JP2006352028A - Rectifier element and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rectifier element capable of improving breakdown voltage while reducing stationary loss, and a manufacturing method thereof. <P>SOLUTION: The rectifier element 10 includes an n<SP>-</SP>semiconductor layer 2 consisting of a wide band gap semiconductor; Schottky electrodes 3 and 5 forming Schottky contact with the n<SP>-</SP>semiconductor layer 2; and a cathode electrode 4 capable of applying potential different from that of the Shottky electrode 5 and electrically connected to the n<SP>-</SP>semiconductor layer 2. The height of the Schottky barrier between the Schottky electrode 5 and the n<SP>-</SP>semiconductor layer 2 is higher than the height of a Schottky barrier between the Schottky electrode 3 and the n<SP>-</SP>semiconductor layer 2. The rectifier element 10 can select a state where the difference in potential between the Schottky electrodes 3, 5 and the cathode electrode 4 changes, thereby applying a current between the Schottky electrode 5 and the cathode electrode 4 and a state where the n<SP>-</SP>semiconductor layer 2 between the Schottky electrode 5 and the cathode electrode 4 is made into a depletion layer to disconnect a current path. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rectifying element and a manufacturing method thereof, and more specifically to a rectifying element applied to a power device and a manufacturing method thereof.

  A wide band gap semiconductor such as silicon carbide (SiC) has a higher band breakdown voltage than silicon (Si), and thus has a high withstand voltage and is stable even at high temperatures. For this reason, power devices using wide band gap semiconductors are expected to be applied to fields requiring high withstand voltage / low loss and high temperature operation, such as control devices for hybrid vehicles, home appliances, or electric power. Here, the power device is a generic term for devices that perform conversion and control of large power. The application field of power devices is expected to expand further in the future.

  Rectifying elements as power devices are roughly classified into pn junction diodes and Schottky barrier diodes (SBD). A pn junction diode has a property that a large reverse current flows during a turn-off transition due to minority carriers accumulated in a semiconductor when a current is applied. For this reason, not only an excessive loss is generated when the switching element is turned on, but it is a source of excessive noise, which is a major factor that hinders the speeding up of the rectifying element. On the other hand, in SBD, the carrier that carries current inside the semiconductor is only the majority carrier, and there is no injection or accumulation of minority carriers even when the current is applied. Therefore, the reverse current at turn-off can be made extremely small. Therefore, in general, the SBD can operate in a high frequency region as compared with the pn junction diode.

  As described above, the SBD using a wide band gap semiconductor is expected as a rectifying element capable of realizing high breakdown voltage, high temperature operation, and high frequency operation.

  FIG. 32 is a cross-sectional view showing a configuration of a conventional SiC-SBD (rectifier element). Referring to FIG. 32, rectifying element 110 includes n-type SiC substrate 101, n-type drift layer 102 formed on the main surface of SiC substrate 101 and having an impurity concentration lower than that of SiC substrate 101, and drift layer An anode electrode 103 formed on the front surface of 102 and a cathode electrode 104 formed on the back surface of SiC substrate 101 are included. In the rectifying element 110, a Schottky barrier is configured by the anode electrode 103 and the drift layer 102, and rectification characteristics are realized by this barrier.

  FIG. 33 is a cross-sectional view showing a configuration of a conventional silicon-based pn junction diode (rectifier element). Referring to FIG. 33, rectifying element 120 includes an n-type Si substrate 111, an n-type drift layer 112 formed on the main surface of Si substrate 111 and having an impurity concentration lower than that of Si substrate 111, and a drift layer. P-type impurity region 115 formed on the surface of 112, anode electrode 113 formed on the surface of p-type impurity region 115, and cathode electrode 114 formed on the back surface of Si substrate 111. In the rectifying element 120, the anode electrode 113 and the p-type impurity region 115 are electrically (ohmically) connected, and a rectifying characteristic is realized by a pn junction including the p-type impurity region 115 and the n-type drift layer 112. The

The configuration of the conventional rectifying element is also disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-53293 (Patent Document 1).
JP 2001-53293 A (Patent Document 1)

  However, in the conventional SBD, it is difficult to improve the breakdown voltage while reducing the steady loss. This will be described below.

  In order to reduce the steady loss, the forward current rising voltage (VF) may be reduced. Since the rising voltage VF is determined by the Schottky barrier height φBn, the impurity concentration of the semiconductor layer (drift layer 102 or drift layer 112) is increased, or the work function of the Schottky electrode (anode electrode 103 or anode electrode 113) is increased. If a small material is selected, the Schottky barrier height φBn becomes low, and the steady loss can be reduced. However, when the Schottky barrier height φBn is lowered, the leakage current increases and the breakdown voltage also decreases when the reverse voltage is applied. On the other hand, when the barrier height φBn of the Schottky electrode is increased in order to improve the breakdown voltage, the rising voltage of the forward current increases and the steady loss increases.

  Accordingly, an object of the present invention is to provide a rectifying element capable of improving a withstand voltage while reducing a steady loss and a manufacturing method thereof.

  The rectifying device of the present invention includes an impurity region made of a wide band gap semiconductor, a first electrode in Schottky contact with the impurity region, a Schottky contact with the impurity region, and electrically connected to the first electrode at the same potential. The second electrode and a third electrode that can apply a potential different from that of the first electrode and are electrically connected to the impurity region. The height of the Schottky barrier between the first electrode and the impurity region is lower than the height of the Schottky barrier between the second electrode and the impurity region. A state in which a current flows between the first electrode and the third electrode due to a change in potential difference between the first electrode, the second electrode, and the third electrode, and between the first electrode and the third electrode It is possible to select a state in which the current path between the first electrode and the third electrode is cut off by forming a depleted impurity region.

  The method of manufacturing a rectifying device according to the present invention includes a step of forming a first electrode so as to make a Schottky contact with an impurity region made of a wide band gap semiconductor, a Schottky contact with the impurity region, and an electrical connection with the first electrode. The step of forming the second electrode having a higher Schottky barrier between the impurity region and the Schottky barrier between the first electrode and the impurity region so as to be connected to the same potential, and a potential different from the first electrode And a third electrode is formed so as to be electrically connected to the impurity region. A state in which a current flows between the first electrode and the third electrode due to a change in potential difference between the first electrode, the second electrode, and the third electrode, and between the first electrode and the third electrode The material of the second electrode is selected so that a state where the current path between the first electrode and the third electrode is cut off can be selected by forming a depleted impurity region.

  According to the rectifying element and the manufacturing method thereof of the present invention, when the potential of the first electrode and the second electrode is higher than the potential of the third electrode (when forward voltage is applied), the first electrode and the third electrode An undepleted portion is formed in the impurity region (drift layer) existing between the first electrode and the third electrode, with this portion serving as a current path, and the current due to the Schottky barrier between the first electrode and the impurity region. It begins to flow between. Further, when the forward applied voltage increases, the current due to the Schottky barrier between the second electrode and the impurity region is added. On the other hand, when the potential of the third electrode is higher than the potential of the first electrode (when reverse voltage is applied), the depletion layer between the second electrode and the impurity region is between the first electrode and the third electrode. It spreads to the impurity region present in the region, eliminates the current path, and interrupts the current between the first electrode and the third electrode.

  As described above, in the rectifying element of the present invention, the current is basically controlled by the two Schottky barriers configured between the first electrode and the impurity region and between the second electrode and the impurity region. Schematically speaking, a structure in which a Schottky barrier due to the first electrode and the impurity region bears the overall electrical characteristics when applied in the forward direction, and a Schottky barrier due to the second electrode and the impurity regions bears in the overall direction when applied in the reverse direction. It has become. In particular, the depletion layer due to the Schottky barrier between the second electrode and the impurity region plays an important role, and is depleted in the impurity region existing between the first electrode and the third electrode with a slight forward voltage. By adjusting the combination of the second electrode and the impurity region so that a non-current path is formed, current flows through the first electrode having a small Schottky barrier, so that steady loss can be reduced. In addition, when the reverse direction is applied, a depletion layer exists in the impurity region so as to completely surround the first electrode, thereby reducing leakage current and improving breakdown voltage.

  Preferably, in the rectifying device of the present invention, the impurity region has a convex portion, the impurity region and the first electrode are in Schottky contact on the upper surface of the convex portion, and the impurity region and the first electrode are on the side surface of the convex portion. The two electrodes are in Schottky contact.

  Preferably, the manufacturing method further includes a step of forming a convex portion in the impurity region. In the step of forming the second electrode, the second electrode is formed on the upper surface of the convex portion, and in the step of forming the third electrode, the third electrode is formed on the side surface of the convex portion.

  Thereby, the inside of the convex portion is defined as a current path between the first electrode and the third electrode. When a reverse voltage is applied, a depletion layer extends from the side surface of the convex portion to the inside, and the inside of the convex portion becomes a depletion layer. Therefore, the current path can be easily interrupted, and the current can be easily controlled. In addition, the breakdown voltage can be improved.

  In the rectifying device of the present invention, preferably, the impurity concentration of the impurity region in the convex portion is lower than the impurity concentration of the impurity region other than the convex portion. As a result, the depletion layer easily extends into the convex portion when the reverse voltage is applied.

  In the rectifying device of the present invention, preferably, the impurity region and the first electrode are in Schottky contact on the upper surface and side surfaces of the convex portion.

  Preferably, in the manufacturing method, the second electrode is formed on the upper surface and the side surface of the convex portion in the step of forming the second electrode.

  Thereby, since the first electrode is formed on the upper surface and the side surface of the convex portion, the surface area of the first electrode in contact with the impurity region can be increased as compared with the case where the first electrode is formed only on the upper surface of the convex portion. it can. Therefore, since the density of the current flowing through the first electrode can be reduced, the amount of forward current can be increased. In addition, when a reverse voltage is applied, a depletion layer extends from the bottom of the convex portion to the inside, and the current path inside the convex portion is interrupted. Therefore, it becomes easy to control the current. In addition, the breakdown voltage can be improved.

  The rectifying element of the present invention preferably includes a plurality of any of the rectifying elements described above. Each of the first electrodes in the plurality of rectifying elements is formed in a matrix shape or a stripe shape in plan view. Thereby, the plurality of rectifying elements are uniformly formed.

  In the rectifying device of the present invention, preferably, the impurity region has a high concentration impurity region having a relatively high impurity concentration, and the high concentration impurity region and the first electrode are in Schottky contact.

  Thereby, only the Schottky barrier between the first electrode and the impurity region can be lowered without lowering the Schottky barrier between the second electrode and the impurity region. Therefore, the steady loss can be reduced without reducing the withstand voltage.

  Preferably, in the rectifying element of the present invention, the impurity region has a p-type impurity region and an n-type impurity region adjacent to each other, the p-type impurity region and the second electrode are in Schottky contact, and the n-type impurity region And the first electrode are in Schottky contact.

  Thereby, the current path between the first electrode and the third electrode can be blocked by the depletion layer between the p-type impurity region and the n-type impurity region. Therefore, when a reverse voltage is applied, a large depletion layer is formed in the impurity region, so that the breakdown voltage can be further improved.

  In the rectifying device of the present invention, preferably, the n-type impurity region has an n-type high concentration impurity region having a relatively high impurity concentration, and the n-type high concentration impurity region and the first electrode are in Schottky contact. ing.

  Thereby, only the Schottky barrier between the first electrode and the impurity region can be lowered without lowering the Schottky barrier between the second electrode and the impurity region. Therefore, the steady loss can be reduced without reducing the withstand voltage.

  Preferably, the manufacturing method further includes a step of forming a thermal oxide film by thermally oxidizing the surface of the impurity region and a step of removing the thermal oxide film.

  Thereby, the damaged portion on the surface of the impurity region can be removed together with the thermal oxide film, so that the contact between the impurity region and the first electrode and the second electrode is improved.

  According to the rectifying element and the manufacturing method thereof of the present invention, the breakdown voltage can be improved while reducing the steady loss.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
FIG. 1 is a cross-sectional view showing a configuration of a rectifying element according to Embodiment 1 of the present invention. 1 is a cross-sectional view taken along the line II in FIGS. 2 and 3 to be described later. Referring to FIG. 1, a rectifying element 10 includes an n ⁺ semiconductor substrate 20, an n ⁻ semiconductor layer 2 as an impurity region, a Schottky electrode 5 as a first electrode, and a Schottky electrode 3 as a second electrode. And an Al (aluminum) electrode 7 and a cathode electrode 4 as a third electrode.

An n ⁻ semiconductor layer 2 is formed on the surface of the n ⁺ semiconductor substrate 20. Schottky electrode 5 is formed in a predetermined region on main surface 1a of n ⁻ semiconductor layer 2, and Schottky electrode 3 is formed on main surface 1a so as to surround the periphery of Schottky electrode 5 in plan view. It is formed (see FIG. 2). Schottky electrode 3 and Schottky electrode 5 are electrically connected to each other at the same potential, and both are in Schottky contact with n ⁻ semiconductor layer 2. An Al electrode 7 is formed on the Schottky electrode 3, and the Schottky electrode 5, the Schottky electrode 3, and the Al electrode 7 constitute an anode electrode 8. A cathode electrode 4 is formed on the back surface 1 b of the n ⁺ semiconductor substrate 20. The cathode electrode 4 and the semiconductor substrate 20 are in ohmic contact.

The n ⁺ semiconductor substrate 20 and the n ⁻ semiconductor layer 2 are made of a wide band gap semiconductor such as SiC, gallium nitride (GaN), or diamond.

FIG. 2 is a diagram showing a planar layout of the rectifying element according to Embodiment 1 of the present invention. 1 and 2, a plurality of rectangular planar shapes are formed on the surface of n ⁻ semiconductor layer (drift layer) 2, which is a low impurity concentration region formed on the surface of n ⁺ semiconductor substrate 20. Schottky electrodes 5 are arranged in a matrix. Schottky electrode 3 is formed on the surface of n ⁻ semiconductor layer 2 so as to cover these matrix-like Schottky electrodes 5. Further, the planar shape of the Schottky electrode 5 may be a polygon or a circle in addition to a rectangle. FIG. 3 is a diagram showing a planar layout of another rectifying element according to Embodiment 1 of the present invention. Referring to FIGS. 1 and 3, an elongated rectangular planar shape (stripe) is formed on the surface of n ⁻ semiconductor layer (drift layer) 2 which is a low impurity concentration region formed on the surface of n ⁺ semiconductor substrate 20. A plurality of Schottky electrodes 5 having a shape) are arranged. Schottky electrode 3 may be formed on the surface of n ⁻ semiconductor layer 2 so as to cover these striped Schottky electrodes 5.

In addition, with reference to FIGS. 1-3, the specific dimension of the rectifier 10 is as follows, for example. The thickness d ₁ of the n ⁻ semiconductor layer 2 is 12 μm or less, the thickness d ₂ of the Schottky electrode 5 is about 0.1 μm, and the width d ₃ is about 0.8 μm. The thickness d ₄ of the n ⁺ semiconductor substrate 20 is about 0.38 mm. The distance d ₅ between adjacent Schottky electrodes 3 is 3 μm. The impurity concentration of the n ⁺ semiconductor substrate 20 is about 1 × 10 ¹⁹ / cm ³ , and the impurity concentration of the n ⁻ semiconductor layer 2 is about 1 × 10 ¹⁵ / cm ³ .

In the rectifying device 10 of the present embodiment, the height of the Schottky barrier φBn ₁ between the Schottky electrode 5 and the n ⁻ semiconductor layer 2 is equal to the Schottky barrier between the Schottky electrode 3 and the n ⁻ semiconductor layer 2. It is lower than the height of φBn ₂ .

Further, the preferred ranges of the Schottky barrier φBn ₁ and the Schottky barrier φBn ₂ vary depending on the impurity concentration of the n ⁻ semiconductor layer 2, the operating temperature, and the semiconductor material. When 4H—SiC is used as the semiconductor material and the impurity concentration of the n ⁻ semiconductor layer 2 is, for example, 1 × 10 ¹⁴ / cm ³ to 1 × 10 ¹⁸ / cm ³ , the Schottky barrier φBn ₁ is 0.68 eV <φBn ₁ <1.05 eV is preferred. By setting 0.68 eV <φBn ₁ , Schottky contact between the n ⁻ semiconductor layer 2 and the Schottky electrode 5 can be ensured even at a temperature of 250 ° C. In addition, by setting φBn ₁ <1.05 eV, the voltage required to flow a current of 1 A / cm ³ can be reduced to 0.3 V or less. Examples of the material of the Schottky electrode 3 in which the Schottky barrier φBn ₁ is in the above range include Cu (copper), Mo (molybdenum), W (tungsten), and Ru (ruthenium).

When the impurity concentration of the n ⁻ semiconductor layer 2 is, for example, 1 × 10 ¹⁵ / cm ³ to 1 × 10 ¹⁸ / cm ³ , the Schottky barrier φBn ₁ is 0.58 eV <φBn ₁ <0.95 eV. Is preferred. By setting 0.58 eV <φBn ₁ , Schottky contact between the n ⁻ semiconductor layer 2 and the Schottky electrode 5 can be ensured even at a temperature of 250 ° C. In addition, by setting φBn ₁ <0.95 eV, the voltage required to flow a current of 1 A / cm ³ can be 0.2 V or less. Examples of the material of the Schottky electrode 3 in which the Schottky barrier φBn ₁ is in the above range include Cr (chromium), Fe (iron), Cu, Mo, or W.

Further, when the impurity concentration of n ⁻ semiconductor layer 2 is, for example, 1 × 10 ¹⁶ / cm ³ to 1 × 10 ¹⁸ / cm ³ , Schottky barrier φBn ₁ is 0.48 eV <φBn ₁ <0.84 eV. Is preferred. By setting 0.48 eV <φBn ₁ , Schottky contact between the n ⁻ semiconductor layer 2 and the Schottky electrode 5 can be secured even at a temperature of 250 ° C. In addition, by setting φBn ₁ <0.84 eV, the voltage required to flow a current of 1 A / cm ³ can be reduced to 0.1 V or less. As a material of the Schottky electrode 3 in which the Schottky barrier φBn ₁ is in the above range, for example, Ti (titanium), Cr, Fe, Cu, Zn (zinc), Mo, Te (tellurium), Sn (tin), Pb ( Lead) or W.

On the other hand, when the impurity concentration of n ⁻ semiconductor layer 2 is, for example, 1 × 10 ¹⁴ / cm ³ to 1 × 10 ¹⁶ / cm ³ , Schottky barrier φBn ₂ is preferably 1.06 eV <φBn ₂ . Thereby, the leakage current at a temperature of 250 ° C. can be set to 1000 μA / cm ² or less. Examples of the material of the Schottky electrode 5 in which the Schottky barrier φBn ₂ is in the above range include Co (cobalt), Ni (nickel), Ge (germanium), Se (selenium), Te, Pd (palladium), and Rh (rhodium). ), Ir (iridium), Pt (platinum), Au (gold), or the like.

When the impurity concentration of n ⁻ semiconductor layer 2 is, for example, 1 × 10 ¹⁴ / cm ³ to 1 × 10 ¹⁷ / cm ³ , Schottky barrier φBn ₂ is preferably 1.16 eV <φBn ₂ . Thereby, the leakage current at a temperature of 250 ° C. can be set to 100 μA / cm ² or less. Examples of the material of the Schottky electrode 5 in which the Schottky barrier φBn ₂ is in the above range include Ni, Pd, Pt, Ir, Au, and the like.

Furthermore, when the impurity concentration of n ⁻ semiconductor layer 2 is, for example, 1 × 10 ¹⁴ / cm ³ to 1 × 10 ¹⁸ / cm ³ , Schottky barrier φBn ₂ is preferably 1.27 eV <φBn ₂ . Thereby, the leakage current at a temperature of 250 ° C. can be set to 10 μA / cm ² or less. Examples of the material of the Schottky electrode 5 in which the Schottky barrier φBn ₂ is in the above range include Ni, Pd, Pt, and Ir.

  Next, a method for measuring the Schottky barrier φBn between the semiconductor surface and the electrode will be described. First, an SBD is manufactured by combining a semiconductor material whose Schottky barrier φBn is to be measured and a Schottky electrode material. Then, forward and reverse anode voltages are respectively applied to the SBD, the magnitude of the anode current flowing at that time is measured, and the relationship between the anode voltage and the anode current is examined. Of these measurement results, the relationship between the forward anode voltage and the anode current is normally as shown in FIG. Referring to FIG. 4, in region I, which is a region where the anode voltage is large, the anode voltage and the anode current are regulated by the resistance component of SBD itself. In the region II where the anode voltage is small, the anode voltage and the anode current are regulated by the Schottky barrier φBn. The relationship between the anode voltage and the anode current as described above is preferably examined at two or more temperatures. In this embodiment, the relationship between the anode voltage and the anode current is examined at seven temperatures of −40 ° C., 25 ° C. (room temperature), 85 ° C., 150 ° C., 200 ° C., 250 ° C., and 300 ° C.

Next, as shown in FIG. 5, with respect to the measurement results at each temperature in the region II, the anode voltage is semi-log plotted against the anode current. Subsequently, a straight line approximating the relationship between the anode voltage and the anode current is drawn by linear approximation. From this straight line, the ideal factor n and the reverse saturation current J _s are defined. Here, the relationship between the anode voltage of the SBD and the anode current is expressed by Expression (1).

In equation (1), J _n is the anode current, J _s is the reverse saturation current, q is the electron elementary quantity, V is the anode voltage, n is the ideal factor, and k _B is the Boltzmann constant. And T is the absolute temperature. Equation (1) is transformed to obtain equation (2).

From equation (2), the slope of the straight line obtained in FIG. 5 is the ideal factor n, and the intercept of the straight line (the anode current J _n when V = 0) is the reverse saturation current J _s. I understand. Therefore, the ideal factor n and the reverse saturation current J _s are defined from the straight line obtained in FIG.

Next, as shown in FIG. 6, the reverse saturation current J _s is semi-log plotted against the temperature (q / k _B T). Then, by linear approximation, a straight line approximating the relationship between the reverse saturation current J _s and the temperature (q / k _B T) is drawn to define the Schottky barrier φBn. Here, according to the theory relating to SBD (Thermionic Emission Theory), the relationship between the anode voltage and the anode current of the SBD is expressed by Expression (3).

In equation (3), A ^* is a Richardson constant. From the equation (3), it can be seen that the slope of the straight line obtained in FIG. 6 becomes the Schottky barrier φBn. Therefore, the Schottky barrier φBn is defined from the straight line obtained in FIG.

The rectifying element 10 has a state in which a current flows between the Schottky electrode 5 and the cathode electrode 4 when the potential between the anode electrode 8 and the cathode electrode 4 changes, and between the Schottky electrode 5 and the cathode electrode 4. It is possible to select a state in which the current path between the Schottky electrode 5 and the cathode electrode 4 is cut off by forming the n ⁻ semiconductor layer 2 present in the depletion layer into a depletion layer. Next, a specific operation principle of the rectifying element 10 in the present embodiment will be described with reference to FIGS.

FIG. 7 is a diagram for explaining the rectifying element in a state where the anode electrode and the cathode electrode are at the same potential. Referring to FIG. 7, when anode electrode 8 and cathode electrode 4 are at the same potential, depletion layer 9a is formed in n ⁻ semiconductor layer 2 due to a Schottky barrier between n ⁻ semiconductor layer 2 and Schottky electrode 3. 9b are formed. Each of the depletion layers 9a and 9b may be connected at a position not shown. The depletion layer 9 a extends downward from the left boundary surface 3 a between the n ⁻ semiconductor layer 2 and the Schottky electrode 3 toward the n ⁺ semiconductor substrate 20 and laterally extends directly below the Schottky electrode 5. Also extends. Depletion layer 9b similarly to the depletion layer 9a is, n ^- also extending in the transverse direction of the semiconductor layer 2 down ^- from Zuchu right boundary surface 3b of the semiconductor layer 2 and the Schottky electrode 3 n.

Here, when the anode electrode 8 and the cathode electrode 4 are at the same potential, the depletion layer 9 a and the depletion layer 9 b extend so as to slightly intersect at the intersection C immediately below the Schottky electrode 5. As a result, the periphery of the Schottky electrode 5 other than the contact portion with the Schottky electrode 3 is covered with the depletion layers 9 a and 9 b, and the n ⁻ semiconductor layer is depleted between the Schottky electrode 5 and the cathode electrode 4. 2 will exist. As a result, the current path between the Schottky electrode 5 and the cathode electrode 4 is interrupted.

In the state of FIG. 7, there is a Schottky barrier between the n ⁻ semiconductor layer 2 and the Schottky electrode 5, and a depletion layer (hereinafter referred to as “n”) extending from the boundary with the Schottky electrode 5 to the inside of the n ⁻ semiconductor layer 2. There is also a depletion layer extending from the Schottky electrode 5). However, since the Schottky barrier φBn ₁ between the Schottky electrode 5 and the n ⁻ semiconductor layer 2 is low, the depletion layer extending from the Schottky electrode 5 is small. For this reason, the depletion layer extending from the Schottky electrode 5 is not shown in FIG.

In the rectifying element 10, the width d _{3 of the} Schottky electrode 5 is depleted so that the depletion layer 9 a and the depletion layer 9 b slightly cross each other with the anode electrode 8 and the cathode electrode 4 at the same potential. The sizes of the layers 9a and 9b are defined. The size of the depletion layers 9 a and 9 b can be defined by the material of the Schottky electrode 3 and the impurity concentration of the n ⁻ semiconductor layer 2.

FIG. 8 is a diagram for explaining the rectifying element when a forward voltage is applied. Referring to FIG. 8, when the potential of anode electrode 8 is higher than the potential of cathode electrode 4 (when a forward voltage is applied), each of depletion layers 9a and 9b is in the drawing more than the state of FIG. Shrink in the horizontal direction (width direction) and upward in the figure. When the depletion layers 9a and 9b contract, a portion (current path) that is not depleted is formed in the n ⁻ semiconductor layer 2 immediately below the Schottky electrode 5. In FIG. 8, the current path has a width d. A current I flows between the Schottky electrode 5 and the cathode electrode 4 through this current path. As the forward voltage increases, each of the depletion layers 9a and 9b contracts, so that the width d of the current path increases and the amount of current flowing increases. As the forward voltage further increases, current also flows from the Schottky barrier between Schottky electrode 3 and n ⁻ semiconductor layer 2, and the current flowing between anode electrode 8 and cathode electrode 4 further increases.

As described above, in the rectifying element 10, the depletion layer 9a and the depletion layer 9b extend so as to slightly intersect with the anode electrode 8 and the cathode electrode 4 being at the same potential. For this reason, when the depletion layers 9 a and 9 b contract even a little, a current path is formed in the n ⁻ semiconductor layer 2 immediately below the Schottky electrode 5 and a current I flows. Therefore, even if the forward voltage applied to the rectifying element 10 is small, the current I flows between the anode electrode 8 and the cathode electrode 4 if a forward voltage higher than the Schottky barrier φBn ₁ is applied.

  FIG. 9 is a diagram for explaining a rectifying element when a reverse voltage is applied. Referring to FIG. 9, when the potential of cathode electrode 4 is higher than the potential of anode electrode 8 (when a reverse voltage is applied), depletion layer 9 in which depletion layer 9a and depletion layer 9b are integrated becomes deep. It extends in the vertical direction. At this time, the current path between the Schottky electrode 5 and the cathode electrode 4 is blocked by the depletion layer 9. Further, when the reverse voltage is further increased, the thickness W of the depletion layer 9 between the Schottky electrode 5 and the cathode electrode 4 is increased, and the leakage current is reduced.

  As described above, in the rectifying element 10, the depletion layer 9 a and the depletion layer 9 b extend so as to slightly cross in the state where the anode electrode 8 and the cathode electrode 4 have the same potential. For this reason, since the current path between the Schottky electrode 5 and the cathode electrode 4 is already cut off while the anode electrode 8 and the cathode electrode 4 are at the same potential, rectification is performed even if the applied reverse voltage is small. No current flows through the element 10.

Then, the manufacturing method of the rectifier in this Embodiment is demonstrated using FIGS. First, referring to FIG. 10, an n ⁺ semiconductor substrate 20 made of SiC is prepared. The n ⁺ semiconductor substrate 20 has an impurity concentration of 1 × 10 ¹⁹ / cm ³ with N (nitrogen) as an impurity. Then, for example, n ⁻ semiconductor layer 2 made of SiC having a thickness of 12 μm or less is epitaxially grown on n ⁺ semiconductor substrate 20. The growth of the n ⁻ semiconductor layer 2 is performed, for example, by a CVD (Chemical Vapor Deposition) method, using SiH ₄ and C ₃ H ₈ as source gases and nitrogen gas as impurity gases. Thereby, the impurity concentration of n ⁻ semiconductor layer 2 is set to 1 × 10 ¹⁵ / cm ³ , for example. Next, dry oxygen (oxygen having a low humidity) is supplied, and the main surface 1a of the n ⁻ semiconductor layer 2 is thermally oxidized at a temperature of about 1200 ° C., so that the thermal oxide film 23 having a thickness of, for example, 50 nm is converted to n ^−. Formed on the main surface 1 a of the semiconductor layer 2.

Next, referring to FIG. 11, thermal oxide film 23 is removed by wet etching using hydrofluoric acid or the like, and main surface 1a of n ⁻ semiconductor layer 2 is exposed. Here, by forming the thermal oxide film 23 and removing the thermal oxide film 23 as described above, the main surface 1a is removed together with the thermal oxide film 23, and the Schottky electrode 3 is formed on a clean surface. be able to. Subsequently, a film to be the Schottky electrode 5 having a thickness of 0.1 μm is formed on the entire main surface 1a by using, for example, vapor deposition.

  Next, referring to FIG. 12, a resist 28 having a predetermined pattern is formed on the film to be the Schottky electrode 5. Then, using this resist 28 as a mask, the film to be the Schottky electrode 5 is wet etched using a solution. Thereby, the Schottky electrode 5 having a predetermined shape is formed.

  Next, referring to FIG. 13, the resist 28 is removed. Then, a Schottky electrode 3 having a thickness of about 0.1 μm is formed on main surface 1a so as to cover Schottky electrode 5 by using, for example, vapor deposition.

Thereafter, an Al electrode 7 having a predetermined shape and a thickness of 3 to 5 μm is formed on the Schottky electrode 3 by using, for example, vapor deposition, and the cathode electrode 4 is formed on the back surface 1b of the n ⁺ semiconductor substrate 20. The rectifying device 10 shown in FIG. 3 is completed through the above steps.

According to the rectifying element 10 of the present embodiment, when a forward voltage is applied, a non-depleted portion is formed in the n ⁻ semiconductor layer 2 existing between the Schottky electrode 5 and the cathode electrode 4. A current flows between the Schottky electrode 5 and the cathode electrode 4 with the portion as a current path. Since the Schottky barrier φBn ₁ between the Schottky electrode 5 and the n ⁻ semiconductor layer 2 is low, the rising voltage of the forward current can be lowered, and the steady loss can be reduced. When a reverse voltage is applied, a depletion layer between Schottky electrode 3 and n ⁻ semiconductor layer 2 extends to make n ⁻ semiconductor layer 2 immediately below Schottky electrode 5 a depletion layer. As a result, the current path between Schottky electrode 5 and n ⁻ semiconductor layer 2 is interrupted. Since Schottky barrier φBn ₂ between Schottky electrode 3 and n ⁻ semiconductor layer 2 is high, a thick depletion layer 9 having a thickness W is formed in n ⁻ semiconductor layer 2 when a reverse voltage is applied. Thereby, the leakage current between the anode electrode 8 and the cathode electrode 4 can be reduced, and the breakdown voltage of the rectifying element can be improved.

  Further, the Schottky electrode 3 is formed so as to surround the periphery of the Schottky electrode 5 when seen in a plan view. Thereby, when the reverse voltage is applied, the depletion layers 9a and 9b extend from the periphery of the Schottky electrode 5, so that the current path between the Schottky electrode 5 and the cathode electrode 4 can be easily cut off. As a result, it becomes easier to control the current.

(Embodiment 2)
FIG. 14 is a cross-sectional view showing the configuration of the rectifying element according to Embodiment 2 of the present invention. Referring to FIG. 14, in rectifying element 10a of the present embodiment, n ⁻ semiconductor layer 2 on n ⁺ semiconductor substrate 20 has convex portion 12 on the main surface. The convex portion 12 is formed by forming a groove 13 in a region other than the convex portion 12 of the n ⁻ semiconductor layer 2. A Schottky electrode 5 is formed on the upper surface 12 a of the convex portion 12. The Schottky electrode 3 is formed so as to cover the Schottky electrode 5, the side surface 12 b of the convex portion 12, and the bottom surface of the groove 13. Thus, the upper surface 12a and the Schottky electrode 5 in the n of the convex portion 12 ^- and the semiconductor layer 2 are in Schottky contact, and a Schottky electrode 3 at the bottom side 12b and the grooves 13 of the projections 12 n ^- semiconductor layer 2 and Schottky contact. An Al electrode 7 is formed on the Schottky electrode 3.

Specific dimensions of the rectifying element 10a are as follows, for example. The height d ₆ of the convex portion 12 is about 1.5 μm, and the width d ₇ is 1 μm. The thickness d ₈ from the lower surface of the n ⁻ semiconductor layer 2 to the bottom surface of the groove 13 is 12 μm or less.

  The other configuration is substantially the same as the configuration of the rectifying element 10 in the first embodiment. Therefore, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

Next, the operating principle of the rectifying element 10a in the present embodiment will be described with reference to FIGS. FIG. 15 is a diagram for explaining the rectifying element in a state where the anode electrode 8 and the cathode electrode 4 are at the same potential. Referring to FIG. 15, when anode electrode 8 and cathode electrode 4 are at the same potential, a depletion layer is formed in n ⁻ semiconductor layer 2 due to a Schottky barrier between n ⁻ semiconductor layer 2 and Schottky electrode 3. 9a and 9b are formed. The depletion layer 9a extends from the side surface 12b on the left side in the figure to the inside of the convex portion 12 (to the right side in the figure) and extends downward from the bottom surface of the groove 13 on the left side in the figure. The depletion layer 9b extends from the side surface 12b on the right side in the drawing to the inside of the convex portion 12 (to the left side in the drawing) and extends downward from the bottom surface of the groove 13 on the left side in the drawing.

Here, when the anode electrode 8 and the cathode electrode 4 are at the same potential, the depletion layer 9 a and the depletion layer 9 b extend so as to slightly intersect at the intersection C immediately below the Schottky electrode 5. As a result, the n ⁻ semiconductor layer 2 existing between the Schottky electrode 5 and the cathode electrode 4, in other words, the convex portion 12 is depleted. As a result, the current path between the Schottky electrode 5 and the cathode electrode 4 is interrupted.

  FIG. 16 is a diagram for explaining a rectifying element when a forward voltage is applied. Referring to FIG. 16, when the potential of anode electrode 8 is higher than the potential of cathode electrode 4 (when a forward voltage is applied), each of depletion layers 9a and 9b is lateral to the state of FIG. Shrink in the direction (width direction) and upward in the figure. In particular, when the depletion layers 9a and 9b contract in the lateral direction in the figure, a portion (current path) that is not depleted is formed inside the convex portion 12. In FIG. 16, the current path has a width d. A current I flows between the Schottky electrode 5 and the cathode electrode 4 through this current path.

  FIG. 17 is a diagram for explaining a rectifying element when a reverse voltage is applied. Referring to FIG. 17, when the potential of cathode electrode 4 is higher than the potential of anode electrode 8 (when a reverse voltage is applied), depletion layer 9 in which depletion layer 9a and depletion layer 9b are integrated becomes lower. Extend in the direction. At this time, the current path between the Schottky electrode 5 and the cathode electrode 4 is blocked by the depletion layer 9. Further, when the reverse voltage is further increased, the thickness W of the depletion layer 9 sandwiched between the Schottky electrode 3 and the cathode electrode 4 is increased, and the leakage current is reduced.

  Then, the manufacturing method of the rectifier 10a in this Embodiment is demonstrated using FIGS. First, the manufacturing process similar to that of the first embodiment is performed to obtain the structure shown in FIG.

Incidentally, n ^- during epitaxial growth of the semiconductor layer 2, by reducing the proportion of the impurity gas used in the CVD method, the portion that is convex portion 12 ^- impurity concentration other portions of the (n top of the semiconductor layer 2) ( It may be lower than the impurity concentration in the lower part of the n ⁻ semiconductor layer 2 so that the depletion layer can easily extend into the convex portion 12 when the reverse voltage is applied. In this case, for example, the impurity concentration in the upper portion of n ⁻ semiconductor layer 2 is set to about 1 × 10 ¹⁵ / cm ^3, and the impurity concentration in the lower portion of n ⁻ semiconductor layer 2 is set to about 1 × 10 ¹⁶ / cm ³ , for example. Further, the thickness of the n ⁻ semiconductor layer 2 in FIG. 10 is preferably about 13 μm.

Next, referring to FIG. 18, an oxide film 24 made of SiO ₂ having a thickness of about 1 μm is formed on thermal oxide film 23 by using, for example, a CVD method. Then, a resist (not shown) having a predetermined pattern is formed on the oxide film 24. Then, using this resist as a mask, the oxide film 24, the thermal oxide film 23, and the upper portion of the n ⁻ semiconductor layer 2 are etched using, for example, RIE. As a result, a groove 13 is formed in the n ⁻ semiconductor layer 2, and a convex portion 12 is formed in a portion not etched. For example, a CF ₄ gas is used for etching the oxide film 24 and the thermal oxide film 23, and a mixed gas of SF ₆ and O ₂ is used for etching the n ⁻ semiconductor layer 2, for example. The n ⁻ semiconductor layer 2 is etched by a depth of 2.5 μm, for example.

Next, referring to FIG. 19, oxide film 24 and thermal oxide film 23 are removed using a solution such as hydrofluoric acid. Thereby, the upper surface 12a of the convex part 12 is exposed. Subsequently, dry oxygen is supplied to thermally oxidize the surface of the n ⁻ semiconductor layer 2 at a temperature of about 1200 ° C., so that the top surface 12 a and the side surface 12 b of the convex portion 12 and the bottom surface of the groove 13 have a thickness. A 50 nm thermal oxide film 25 is formed.

Next, referring to FIG. 20, thermal oxide film 25 is removed using a solution such as hydrofluoric acid to make the surface of n ⁻ semiconductor layer 2 a clean surface. Subsequently, a film to be the Schottky electrode 5 having a thickness of about 0.1 μm is formed on the upper surface 12 a and the side surface 12 b of the convex portion 12 and the bottom surface of the groove 13 by using, for example, vapor deposition.

  Next, referring to FIG. 21, a resist (not shown) having a predetermined pattern is formed on the film to be Schottky electrode 5. Then, using this resist as a mask, Schottky electrode 5 is etched using a solution or the like. Thereby, the film to be the Schottky electrode 5 existing on the side surface 12b of the convex portion 12 and the bottom portion of the groove 13 is removed, and the Schottky electrode 5 is formed on the upper surface 12a.

  Next, referring to FIG. 22, the thickness is 0.1 to 0.2 μm so as to cover Schottky electrode 5, side surface 12 b of convex portion 12, and bottom surface of groove 13 by using, for example, vapor deposition. About the same Schottky electrode 3 is formed.

Thereafter, the Al electrode 7 is formed on the Schottky electrode 3 and the cathode electrode 4 is formed on the back surface 1b of the n ⁺ semiconductor substrate 20 by the same method as in the first embodiment. The rectifying element 10a shown in FIG. 14 is completed through the above steps.

  According to the rectifying element 10a of the present embodiment, the inside of the convex portion 12 is defined as a current path. When a reverse voltage is applied, the depletion layers 9a and 9b extend from the side surface 12b of the convex portion 12 to the inside, and the inside of the convex portion 12 becomes a depletion layer. Therefore, the current path can be easily interrupted, and the current can be easily controlled. In addition, the breakdown voltage can be improved.

(Embodiment 3)
FIG. 23 is a cross-sectional view showing the configuration of the rectifying element according to Embodiment 3 of the present invention. Referring to FIG. 23, Schottky electrode 3 is formed on the bottom surface of groove 13 in rectifying element 10b of the present embodiment. The end of the Schottky electrode 3 is in contact with the side surface 12 b of the convex portion 12, whereby the Schottky electrode 3 is formed below the side surface 12 b of the convex portion 12 by the thickness of the Schottky electrode 3. Further, the Schottky electrode 5 is formed on the upper surface of the convex portion 12 and the upper portion of the side surface 12 b and on the Schottky electrode 3. In other words, n the upper surface 12a and side surfaces 12b upper portion of the convex portion 12 ^- and the semiconductor layer 2 and the Schottky electrode 5 are in Schottky contact, n in the side surface 12b lower part of the protrusion 12 ^- semiconductor layer 2 and the Schottky electrode 3 is in Schottky contact.

Specific dimensions of the rectifying element 10b are as follows, for example. The vertical height d ₉ of the Schottky electrode 5 in the drawing is, for example, 1.0 μm, and the thickness d ₁₀ of the Schottky electrode 3 is, for example, 0.5 μm.

  Other configurations are almost the same as the configuration of the rectifying element 10a in the second embodiment. Therefore, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

  The rectifying element 10b according to the present embodiment includes a state in which a current flows between the Schottky electrode 5 and the cathode electrode 4 by the depletion layers 9a and 9b extending from the bottom of the side surface 12b of the convex portion 12, and the Schottky electrode 5 and the cathode A state in which a current path between the electrode 4 and the electrode 4 is cut off can be selected. FIG. 23 shows a state where the current path is interrupted by the depletion layers 9a and 9b.

  Then, the manufacturing method of the rectifier 10b in this Embodiment is demonstrated using FIGS. 24-26. First, the structure shown in FIG. 19 is obtained through the same manufacturing process as that of the second embodiment.

Next, referring to FIG. 24, thermal oxide film 25 is removed by, for example, RIE to make the surface of n ⁻ semiconductor layer 2 a clean surface. Subsequently, a film to be the Schottky electrode 3 having a thickness of 0.5 μm is formed on the top surface 12 a and the side surface 12 b of the convex portion 12 and the bottom surface of the groove 13 by using, for example, vapor deposition. A resist 28 having a predetermined pattern is formed so as to cover the film to be the Schottky electrode 3 on the bottom surface of the groove 13.

  Next, referring to FIG. 25, using this resist 28 as a mask, the film that becomes Schottky electrode 3 is etched with a solution or the like. As a result, the Schottky electrode 3 is formed at the bottom of the groove 13.

  Next, referring to FIG. 26, the Schottky electrode 5 having a thickness of about 0.1 μm is formed so as to cover the Schottky electrode 3 and the upper surface 12a and the side surface 12b of the convex portion 12 by using, for example, vapor deposition. Form.

  Thereafter, the Al electrode 7 is formed on the Schottky electrode 5 and the cathode electrode 4 is formed on the back surface 1 b of the semiconductor substrate 20 by the same method as in the first embodiment. The rectifying element 10b shown in FIG. 23 is completed through the above steps.

According to the rectifying element 10b of the present embodiment, the Schottky electrode 5 and the n ⁻ semiconductor layer 2 are in Schottky contact on the upper surface 12a and the side surface 12b of the convex portion 12, and therefore, Schottky contact only on the upper surface of the convex portion. Compared with the case, the surface area of the electrode in Schottky contact can be increased. Therefore, the amount of forward current can be increased.

In addition, since the n ⁻ semiconductor layer 2 and the Schottky electrode 3 are in Schottky contact with the side surface 12 b of the convex portion 12, the depletion layers 9 a and 9 b extend from the side surface 12 b of the convex portion 12, thereby Since the current path can be easily interrupted by forming a depletion layer, the current can be easily controlled. In addition, the breakdown voltage can be improved.

(Embodiment 4)
FIG. 27 is a cross-sectional view showing a configuration of a rectifying element according to Embodiment 4 of the present invention. Referring to FIG. 27, the configuration of rectifying element 10c in the present embodiment is an n-type semiconductor layer in which n ⁻ semiconductor layer 2 is a high-concentration impurity region, compared with the configuration of rectifying element 10 in the first embodiment. It differs in that it has 2a. The n-type semiconductor layer 2a, n ^- higher impurity concentration than the semiconductor layer 2, n in beneath the Schottky electrode 5 ^- is formed on the surface of the semiconductor layer 2. Thereby, the n-type semiconductor layer 2a and the Schottky electrode 5 are in Schottky contact.

  The other configuration is substantially the same as the configuration of the rectifying element 10 in the first embodiment. Therefore, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

According to the rectifying element 10c of the present embodiment, only the Schottky barrier φBn ₁ between the Schottky electrode 5 and the semiconductor layer is not lowered without reducing the Schottky barrier φBn ₂ between the Schottky electrode 3 and the semiconductor layer. Can be reduced. Therefore, the steady loss can be reduced without reducing the withstand voltage.

  It is to be noted that the same effect as that of the present embodiment can be obtained, for example, by the configuration shown in FIGS. 28 and 29 below.

The configuration of rectifying element 10d shown in FIG. 28 is that n ⁻ semiconductor layer 2 has n-type semiconductor layer 2a as a high-concentration impurity region, compared with the configuration of rectifying element 10a of the second embodiment. Different. The n-type semiconductor layer 2 a has a higher impurity concentration than the n ⁻ semiconductor layer 2 and is formed on the upper surface 12 a of the convex portion 12. Thereby, the n-type semiconductor layer 2a and the Schottky electrode 5 are in Schottky contact.

In addition, in the configuration of the rectifying element 10e shown in FIG. 29, the n ⁻ semiconductor layer 2 has an n-type semiconductor layer 2a as a high-concentration impurity region, compared with the configuration of the rectifying element 10b of the third embodiment. It is different in point. The impurity concentration is relatively higher than that of the n ⁻ semiconductor layer 2 and is formed on the upper surface 12 a of the convex portion 12. Thereby, the n-type semiconductor layer 2a and the Schottky electrode 5 are in Schottky contact.

In the present embodiment, the case where the n-type semiconductor layer 2a is formed as the high-concentration impurity region has been described. However, a p ⁻ semiconductor layer is formed instead of the n ⁻ semiconductor layer 2, and the n-type semiconductor is formed. Even if a p-type impurity region is formed instead of the layer 2a, the same effect can be obtained.

(Embodiment 5)
FIG. 30 is a cross-sectional view showing the configuration of the rectifying element according to Embodiment 5 of the present invention. Referring to FIG. 30, the configuration of rectifying element 10f of the present embodiment is a p-type semiconductor layer in which n ⁻ semiconductor layer 2 is a p-type impurity region, compared to the configuration of rectifying element 10 of the first embodiment. It differs in that it has 2b. The p-type semiconductor layer 2b is formed on the bottom surface of the groove 13 (the shoulder of the convex portion 12), and the p-type semiconductor layer 2b and the Schottky electrode 3 are in electrical contact. Further, the n ⁻ semiconductor layer 2 as the n-type impurity region is in Schottky contact with the Schottky electrode 5 on the upper surface 12 a and the side surface 12 b of the convex portion 12. The p-type semiconductor layer 2b and the n ⁻ semiconductor layer 2 are adjacent to each other.

  Other configurations are almost the same as the configuration of the rectifying element 10a in the second embodiment. Therefore, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

According to the rectifying element 10f of the present embodiment, the current path between the Schottky electrode 5 and the cathode electrode 4 can be blocked by the depletion layer between the p-type semiconductor layer 2b and the n ⁻ semiconductor layer 2. it can. Thereby, a large depletion layer is formed in the n ⁻ semiconductor layer 2 when a reverse voltage is applied, so that the breakdown voltage can be improved.

(Embodiment 6)
FIG. 31 is a cross-sectional view showing a configuration of a rectifying element according to Embodiment 6 of the present invention. Referring to FIG. 31, the configuration of rectifying element 10g of the present embodiment is such that n-type semiconductor layer 2a as a high-concentration n-type impurity region is formed as compared with the configuration of rectifying element 10f of the fifth embodiment. Are different. The n-type semiconductor layer 2 a has a higher impurity concentration than the n ⁻ semiconductor layer 2 and is formed on the upper surface 12 a of the convex portion 12. Thereby, the n-type semiconductor layer 2a and the Schottky electrode 5 are in Schottky contact.

  Other configurations are almost the same as the configuration of the rectifying element 10a in the second embodiment. Therefore, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

According to the rectifying element 10g of the present embodiment, only the Schottky barrier φBn ₁ between the Schottky electrode 5 and the semiconductor layer is reduced without reducing the Schottky barrier φBn ₂ between the Schottky electrode 3 and the semiconductor layer. Can be reduced. Therefore, the steady loss can be reduced without reducing the withstand voltage.

  The embodiment disclosed above should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above embodiments but by the scope of claims, and is intended to include all modifications and variations within the scope and meaning equivalent to the scope of claims.

  The rectifying element and the manufacturing method thereof according to the present invention are suitable for a rectifying element applied to a power device and a manufacturing method thereof.

It is sectional drawing which shows the structure of the rectifier in Embodiment 1 of this invention, Comprising: It is sectional drawing which follows the II line | wire of FIG. 2 and FIG. It is a top view which shows the structure of the rectifier in Embodiment 1 of this invention. It is a top view which shows the structure of the other rectifier in Embodiment 1 of this invention. It is a figure which shows typically the relationship between the forward anode voltage and anode current in a Schottky diode. FIG. 5 is a semi-log plot of the anode voltage of FIG. 4 against the anode current. FIG. 6 is a semi-log plot of reverse saturation current J _s against temperature (q / k _B T). In Embodiment 1 of this invention, it is a figure for demonstrating the rectifier in the state in which an anode electrode and a cathode electrode are the same electric potential. In Embodiment 1 of this invention, it is a figure for demonstrating the rectifier element in case a forward voltage is applied. In Embodiment 1 of this invention, it is a figure for demonstrating the rectifier in the case where a reverse voltage is applied. It is sectional drawing which shows the 1st process of the manufacturing method of the rectifier in Embodiment 1 of this invention. It is sectional drawing which shows the 2nd process of the manufacturing method of the rectifier in Embodiment 1 of this invention. It is sectional drawing which shows the 3rd process of the manufacturing method of the rectifier in Embodiment 1 of this invention. It is sectional drawing which shows the 4th process of the manufacturing method of the rectifier in Embodiment 1 of this invention. It is sectional drawing which shows the structure of the rectifier in Embodiment 2 of this invention. In Embodiment 2 of this invention, it is a figure for demonstrating the rectifier in the state in which an anode electrode and a cathode electrode are the same electric potential. In Embodiment 2 of this invention, it is a figure for demonstrating the rectifier in the case where a forward voltage is applied. In Embodiment 2 of this invention, it is a figure for demonstrating the rectification element in case a reverse direction voltage is applied. It is sectional drawing which shows the 1st process of the manufacturing method of the rectifier in Embodiment 2 of this invention. It is sectional drawing which shows the 2nd process of the manufacturing method of the rectifier in Embodiment 2 of this invention. It is sectional drawing which shows the 3rd process of the manufacturing method of the rectifier in Embodiment 2 of this invention. It is sectional drawing which shows the 4th process of the manufacturing method of the rectifier in Embodiment 2 of this invention. It is sectional drawing which shows the 5th process of the manufacturing method of the rectifier in Embodiment 2 of this invention. It is sectional drawing which shows the structure of the rectifier in Embodiment 3 of this invention. It is sectional drawing which shows the 1st process of the manufacturing method of the rectifier in Embodiment 3 of this invention. It is sectional drawing which shows the 2nd process of the manufacturing method of the rectifier in Embodiment 3 of this invention. It is sectional drawing which shows the 3rd process of the manufacturing method of the rectifier in Embodiment 3 of this invention. It is sectional drawing which shows the structure of the rectifier in Embodiment 4 of this invention. It is sectional drawing which shows the structure of the other rectifier in Embodiment 4 of this invention. It is sectional drawing which shows the structure of the further another rectifier in Embodiment 4 of this invention. It is sectional drawing which shows the structure of the rectifier in Embodiment 5 of this invention. It is sectional drawing which shows the structure of the other rectifier in Embodiment 6 of this invention. It is sectional drawing which shows the structure of the conventional SiC-SBD (rectifier element). It is sectional drawing which shows the structure of the conventional silicon-type pn junction diode (rectifier element).

Explanation of symbols

1a main surface, 1b back surface, 2,102, 112 n ^- semiconductor layer (drift layer), 2a n-type semiconductor layer, 2b p-type semiconductor layer, 3,5 Schottky electrode, 3a, 3b interface, 4,104, 114 cathode electrode, 7 Al electrode, 8, 103, 113 anode electrode, 9, 9a, 9b depletion layer, 10, 10a-10g, 110, 120 rectifier element, 12 convex part, 12a upper surface, 12b side surface, 13 groove, 20 n ⁺ semiconductor substrate, 23, 25 thermal oxide film, 24 oxide film, 28 resist, 101 SiC substrate, 111 Si substrate, 115 p-type impurity region.

Claims (12)

An impurity region made of a wide band gap semiconductor;
A first electrode in Schottky contact with the impurity region;
A second electrode in Schottky contact with the impurity region and electrically connected to the same potential as the first electrode;
A third electrode capable of applying a potential different from that of the first electrode and electrically connected to the impurity region;
The Schottky barrier height between the first electrode and the impurity region is lower than the Schottky barrier height between the second electrode and the impurity region,
A state in which a current flows between the first electrode and the third electrode by changing a potential difference between the first electrode, the second electrode, and the third electrode, and the first electrode and the third electrode A rectifying element capable of selecting a state in which a current path between the first electrode and the third electrode is cut off by depleting the impurity region existing between the three electrodes. The impurity region has a convex portion,
The impurity region and the first electrode are in Schottky contact on an upper surface of the convex portion, and the impurity region and the second electrode are in Schottky contact on a side surface of the convex portion. 1. The rectifying device according to 1.   The rectifying device according to claim 2, wherein an impurity concentration of the impurity region in the convex portion is lower than an impurity concentration of the impurity region other than the convex portion.   4. The rectifying device according to claim 2, wherein the impurity region and the first electrode are in Schottky contact on an upper surface and a side surface of the convex portion. 5. A plurality of rectifying elements according to claims 1 to 4,
Each of the first electrodes in the plurality of rectifying elements is formed in a matrix shape or a stripe shape in plan view.   6. The impurity region according to claim 1, wherein the impurity region has a high concentration impurity region having a relatively high impurity concentration, and the high concentration impurity region and the first electrode are in Schottky contact. The rectifying device described in 1.   The impurity region has a p-type impurity region and an n-type impurity region adjacent to each other, the p-type impurity region and the second electrode are in Schottky contact, and the n-type impurity region and the first electrode The rectifying element according to claim 1, wherein the rectifier and the Schottky contact with each other.   The n-type impurity region has an n-type high-concentration impurity region having a relatively high impurity concentration, and the n-type high-concentration impurity region and the first electrode are in Schottky contact. 8. The rectifying device according to 7. Forming a first electrode in Schottky contact with an impurity region made of a wide band gap semiconductor;
Schottky contact with the impurity region and electrically connected to the same potential as the first electrode, the region between the impurity region rather than the Schottky barrier between the first electrode and the impurity region. Forming a second electrode having a high Schottky barrier;
A step of forming a third electrode so that a potential different from that of the first electrode can be applied and electrically connected to the impurity region;
A state in which a current flows between the first electrode and the third electrode by changing a potential difference between the first electrode, the second electrode, and the third electrode, and the first electrode and the third electrode The second electrode is configured so that a state in which a current path between the first electrode and the third electrode is cut off can be selected by depleting the impurity region existing between the three electrodes. A method of manufacturing a rectifying element, wherein the material is selected. Further comprising forming a protrusion in the impurity region,
Forming the second electrode on an upper surface of the convex portion in the step of forming the second electrode, and forming the third electrode on a side surface of the convex portion in the step of forming the third electrode. The method for manufacturing a rectifying device according to claim 9.   The method of manufacturing a rectifying device according to claim 10, wherein the second electrode is formed on an upper surface and a side surface of the convex portion in the step of forming the second electrode. Forming a thermal oxide film by thermally oxidizing the surface of the impurity region;
The method for manufacturing a rectifying device according to claim 9, further comprising a step of removing the thermal oxide film.

Images