JP2013232578A - Schottky barrier diode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Schottky barrier diode capable of simultaneously achieving low on-resistance and low leakage current.SOLUTION: A Schottky barrier diode includes: an electron travel layer comprising a group III nitride-based compound semiconductor; an electron supply layer formed on the electron travel layer and comprising a group III nitride-based compound semiconductor having a higher band gap energy as compared with the electron travel layer; a cathode electrode formed so as to be brought into ohmic contact with the electron supply layer; and an anode electrode electrically isolated from the electron supply layer and formed so as to be brought into Schottky contact with the electron travel layer.

Description

  The present invention relates to a Schottky barrier diode.

  Conventionally, wide band gap group III nitride compound semiconductors, particularly gallium nitride (GaN) compound semiconductors, have been used as semiconductor materials for semiconductor elements for high frequency devices (hereinafter referred to as GaN semiconductor elements). ). In a GaN-based semiconductor element, a buffer layer and a GaN doped layer are formed on the surface of a semiconductor substrate, for example, using a metal-organic chemical vapor deposition (MOCVD) method. Recently, wide band gap semiconductor elements have been studied as devices that handle high withstand voltages and large currents in recognition that they can be applied to power devices for power devices in addition to high frequency applications. Power devices are roughly divided into transistors and diodes. Conventionally, silicon has been used as a semiconductor material in power devices, but silicon carbide (SiC) has been used because of its low resistance, and devices using GaN are also being studied.

  FIG. 12 is a schematic cross-sectional view of a Schottky barrier diode using a known GaN-based semiconductor (see, for example, Patent Document 1). In a Schottky barrier diode 1000 shown in FIG. 12, a buffer layer 1002 for laminating a GaN layer, an undoped u-GaN layer 1003, and an aluminum gallium nitride (AlGaN) layer 1004 are sequentially laminated on a substrate 1001. . The AlGaN layer 1004 is a mixed crystal of AlN and GaN, and the characteristics of the band gap, spontaneous polarization, and piezoelectric polarization change depending on the composition ratio. At the interface between the u-GaN layer 1003 and the AlGaN layer 1004, there is a two-dimensional electron gas (2DEG) layer 1003a whose concentration is controlled by controlling the Al composition ratio and thickness of the AlGaN layer 1004. Is formed. The 2DEG layer 1003a serves as a path for flowing electrons.

  Since the 2DEG layer 1003a has a small electron impurity scattering, the 2DEG layer 1003a becomes a high-mobility and low-resistance electrically conductive layer, and provides a current path between electrodes formed on the AlGaN layer 1004. Schottky barrier diode 1000 has two main electrodes. The anode electrode 1005 is in Schottky contact with the AlGaN layer 1004 and is electrically connected to the 2DEG layer 1003a by electron tunneling current. The cathode electrode 1006 is in ohmic contact with the AlGaN layer 1004.

  Here, when a positive bias voltage is applied to the cathode electrode 1006 side, the anode electrode 1005 side is in a reverse bias state, and the 2DEG layer 1003a under the anode electrode is depleted and maintains a high breakdown voltage. On the other hand, when a positive bias voltage is applied to the anode electrode 1005 side, electrons flow from the cathode electrode 1006 side to the anode electrode 1005 side, a large current flows, and the diode functions as a so-called rectifying characteristic. As a result, the Schottky barrier diode 1000 can be used for a power device. Since the Schottky barrier diode 1000 has a low band resistance of the 2DEG layer 1003a and a wide band gap of the GaN material, the insulation electric field strength is more than an order of magnitude larger than that of silicon, and a high breakdown voltage can be realized. Is expected.

  In addition, the Schottky barrier diode 1000 has a feature that it can be switched at high speed because there is no accumulation of minority carriers. The buffer layer 1002 formed on the substrate 1001 is inserted to form the u-GaN layer 1003 and the AlGaN layer 1004 thereon, and is formed of a different substrate made of a material different from GaN, such as silicon or the like. By absorbing the difference in thermal expansion coefficient and lattice constant from sapphire, SiC, etc., the u-GaN layer 1003 and the AlGaN layer 1004 with good crystallinity are stacked. In general, the buffer layer 1002 has a high resistance or insulating characteristic and is used to maintain a breakdown voltage in a high breakdown voltage element. Further, as the substrate 1001, recently, a silicon substrate that is high quality, inexpensive, and capable of using a large diameter is often used.

As a semiconductor element used in a power device, a high withstand voltage and a low conduction resistance (on-resistance) as described above are great merits, but when maintaining a high withstand voltage in an off state, there is a large gap between the electrodes. When a voltage is applied, a leakage current may flow. Since this leak current is generated when a high voltage is applied, it causes power loss. This lost power is converted into heat in the device, increasing the temperature of the device, and electrons accelerated by a large internal electric field become hot electrons that are injected and accumulated in unnecessary locations, causing deterioration of reliability. There is a problem of inviting. For this reason, it is said that at least the leakage current must be suppressed to 1 mA / cm ² or less at room temperature.

Osamu Machida et al., Proceedings of the Annual Conference of the Institute of Electrical Engineers of Japan, volume 4, p.

A major factor that determines the leakage current of a Schottky barrier diode using a GaN-based semiconductor is the electron concentration (2DEG concentration) of the 2DEG layer. FIG. 13 is a diagram showing the state of the energy band at the interface between the anode electrode 1005, the AlGaN layer 1004, and the u-GaN layer 1003. Symbol E1 indicates the Fermi level of the metal constituting the anode electrode 1005, and symbol E2 indicates the Fermi level of the AlGaN layer 1004 and the u-GaN layer 1003. In the AlGaN layer 1004 arranged for generating the 2DEG layer 1003a, a large electric field indicated by an arrow Ar1 is generated even when no voltage is applied. This is because an effective charge due to polarization exists at the AlGaN / GaN interface. The electric field strength E of this electric field is expressed by the following formula (1) using the electron concentration N _2deg of the 2DEG layer 1003a.

E = _{qN 2deg} / ε _AlGaN (1)
Here, q is an elementary charge, and ε _AlGaN is a dielectric constant of AlGaN.

  As can be seen from the relationship of Expression (1), as the 2DEG concentration increases, the electric field strength in the AlGaN layer 1004 increases in proportion to the increase. On the other hand, the leakage current flowing out from the anode electrode 1005 (Schottky electrode) is closely related to the electric field strength E, and is known to depend exponentially on the electric field by the well-known thermal field emission theory. ing. For this reason, there is a close relationship between the 2DEG concentration and the leakage current. Specifically, the following formula (2) is established.

E x R _2deg = (μ) ^-1 = constant (2)
Here, R _2deg : sheet resistance of 2DEG layer, μ: electron mobility of 2DEG layer.

  For this reason, lowering the electric field strength to suppress the leakage current and lowering the resistance of the 2DEG layer are in a trade-off relationship, that is, a conflicting relationship. Therefore, it has been difficult to simultaneously reduce the on-resistance and the leakage current.

  The present invention has been made in view of the above, and an object of the present invention is to provide a Schottky barrier diode that can simultaneously realize a low on-resistance and a low leakage current.

  In order to solve the above-described problems and achieve the object, a Schottky barrier diode according to the present invention is formed on an electron transit layer composed of a group III nitride compound semiconductor, and the electron transit layer, An electron supply layer composed of a group III nitride compound semiconductor having a higher band gap energy than the electron transit layer, a cathode electrode formed in ohmic contact with the electron supply layer, and the electron supply layer And an anode electrode formed so as to be in Schottky contact with the electron transit layer.

  The Schottky barrier diode according to the present invention is the Schottky barrier diode according to the above invention, wherein the electron supply layer has a mesa shape on the electric traveling layer, and the anode electrode is formed of the mesa-shaped electron supply layer. The surface of the electron transit layer exposed on the side portion side is in Schottky contact.

  The Schottky barrier diode according to the present invention further includes an insulating film interposed in a part of an interface between the anode electrode and the electron transit layer in the above invention, and the insulating film includes the anode electrode and the anode electrode. The anode is interposed in a region between a region where the electron transit layer is in contact with a region where a two-dimensional electron gas is generated at an interface between the electron transit layer and the electron supply layer, and the anode When a positive bias voltage is applied between the electrode and the cathode electrode, an electron storage layer is formed at the interface between the electron transit layer and the insulating film, and is electrically connected to the two-dimensional electron gas. It is characterized by that.

  In the above invention, the Schottky barrier diode according to the present invention is interposed in a part of the interface between the anode electrode and the electron transit layer, and is formed on the side wall of the mesa-shaped electron supply layer. A sidewall protective film is provided.

  The Schottky barrier diode according to the present invention is characterized in that, in the above invention, an insulating protective film is formed in a region between the anode electrode and the cathode electrode.

  The Schottky barrier diode according to the present invention is the Schottky barrier diode according to the above invention, wherein the electron transit layer is an interface between the anode electrode and the electron transit layer and the electron supply layer from the region where the anode electrode and the electron transit layer contact In addition, a low resistance region which is n-type doped and has a lower resistance than the surroundings is provided between the region where the two-dimensional electron gas is generated.

  The Schottky barrier diode according to the present invention is characterized in that, in the above invention, the low resistance region is formed by ion implantation.

  The Schottky barrier diode according to the present invention is characterized in that, in the above invention, the low resistance region is formed by regrowth of a semiconductor layer.

  The Schottky barrier diode according to the present invention is characterized in that, in the above invention, a cap layer formed on the electron supply layer is provided.

  The Schottky barrier diode according to the present invention is characterized in that, in the above invention, at least a part of the cap layer is doped p-type.

  The Schottky barrier diode according to the present invention is characterized in that, in the above invention, the cathode electrode is connected to the electron supply layer through the cap layer.

  According to the present invention, it is possible to simultaneously realize a low on-resistance and a low leakage current.

FIG. 1 is a schematic cross-sectional view of the Schottky barrier diode according to the first embodiment. FIG. 2 is a diagram showing characteristics of the Schottky barrier diode shown in FIG. 1 and the Schottky barrier diode shown in FIG. FIG. 3 is a schematic cross-sectional view of the Schottky barrier diode according to the first embodiment. FIG. 4 is a schematic cross-sectional view of the Schottky barrier diode according to the second embodiment. FIG. 5 is a schematic cross-sectional view of the Schottky barrier diode according to the third embodiment. FIG. 6 is a schematic cross-sectional view of a Schottky barrier diode according to the fourth embodiment. FIG. 7 is a schematic cross-sectional view of a Schottky barrier diode according to the fifth embodiment. FIG. 8 is a schematic cross-sectional view of a Schottky barrier diode according to the sixth embodiment. FIG. 9 is a schematic cross-sectional view of a Schottky barrier diode according to the seventh embodiment. FIG. 10 is a schematic cross-sectional view of a Schottky barrier diode according to the eighth embodiment. FIG. 11 is a schematic cross-sectional view of a Schottky barrier diode according to the ninth embodiment. FIG. 12 is a schematic cross-sectional view of the Schottky barrier diode according to the tenth embodiment. FIG. 13 is a schematic cross-sectional view of a Schottky barrier diode according to the eleventh embodiment.

  Embodiments of a Schottky barrier diode according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In the drawings, the same or corresponding elements are denoted by the same reference numerals as appropriate, and repeated descriptions are omitted as appropriate. Furthermore, it should be noted that the drawings are schematic, and dimensional relationships between elements may differ from actual ones. Even between the drawings, there are cases in which portions having different dimensional relationships and ratios are included.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view of a Schottky barrier diode according to Embodiment 1 of the present invention. The Schottky barrier diode 10 is formed of a buffer layer 2 in which a plurality of AlN / GaN structures are stacked on a substrate 1 made of silicon, and GaN formed on the buffer layer 2 and doped n-type. An electron transit layer 3, an electron supply layer 4 formed on the electric transit layer 3 and made of AlGaN having a higher band gap energy than the electron transit layer 3, and formed on the electron supply layer 4 and made of GaN The cap layer 5 is provided. The cap layer 5 may be non-doped or n-doped GaN. A 2DEG layer 3 a is formed at the interface between the electron transit layer 3 and the electron supply layer 4.

  The electron supply layer 4 and the cap layer 5 are formed in a mesa shape by etching or the like, whereby the surface 3b which is a part of the surface of the electron transit layer 3 is exposed on the side portion 4a side of the electron supply layer 4. .

  The Schottky barrier diode 10 further includes an insulating film 6, which is a passivation film made of, for example, SiN, an anode electrode 7, and a cathode electrode 8.

  The insulating film 6 is formed so as to cover a part of the surface of the cap layer 5, the surface of the mesa-shaped side wall W, and a part of the surface 3 b of the electron transit layer 3. The anode electrode 7 is in Schottky contact with the electron transit layer 3 on the surface 3 b of the electron transit layer 3, while being electrically insulated from the electron supply layer 4 by the insulating film 6. The cathode electrode 8 is in ohmic contact with the surface of the cap layer 5 that is not covered with the insulating film 6, and is in ohmic contact with the electron supply layer 4 through the cap layer 5. Here, the cathode electrode 8 is in ohmic contact with the electron supply layer 4 via the cap layer, but the cap layer directly under the cathode electrode may be removed and directly contacted with the electron supply layer 4. The cap layer 5 has an effect of stabilizing the surface of the electron supply layer 4. Instead of the cap layer 5, an insulating film used as a mask when forming a mesa shape may be left. When the cap layer 5 is an insulating film, an opening may be provided in the cap layer 5 so that the cathode electrode 8 and the electron supply layer 4 are in direct ohmic contact.

  In this Schottky barrier diode 10, the electron supply layer 4 which is an AlGaN layer and the Schottky junction interface (the junction interface between the anode electrode 7 and the surface 3b of the electron transit layer 3) are shifted in the paper width direction. It can be seen that the high electric field in the electron supply layer 4 does not act on the Schottky junction interface. At the time of reverse bias in which a negative voltage is applied to the anode electrode 7, the depletion layer spreads in the electron transit layer 3 at the Schottky junction interface and maintains a high voltage, but the leakage current depends on the carrier concentration of the electron transit layer 3. It is prescribed. For this reason, by appropriately controlling the carrier concentration of the electron transit layer 3, the leakage current can be controlled while reducing the correlation with the 2DEG concentration. Also, when the Schottky electrode is in contact with AlGaN, many interface states are generated, so the interface characteristics are not stable and the Schottky characteristics tend to vary. However, in the structure of this embodiment, the Schottky junction portion with AlGaN Therefore, it is possible to obtain an effect that the interface characteristics are stable and good characteristics with little variation can be obtained.

Specifically, the carrier concentration of the electron transit layer 3 is preferably about 1 × 10 ¹⁵ to 1 × 10 ¹⁷ cm ⁻³ . As a result, an increase in leakage current can be suppressed and resistance to the 2DEG layer 3a can be suppressed. Further, when the thickness of the electron transit layer 3 is d, the sheet carrier concentration, which is the product of the carrier concentration Ngan and d, is preferably smaller than the 2DEG concentration. Since a typical 2DEG concentration is about 1 × 10 ¹³ cm ⁻² , it is preferable that the following formula (3) is satisfied.

d × Ngan <1 × 10 ¹³ cm ⁻² (3)

For example, when d is 100 nm, Ngan is preferably smaller than 1 × 10 ¹⁸ cm ⁻³ . Under this condition, the electron mobility of the 2DEG layer 3a is much higher than the electron mobility of the electron transit layer 3, so that most of the conduction current flows to the 2DEG layer 3a.

  FIG. 2 is a diagram showing characteristics of the Schottky barrier diode 10 according to the first embodiment shown in FIG. 1 and the known Schottky barrier diode 1000 shown in FIG. The horizontal axis indicates the 2DEG sheet density, and the vertical axis indicates the leakage current at the time of reverse bias of 100V. The black circle data point and the approximate straight line indicated by the solid line are the characteristics of the Schottky barrier diode 1000, and the black triangle data point are the characteristics of the Schottky barrier diode 10.

  As shown in FIG. 2, in the Schottky barrier diode 1000, there is a correlation between the 2DEG sheet concentration and the leakage current, and increasing the 2DEG sheet concentration to reduce the on-resistance increases the leakage current. . However, in the Schottky barrier diode 10, an increase in leakage current is suppressed even if the 2DEG sheet concentration is increased to reduce the on-resistance. As a result, a low on-resistance and a low leakage current can be realized simultaneously.

(Embodiment 2)
FIG. 3 is a schematic cross-sectional view of a Schottky barrier diode according to the second embodiment of the present invention. The Schottky barrier diode 20 is obtained by replacing the electron transit layer 3 in the Schottky barrier diode 10 of Embodiment 1 with an electron transit layer 13 made of non-doped u-GaN. A 2DEG layer 13 a is formed on the electron transit layer 13. In the Schottky barrier diode 20, it is possible to further reduce the leakage current by lowering the electric field at the anode electrode 7 as compared with the first embodiment.

  In the Schottky barrier diode 10, the resistance between the Schottky junction region and the 2DEG layer 3 a is reduced by configuring the electron transit layer 3 with doped GaN. In contrast, in the Schottky barrier diode 20, the insulating film 6 is interposed between the anode electrode 7 and the electron transit layer 13 in a region between the Schottky junction region and the 2DEG layer 13a. As a result, when a positive bias voltage is applied between the anode electrode 7 and the cathode electrode 8, a low-resistance electron accumulation layer 13c is formed at the interface between the electron transit layer 13 and the insulating film 6, and the 2DEG layer It is electrically connected to 13a. This reduces the resistance between the Schottky junction region and the 2DEG layer 13a.

At this time, since it is necessary to form a sufficient electron storage layer 13c with a positive bias of about 1 V, it is necessary to control the thickness of the insulating film 6 in the inserted portion. From the experimental facts so far, if the thickness of the insulating film 6 in this portion is set to about 20 nm to 100 nm, the electron storage layer 13 c having a sufficient electron concentration is formed on the surface of the electron transit layer 13. At this time, the insulating film 6 may be SiO ₂ , SiN, Al ₂ O ₃ , or a composite film thereof in manufacturing. It is known that the SiN film and the Al ₂ O ₃ film have few interface states with the GaN layer and the AlGaN layer. Therefore, it is preferable to use these films as the insulating film 6 because the electron storage layer 13c can be formed more easily.

(Embodiment 3)
FIG. 4 is a schematic cross-sectional view of a Schottky barrier diode according to Embodiment 3 of the present invention. The Schottky barrier diode 30 is obtained by interposing the breakdown voltage maintaining layer 14 made of undoped u-GaN between the buffer layer 2 and the electron transit layer 3 in the Schottky barrier diode 10 of the first embodiment. is there.

  Here, the breakdown voltage of the element may be determined by the total thickness of the semiconductor layer immediately above the buffer layer. When the doped electron transit layer 3 for maintaining the breakdown voltage becomes thick, the relationship of the above formula (3) may not be established. On the other hand, in the Schottky barrier diode 30, the carrier concentration of the electron transit layer 3 is expressed by the formula (3) while maintaining the device breakdown voltage by inserting the breakdown voltage maintaining layer 14 composed of undoped u-GaN. It can be controlled to a suitable value such that

(Embodiment 4)
FIG. 5 is a schematic cross-sectional view of a Schottky barrier diode according to Embodiment 4 of the present invention. In the Schottky barrier diode 40, the cap layer 5 is replaced with the p-type doped cap layer 15 in the Schottky barrier diode 10 of the first embodiment, and the cathode electrode 16 is directly in ohmic contact with the electron supply layer 4. It is composed. The insulating film 6 is provided with an opening 6a so that the cap layer 15 can make Schottky contact with the anode electrode 7.

  When the cap layer 15 is made of p-GaN, the acceptor in p-GaN and the polarization charge at the AlGaN / GaN interface (interface between the electron supply layer 4 and the electron transit layer 3) are neutralized, which is effective. The effect of weakening the electric field is exhibited. This has the advantage that the 2DEG layer 3a is easily depleted and a high breakdown voltage is easily obtained. Even when the cap layer 15 is not doped p-type, by setting the film thickness to 30 nm or more, polarization charges at the cap layer / AlGaN interface and the 2DEG layer interface can be easily canceled, and the same effect can be obtained. Can be obtained.

  Although the cap layer 15 is in contact with the cathode electrode 16 in the figure, it is not always necessary to be in contact. However, when the cap layer 15 which is a p-GaN layer is in contact with the cathode electrode 16, the portion becomes a Schottky contact. As a result, since a voltage is applied also from that portion, there is an advantage that an electric field is uniformly applied to the entire insulating film 6 in the lateral direction, and local electric field concentration is prevented from being broken.

  In order to form p-type GaN, doping with Mg or C is generally performed. By doping these dopants, a similar effect can be obtained even when the cap layer 15 is not p-type.

(Embodiment 5)
FIG. 6 is a schematic cross-sectional view of a Schottky barrier diode according to the fifth embodiment of the present invention. The Schottky barrier diode 50 is the same as the Schottky barrier diode 40 of the fourth embodiment, further including the breakdown voltage maintaining layer 14 of the third embodiment.

  This Schottky barrier diode 50 has the effects of both the third and fourth embodiments. Further, in the case of the doped electron transit layer 3, when a high voltage is applied, the 2DEG layer 3 a and the electron transit layer 3 may not be easily depleted, but the cap layer 15 that is a p-GaN layer. Since it becomes easy to be depleted as described above by the combination with, this can be improved.

(Embodiment 6)
FIG. 7 is a schematic cross-sectional view of a Schottky barrier diode according to Embodiment 6 of the present invention. The Schottky barrier diode 60 is obtained by replacing the electron transit layer 3 with the electron transit layer 17 mainly composed of undoped u-GaN in the Schottky barrier diode 10 of the first embodiment.

  In the electron transit layer 17, a 2DEG layer 17a is formed. The anode electrode 7 is in Schottky contact with the electron transit layer 17 on a surface 17 b that is a part of the surface of the electron transit layer 17. The electron transit layer 17 has a low resistance region 17c having a resistance lower than that of u-GaN formed by ion implantation. The low resistance region 17c can be formed in an n-type by implanting Si ions into u-GaN, for example. According to the ion implantation method, since the low resistance region 17c can be locally formed, it is possible to limit the dopant to a necessary minimum doping amount. Therefore, there is an advantage that a high breakdown voltage can be easily obtained. Further, since the control of the ion implantation amount and the implantation region is easy, there is an advantage that the controllability is remarkably improved.

(Embodiment 7)
FIG. 8 is a schematic cross-sectional view of a Schottky barrier diode according to Embodiment 7 of the present invention. The Schottky barrier diode 70 is obtained by replacing the electron transit layer 3 in the Schottky barrier diode 50 of the fifth embodiment with the electron transit layer 17 of the sixth embodiment. This Schottky barrier diode 70 has the effects of both the fifth and sixth embodiments.

(Embodiment 8)
FIG. 9 is a schematic cross-sectional view of a Schottky barrier diode according to Embodiment 8 of the present invention. In the Schottky barrier diode 80, the electron transit layer 17 in the Schottky barrier diode 60 of the sixth embodiment is replaced with an electron transit layer 18 made of non-doped u-GaN, and the electron transit layer 17 is replaced with a low resistance region 17c. The corresponding part is constituted by the regrowth layer 19 made of GaN doped n-type. In the electron transit layer 17, a 2DEG layer 17a is formed.

  The regrowth layer 19 is formed by regrowth of a GaN crystal. Accordingly, the crystallinity is good and the surface state is also good. Therefore, a good Schottky junction interface with the anode electrode 7 can be formed.

(Embodiment 9)
FIG. 10 is a schematic cross-sectional view of a Schottky barrier diode according to the ninth embodiment of the present invention. The Schottky barrier diode 90 is similar to the Schottky barrier diode 80 of the eighth embodiment except that the cap layer 5 is replaced with a p-type doped cap layer 15 and the cathode electrode 8 is replaced with the electron supply layer 4. The insulating film 6 is provided with an opening 6a so that the cap layer 15 can be in Schottky contact with the anode electrode 7. This Schottky barrier diode 90 has the effects of both the fourth and eighth embodiments.

(Embodiment 10)
FIG. 11 is a schematic cross-sectional view of a Schottky barrier diode according to the tenth embodiment of the present invention. The Schottky barrier diode 100 is the same as the Schottky barrier diode 60 of Embodiment 6, except that the insulating film 6 is formed so as not to cover the surface of the mesa-shaped side wall W and the surface 17b of the electron transit layer 17. An insulating side wall protective film 21 is formed.

  The shorter the distance between the Schottky junction region and the 2DEG layer 17a, the smaller the resistance, and the lower the on-resistance of the entire device. Therefore, in the Schottky barrier diode 100, a side wall protective film 21 called a so-called side wall insulating film is formed. This sidewall insulating film is one of self-alignment techniques known as LSI techniques. If this technology is used, the distance between the Schottky junction region and the 2DEG layer 16a can be reduced to substantially the same distance as the mesa-shaped step (for example, 0.5 μm), which is effective in reducing the on-resistance. is there. Further, since the lateral width of the Schottky barrier diode 100 is narrowed, the overall size can be reduced.

  In the above embodiment, another thick wiring metal for wiring, or a metal film such as Al, AlSi, or Cu may be laminated on the anode electrode or the cathode electrode.

  The Schottky barrier diode according to the present invention is useful for power conversion devices such as inverters that require high withstand voltage, motor drive devices, power devices used in various power supply devices, uninterruptible power supplies, and the like.

  Further, the present invention is not limited by the above embodiment. What was comprised combining each component mentioned above suitably is also contained in this invention. Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspect of the present invention is not limited to the above-described embodiment, and various modifications can be made.

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Buffer layer 3, 13, 17, 18 Electron travel layer 3a, 13a, 17a 2 DEG layer 3b, 17b Surface 4 Electron supply layer 4a Side part 5, 15 Cap layer 6 Insulating film 6a Opening 7 Anode electrode 8, 16 Cathode Electrode 10-100 Schottky barrier diode 13c Electron storage layer 14 Withstand voltage maintaining layer 17c Low resistance region 19 Regrown layer 21 Side wall protective film Ar1 Arrow E1, E2 Fermi level E2 Symbol W Side wall

Claims (11)

An electron transit layer composed of a group III nitride compound semiconductor;
An electron supply layer formed on a group III nitride compound semiconductor formed on the electric transit layer and having a band gap energy higher than that of the electron transit layer;
A cathode electrode formed in ohmic contact with the electron supply layer;
An anode electrode that is electrically insulated from the electron supply layer and formed so as to be in Schottky contact with the electron transit layer;
A Schottky barrier diode comprising: The electron supply layer has a mesa shape on the electric traveling layer,
2. The Schottky barrier diode according to claim 1, wherein the anode electrode is in Schottky contact with a surface of the electric traveling layer exposed on a side of the mesa-shaped electron supply layer. Comprising an insulating film interposed in part of the interface between the anode electrode and the electron transit layer;
The insulating film is interposed between a region where the anode electrode and the electron transit layer are in contact with a region where a two-dimensional electron gas is generated at an interface between the electron transit layer and the electron supply layer. Inserted, and
When a positive bias voltage is applied between the anode electrode and the cathode electrode, an electron storage layer is formed at the interface of the electron transit layer with the insulating film, and electrically with the two-dimensional electron gas. The Schottky barrier diode according to claim 2, wherein the Schottky barrier diode is connected.   3. The shot according to claim 2, further comprising a sidewall protective film interposed on a part of an interface between the anode electrode and the electron transit layer and formed on a sidewall of the mesa-shaped electron supply layer. Key barrier diode.   The Schottky barrier diode according to any one of claims 1 to 4, further comprising an insulating protective film formed in a region between the anode electrode and the cathode electrode.   The electron transit layer is n between a region where the anode electrode and the electron transit layer are in contact with a region where a two-dimensional electron gas is generated at the interface between the electron transit layer and the electron supply layer. The Schottky barrier diode according to claim 1, wherein the Schottky barrier diode is doped with a mold and has a low resistance region whose resistance is lower than that of the surrounding area.   The Schottky barrier diode according to claim 6, wherein the low resistance region is formed by ion implantation.   The Schottky barrier diode according to claim 6, wherein the low resistance region is formed by regrowth of a semiconductor layer.   The Schottky barrier diode according to claim 1, further comprising a cap layer formed on the electron supply layer.   The Schottky barrier diode according to claim 9, wherein at least a part of the cap layer is doped p-type.   11. The Schottky barrier diode according to claim 9, wherein the cathode electrode is connected to the electron supply layer through the cap layer.

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