KR20150072199A - Power Semiconductor Device and Power semiconductor circuit including the device - Google Patents

Abstract

A power semiconductor device according to an embodiment of the present invention includes: a cathode; a first conductivity type nitride semiconductor layer which is arranged on the cathode and has an upper side on which a concave part and a convex part are at least one time alternatively stacked; a conductivity type nitride semiconductor layer which are arranged on either the bottom or the side of the concave part; and an anode arranged on the second conductivity type nitride semiconductor layer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a power semiconductor device and a power semiconductor circuit including the power semiconductor device.

Embodiments relate to power semiconductor devices and power semiconductor circuits comprising them.

Generally, diodes used in circuits suitable for high-voltage switching are reverse-operated. In a situation where the cathode voltage is higher than the anode voltage, the reverse leakage current should be as small as possible and can withstand high voltages, such as at least 600 volts or 1200 volts .

Power semiconductor devices, such as Schottky barrier diodes (SBDs), which are a type of diodes, are used as core components of Switch-Mode Power Supply (SMPS) together with transistors. This is because the SBD has excellent switching speed and on-state performance.

GaN has advantageous physical properties that can be applied to power semiconductor devices such as wide bandgap, two-dimensional electron gas (2DEG) channel, high mobility, and high critical electric field. The SBD implemented using a semiconductor such as GaN has a high breakdown voltage of 600 V or less and a low threshold voltage of 1 volt or less and exhibits stable switching characteristics even at a high temperature and also has a commercially available silicon (Si) high recovery diode (FRD: Fast Recovery Diode) and SiC SBD.

1 shows a cross-sectional view of a conventional vertical SBD.

FIG. 2 shows an energy band diagram of the vertical SBD shown in FIG. 1, and Ec represents the energy level of the conduction band.

The vertical SBD of Fig. 1 is composed of a cathode 10, an anode 20 and a nitride semiconductor layer 30. The nitride semiconductor layer 30 is composed of an n + GaN layer 32 and an n - GaN layer 34.

When a large reverse bias voltage is applied to the vertical SBD shown in FIG. 1, the reverse leakage current becomes large. If a SiC layer is disposed instead of the nitride semiconductor layer 30 between the cathode 10 and the anode 20, a p-type region spaced apart at a narrow interval below the anode 20 is formed, One reverse leakage current can be reduced.

1, there is a problem that it is difficult to form a p-type region under the anode 20 when the GaN layer 30 is formed between the cathode 10 and the anode 20 instead of the SiC layer .

Additionally, as shown in FIG. 1, the leakage current mainly occurs in the conventional vertical SBD through the trap states associated with the screw dislocation 36. These screw defects 36 are made side by side along the c-axis and directly contact the anode 20 with the surface of the epitaxially grown GaN layer 30 intercepted.

2, electrons from the anode 20 can easily enter the screw defects 36 in the direction of the arrow 40. As shown in FIG. The reverse leakage current can be increased by Poole-Frenkel transport of electrons through the screw defect 36 because the electric field 42 at the interface between the anode 20 and the GaN layer 34 is very high. As such, when the reverse leakage current of the SBD is large, the SBD may not be suitable for high voltage applications, and power semiconductor devices such as SBD may cause reliability problems, and improvement is required.

The embodiment provides a power semiconductor device and a power semiconductor circuit including the power semiconductor device in which a large amount of reverse leakage current does not occur.

A power semiconductor device according to an embodiment includes a negative electrode; A first conductive type nitride semiconductor layer which is disposed on the cathode and in which recesses and convex portions are alternately arranged repeatedly at least once; A second conductive semiconductor layer disposed on at least one of a bottom surface and a side surface of the concave portion; And a cathode disposed on the second conductive semiconductor layer.

The concave portion and the convex portion may be alternately arranged in a cyclic or non-cyclic manner.

The power semiconductor device further includes a Schottky electrode disposed on the convex portion and forming a Schottky junction with the first conductive type nitride semiconductor layer, wherein the second conductive type semiconductor layer extends from a side surface of the concave portion And may be disposed to cover the side surface and the upper surface of the Schottky electrode. In this case, the second conductivity type semiconductor layer may include a material that makes ohmic contact with the anode and the Schottky electrode, respectively.

Alternatively, the power semiconductor device may further include a Schottky electrode disposed on the second conductive type semiconductor layer in the recess, and the anode may be disposed on the Schottky electrode and the convex portion. In this case, the second conductivity type semiconductor layer may include a material that makes an ohmic contact with the Schottky electrode.

The Schottky electrode may comprise a refractory metal or a mixture of the refractory metals.

The Schottky electrode may be formed of at least one selected from the group consisting of Ni (Nickel), TiN (Titanium Nitride), WN (Tungsten Nitride), WSi _x (Tungsten Silicide), where X is a natural number, W (tungsten) , Cr (Chromium), Mo (Molybdenum), or Ag (Argentum).

The anode of claim at least one of a second layer disposed on the first layer or the first layer, the first layer is Ni (Nickel), TiN (Titanium Nitride), WN (Tungsten Nitride), WSi X (Tungsten At least one material selected from the group consisting of Silicide (where X is a natural number), W (Tungsten), Pt (Platinum), Au (Aurum), Cr (Chromium), Mo (Molybdenum) The second layer may comprise Au.

The second conductive semiconductor layer may include a material forming a pn junction with the first conductive nitride semiconductor layer. For example, the second conductive semiconductor layer may include NiO.

The aspect ratio, which is the ratio of the height to the width of the convex portion, may be 0.5 to 1.5.

The width of the convex portion may be 0.5 탆 to 4 탆.

The width of the concave portion may be 0.5 탆 to 1.5 탆.

The second conductivity type semiconductor layer may have a thickness of 20 nm to 300 nm.

The concave portion and the convex portion may have a planar shape alternately arranged in the horizontal direction or the vertical direction.

Alternatively, the concave portion and the convex portion may have a planar shape alternately arranged in a checkerboard shape.

Alternatively, the recess may have a polygonal or circular planar shape.

At least one of the concave portion and the convex portion may have a sloped cross-sectional shape.

The power semiconductor circuit according to another embodiment includes: the power semiconductor element; And a passive device electrically connected to the power semiconductor device.

The power semiconductor device and the power semiconductor circuit including the power semiconductor device according to the embodiment have a structure in which the second conductivity type semiconductor layer between the anode and the first conductive type second nitride semiconductor layer is disposed so as not to generate a large reverse leakage current, The second conductivity type semiconductor layer, the second conductivity type semiconductor layer, the second conductivity type semiconductor layer, the first conductivity type nitride semiconductor layer, the second conductivity type semiconductor layer, .

1 shows a cross-sectional view of a conventional vertical SBD.
Fig. 2 shows an energy band diagram of the vertical SBD shown in Fig.
3 is a cross-sectional view of a power semiconductor device according to an embodiment.
4A to 4C are enlarged cross-sectional views illustrating embodiments of the portion 'A' shown in FIG.
5 is a cross-sectional view of a power semiconductor device according to another embodiment.
6 is a cross-sectional view of a power semiconductor device according to another embodiment.
FIG. 7 shows an energy band diagram when a reverse bias voltage is applied to the power semiconductor device illustrated in FIGS. 3-6. FIG.
FIGS. 8A to 8F are simulation results showing a two-dimensionally enlarged view of the depletion region as the reverse bias voltage is increased in one section of the diode in the power semiconductor device illustrated in FIG. 3. FIG.
Fig. 9 is a graph showing the relationship between the electric field and the resistance in the Schottky junction depending on the aspect ratios.
Figure 10 shows a top view of one embodiment of the power semiconductor device illustrated in Figures 3-6.
Figure 11 shows a top view of another embodiment of the power semiconductor device illustrated in Figures 3-6.
Figure 12 shows a plan view of another embodiment of the power semiconductor device illustrated in Figures 3-6.
Figure 13 shows a top view of another embodiment of the power semiconductor device illustrated in Figures 3-6.
Figs. 14A to 14E show process cross-sectional views for explaining the manufacturing method of the power semiconductor device illustrated in Fig. 3. Fig.
15A and 15B show characteristic graphs of the current-voltage characteristics of the present embodiment and those of the present embodiment, respectively.
16 shows a circuit diagram of the power semiconductor device according to the embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings in order to facilitate understanding of the present invention. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. Embodiments of the invention are provided to more fully describe the present invention to those skilled in the art.

In the description of the present embodiment, in the case of being described as being formed "on or under" of each element, the upper (upper) or lower (lower) on or under includes both the two elements being directly in contact with each other or one or more other elements being indirectly formed between the two elements.

Also, when expressed as "on" or "on or under", it may include not only an upward direction but also a downward direction with respect to one element.

It is also to be understood that the terms "first" and "second", "upper" and "lower", etc., as used below, do not necessarily imply or imply any physical or logical relationship or order between such entities or elements And may be used only to distinguish one entity or element from another entity or element.

3 shows a cross-sectional view of a power semiconductor device 100A according to one embodiment.

3, the power semiconductor device 100A according to the embodiment includes a cathode 110, an anode 120-1, a first conductive type nitride semiconductor layer 130-1, a second conductive type semiconductor layer 140 -1) and a Schottky electrode 150-1. Hereinafter, the power semiconductor device 100A is described as performing a function of a vertical Schottky barrier diode (SBD), but the embodiment is not limited thereto.

The first conductive type nitride semiconductor layer 130-1 is disposed on the cathode 110. [

The cathode 110 may include a single layer or a multilayer structure including at least one of aluminum (Al), titanium (Ti), chrome (Cr), nickel (Ni), copper (Cu), and gold (Au). For example, the cathode 110 may be implemented as a double layer structure of Ti / Au.

The concave portion 134A and the convex portion 134B may be alternately arranged in the form of an array by repeating alternately at least once on the first conductive type nitride semiconductor layer 130-1.

The first conductive type nitride semiconductor layer 130-1 may include a first conductive type first nitride semiconductor layer 132 and a first conductive type second nitride semiconductor layer 134-1. The first conductive type first nitride semiconductor layer 132 is disposed on the cathode 110 and the first conductive type second nitride semiconductor layer 134-1 is disposed on the first conductive type first nitride semiconductor layer 132 do.

Each of the first conductive type first nitride semiconductor layer 132 and the first conductive type second nitride semiconductor layer 134-1 is made of Al _x In _y Ga _(1-xy) N (0? X? 1, 0? _Y 1, 0? X + y? 1). When each of the first conductive type first nitride semiconductor layer 132 and the first conductive type second nitride semiconductor layer 134-1 is an n-type semiconductor layer, the first conductive type dopant is at least one selected from the group consisting of phosphorus (P), arsenic ), And the like. In addition, each of the first conductive type first nitride semiconductor layer 132 and the first conductive type second nitride semiconductor layer 134-1 may be formed as a single layer or multiple layers, but the present invention is not limited thereto.

In addition, the doping concentration of the first conductive type dopant in the first conductive type first nitride semiconductor layer 132 may be higher than the doping concentration of the first conductive type dopant in the first conductive type second nitride semiconductor layer 134-1 have. For example, the doping concentration of the first conductive type second nitride semiconductor layer 134-1 may be 2 x 10 ¹⁶ atoms / cm 3, and the thickness of the first conductive type second nitride semiconductor layer 134-1 May be 6 [mu] m, and the embodiment is not limited to the doping concentration and thickness of each of these layers 132 and 134-1.

As described above, when the first conductive type nitride semiconductor layer 130-1 includes the first conductive type first nitride semiconductor layer 132 and the first conductive type second nitride semiconductor layer 134-1, The concave portion 134A and the convex portion 134B may be disposed above the first conductive type second nitride semiconductor layer 134-1.

Also, the concave portion 134A and the convex portion 134B can be alternately arranged repeatedly, cyclically or non-cyclically. Each of the concave portion 134A and the convex portion 134B may have various shapes. These various forms will be described with reference to Figs. 4A to 4C, but the embodiments are not limited thereto.

4A to 4C are enlarged cross-sectional views of embodiments (A1, A2, A3) of the portion "A" shown in FIG.

At least one of the concave portion 134A or the convex portion 134B may have a sloped cross-sectional shape. Here, the angle? May be positive or negative. For example, as illustrated in FIG. 4A, the convex portion 134B may have a cross-sectional shape inclined at a positive angle?.

The bottom surface of the concave portion 134A may have a flat cross-sectional shape as illustrated in Fig. 4A, but both ends 134AA and 134AB may have a sloped cross-sectional shape as illustrated in Fig. 4B.

On the other hand, the second conductivity type semiconductor layer 140-1 may be disposed on at least one of the bottom surface 134A-1 and the side surface 134A-2 of the concave portion 134A. For example, as illustrated in FIG. 3, the second conductive type semiconductor layer 140-1 may be disposed on the bottom surface of the concave portion 134A and on the side surface.

The anode 120-1 is disposed on the second conductive type semiconductor layer 140-1.

According to the embodiment, the power semiconductor element 100A may further include a Schottky electrode 150-1, as illustrated in Fig. The Schottky electrode 150-1 is disposed on the convex portion 134B of the first conductive type second nitride semiconductor layer 134-1 at 134B-1 and the first conductive type second nitride semiconductor layer 134 -1) and a Schottky junction. That is, the Schottky electrode 150-1 forms a Schottky barrier above the first conductive type second nitride semiconductor layer 134-1. The second conductive semiconductor layer 140-1 extends from the side surface 134A-2 of the concave portion 134A and covers the side surface 152 and the upper surface 154 of the Schottky electrode 150-1. . Further, the second conductivity type semiconductor layer 140-1 forms an ohmic contact with the Schottky electrode 150-1. Accordingly, the second conductivity type semiconductor layer 140 illustrated in FIG. 3 may include a material that is in ohmic contact with the anode 120-1 and in ohmic contact with the Schottky electrode 150-1.

The second conductive semiconductor layer 140-1 may have various cross-sectional shapes depending on the cross-sectional shape of the concave portion 134A and the convex portion 134B.

4A to 4C, the second conductive semiconductor layer 140-1 includes first, second, and third segments 142A and 142B, a first segment 144, a third segment 146A and 146B, 148 may be repeatedly arranged. The first and second segments 142A and 142B are disposed on the bottom surface 134A-1 of the concave portion 134A and the second and fourth segments 144 and 148 are formed on both sides 134A-2 of the concave portion 134A And the third segments 146A and 146B are disposed on the side surface 152 of the Schottky electrode 150-1 and the upper surface 154 of the Schottky electrode 150-1 Section.

At least one of the second or fourth segments 144, 148 may have a cross-sectional shape that is inclined at a constant angle [theta]. For example, as shown in FIG. 4A, the second segment 144 may have a cross-sectional shape that is inclined at a positive angle?.

Also, the first segment 142A may have a flat cross-sectional shape as illustrated in FIGS. 4A and 4C, and the first segment 142B may have a sloped end 134AA, as illustrated in FIG. 4B, 134AB) cross-sectional shape.

Also, the third segment 146A may have a rectangular cross-sectional shape as illustrated in FIGS. 4A and 4B, and the third segment 146B may have a round cross-sectional shape at its edge as illustrated in FIG. 4C It is possible.

Each of the convex portions 134B in the above-described power semiconductor device 100A can implement the SBD. That is, the power semiconductor device 100A may be implemented as a plurality of SDB arrays. At this time, the first conductive type second nitride semiconductor layer 134-1 and the second conductive type semiconductor layer 140-1 in the concave portion 134A of the power semiconductor device 100A take the form of a pn diode. Also, the Schottky electrode 150-1 forms a Schottky junction with the first conductive type second nitride semiconductor layer 134-1, but is in ohmic contact with the second conductive type semiconductor layer 140-1. Therefore, by forming a low resistance path from the Schottky electrode 150-1 to the anode 120-1 through the second conductivity type semiconductor layer 140-1, the current-voltage characteristic of the power semiconductor element 100 becomes Can be improved.

In addition, the Schottky electrode 150-1 may be arranged in various forms as shown in FIG.

5 shows a cross-sectional view of a power semiconductor device 100B according to another embodiment.

The power semiconductor device 100B illustrated in FIG. 5 does not include the Schottky electrode 150-1. That is, the bottom surface 134A-1 and the side surface 134A-2 of the concave portion 134A on the upper portion of the first conductive type second nitride semiconductor layer 134-2 in the power semiconductor element 100B illustrated in Fig. The second conductive semiconductor layer 140-2 is disposed in the same manner as the power semiconductor device 100B illustrated in FIG. However, the Schottky electrode 150-1 is not disposed on the convex portion 134B of the power semiconductor element 100B illustrated in Fig.

Therefore, in the power semiconductor device 100A illustrated in FIG. 3, the second conductivity type semiconductor layer 140-1 is formed in the concave portion 134A and the convex portion (not shown) of the first conductive type second nitride semiconductor layer 134-1 The second conductive semiconductor layer 140-2 in the power semiconductor device 100B illustrated in Figure 5 is disposed over the entire surface of the bottom surface 134A-1 of the concave portion 134A and the bottom surface 134A- -2 and is not disposed in the convex portion 134B.

In addition, in the power semiconductor device 100A illustrated in FIG. 3, the anode 120-1 is disposed over the entire second conductive semiconductor layer 140-1, while the power semiconductor device 100A illustrated in FIG. The anode 120-2 is disposed on the second semiconductor layer 140-2 while filling the concave portion 134A and disposed on the convex portion 134B.

Except for this, the power semiconductor device 100B illustrated in FIG. 5 is the same as the power semiconductor device illustrated in FIG. 3, so that duplicated portions will not be described in detail.

6 shows a cross-sectional view of a power semiconductor device 100C according to another embodiment.

Unlike the anode 120-1 of the power semiconductor device 100A illustrated in FIG. 3, the anode 120-3 of the power semiconductor device 100C illustrated in FIG. 6 includes the first anode 120-3A, 2 anode 120-3B. The first anode 120-3A is disposed on the Schottky electrode 150-2 disposed on the concave portion 134A as well as on the convex portion 134B and the second anode 120-3B is disposed on the Schottky electrode 150-2 disposed on the concave portion 134A, Is disposed between the Schottky electrode 150-2 and the second conductivity type semiconductor layer 140-3 at the second electrode layer 134A.

The power semiconductor device 100B illustrated in FIG. 6 includes the Schottky electrode 150-2, but the Schottky electrode 150-2 is different from the Schottky electrode 150-1 illustrated in FIG. . That is, the Schottky electrode 150-1 illustrated in FIG. 3 is formed between the second conductivity type semiconductor layer 140-1 and the first conductive type second nitride semiconductor layer 134-1 at the convex portion 134B While the Schottky electrode 150-2 illustrated in FIG. 6 is disposed on the second conductivity type semiconductor layer 140-3 and the second anode 120-3B disposed in the concave portion 134A.

Except for the differences described above, the power semiconductor device 100C illustrated in FIG. 6 is the same as the power semiconductor device 100A illustrated in FIG. 3, so that detailed description of overlapping portions will be omitted. That is, the first conductive type second nitride semiconductor layers 134-2 and 134-3 shown in FIGS. 5 and 6 correspond to the first conductive type second nitride semiconductor layer 134-1 shown in FIG. 3 Therefore, redundant description thereof will be omitted.

The Schottky electrodes 150-1 and 150-2 illustrated in Figures 3 and 6, respectively, may include a refractory metal and a material having a high work function or a mixture of refractory metals. For example, the Schottky electrodes 150-1 and 150-2 may be formed of a metal such as Ni (Nickel), TiN (Titanium Nitride), WN (Tungsten Nitride), WSi _x (Tungsten Silicide) Tungsten, Pt, Auram, Cr, Chromium, Molybdenum, or Ag.

Further, the anodes 120-1, 120-2, and 120-3 may include at least one of a first layer or a second layer disposed over the first layer. Here, the first layer may comprise a refractory metal and a material having a high work function or a mixture of refractory metals. For example, the first layer may be formed of a material selected from the group consisting of Ni (Nickel), TiN (Titanium Nitride), WN (Tungsten Nitride), WSi _x (Tungsten Silicide) (Aurum), Cr (Chromium), Mo (Molybdenum), or Ag (Argentum), and the second layer may include Au. For example, the anodes 120-1, 120-2, and 120-3 may be a double layer structure of Ni / Au.

The second conductivity type semiconductor layers 140-1, 140-2, and 140-3 in the power semiconductor devices 100A, 100B, and 100C illustrated in FIGS. 3, 5, 134A-1 and side 134A-2, the embodiments are not so limited. That is, according to another embodiment, the second conductivity type semiconductor layers 140-1, 140-2, and 140-3 may be disposed only on the bottom surface 134A1- or the side surface 134A-2 of the concave portion 134A Of course.

When the second conductivity type semiconductor layers 140-1, 140-2, and 140-3 are p-type semiconductor layers, the second conductivity type dopant may be a p-type dopant such as B (boron).

The second conductivity type semiconductor layers 140-1, 140-2, and 140-3 are formed in the same manner as the first conductivity type second nitride layers 130-1, 130-2, and 130-3 of the first conductivity type nitride semiconductor layers 130-1, 130-2, And a material that forms a pn junction with the semiconductor layers 134-1, 134-2, and 134-3. For example, the first conductive type second nitride semiconductor layers 134-1, 134-2, and 134-3 include GaN, and the second conductive type semiconductor layers 140-1, 140-2, and 140-3 ) May comprise an insulator or NiO. Similar pinch-off effects can be obtained if the second conductivity type semiconductor layers 140-1, 140-2, and 140-3 include an insulator such as SiO ₂ instead of NiO. However, referring to FIG. 3, when the second conductivity type semiconductor layer 140-1 is formed of NiO, the following advantages are obtained when the second conductivity type semiconductor layer 140-1 is formed of an insulator.

First, the NiO layer 140-1 may serve as a low resistance conductor between the Schottky electrode 150-1 and the anode 120-1. In order to allow current to flow through the power semiconductor element 100A, the insulating layer must be removed in this region 140-1.

Also, the NiO layer 140-1 can easily absorb a hole, which is a carrier generated when a reverse bias voltage is applied to the power semiconductor element 100A and the electric field is high. For this reason, the power semiconductor element 100A can be made stronger in the breakdown condition.

In addition, the NiO layer 140-1 can inject a hole as a carrier into the first conductive type second nitride semiconductor layer 134-1 when a forward bias voltage is applied to the power semiconductor element 100A. Accordingly, conductivity modulation can be performed at which the resistance of the first conductive type nitride semiconductor layer 130-1 is reduced. In particular, the smaller the width x1 of the convex portion 134B, the further the resistance can be reduced. Therefore, the surge current capability of the power semiconductor device 100A is further improved.

4A to 4C, the first thicknesses t1, t11, and t12 of the first segments 142A and 142B of the second conductivity type semiconductor layer 140-1 and the second thicknesses t1, The second thickness t2 of the first segments 144 and 148 and the third thickness t3, t31 and t32 of the third segments 146A and 146B disposed on the Schottky electrode 150-1 are equal to each other It may or may not be.

The first and second thicknesses t1, t11, t12, and t2 of the NiO layer 140-1 should be sufficiently thick so as to withstand the maximum reverse voltage without causing punch-through. For example, if the first and second thicknesses t1, t11, t12, t2 are too thin, it may be difficult to withstand this maximum reverse voltage. However, if the first and second thicknesses t1, t11, t12, and t2 are too large, the series resistance of the diode in the ON state of the power semiconductor element 100A may increase and manufacturing cost may increase. For example, each of the first to third thicknesses t1, t11, t12, t2, t3, t31, t32 may be 20 nm to 300 nm.

FIG. 7 shows an energy band diagram when a reverse bias voltage is applied to the power semiconductor devices 100A, 100B, and 100C illustrated in FIGS. 3-6. Here, Ec represents the energy level of the conduction band and Ev represents the energy level of the valence band. Reference numeral 120 denotes the anodes 120-1, 120-2, and 120-3 illustrated in FIGS. 3 to 6, 140 denotes a second conductive semiconductor layer illustrated in FIGS. 3 to 6, 134 - 'correspond to the first conductive type second nitride semiconductor layers 134 - 1, 134 - 2, and 134 - 3 illustrated in FIGS. 3 to 6, ).

Referring to FIG. 7, the second conductive semiconductor layer 140 forms a heterojunction with the first conductive type second nitride semiconductor layer 134. Therefore, electrons can not enter the screw potential 36 into the first conductive type second nitride semiconductor layer 134 because the electrons do not exist in the second conductive type semiconductor layer 140. Therefore, when a very high reverse voltage is applied to the power semiconductor devices 100A to 100C, a very high electric field (not shown) is formed at the boundary between the second conductivity type semiconductor layer 140 and the first conductive type second nitride semiconductor layer 134 The reverse leakage current does not largely occur.

FIGS. 8A to 8F are simulation results showing two-dimensionally a state in which a depletion region is unfolded as a reverse bias voltage is increased in one section of a diode in the power semiconductor device 100A illustrated in FIG. 3 to be.

8A, 8B, 8C, 8D, 8E and 8F show that the voltages Vac applied to the cathodes 120-1 and the cathodes 110 are 0 volts, -10 volts, -50 volts, 100 volts, -300 volts, and -600 volts, respectively. Here, Ec represents the energy level of the conduction band edge, which is measured based on the voltage applied to the anode 120-1, and the unit is eV.

Referring to FIGS. 8A to 8F, the electric field is low as the interval of Ec is larger. When a reverse bias voltage is applied to the power semiconductor device 100A, the depletion region of the pn junction formed by the first conductive type second nitride semiconductor layer 134-1 and the second conductive type semiconductor layer 140-1 Is unfolded from the side of the protrusion 134B and pinches off the protrusion 134B. As a result, the electric field near the Schottky junction between the Schottky electrode 150-1 and the first conductive type second nitride semiconductor layer 134-1 at a high reverse bias voltage is suppressed. Further, the electric field in the vicinity of the pn junction between the second conductive type semiconductor layer 140-1 and the first conductive type second nitride semiconductor layer 134-1 is not suppressed. However, the leakage current density is much smaller at the pn junction than at the Schottky junction.

3 to 6, the aspect ratio, which is the ratio of the height y to the width x1 of the convex portion 134B, affects the characteristics of the power semiconductor elements 100A to 100C I can go crazy. For example, referring to FIG. 3, the electric field at the Schottky junction between the Schottky electrode 150-1 and the first conductive type second nitride semiconductor layer 134-1 and the resistance (Rsp: specific ON resistance (Y / x1) of the convex portion 134B. At a high aspect ratio (y / x1), the electric field is reduced but the resistance Rsp is increased.

9 is a graph showing a relationship in which the electric field (E-field) and the resistance Rsp in the Schottky junction depend on the aspect ratio, in which the abscissa indicates the external form ratio, the ordinate on the left indicates the electric field, And the resistance Rsp. Reference numerals 212 and 214 denote the electric field when the width x1 of the convex portion 134B is 2 占 퐉 and 1 占 퐉 respectively and reference numerals 312 and 314 denote convex portions 134B (X1) of 1 占 퐉 and 2 占 퐉, respectively.

Referring to FIG. 9, if the external shape ratio is less than 0.5, the decrease of the electric field may be insignificant. If the external form ratio is larger than 1.5, the resistance Rsp may become large and the device 100A may be difficult to manufacture. Thus, the aspect ratio (y / x1) may be 0.5 to 1.5.

In addition, the width x1 of the convex portion 134B shown in Figs. 3 to 6 may affect the characteristics of the power semiconductor elements 100A to 100C. If the width x1 of the convex portion 134B is less than 0.5 mu m, it may be difficult to manufacture the element 100A. Therefore, the width x1 of the convex portion 134B may be 0.5 mu m to 4 mu m.

The resistance Rsp of the power semiconductor elements 100A to 100C may depend on the width x2 of the concave portion 134A. If the width x2 of the concave portion 134A is larger than 1.5 占 퐉, the resistance Rsp may increase and if the width x2 of the concave portion 134A is smaller than 0.5 占 퐉, It can be difficult. Therefore, the width x2 of the concave portion 134A may be 0.5 mu m to 1.5 mu m.

Figs. 10-13 illustrate plan views of the power semiconductor devices 100A-100C illustrated in Figs. 3-6. Here, '130' corresponds to the first conductive type nitride semiconductor layers 130-1, 130-2, and 130-3. In FIGS. 10 to 13, the second conductivity type semiconductor layers 140-1, 140-2 and 140-3 and the Schottky electrodes 150-1 and 150-2 are omitted for convenience. However, not only the second conductivity type semiconductor layers 140-1, 140-2, 140-3 may be disposed on at least one of the bottom surface or the side surface of the concave portion 134A, The Schottky electrode 150-1 illustrated in FIG. 3 may be disposed on the upper portion or the Schottky electrode 150-2 illustrated in FIG. 6 may be disposed on the recessed portion 134A.

According to one embodiment, as illustrated in Fig. 10, the concave portion 134A and the convex portion 134B may have a planar shape arranged alternately and repeatedly in the horizontal direction. Alternatively, unlike the example illustrated in Fig. 10, the concave portion 134A and the convex portion 134B may have a planar shape arranged alternately and repeatedly in the vertical direction.

According to another embodiment, as illustrated in Fig. 11, the concave portion 134A and the convex portion 134B may have a planar shape arranged in a checkered pattern.

According to another embodiment, as illustrated in FIG. 12, the recess 134A may have a polygonal planar shape, for example, a hexagonal planar shape. In the embodiment illustrated in Fig. 10 or 11, the area occupied by the concave portion 134A and the convex portion 134B is the same. However, in the embodiment illustrated in Fig. 12, the area occupied by the concave portion 134A is 1/3 of the total area, while the area occupied by the convex portion 134B is 2/3 of the total area.

According to another embodiment, as illustrated in Fig. 13, the recess 134A may have a circular planar shape. In the embodiment illustrated in FIG. 11 or 12, since the edge of the recess 134A is angularly planar, the electric field can be concentrated at the edge, while the edge of the recess 134A, as illustrated in FIG. 13, This field concentration can be reduced if the seat is formed in a circular planar shape.

Hereinafter, a method of manufacturing the power semiconductor element 100A illustrated in FIG. 3 will be described with reference to FIGS. 14A to 14E, which are described below, but the power semiconductor element 100A illustrated in FIG. 3 is the same as FIGS. 14A to 14E May also be produced by a method other than the method shown in Fig. It is of course also possible that the power semiconductor devices 100B and 100C illustrated in Fig. 5 or 6 may be fabricated at the level of those skilled in the art by modifying the process sectional views shown in Figs. 14A to 14E.

Figs. 14A to 14E show process cross-sectional views for explaining a manufacturing method of the power semiconductor element 100A illustrated in Fig. 3.

Referring to FIG. 14A, a first conductive type first nitride semiconductor layer 132 and a first conductive type second nitride semiconductor layer 134-1 are sequentially formed. For example, the first conductive type first and second nitride semiconductor layers 132 and 134-1 may be formed by MOCVD (Metal Organic Chemical Vapor Deposition). In addition, the first conductive type second nitride semiconductor layer (134-1) may be formed at a doping concentration of 2x10 ¹⁶ atoms / ㎤ a thickness of 6 ㎛.

14B, a Schottky metal layer 150-1 may be deposited on the first conductive type second nitride semiconductor layer 134-1 by sputtering to have a thickness of 300 nm. have.

Referring to FIG. 14C, the Schottky metal layer 150-1 and the first conductive type second nitride semiconductor layer 134-1 are subjected to reactive ion etching (RIE) to have a width (x2 ) And the depth y can be formed at a plurality of intervals of 1 占 퐉.

14D, the second conductive semiconductor layer 140-1 is formed on the side surfaces of the concave portion 134A of the first conductive type nitride semiconductor layer 130-1 and the Schottky electrode 150-1, And can be deposited to a thickness of 20 nm to 300 nm while covering the upper portion. For example, Ni is deposited on the Schott electrode 150-1 and the second conductive type second nitride semiconductor layer 134-1 by sputtering, and then Ni is deposited at a temperature of 500 to 700 DEG C in an oxygen atmosphere, The p-type semiconductor layer having an energy band gap of 3.7 eV can be formed as the second conductivity type semiconductor layer 140-1.

14E, an anode 120-1 is formed on the second conductive type semiconductor layer 140-1, a cathode 110-1 is formed on the lower side of the first conductive type nitride semiconductor layer 130-1, ) Can be formed. For example, Ni may be formed on the second conductive type semiconductor layer 140-1 at a thickness of 10 nm to 1000 nm, for example, 200 nm, and may be formed on the Ni to have a thickness of 10 nm to 10000 nm, for example, Au may be formed to a thickness to form the anode 120-1. In addition, Ti may be formed under the first conductive type nitride semiconductor layer 130-1, and Au may be formed on the Ti to form the cathode 110. Alternatively, Au may be formed under the first conductive type nitride semiconductor layer 130-1, and Ti may be formed on Au to form the cathode 110. [

15A and 15B show characteristic graphs of the current-voltage characteristics of the present embodiment and those of the present embodiment, respectively. In each graph, the abscissa represents the voltage and the ordinate the current.

The first conductivity type nitride semiconductor layers 130-1, 130-2, and 130-3 and the second conductivity type semiconductor layers 140-1, 140-2, and 140-3 in the power semiconductor devices 100A to 100C described above, 15b, respectively, the electric field near the Schottky junction is kept low when a high reverse bias voltage is applied to the power semiconductor elements 100A to 100C, The reverse leakage current can be reduced as shown.

The power semiconductor devices described above can be used in various fields such as photodetectors, gas sensors, liquid sensors, pressure sensors, multi-function sensors such as pressure and temperature, sensor, a power switching transistor, a microwave transistor, a power converter, and the like.

Hereinafter, the configuration and operation of the power converter including the power semiconductor device according to the above-described embodiment will be described with reference to the accompanying drawings.

16 shows a circuit diagram of the power semiconductor device according to the embodiment. Here, Vdc represents a DC supply voltage.

The power semiconductor device shown in FIG. 16 includes a freewheel diode 300 and an IGBT (Isulated Gate Bipolar Transistors) 400 and an inductor L as a passive element.

The freewheel diode 300 shown in FIG. 16 is functionally separated to operate as a pn diode D or an SBD, and has a gate for selecting a separated function. Such a diode 300 is also referred to as a gate controlled diode. Here, the SBD may correspond to the power semiconductor devices 100A, 100B, and 100C shown in FIG. 3, FIG. 5, or FIG.

The gate control diode 300 operates as a pn diode D in the conduction state and acts as the SBD in the reverse direction to take full advantage of the two types.

The gate of the IGBT 400 connected in series with the gate control diode 300 maintains the turn-off state until just before the IGBT 400 is turned on. The gate of the gate control diode 300 is connected to the gate of the pn diode D To switch to the SBD, it is turned on to be in the conducting state to prepare for the reverse state.

Since the Schottky diode is already in the conductive state when the gate of the IGBT 400 is turned on, the accumulated charge amount is much smaller than the charge amount in the case of the pn diode (D). Therefore, the reverse current can be reduced. Also, just before the IGBT 400 is turned off, the gate of the gate control diode 300 switches from the SBD to the pn diode D to reduce the forward voltage in the conduction state. After turning on and just before the IGBT 400 is turned on again, the pn diode D becomes conductive and the conductive state is switched from the pn diode D to the SBD. The above-described operation is repeatedly performed.

To further drive the gate control diode 300 and the IGBT 400, a gate drive circuit (not shown) may be further arranged. The gate drive circuit generates a gate control signal (V _GA ) to be supplied to the gate control diode (300) to switch the gate from the pn diode (D) to the SBD. Further, the gate driving circuit generates the gate control signal (V _GE ) and outputs it to the IGBT (400).

That is, at least the pn diode D operates when the current flows forward through the gate control diode 300, and the gate drive circuit operates such that the SBD operates mainly when the gate control diode 300 recovers in the reverse direction 300, and 400, respectively.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood that various modifications and applications are possible. For example, each component specifically shown in the embodiments can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

100A, 100B, 100C: power semiconductor device 110: cathode
120, 120-1, 120-2, 120-3: anode
130-1, 130-2, and 130-3: a first conductive type nitride semiconductor layer
132: first conductive type first nitride semiconductor layer
134, 134-1, 134-2, and 134-3: a first conductive type second nitride semiconductor layer
134A: concave portion 134B: convex portion
140, 140-1, 140-2, 140-3: a second conductivity type semiconductor layer
142A, 142B: first segment 144: second segment
146A, 146B: third segment 148: fourth segment
150-1, 150-2: Schottky electrode

Claims (22)

cathode;
A first conductive type nitride semiconductor layer which is disposed on the cathode and in which recesses and convex portions are alternately arranged repeatedly at least once;
A second conductive semiconductor layer disposed on at least one of a bottom surface and a side surface of the concave portion; And
And a positive electrode disposed on the second conductive type semiconductor layer. The power semiconductor element according to claim 1, wherein the concave portion and the convex portion are periodically alternately repeatedly arranged. The power semiconductor element according to claim 1, wherein the concave portion and the convex portion are alternately and repeatedly arranged in an aperiodic manner. 2. The nitride semiconductor light emitting device according to claim 1, further comprising a Schottky electrode disposed on the convex portion and forming a Schottky junction with the first conductive type nitride semiconductor layer,
And the second conductivity type semiconductor layer extends from a side surface of the recess to cover the side surface and the upper surface of the Schottky electrode. The semiconductor light emitting device according to claim 1, further comprising a Schottky electrode disposed on the second conductivity type semiconductor layer in the recess,
Wherein the anode is disposed on the Schottky electrode and the convex portion. The power semiconductor device according to claim 4, wherein the second conductivity type semiconductor layer includes a material which makes ohmic contact with the anode and the Schottky electrode, respectively. 6. The power semiconductor device of claim 5, wherein the second conductivity type semiconductor layer comprises a material in ohmic contact with the Schottky electrode. The power semiconductor device according to claim 4 or 5, wherein the Schottky electrode comprises a refractory metal or a mixture of refractory metals. 5. The method of claim 4 or 5, wherein the Schottky electrode is Ni (Nickel), TiN (Titanium Nitride), WN (Tungsten Nitride), WSi X (Tungsten Silicide) ( where, X is a natural number), W (Tungsten) , Pt (Platinum), Au (Aurum), Cr (Chromium), Mo (Molybdenum), or Ag (Argentum). The method of claim 1,
A first layer or a second layer disposed over the first layer,
The first layer may include at least one selected from the group consisting of Ni (Nickel), TiN (Titanium Nitride), WN (Tungsten Nitride), WSi _x (Tungsten Silicide), where X is a natural number, W, Tungsten, , Cr (Chromium), Mo (Molybdenum), or Ag (Argentum), and the second layer comprises Au. The method of claim 1, wherein the second conductive semiconductor layer
And a material forming a pn junction with the first conductive type nitride semiconductor layer. 12. The power semiconductor device according to claim 11, wherein the second conductivity type semiconductor layer comprises NiO. The power semiconductor device according to claim 1, wherein the aspect ratio of the height of the convex portion to the width is 0.5 to 1.5. The power semiconductor device according to claim 1, wherein a width of the convex portion is 0.5 占 퐉 to 4 占 퐉. The power semiconductor device according to claim 1, wherein the width of the recess is 0.5 탆 to 1.5 탆. The power semiconductor device according to claim 1, wherein the second conductivity type semiconductor layer has a thickness of 20 nm to 300 nm. The power semiconductor element according to claim 2 or 3, wherein the concave portion and the convex portion have a planar shape alternately arranged in a horizontal direction. The power semiconductor element according to claim 2 or 3, wherein the concave portion and the convex portion have a planar shape alternately arranged in the vertical direction. The power semiconductor element according to claim 2 or 3, wherein the concave portion and the convex portion have a planar shape alternately arranged in a checkerboard shape. The power semiconductor device according to claim 1, wherein the recess has a polygonal or circular planar shape. The power semiconductor element according to claim 1, wherein at least one of the concave portion or the convex portion has a sloped cross-sectional shape. A power semiconductor device according to any one of claims 1 to 7, 10 to 18, and 20 to 21, And
And a passive element electrically coupled to the power semiconductor device.

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