is dissolved or dispersed in an organic solvent or water in the form of a complex or a salt can be preferably used. Examples of the form of the complex include an acetylacetonate complex, a carbonyl complex, an ammine complex, and a hydride complex. The form of the salt is, for example, an organic metal salt (for example, metal acetate, metal oxalate, metal citrate, etc.), a metal sulfide salt, a nitrified metal salt, a phosphor oxide metal salt, a halogenated metal salt (for example, metal chloride). Salts, metal bromide salts, metal iodide salts, etc.) and the like.

Further, it is preferable to mix an additive such as a hydrohalic acid or an oxidizing agent with the raw material solution. Examples of the hydrohalogen acid include hydrobromic acid, hydrochloric acid, and hydroiodide, and among them, hydrobromic acid or hydroiodide because a better quality film can be obtained. Is preferable. Examples of the oxidizing agent include hydrogen peroxide (H ₂ O ₂ ), sodium peroxide (Na ₂ O ₂ ), barium peroxide (BaO ₂ ), benzoyl peroxide (C ₆ H ₅ CO) ₂ O ₂ and the like. Peroxides, hypochlorous acid (HClO), perchloric acid, nitric acid, ozone water, organic peroxides such as peracetic acid and nitrobenzene can be mentioned.

The raw material solution may contain a dopant. By including the dopant in the raw material solution, doping can be performed satisfactorily. The dopant is not particularly limited as long as it does not interfere with the object of the present invention. Examples of the dopant include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium and niobium, and p-type dopants. The concentration of the dopant may be usually about 1 × 10 ¹⁶ / cm ³ to 1 × 10 ²² / cm ³ , and the concentration of the dopant may be as low as about 1 × 10 ¹⁷ / cm ³ or less, for example. You may. Further, according to the present invention, the dopant may be contained in a high concentration of about 1 × 10 ²⁰ / cm ³ or more. In the present invention, it is preferably contained at a carrier concentration of 1 × 10 ¹⁷ / cm ³ or more.

The solvent of the raw material solution is not particularly limited, and may be an inorganic solvent such as water, an organic solvent such as alcohol, or a mixed solvent of an inorganic solvent and an organic solvent. In the present invention, the solvent preferably contains water, and more preferably water or a mixed solvent of water and alcohol.

(Transport process)
In the transport step, the mist or the droplets are transported to the film forming chamber by the carrier gas. The carrier gas is not particularly limited as long as the object of the present invention is not impaired, and for example, an inert gas such as oxygen, ozone, nitrogen or argon, or a reducing gas such as hydrogen gas or forming gas is a suitable example. Can be mentioned. Further, the type of the carrier gas may be one type, but may be two or more types, and a diluted gas having a reduced flow rate (for example, a 10-fold diluted gas) or the like is further used as the second carrier gas. May be good. Further, the carrier gas may be supplied not only at one place but also at two or more places. The flow rate of the carrier gas is not particularly limited, but is preferably 0.01 to 20 L / min, and more preferably 1 to 10 L / min. In the case of the diluted gas, the flow rate of the diluted gas is preferably 0.001 to 2 L / min, more preferably 0.1 to 1 L / min.

(Film formation process)
In the film forming step, the semiconductor film is formed on the substrate by thermally reacting the mist or the droplet in the film forming chamber. The thermal reaction may be any effect as long as the mist or droplet reacts with heat, and the reaction conditions and the like are not particularly limited as long as the object of the present invention is not impaired. In this step, the thermal reaction is usually carried out at a temperature equal to or higher than the evaporation temperature of the solvent, but is preferably not too high (for example, 1000 ° C.) or lower, more preferably 650 ° C. or lower, and most preferably 300 ° C. to 650 ° C. preferable. Further, the thermal reaction may be carried out in any of vacuum, non-oxygen atmosphere, reducing gas atmosphere and oxygen atmosphere as long as the object of the present invention is not impaired, but the thermal reaction may be carried out in a non-oxygen atmosphere or oxygen. It is preferably done in an atmosphere. Further, it may be carried out under any conditions of atmospheric pressure, pressurization and depressurization, but in the present invention, it is preferably carried out under atmospheric pressure. The film thickness can be set by adjusting the film formation time.

(Hypokeimenon)
The substrate is not particularly limited as long as it can support the semiconductor film. The material of the substrate is not particularly limited as long as it does not impair the object of the present invention, and may be a known substrate, an organic compound, or an inorganic compound. The shape of the substrate may be any shape and is effective for any shape, for example, plate-like, fibrous, rod-like, columnar, prismatic, such as a flat plate or a disk. Cylindrical, spiral, spherical, ring-shaped and the like can be mentioned, but in the present invention, a substrate is preferable. The thickness of the substrate is not particularly limited in the present invention.

The substrate is not particularly limited as long as it has a plate shape and serves as a support for the semiconductor film. It may be an insulator substrate, a semiconductor substrate, a metal substrate or a conductive substrate, but the substrate is preferably an insulator substrate, and the surface is made of metal. A substrate having a film is also preferable. The substrate includes, for example, a base substrate containing a substrate material having a corundum structure as a main component, a substrate substrate containing a substrate material having a β-galia structure as a main component, and a substrate material having a hexagonal structure as a main component. Examples include a base substrate. Here, the "main component" means that the substrate material having the specific crystal structure has an atomic ratio of preferably 50% or more, more preferably 70% or more, still more preferably 90, based on all the components of the substrate material. It means that it is contained in% or more, and may be 100%.

The substrate material is not particularly limited and may be known as long as it does not interfere with the object of the present invention. As the substrate material having the above-mentioned corundum structure, for example, α-Al ₂ O ₃ (sapphire substrate) or α-Ga ₂ O ₃ is preferably mentioned, and a-plane sapphire substrate, m-plane sapphire substrate, and r-plane sapphire substrate are preferable. , C-plane sapphire substrate, α-type gallium oxide substrate (a-plane, m-plane or r-plane) and the like are more preferable examples. As the base substrate containing the substrate material having a β-Galia structure as a main component, for example, β-Ga ₂ O ₃ substrate or Ga ₂ O ₃ and Al ₂ O ₃ are included, and Al ₂ O ₃ is more than 0 wt%. Examples thereof include a mixed crystal substrate having a content of 60 wt% or less. Examples of the base substrate containing a substrate material having a hexagonal structure as a main component include a SiC substrate, a ZnO substrate, and a GaN substrate.

In the present invention, an annealing treatment may be performed after the film forming step. The annealing treatment temperature is not particularly limited as long as it does not impair the object of the present invention, and is usually 300 ° C. to 650 ° C., preferably 350 ° C. to 550 ° C. The annealing treatment time is usually 1 minute to 48 hours, preferably 10 minutes to 24 hours, and more preferably 30 minutes to 12 hours. The annealing treatment may be carried out in any atmosphere as long as the object of the present invention is not impaired, but it is preferably in a non-oxygen atmosphere, and more preferably in a nitrogen atmosphere.

Further, in the present invention, the semiconductor film may be provided directly on the substrate, or the semiconductor film may be provided via another layer such as a buffer layer (buffer layer) or a stress relaxation layer. .. The means for forming each layer is not particularly limited and may be known means, but in the present invention, the mist CVD method is preferable.

In the present invention, the semiconductor film may be used in a semiconductor device as the semiconductor region after using a known means such as peeling from the substrate or the like, or may be used as it is in the semiconductor device as the semiconductor region. good.

The barrier height adjusting region is not particularly limited as long as it is a region in which the barrier height with the barrier electrode or the semiconductor region is smaller than the barrier height at the interface between the semiconductor region and the barrier electrode. The barrier height adjusting region is usually composed of a conductive material having a smaller barrier height with the barrier electrode or the semiconductor region than the barrier height at the interface between the semiconductor region and the barrier electrode. Here, the "main component" includes the conductive material in an atomic ratio of preferably 50% or more, more preferably 70% or more, still more preferably 90% or more with respect to all the components of the barrier height adjusting region. It means that it is possible to be 100%. The conductive material is not particularly limited as long as it does not impair the object of the present invention, but is preferably a metal oxide or a metal. Examples of the metal oxide include those exemplified as the main component of the semiconductor region. Examples of the metal include those exemplified as the barrier electrode. Further, the barrier height is adjusted by using known means to control the oxygen concentration, the impurity concentration, the interface state density, the termination structure, the crystal structure and the surface unevenness, and to modulate the work function and electron affinity. May be done by.
In the present invention, it is preferable that the barrier height of the Schottky barrier between the barrier height adjusting region and the barrier electrode is adjusted to be less than 1 eV. By adjusting to such a preferable barrier height, the semiconductor characteristics (for example, on / off ratio, switching characteristics, etc.) of the semiconductor device of the present invention can be further improved.

The means for forming the barrier height adjusting region is not particularly limited as long as the object of the present invention is not impaired, and may be known means. For example, a means of forming a film composed of a main component of the barrier height adjusting region on the semiconductor region and then providing a plurality of trenches can be mentioned. Further, for example, a part of the semiconductor region is surface-modified by using a known surface treatment means such as dry etching, wet etching, plasma treatment, ultraviolet treatment, heat treatment, or surface treatment with an organic solvent or an organic acid. A means for adjusting the barrier height by forming a barrier electrode in the surface-modified region and then forming a barrier height adjusting region, or one of the interfaces where the semiconductor region and the barrier electrode form a bond. Examples thereof include means for forming a barrier height adjusting region by subjecting a partial region to heat treatment (for example, electron beam annealing, laser annealing, etc.) or ultraviolet treatment after interface formation or at the time of interface formation. Furthermore, in the present invention, the barrier height adjusting region may be formed by combining the above means. The means for forming the barrier height adjusting region may be implemented in a vacuum atmosphere, an atmospheric atmosphere, or a specific gas atmosphere.

Further, the semiconductor device of the present invention usually includes an ohmic electrode. A known electrode material may be used as the ohmic electrode, and the electrode material is not particularly limited as long as the object of the present invention is not impaired, but it is preferable that the ohmic electrode contains a metal of Group 4 or Group 11 of the Periodic Table. The suitable Group 4 or Group 11 metal of the periodic table used for the ohmic electrode may be the same as the metal contained in the Schottky electrode. Further, the ohmic electrode may be a single metal layer or may include two or more metal layers. The means for forming the ohmic electrode is not particularly limited, and examples thereof include known means such as a vacuum vapor deposition method and a sputtering method. Further, the metal constituting the ohmic electrode may be an alloy. In the present invention, the ohmic electrode preferably contains Ti and / and Au.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the drawings, but the present invention is not limited to these embodiments.

FIG. 1 shows a junction barrier Schottky diode (JBS), which is one of the preferred embodiments of the present invention. In the semiconductor device of FIG. 1, a barrier electrode 2 provided on the semiconductor region and capable of forming a shotky barrier between the semiconductor region 3 and the barrier electrode 2 and the semiconductor region 3 are provided. It includes a barrier height adjusting region provided between the semiconductor regions 3 and capable of forming a shot key barrier having a barrier height smaller than the barrier height of the shot key barrier of the barrier electrode 2. The barrier height adjusting region 1 is provided on the semiconductor region 3. In the present invention, it is preferable that the barrier height adjusting regions are provided at regular intervals, and it is more preferable that a plurality of the barrier height adjusting regions are provided between the inside of the barrier electrode and the semiconductor region. With such a preferred embodiment, the JBS is configured so as to be excellent in thermal stability and adhesion, the leakage current is further reduced, and the semiconductor characteristics such as withstand voltage are further excellent. The semiconductor device of FIG. 1 includes an ohmic electrode 4 on the semiconductor region 3.

The means for forming each layer of the semiconductor device of FIG. 1 is not particularly limited as long as the object of the present invention is not impaired, and may be known means. For example, a means of forming a film by a vacuum vapor deposition method, a CVD method, a sputtering method, various coating techniques, or the like, and then patterning by a photolithography method, or a means of directly performing patterning by using a printing technique or the like can be mentioned.

Hereinafter, a preferable manufacturing process and the like of the semiconductor device of FIG. 1 will be described with reference to FIG. FIG. 2A shows a laminated body in which the ohmic electrode 4 is laminated on the semiconductor substrate as the semiconductor region 3. Then, the barrier height adjusting region 1 is formed on the semiconductor region 3 as shown in FIG. 2 (b) by using the photolithography method for the laminated body of FIG. 2 (a). After obtaining the laminate of FIG. 2B, the barrier electrode 2 is formed on the barrier height adjusting region 1 and the semiconductor region 3 by the dry method (preferably vacuum vapor deposition method or sputtering), the wet method, or the like, and FIG. The laminated body of 2 (c) is obtained. The laminated body of FIG. 2C has a structure in which the barrier height adjusting region 1 is provided on the semiconductor region 3.

FIG. 3 shows a junction barrier Schottky diode (JBS), which is one of the preferred embodiments of the present invention. The semiconductor device of FIG. 3 is mainly different from the semiconductor device of FIG. 1 in that a guard ring 5 is provided on the outer peripheral portion of the barrier electrode. With such a configuration, a semiconductor device having more excellent semiconductor characteristics such as withstand voltage can be obtained. In the present invention, by embedding a part of the guard ring 5 in the surface of the semiconductor region 3, the withstand voltage can be made more effective and better. Furthermore, by using a metal having a high barrier height for the guard ring, the guard ring can be provided in an industrially advantageous manner together with the formation of the barrier electrode, which does not affect the semiconductor region so much and does not deteriorate the on-resistance. Can be formed into.

A material having a high barrier height is usually used for the guard ring. Examples of the material used for the guard ring include a conductive material having a barrier height of less than 1 eV, and may be the same as the electrode material. In the present invention, the material used for the guard ring has a high degree of freedom in designing the pressure-resistant structure, a large number of guard rings can be provided, and the pressure resistance can be flexibly improved. It is preferable to have it. The shape of the guard ring is not particularly limited, and examples thereof include a U-shape, an L-shape, and a band shape. The number of guard rings is not particularly limited, but is preferably 3 or more, and more preferably 6 or more.

Hereinafter, a preferable manufacturing process and the like of the semiconductor device of FIG. 3 will be described with reference to FIGS. 4 and 5. FIG. 4A shows a laminated body in which the ohmic electrode 4 is laminated on the semiconductor substrate as the semiconductor region 3. Then, the barrier height adjusting region 1 is formed on the semiconductor region 3 as shown in FIG. 4 (b) by the photolithography method for the laminated body of FIG. 4 (a). In the laminated body of FIG. 4B, the barrier height adjusting region 1, the semiconductor region 3, and the ohmic electrode 4 are laminated. After obtaining the laminate of FIG. 4B, the barrier electrode 2 is formed on the barrier height adjusting region 1 and the semiconductor region 3 by the dry method (preferably vacuum vapor deposition method or sputtering), the wet method, or the like, and FIG. The laminated body of 4 (c) is obtained.

Then, the laminated body of FIG. 4C is etched by a photolithography method to remove a part of the barrier electrode 2 and a part of the semiconductor region 3 as shown in FIG. 5D. After obtaining the laminate of FIG. 5D, a guard ring 5 is formed on the semiconductor region 3 exposed on the surface by the dry method (preferably vacuum vapor deposition method or sputtering), the wet method, or the like. The laminated body of FIG. 5 (e) is obtained. In the laminated body of FIG. 5 (e), a guard ring 5, a barrier electrode 2, a barrier height adjusting region 1, a semiconductor region 3 and an ohmic electrode 4 are laminated, respectively. After obtaining the laminate of FIG. 5 (e), etching using a photolithography method is performed to remove unnecessary portions to obtain the laminate of FIG. 5 (f). In the laminated body of FIG. 5 (f), the barrier height adjusting region 1 is provided on the semiconductor region 3, and the guard ring 5 having an embedded structure is provided in the peripheral portion of the semiconductor region 3, so that the withstand voltage and the like are improved. Are better.

The semiconductor device is particularly useful for power devices. Examples of the semiconductor device include a diode or a transistor (for example, MESFET), and among them, a diode is preferable, and a junction barrier Schottky diode (JBS) is more preferable.

In addition to the above-mentioned matters, the semiconductor device of the present invention is suitably used as a power module, an inverter or a converter by using known means, and further preferably used for a semiconductor system using a power supply device or the like. .. The power supply device can be manufactured from the semiconductor device or as the semiconductor device by connecting to a wiring pattern or the like by using a known means. FIG. 6 shows an example of a power supply system. In FIG. 6, a power supply system is configured by using the plurality of power supply devices and control circuits. As shown in FIG. 7, the power supply system can be used in a system device in combination with an electronic circuit. An example of the power supply circuit diagram of the power supply device is shown in FIG. FIG. 8 shows a power supply circuit of a power supply device including a power circuit and a control circuit. A DC voltage is switched at a high frequency by an inverter (PWM: A to D), converted to AC, and then isolated and transformed by a transformer. This is performed, rectified by a rectifying MOSFET (A to B'), smoothed by a DCL (smoothing coils L1 and L2) and a capacitor, and a DC voltage is output. At this time, the output voltage is compared with the reference voltage by the voltage comparator, and the inverter and the rectifier MOSFET are controlled by the PWM control circuit so as to obtain the desired output voltage.

(Reference example 1: Adjustment of barrier height by annealing)
1-1. Formation of n-type semiconductor layer 1-1-1. Film formation device The mist CVD device 19 used in the reference example will be described with reference to FIG. The mist CVD device 19 includes a susceptor 21 on which the substrate 20 is placed, a carrier gas supply means 22a for supplying the carrier gas, and a flow control valve 23a for adjusting the flow rate of the carrier gas sent out from the carrier gas supply means 22a. , A carrier gas (diluted) supply means 22b for supplying a carrier gas (diluted), a flow control valve 23b for adjusting the flow rate of the carrier gas sent out from the carrier gas (diluted) supply means 22b, and a raw material solution 24a are accommodated. A supply pipe 27 composed of a mist generation source 24, a container 25 in which water 25a is placed, an ultrasonic transducer 26 attached to the bottom surface of the container 25, and a quartz tube having an inner diameter of 40 mm, and a peripheral portion of the supply tube 27. It is equipped with a heater 28 installed in. The susceptor 21 is made of quartz, and the surface on which the substrate 20 is placed is inclined from the horizontal plane. By making both the supply tube 27 and the susceptor 21 serving as the film forming chamber from quartz, it is possible to prevent impurities derived from the apparatus from being mixed in the film formed on the substrate 20.

1-1-2. Preparation of raw material solution A 0.1 M gallium bromide aqueous solution contained 20% by volume of hydrobromic acid, and this was used as a raw material solution.

1-1-3. Preparation for film formation 1-1-2. The raw material solution 24a obtained in 1) was housed in the mist generation source 24. Next, as the substrate 20, a sapphire substrate was placed on the susceptor 21, and the heater 28 was operated to raise the temperature in the film forming chamber 27 to 480 ° C. Next, the flow control valves 23a and 23b are opened, carrier gas is supplied into the film forming chamber 27 from the carrier gas supply means 22a and 22b which are carrier gas sources, and the atmosphere of the film forming chamber 27 is sufficiently filled with the carrier gas. After the substitution, the flow rate of the carrier gas was adjusted to 5 L / min, and the flow rate of the carrier gas (diluted) was adjusted to 0.5 L / min. Nitrogen was used as the carrier gas.

1-1-4. Semiconductor film formation Next, the ultrasonic transducer 26 was vibrated at 2.4 MHz, and the vibration was propagated to the raw material solution 24a through water 25a to atomize the raw material solution 24a to generate mist. This mist was introduced into the film forming chamber 27 by the carrier gas, and the mist reacted in the film forming chamber 27 at 510 ° C. under atmospheric pressure to form a semiconductor film on the substrate 20. The film thickness was 2.5 μm, and the film formation time was 180 minutes.

1-1-5. Evaluation 1-1-4. When the phase of the membrane obtained in ₁ was identified _, the obtained membrane was α-Ga 203.

1-2. Formation of n + type semiconductor layer Except that hydrochloric acid was contained in a 0.05 M gallium acetylacetonate aqueous solution in a volume ratio of 1.5% and tin chloride in 0.2%, respectively, and these were used as raw material solutions. In the same manner as above 1-1. A semiconductor film was formed on the n-type semiconductor layer obtained in 1. When the phase of the obtained membrane was identified using an XRD diffractometer _, the obtained membrane was α _- Ga 203.

1-3. Formation of Ohmic Electrode A Ti layer and an Au layer were laminated on an n + type semiconductor layer by electron beam deposition, respectively. The thickness of the Ti layer was 35 nm, and the thickness of the Au layer was 175 nm.

1-4. Formation of Schottky Electrode After peeling off the sapphire substrate, a Pt layer was laminated on an n-type semiconductor layer by electron beam vapor deposition. Then, an annealing treatment was performed at 400 ° C. for 30 seconds in a nitrogen atmosphere using a high-speed annealing device (RTA) to form an annealed Pt layer. In addition, a Pt layer that had not been annealed was also formed by being subjected to photolithography and etching treatment.

1-5. Evaluation IV measurements were performed. As a result, the barrier height of the unannealed Pt layer was 1.5 eV, and the barrier height of the annealed Pt layer was 0.9 eV. The IV measurement result of the annealed Pt layer is shown in FIG.

The semiconductor device of the present invention can be used in all fields such as semiconductors (for example, compound semiconductor electronic devices, etc.), electronic parts / electrical equipment parts, optical / electrophotographic related devices, industrial parts, etc., but is particularly useful for power devices. be.

1 Barrier height adjustment area 2 Barrier electrode 3 Semiconductor area 4 Ohmic electrode 5 Guard ring 19 Mist CVD device 20 Board 21 Suceptor 22a Carrier gas supply means 22b Carrier gas (dilution) supply means 23a Flow control valve 23b Flow control valve 24 Mist generation source 24a Raw material solution 25 Container 25a Water 26 Ultrasonic transducer 27 Supply pipe 28 Heater 29 Exhaust port

Claims (12)

A semiconductor device including at least a semiconductor region containing a crystalline oxide semiconductor as a main component and a barrier electrode provided on the semiconductor region, wherein the semiconductor device is located between the semiconductor region and the barrier electrode. A barrier height adjusting region is provided in which the barrier height with the barrier electrode is smaller than the barrier height at the interface between the semiconductor region and the barrier electrode, and a plurality of the barrier height adjusting regions are provided on the semiconductor region. Semiconductor equipment. The semiconductor device according to claim 1, wherein a plurality of the barrier height adjusting regions are provided between the inside of the barrier electrode and the semiconductor region. The semiconductor device according to claim 1 or 2, wherein a guard ring is provided on the outer peripheral portion of the barrier electrode. The semiconductor device according to claim 3, wherein a part or all of the guard ring is embedded in the surface of the semiconductor region. The semiconductor device according to any one of claims 1 to 4, wherein the barrier height at the interface between the barrier electrode and the barrier height adjusting region is less than 1 eV. The semiconductor device according to any one of claims 1 to 5, wherein the electrode material of the barrier electrode is metal. The semiconductor device according to any one of claims 1 to 6 , wherein the semiconductor region contains a gallium compound as a main component. The semiconductor device according to any one of claims 1 to 7 , wherein the semiconductor region contains α-Ga ₂ O ₃ or a mixed crystal thereof as a main component. The semiconductor device according to any one of claims 1 to 8 , which is a diode. The semiconductor device according to claim 9 , which is a junction barrier Schottky diode. The semiconductor device according to any one of claims 1 to 10 , which is a power device. A semiconductor system including a semiconductor device, wherein the semiconductor device is the semiconductor device according to any one of claims 1 to 11 .

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