MOS junction barrier Schottky diode

Abstract

An MOS junction barrier Schottky diode relates to the technical field of power semiconductor devices. The N-type substrate, the N-type epitaxial layer, the deep P region, the trench gate, the trench gate oxide layer, the conductive enhancement region and the isolation oxide layer are arranged between the cathode metal and the anode metal, the lower surface of the N-type substrate is in contact with the cathode metal, the upper surface of the N-type substrate is in contact with the lower surface of the N-type epitaxial layer, and the upper surface of the N-type epitaxial layer is in contact with the P region. The conductive enhancement region is arranged on the outer surface of the trench gate oxide layer and is in contact with the N-type epitaxial layer, and a part of the trench gate oxide layer, the conductive enhancement region, the isolation oxide layer and a part of the deep P region are respectively in contact with a part of the anode metal. According to the MOS junction barrier Schottky diode structure, the groove gate MOS structure is inserted into the adjacent P region of a traditional junction barrier Schottky (JBS) diode, so that the carrier density at a channel is improved, the channel resistance is reduced, and the reverse electric leakage characteristic and the forward voltage drop are further improved.

Description

Technical Field

[0001] The invention relates to the technical field of power semiconductor devices, and in particular to a MOS junction barrier Schottky diode structure. Background Art

[0002] In traditional Schottky barrier diodes, the forward conduction current flows through the Schottky barrier, and the reverse blocking capability also depends on the height of the Schottky barrier, that is, there is a serious coupling problem between the on-state voltage drop and the reverse leakage current. The junction barrier Schottky (JBS) diode inserts deep P regions on both sides of the Schottky contact, and uses the shielding effect of the PN junction barrier on the Schottky contact to reduce the coupling relationship between the two. However, the conductivity of the drift region of the JBS diode is limited by the doping concentration, so that its forward voltage drop cannot be further reduced, and the coupling with the reverse leakage current has not been relieved to the maximum extent.

[0003] Therefore, the prior art is insufficient and needs to be improved. Summary of the invention

[0004] In order to overcome the above technical problems, the present invention provides a MOS Junction Barrier Schottky (MJBS) diode structure.

[0005] The solution to the technical problem provided by the present invention is to provide a MOS junction barrier Schottky diode structure, comprising a cathode metal, an anode metal, an N-type substrate, an N-type epitaxial layer, a deep P region, a groove gate, a groove gate oxide layer, an isolation oxide layer, a conductive enhancement region, a Schottky contact and an ohmic contact. The N-type substrate, the N-type epitaxial layer, the deep P region, the groove gate, the groove gate oxide layer and the isolation oxide layer are arranged between the cathode metal and the anode metal. The lower surface of the N-type substrate contacts the cathode metal, and the upper surface contacts the lower surface of the N-type epitaxial layer. The upper surface of the N-type epitaxial layer partially contacts the deep P region. The conductive enhancement region is arranged on the outer surface of the groove gate oxide layer and contacts the N-type epitaxial layer. Parts of the groove gate oxide layer, the conductive enhancement region, the isolation oxide layer and part of the deep P region are respectively in contact with parts of the anode metal.

[0006] Preferably, the trench gate oxide layer is in a surrounding structure, with an outer surface thereof in contact with the conductive enhancement region, an inner surface in contact with the trench gate, and the trench gate oxide layer also in contact with the anode metal.

[0007] Preferably, the MOS junction barrier Schottky diode structure is a wide bandgap material diode.

[0008] Preferably, the portion where the anode metal contacts the N-type epitaxial layer is a Schottky contact, and the length of the Schottky contact is 0.1-1 μm.

[0009] Preferably, the portion where the anode metal contacts the deep P region is an ohmic contact, and the length of the contact is 0.1 to 3 μm.

[0010] Preferably, the thickness of the N-type epitaxial layer is 1-40 μm, and the doping concentration is 1×10 14 cm -3 ~1×10 17 cm -3 .

[0011] Preferably, the thickness of the conductive enhancement region is 0.1-0.2 μm, and the doping concentration is 1×10 14 cm -3 ~1×10 17 cm -3 , and the doping concentration of the conductive enhancement region is not lower than the doping concentration of the N-type epitaxial layer.

[0012] Preferably, the depth of the trench gate is 0.5-3 μm, and the thickness of the trench gate oxide layer is 40-100 nm.

[0013] Preferably, the depth of the deep P region is 1-4 μm and greater than the depth of the trench gate, and its doping concentration is 1×10 17 cm -3 ~1×10 20 cm -3 .

[0014] Compared with the prior art, the MOS junction barrier Schottky diode structure of the present invention has the following advantages:

[0015] The MOS junction barrier Schottky diode structure of the present invention is formed by inserting a MOS structure into the adjacent deep P region of the traditional JBS diode, that is, introducing a MOS barrier outside the PN junction barrier of the JBS diode, and the two work together to form a channel barrier. When the device is forward biased, the gate of the MOS structure and the Schottky anode simultaneously obtain positive voltage, attracting electrons in the N-type epitaxial layer (drift region) to accumulate in the conductive enhancement region, forming an electron accumulation layer, such as Figure 2 As shown, when the MJBS is forward-conducted, most of the current lines flow through the electron accumulation layer, so that the diode current is mainly conducted along the accumulation layer channel with high electron concentration, which is conducive to reducing the forward voltage drop; when reverse biased, the gate obtains a negative voltage, which repels the electrons in the N-type epitaxial layer, forms an electron depletion layer near the gate, and is connected to the adjacent depletion region of the PN junction formed by the deep P region and the N-type epitaxial layer, which plays a shielding role for the Schottky contact and can ensure a low order of magnitude of leakage current. Therefore, the MOS junction barrier Schottky diode structure of the present invention can reduce the coupling effect between the forward voltage drop and the reverse leakage to a greater extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a specific structural diagram of the MOS junction barrier Schottky diode structure of the present invention.

[0017] Figure 2 It is a forward conduction current line distribution diagram of the MOS junction barrier Schottky diode structure of the present invention.

[0018] Figure 3 It is a specific structural diagram of a modified embodiment of the MOS junction barrier Schottky diode structure of the present invention.

[0019] Description of reference numerals:

[0020] 1. Cathode metal; 2. N-type substrate; 3. N-type epitaxial layer; 4. Deep P region; 5. Trench gate; 6. Trench gate oxide layer; 7. Conductivity enhancement region; 8. Isolation oxide layer; 9. Schottky contact; 10. Ohmic contact; 11. Anode metal. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and implementation examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] Example 1

[0023] See also Figure 1 The present invention provides a MOS junction barrier Schottky diode structure, comprising a cathode metal 1, an N-type substrate 2, an N-type epitaxial layer 3, a deep P region 4, a groove gate 5, a groove gate oxide layer 6, a conductive enhancement region 7, an isolation oxide layer 8, a Schottky contact 9, an ohmic contact 10, and an anode metal 11, wherein the N-type substrate 2, the N-type epitaxial layer 3, the deep P region 4, the groove gate 5, the groove gate oxide layer 6, the conductive enhancement region 7 and the isolation oxide layer 8 are arranged between the cathode metal 1 and the anode metal 11, wherein the deep P region 4 is arranged between the two The lower surface of the N-type substrate 2 is in contact with the cathode metal 1, and the upper surface is in contact with the lower surface of the N-type epitaxial layer 3. The upper surface of the N-type epitaxial layer 3 is partially in contact with the deep P region 4. The two deep P regions 4 are arranged on both sides of the groove gate oxide layer 6 and extend from the upper surface of the N-type epitaxial layer 3 into the body. The conductive enhancement region 7 is arranged on the outer surface of the groove gate oxide layer 6 and contacts the N-type epitaxial layer 3. Part of the groove gate oxide layer 6, the conductive enhancement region 7, the isolation oxide layer 8 and part of the deep P region 4 are respectively in contact with part of the anode metal 11.

[0024] Preferably, the MOS junction barrier Schottky diode structure of the present invention is a wide bandgap material diode, which may specifically be a silicon carbide diode or a gallium nitride diode, including but not limited to these, and may also be other specific types of wide bandgap material diodes, which may be specifically selected in practice.

[0025] Furthermore, the thickness of the N-type epitaxial layer 3 is 1-40 μm, and the doping concentration is 1×10 14 cm -3 ~1×10 17cm -3 The thickness of the conductive enhancement region 7 is 0.1-0.2 μm, and its doping concentration is 1×10 15 cm -3 ~1×10 17 cm -3 In the present invention, it is preferred that the doping concentration of the conductive enhancement region 7 is not lower than the doping concentration of the N-type epitaxial layer 3 .

[0026] Furthermore, the trench gate oxide layer 6 is in an enclosing structure, the outer surface of the trench gate oxide layer 6 contacts the conductive enhancement region 7 , the inner surface of the trench gate oxide layer 6 contacts the trench gate 5 and the isolation oxide layer 8 , and the trench gate oxide layer 6 also contacts the anode metal 11 .

[0027] Preferably, the depth of the trench gate 5 is 0.5-3 μm, and the thickness of the trench gate oxide layer 6 is 40-100 nm; the depth of the deep P region 4 is 1-4 μm and greater than the depth of the trench gate 5, wherein the doping concentration of the deep P region 4 is 1×10 17 cm -3 ~1×10 20 cm -3 .

[0028] The MOS junction barrier Schottky diode structure of the present invention is basically the same as the JBS diode in terms of turn-on voltage, but is 0.1-0.2V lower in forward conduction voltage drop than the JBS diode, and the reverse leakage current is 2 orders of magnitude lower.

[0029] Preferably, the structure of the anode metal 11 of the present invention is a flat plate type.

[0030] Example 2

[0031] See also Figure 3 As a structure of a variant embodiment of the MOS junction barrier Schottky diode structure of the present invention, the structure of this variant embodiment includes cathode metal 1, N-type substrate 2, N-type epitaxial layer 3, deep P region 4, trench gate 5, trench gate oxide layer 6, conductive enhancement region 7, isolation oxide layer 8, Schottky contact 9, ohmic contact 10, and anode metal 11, wherein the connection relationship, size, and doping concentration between cathode metal 1, N-type substrate 2, N-type epitaxial layer 3, trench gate 5, trench gate oxide layer 6, conductive enhancement region 7, isolation oxide layer 8, and Schottky contact 9 are consistent with those of the first embodiment. The difference between the two is that the deep P region 4 of this variant embodiment is composed of a P-type doped region around a deep trench opening on the upper surface of the N-type epitaxial layer 3, and the portion of the anode metal 11 in contact with the deep P region 4 constitutes an ohmic contact 10, and the length of the ohmic contact is 0.1 to 3 μm.

[0032] Compared with the prior art, the MOS junction barrier Schottky diode structure of the present invention has the following advantages:

[0033] The MOS junction barrier Schottky diode structure of the present invention is formed by inserting a MOS structure into the adjacent deep P region of the traditional JBS diode, that is, introducing a MOS barrier outside the PN junction barrier of the JBS diode, and the two work together to form a channel barrier. When the device is forward biased, the gate of the MOS structure and the Schottky anode simultaneously obtain positive voltage, attracting electrons in the N-type epitaxial layer (drift region) to accumulate in the conductive enhancement region, forming an electron accumulation layer, such as Figure 2 As shown, when the MJBS is forward-conducted, most of the current lines flow through the electron accumulation layer, so that the diode current is mainly conducted along the accumulation layer channel with high electron concentration, which is conducive to reducing the forward voltage drop; when reverse biased, the gate obtains a negative voltage, which repels the electrons in the N-type epitaxial layer, forms an electron depletion layer near the gate, and is connected to the adjacent depletion region of the PN junction formed by the deep P region and the N-type epitaxial layer, which plays a shielding role for the Schottky contact and can ensure a low order of magnitude of leakage current. Therefore, the MOS junction barrier Schottky diode structure of the present invention can reduce the coupling effect between the forward voltage drop and the reverse leakage to a greater extent.

[0034] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. Any modifications, equivalent substitutions and improvements made within the concept of the present invention should be included in the patent protection scope of the present invention.

Claims

1. A MOS junction barrier Schottky diode, characterized in that: The MOS junction barrier Schottky diode structure comprises a cathode metal (1), an anode metal (11), an N-type substrate (2), an N-type epitaxial layer (3), a deep P region (4), a groove gate (5), a groove gate oxide layer (6), a conductive enhancement region (7), an isolation oxide layer (8), a Schottky contact (9) and an ohmic contact (10); the N-type substrate (2), the N-type epitaxial layer (3), the deep P region (4), the groove gate (5), the groove gate oxide layer (6), the conductive enhancement region (7) and the isolation oxide layer (8) are arranged between the cathode metal (1) and the anode metal (11); the N-type substrate (2) The lower surface is in contact with the cathode metal (1), the upper surface is in contact with the lower surface of the N-type epitaxial layer (3), the upper surface of the N-type epitaxial layer (3) is partially in contact with the deep P region (4), the conductive enhancement region (7) is arranged on the outer surface of the trench gate oxide layer (6) and is in contact with the N-type epitaxial layer (3), the trench gate oxide layer (6) is in an enclosing structure, and its inner surface is in contact with the trench gate (5), the isolation oxide layer (8) is arranged on the upper surface of the trench gate (5), and parts of the trench gate oxide layer (6), the conductive enhancement region (7), the isolation oxide layer (8) and parts of the deep P region (4) are respectively in contact with parts of the anode metal (11).

2. The MOS junction barrier Schottky diode structure according to claim 1, characterized in that :The MOS junction barrier Schottky diode structure is a wide bandgap material diode.

3. The MOS junction barrier Schottky diode structure according to claim 1, characterized in that The portion where the anode metal (11) contacts the N-type epitaxial layer (3) is a Schottky contact (9), and the length of the Schottky contact (9) is 0.1 to 1 μm.

4. The MOS junction barrier Schottky diode structure according to claim 1, characterized in that The portion where the anode metal (11) contacts the deep P region (4) is an ohmic contact (10), and the length of the ohmic contact (10) is 0.1 to 3 μm.

5. The MOS junction barrier Schottky diode structure according to claim 1, characterized in that The thickness of the N-type epitaxial layer (3) is 1 to 40 μm, and the doping concentration is 1×10 14 cm -3 ~1×10 17 cm -3 .

6. The MOS junction barrier Schottky diode structure according to claim 1, characterized in that The thickness of the conductive enhancement region (7) is 0.1 to 0.2 μm, and its doping concentration is 1×10 14 cm -3 ~1×10 17 cm -3 , and the doping concentration of the conductive enhancement region (7) is not lower than the doping concentration of the N-type epitaxial layer (3).

7. The MOS junction barrier Schottky diode structure according to claim 1, characterized in that : The depth of the groove gate (5) is 0.5-3 μm, the thickness of the groove gate oxide layer (6) is 40-100 nm, and the thickness of the isolation oxide layer (8) is 0.5-1.5 μm.

8. The MOS junction barrier Schottky diode structure according to claim 1, characterized in that The depth of the deep P region (4) is 1-4 μm and greater than the depth of the trench gate (5), and its doping concentration is 1×10 17 cm -3 ~1×10 20 cm -3 .

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