KR20220096786A - Schottky barrier diode and method for manufacturing the same - Google Patents

Abstract

Provided is a Schottky barrier diode, which comprises: a first semiconductor layer including a Ga_2O_3-based monocrystal; a second semiconductor layer disposed on the first semiconductor layer to include a Ga_2O_3-based monocrystal; a third semiconductor layer disposed on the second semiconductor layer to have a trench opened toward the surface opposite to the surface facing the second semiconductor layer and include a Ga_2O_3-based monocrystal; an anode electrode disposed on the third semiconductor layer and in the trench; a cathode electrode disposed under the first semiconductor layer; and an insulation unit disposed on the bottom surface of the trench. Accordingly, an electrical current in an on-state can be reduced and resistance in the on-state can be minimized. In addition, current leakage caused by focusing on an electric field in a lower end of the trench can be reduced.

Description

Schottky barrier diode and manufacturing method thereof

The present invention relates to a Schottky barrier diode and a method for manufacturing the same.

A power semiconductor device requires a low on-resistance or low saturation voltage in order to reduce power loss in the conduction state while allowing a very large current to flow. In addition, a characteristic capable of withstanding a reverse high voltage applied to both ends of the power semiconductor device in an off state or a moment when the switch is turned off, that is, a high breakdown voltage characteristic is basically required.

The concentration and thickness of the epitaxy layer region or drift region of the raw material for manufacturing the power semiconductor device are determined according to the rated voltage required by the power system. According to the Poisson equation, the higher the breakdown voltage is, the lower the concentration and the thicker the drift region, but this increases the on-resistance and reduces the forward current density. The structure of the power semiconductor device should be designed to overcome such a trade-off relationship as much as possible.

With the recent trend of large and large-capacity applications, the need for power semiconductor devices having high breakdown voltage, high current, and high-speed switching characteristics is emerging. In the case of gallium oxide (Ga ₂ O ₃ )-based power devices, due to superior characteristics than existing silicon (Si) devices and gallium nitride (GaN) devices and silicon carbide (SiC) devices that are currently in mass production, the It is pointed out as a device that can satisfy the characteristics.

However, in general, in order to improve the leakage current reduction characteristics of a Schottky Barrier Diode (SBD), a p-type semiconductor is formed at the bottom of the Schottky junction by an ion implantation process (Junction Barrier Schottky, JBS). ) structure is applied, but in the case of gallium oxide material, it is difficult to apply the JBS structure because it is difficult to form a p-type semiconductor.

One embodiment provides a Schottky barrier diode capable of reducing leakage current due to electric field concentration at the bottom of a trench while minimizing a decrease in on-state current and an increase in on-resistance.

Another embodiment provides a method of manufacturing a Schottky barrier diode.

According to one embodiment, a first semiconductor layer including a Ga ₂ O ₃ based single crystal, located on the first semiconductor layer, and located on the second semiconductor layer including a Ga ₂ O ₃ based single crystal, the second semiconductor layer, A third semiconductor layer including a Ga ₂ O ₃ based single crystal having a trench opening to a surface opposite to the surface opposite to the second semiconductor layer, an anode electrode positioned on and in the trench on the third semiconductor layer, and a first semiconductor layer Provided is a Schottky barrier diode including a cathode electrode positioned below and an insulating portion positioned on a bottom surface of a trench.

The trench may pass through the third semiconductor layer.

The insulating portion may be located on the entire bottom surface of the trench.

A thickness of the insulating portion may be smaller than a depth of the trench.

The insulating part may include SiO ₂ , Al ₂ O ₃ , HfO ₂ , Si ₂ N ₃ , or a combination thereof.

The donor concentration of the second semiconductor layer may be 1.0Х10 ¹⁴ cm ^-3 to 1.0Х10 ¹⁷ cm ^-3 .

The donor concentration of the third semiconductor layer may be 1.0Х10 ¹⁴ cm ^-3 to 1.0Х10 ¹⁷ cm ^-3 .

The donor concentration of the third semiconductor layer may be higher than or equal to the donor concentration of the second semiconductor layer.

According to another embodiment, forming a first semiconductor layer including a Ga ₂ O ₃ based single crystal, forming a second semiconductor layer including a Ga ₂ O ₃ based single crystal on the first semiconductor layer, a second semiconductor Forming a third semiconductor layer including a Ga ₂ O ₃ based single crystal on the layer, forming a trench by etching the third semiconductor layer, forming an insulating portion on a bottom surface of the trench, on the third semiconductor layer, and A method of manufacturing a Schottky barrier diode is provided, comprising: forming an anode electrode inside the trench; and forming a cathode electrode under the first semiconductor layer.

The forming of the insulating portion may be performed by forming an insulating layer on the entire surface of the third semiconductor layer in which the trench is formed, and removing the insulating layer in the remaining portion except for the bottom surface of the trench through an etch back process.

The Schottky barrier diode according to the exemplary embodiment may reduce leakage current due to electric field concentration at the bottom of the trench while minimizing reduction in on-state current and increase in on-resistance.

1 is a diagram illustrating a cross-section of a Schottky barrier diode according to an embodiment.
2 is a diagram illustrating a cross-section of a Schottky barrier diode according to another embodiment.
3 is a view sequentially illustrating a method of manufacturing a Schottky barrier diode according to an exemplary embodiment.
4 and 5 are the off-state leakage current measurement results of the Schottky barrier diodes manufactured in Example 1 and Comparative Example 1, respectively.

Advantages and features of the techniques described hereinafter, and methods of achieving them, will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the implemented form may not be limited to the embodiments disclosed below. Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used with meanings commonly understood by those of ordinary skill in the art. In addition, terms defined in a commonly used dictionary are not to be interpreted ideally or excessively unless clearly defined in particular. In the entire specification, when a part "includes" a certain component, this means that other components may be further included, rather than excluding other components, unless otherwise stated.

The singular also includes the plural, unless the phrase specifically dictates otherwise.

In order to clearly express various layers and regions in the drawings, the thicknesses are enlarged. Throughout the specification, like reference numerals are assigned to similar parts.

When a part, such as a layer, film, region, plate, etc., is said to be “on” another part, it includes not only cases where it is “directly on” another part, but also cases where there is another part in between. Conversely, when we say that a part is "just above" another part, we mean that there is no other part in the middle.

A Schottky barrier diode according to an exemplary embodiment includes a first semiconductor layer including a Ga ₂ O ₃ based single crystal, located on the first semiconductor layer, and a second semiconductor layer including a Ga ₂ O ₃ based single crystal and a second semiconductor layer A third semiconductor layer comprising a Ga ₂ O ₃ based single crystal, which is positioned thereon and has a trench opened to a surface opposite to the surface facing the second semiconductor layer, an anode electrode located on and in the trench on the third semiconductor layer, and a second 1 It includes a cathode electrode positioned under the semiconductor layer, and an insulating part positioned on a bottom surface of the trench.

1 is a diagram illustrating a cross-section of a Schottky barrier diode according to an embodiment, and FIG. 2 is a diagram illustrating a cross-section of a Schottky barrier diode according to another embodiment.

1 and 2 , the Schottky barrier diode 10 includes a first semiconductor layer 100 , a second semiconductor layer 200 positioned on the first semiconductor layer 100 , and a second semiconductor layer 200 . It may include a third semiconductor layer 300 positioned above, an anode electrode 500 positioned on the third semiconductor layer 300 , and a cathode electrode 600 positioned under the first semiconductor layer 100 .

In the Schottky barrier diode 10, by applying a forward voltage (the anode electrode 500 side is a positive potential) between the anode electrode 500 and the cathode electrode 600, the anode electrode ( 500 ) and the energy barrier at the interface between the second semiconductor layer 200 is lowered, and a current flows from the anode electrode 500 to the cathode electrode 600 . On the other hand, when a reverse voltage (negative potential on the anode electrode 500 side) is applied between the anode electrode 500 and the cathode electrode 600, no current flows due to the Schottky barrier.

The first semiconductor layer 100 may include, as a donor, an n+-type Ga ₂ O ₃ based single crystal including a group IV element such as Si or Sn. The donor concentration of the first semiconductor layer 100 may be, for example, 1.0Х10 ¹⁸ cm ^-3 to 1.0Х10 ²⁰ cm ^-3 .

The Ga ₂ O ₃ single crystal refers to a Ga ₂ O ₃ single crystal or a Ga ₂ O ₃ single crystal to which an element such as Al or In is added. For example, Al and In are added Ga ₂ O ₃ single crystal (Ga _x Al _y In _(1-xy) ) ₂ O ₃ (0<x≤1, 0≤y<1, 0<x+y≤1 ) can be When Al is added, the band gap is widened, and when In is added, the band gap is narrowed. In addition, the Ga ₂ O ₃ single crystal may have, for example, an α-type or a β-type crystal structure.

The second semiconductor layer 200 may include, as a donor, an n-type Ga ₂ O ₃ based single crystal including a group IV element such as Si or Sn. The donor concentration of the second semiconductor layer 200 is lower than the donor concentration of the first semiconductor layer 100 . For example, the donor concentration of the second semiconductor layer 200 may be 1.0Х10 ¹⁴ cm ^-3 to 1.0Х10 ¹⁷ cm ^-3 . The second semiconductor layer 200 may be, for example, an epitaxial layer epitaxially grown on the first semiconductor layer 100 that is a Ga ₂ O ₃ based single crystal substrate.

The third semiconductor layer 300 may include, as a donor, an n-type Ga ₂ O ₃ based single crystal including a group IV element such as Si or Sn. For example, the donor concentration of the third semiconductor layer 300 may be 1.0Х10 ¹⁴ cm ^-3 to 1.0Х10 ¹⁷ cm ^-3 .

The donor concentration of the third semiconductor layer 300 may be lower than the donor concentration of the first semiconductor layer 100 and higher than or equal to the donor concentration of the second semiconductor layer 200 . When the donor concentration of the third semiconductor layer 300 is the same as that of the second semiconductor layer 200 , the third semiconductor layer 300 may be a part of the second semiconductor layer 200 . In this case, the second semiconductor layer 200 and the third semiconductor layer 300 may be simultaneously formed.

When the donor concentration of the third semiconductor layer 300 is higher than the donor concentration of the second semiconductor layer 200 , the third semiconductor layer 300 is epitaxially grown on the second semiconductor layer 200 , for example. It can be a layer. The third semiconductor layer 300 may minimize a decrease in on-state current and an increase in on-resistance due to the insulating part 420 , which will be described later.

1 shows a case where the donor concentration of the third semiconductor layer 300 is higher than the donor concentration of the second semiconductor layer 200, and FIG. 2 shows that the donor concentration of the third semiconductor layer 300 is the second semiconductor layer ( 200) of the donor concentration is shown.

The third semiconductor layer 300 has a trench 410 that is opened to a surface opposite to the surface facing the second semiconductor layer 200 .

In general, a junction barrier Schottky (JBS) structure in which a p-type semiconductor is formed at the bottom of a Schottky junction by an ion implantation process in order to improve the leakage current reduction characteristics of a Schottky Barrier Diode (SBD). However, in the case of gallium oxide (Ga ₂ O ₃ ) material, it is difficult to apply the JBS structure because it is difficult to form a p-type semiconductor. Accordingly, the trench 410 structure is applied for the purpose of reducing the on-resistance of the device. As the junction area between the anode electrode 500 and the gallium oxide (Ga ₂ O ₃ ) increases through the trench 410 , the current increases and the on-resistance decreases.

The depth of the trench 410 may be greater than, equal to, or shallower than the thickness of the third semiconductor layer 300 . That is, when the depth of the trench 410 is greater than the thickness of the third semiconductor layer 300 , the trench 410 passes through the third semiconductor layer 300 , and the bottom surface of the trench 410 is the second semiconductor layer. (200) may be located. When the depth of the trench 410 is equal to the thickness of the third semiconductor layer 300 , the trench 410 passes through the third semiconductor layer 300 , and the bottom surface of the trench 410 is the second semiconductor layer 200 . ) and the third semiconductor layer 300 . When the depth of the trench 410 is shallower than the thickness of the third semiconductor layer 300 , the trench 410 is located in the third semiconductor layer 300 , and the bottom surface of the trench 410 is the third semiconductor layer 300 . can be located in

On the other hand, although the effect of reducing the on-resistance and increasing the current density can be obtained through the trench 410 as described above, the breakdown voltage is higher than that of a general Schottky barrier diode due to the electric field concentrated at the bottom of the trench 410 during off-state operation. There is a disadvantage in that it decreases and the leakage current increases.

Accordingly, the Schottky barrier diode 10 according to an embodiment includes the insulating portion 420 positioned on the bottom surface of the trench 410 . The insulating part 420 may reduce leakage current due to the concentration of an electric field at the lower end of the trench 410 .

The insulating part 420 may be located on a part or the whole of the bottom surface of the trench 410 . 1 and 2 illustrate that the insulating portion 420 covers the entire bottom surface of the trench 410 .

The insulating part 420 is positioned in the third semiconductor layer 300 , between the third semiconductor layer 300 and the second semiconductor layer 200 , or the second semiconductor layer according to the depth of the trench 410 . (200) may be located. That is, when the depth of the trench 410 is greater than the thickness of the third semiconductor layer 300 , the insulating part 420 may be located in the second semiconductor layer 200 . When the depth of the trench 410 is equal to the thickness of the third semiconductor layer 300 , the insulating part 420 may be positioned between the third semiconductor layer 300 and the second semiconductor layer 200 . When the depth of the trench 410 is shallower than the thickness of the third semiconductor layer 300 , the insulating part 420 may be positioned between the third semiconductor layer 300 and the second semiconductor layer 200 . 1 and 2 illustrate that the insulating portion 420 is positioned between the third semiconductor layer 300 and the second semiconductor layer 200 of the trench 410 .

The thickness of the insulating portion 420 may be smaller than the depth of the trench 410 . When the thickness of the insulating portion 420 is greater than the depth of the trench 410 , the effect of reducing the on-resistance and increasing the current density obtained through the formation of the trench 410 may be insignificant.

The insulating portion 420 may include a material having a high dielectric constant in order to reduce leakage current due to electric field concentration at the lower end of the trench 410 . For example, the insulating part 420 may include SiO ₂ , Al ₂ O ₃ , HfO ₂ , Si ₂ N ₃ , or a combination thereof.

The anode electrode 500 is positioned on the third semiconductor layer 300 and in the trench 410 , and is in Schottky contact with the second semiconductor layer 200 and/or the third semiconductor layer 300 . The anode electrode 500 may include Pt, Pd, Au, Ni, Ag, Cu, Al, Mo, In, Ti, polycrystalline Si, oxides thereof, nitrides thereof, or alloys thereof. In addition, the anode electrode 500 may include a multilayer structure in which different metal films are stacked, for example, Pt/Au, Pt/Al, Pd/Au, Pd/Al, or Pt/Ti/Au and Pd/Ti/Au. can

As the anode electrode 500 is also located in the trench 410 , it may include a groove that is opened to a surface opposite to the surface facing the trench 410 at a position corresponding to the trench 410 .

The cathode electrode 600 is positioned under the first semiconductor layer 100 and is in ohmic contact with the first semiconductor layer 100 . The cathode electrode 600 may include a metal such as Ti. In addition, the cathode electrode 600 may include a multilayer structure in which different metal films are stacked, for example, Ti/Au or Ti/Al. In this case, in order to ensure ohmic contact between the cathode electrode 600 and the first semiconductor layer 100 , a layer in contact with the first semiconductor layer 100 of the cathode electrode 600 may include Ti.

3 is a view sequentially illustrating a method of manufacturing a Schottky barrier diode according to an exemplary embodiment.

Referring to FIG. 3 , a substrate for the first semiconductor layer 100 including an n+ type Ga ₂ O ₃ based single crystal is prepared, and the n− type is formed on the first surface of the first semiconductor layer 100 by first epitaxial growth. A second semiconductor layer 200 including a Ga ₂ O ₃ based single crystal is formed ( S1 ), and a third layer including an n-type Ga ₂ O ₃ based single crystal is formed by a second epitaxial growth on the second semiconductor layer 200 . A semiconductor layer 300 is formed (S2).

Here, the third semiconductor layer 300 may be formed by implanting n ions into the second semiconductor layer 200 instead of epitaxial growth. Also, for example, when the doping concentration of the third semiconductor layer 300 is the same as that of the second semiconductor layer 200 , the forming step of the third semiconductor layer 300 may be omitted.

The third semiconductor layer 300 and optionally the second semiconductor layer 200 are etched to form a trench 410 ( S3 ). For example, a buffer layer including a transmissive portion is disposed on the third semiconductor layer 300 , and then the third semiconductor layer 300 and optionally the second semiconductor layer 200 are etched using the buffer layer as a mask to form a plurality of trenches. (410) is formed. The buffer layer may include silicon oxide (SiO ₂ ) or silicon nitride (SiN _x ) having a good etch selectivity.

Here, the etching of the third semiconductor layer 300 and the second semiconductor layer 200 may be performed using at least one of SF ₆ , NF ₃ and Cl ₂ gas. The etching may be performed in the chamber, the pressure may be 30 mT or more, the amount of the etching gas may be 30 sccm or more, the source power may be 300 W, and the bias power may be 200 W or less.

Depending on the degree of etching of the trench 410 , the bottom surface of the trench 410 is located on the third semiconductor layer 300 , between the third semiconductor layer 300 and the second semiconductor layer 200 , or the second It may be located in the semiconductor layer 200 .

An insulating portion 420 is formed on the bottom surface of the trench 410 ( S4 and S5 ).

For example, in the insulating part 420 , the insulating layer 421 is formed on the entire surface of the third semiconductor layer 300 in which the trench 410 is formed ( S4 ), and the trench 410 is formed by an etch back process. This may be achieved by removing the insulating layer 421 of the remaining portion except for the bottom surface (S5).

Next, the anode electrode 500 is formed on the third semiconductor layer 300 and in the trench 410 , and the cathode electrode 600 is formed on the second surface of the first semiconductor layer 100 .

Hereinafter, specific embodiments of the invention are presented. However, the examples described below are only for specifically illustrating or explaining the invention, and thus the scope of the invention is not limited thereto.

In the Schottky barrier diode of the first embodiment, as shown in FIG. 2 , the insulating part 420 is installed on the bottom surface of the trench 410 , but the doping concentration of the third semiconductor layer 300 is the second semiconductor layer 200 . ), and the Schottky barrier diode of Example 2 is provided with an insulating part 420 on the bottom surface of the trench 410 as shown in FIG. 1, but the third semiconductor layer 300 was manufactured so that the doping concentration of the second semiconductor layer 200 was higher than that of the second semiconductor layer 200, and the Schottky barrier diode of Comparative Example 1 was performed except that the insulating part 420 was not installed on the bottom surface of the trench 410 It was prepared in the same manner as in Example 1.

4 and 5 are the off-state leakage current measurement results of the Schottky barrier diodes manufactured in Example 1 and Comparative Example 1, respectively. The off-state leakage current of FIGS. 4 and 5 was measured using a Sentaurus TCAD manufactured by Synopsys.

Referring to FIGS. 4 and 5 , it can be seen that the Schottky barrier diode manufactured in Example 1 includes an insulating part, thereby suppressing leakage current at the lower end of the trench (A).

In addition, the electrical characteristics of the Schottky barrier diodes prepared in Examples 1, 2 and Comparative Example 1 were measured, and the results are summarized in Table 1. Electrical characteristics of the Schottky barrier diodes prepared in Examples 1, 2 and Comparative Example 1 were measured using a Sentaurus TCAD manufactured by Synopsys.

division Breakdown voltage (V)
@ Ir=1E-8A/㎛ Leakage current (A/㎛)
@ Vr=600V on resistance
(mΩ·㎠) Performance index ¹⁾
(MW/cm2) Comparative Example 1 810 2.547E-10 1.55 423 Example 1 (Single Epilayer) 1005 2.012E-11 1.95 517 Example 2 (Double Epilayer) 992 2.372E-11 1.92 513

1) figure of merits = breakdown voltage ² / on-resistance

Referring to Table 1, it can be seen that in the Schottky barrier diode manufactured in Example 2, the breakdown voltage is increased by 22% and the off-state leakage current is reduced by 91%.

That is, although the on-resistance increases due to the reduction of the Schottky area due to the insulating part, the figure of merit of the device including both breakdown voltage and on-resistance characteristics increases by 21%. This means that the breakdown voltage of the Schottky barrier diode manufactured in the embodiment is higher when designed with the same on-resistance, or that the on-resistance of the Schottky barrier diode manufactured in the embodiment is lower when designed with the same breakdown voltage do.

Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also presented. It belongs to the scope of the right of the invention.

10: Schottky barrier diode
100: first semiconductor layer
200: second semiconductor layer
300: third semiconductor layer
410: trench
420: insulation
421: insulating layer
500: anode electrode
600: cathode electrode

Claims (10)

Ga ₂ O ₃ A first semiconductor layer comprising a single crystal,
A second semiconductor layer positioned on the first semiconductor layer and comprising a Ga ₂ O ₃ based single crystal;
A third semiconductor layer positioned on the second semiconductor layer and including a Ga ₂ O ₃ based single crystal having a trench opened to a surface opposite to the surface facing the second semiconductor layer;
an anode electrode positioned over the third semiconductor layer and in the trench; and
and a cathode electrode positioned under the first semiconductor layer,
A schottky barrier diode comprising an insulating portion positioned on a bottom surface of the trench. In claim 1,
and the trench passes through the third semiconductor layer. In claim 1,
The insulating portion is located on the entire bottom surface of the trench, Schottky barrier diode. In claim 1,
The thickness of the insulating portion is less than the depth of the trench, Schottky barrier diode. In claim 1,
The insulating portion comprises SiO ₂ , Al ₂ O ₃ , HfO ₂ , Si ₂ N ₃ , or a combination thereof, a Schottky barrier diode. In claim 1,
The donor concentration of the second semiconductor layer is 1.0Х10 ¹⁴ cm ^-3 to 1.0Х10 ¹⁷ cm ^-3 , a Schottky barrier diode. In claim 1,
The third semiconductor layer has a donor concentration of 1.0Х10 ¹⁴ cm ^-3 to 1.0Х10 ¹⁷ cm ^-3 , a Schottky barrier diode. In claim 1,
and a donor concentration in the third semiconductor layer is greater than or equal to a donor concentration in the second semiconductor layer. Forming a first semiconductor layer comprising a Ga ₂ O ₃ single crystal,
forming a second semiconductor layer including a Ga ₂ O ₃ based single crystal on the first semiconductor layer;
forming a third semiconductor layer including a Ga ₂ O ₃ based single crystal on the second semiconductor layer;
forming a trench by etching the third semiconductor layer;
forming an insulating part on the bottom surface of the trench;
forming an anode electrode over the third semiconductor layer and in the trench; and
forming a cathode electrode under the first semiconductor layer
Including, a method of manufacturing a Schottky barrier diode. In claim 9,
The step of forming the insulating part,
forming an insulating layer on the entire surface of the third semiconductor layer in which the trench is formed;
A method of manufacturing a Schottky barrier diode comprising removing the insulating layer of the remaining portion except for the bottom surface of the trench by an etch back process.

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