Schottky diode device with ultralow electric leakage

Abstract

The device comprises a substrate layer and an epitaxial layer, the epitaxial layer is located on the surface of the substrate layer, an arc-shaped groove is formed in the epitaxial layer, a certain distance is formed between the top of the arc-shaped groove and the surface of the epitaxial layer, and a metal potential barrier is arranged on the surface of the epitaxial layer; the side wall of the arc-shaped groove is bent outwards to be in an arc shape, an arc-shaped groove oxide layer is arranged on the surface of the inner wall of the arc-shaped groove, polycrystalline silicon filler is arranged in the arc-shaped groove, and the metal potential barrier is connected with the polycrystalline silicon filler. According to the device, the metal potential barrier is not only in contact with the epitaxial layer at the plane position, but also in contact with the epitaxial layer on the vertical structure to form a Schottky junction, the junction area is larger, and the conduction voltage drop of the device can be effectively reduced; the device adopts an arc-shaped groove structure, and compared with a traditional right-angle groove structure, the arc-shaped groove structure has a strong shielding effect under the condition that the device is turned off, the surface barrier height of the device is reduced, and the leakage current of the Schottky diode can be effectively reduced.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, and in particular to a Schottky diode device with ultra-low leakage. Background Art

[0002] Schottky diode is a low-power, high-current, ultra-high-speed semiconductor device with extremely short reverse recovery time (as low as a few nanoseconds) and forward voltage drop of only about 0.4V. Its rectified current can reach thousands of amperes. Due to these characteristics, Schottky diodes are often used in high-frequency, low-voltage, high-current rectification, freewheeling and protection circuits, and as rectifier diodes or small-signal detector diodes in microwave communications and other fields. They are widely used in color TV secondary power supply rectification and high-frequency power supply rectification.

[0003] However, the application of Schottky diodes in high voltage fields is limited, mainly due to its barrier lowering effect, which will lead to large leakage current under high voltage. With the successful promotion of TMBS (trench gate Schottky diode), the voltage application range of Schottky diodes has been expanded to 300V. Compared with the planar gate structure, the trench gate design effectively suppresses the surface barrier lowering effect, reduces the leakage current of the device, and improves the application ability of Schottky diodes in medium and high voltage fields. However, even trench gate Schottky diodes may still have high leakage currents of several milliamperes under high temperature conditions, which is a big gap compared with the leakage current of PN junction devices, which is usually maintained at the microampere level. This problem affects the power consumption efficiency of the system and increases the heat dissipation requirements.

[0004] In order to obtain low leakage and high reliability devices, one method introduces a composite barrier into the traditional Schottky diode structure, and adjusts the barrier height by adding a layer of dielectric material (such as silicon oxide or silicon nitride) at the metal-semiconductor interface. This composite barrier structure can accurately control the barrier height through the thickness and material properties of the dielectric material, thereby reducing leakage current and improving device reliability. The composite barrier reduces leakage current while improving performance stability at high temperatures. The introduction of the dielectric layer may increase process complexity and lead to an increase in interface resistance, thereby increasing the forward voltage drop and increasing device conduction losses.

[0005] Another commonly used method is to form a local barrier control region by selectively injecting a medium or low concentration of P-type or N-type dopant (such as Ga or As) in the Schottky contact area. This method can locally adjust the barrier height to make the barrier distribution more uniform while reducing leakage current. This method can effectively reduce leakage current and reduce the electric field concentration effect in the barrier area to a certain extent, thereby improving the reliability of the device. Local doping may introduce additional process steps, leading to uneven injection problems, and may increase the forward voltage drop of the device, thereby affecting the overall conduction performance. Summary of the invention

[0006] In order to obtain low leakage current without affecting the forward voltage drop of the device at room temperature, the present invention proposes a Schottky diode device with ultra-low leakage, in which the metal barrier not only contacts the epitaxial layer in a planar position, but also contacts the epitaxial layer in a vertical structure to form a Schottky junction, with a larger junction area, which can effectively reduce the on-state voltage drop of the device; the feature of the present invention is that it adopts an arc-shaped groove structure. Compared with the traditional right-angle groove structure, when the device is turned off, the arc-shaped groove structure has a stronger shielding effect, reduces the height of the barrier on the device surface, and can effectively reduce the leakage current of the Schottky diode.

[0007] The technical solution provided by the present invention is as follows:

[0008] A Schottky diode device with ultra-low leakage comprises a substrate layer and an epitaxial layer;

[0009] The epitaxial layer is located on the surface of the substrate layer, at least one arc-shaped groove is arranged in the epitaxial layer, the top of the arc-shaped groove is at a first distance from the surface of the epitaxial layer, a vertical groove extending to the surface of the epitaxial layer is arranged in the epitaxial layer located at the top of the arc-shaped groove, a metal barrier is arranged on the surface of the epitaxial layer and in the vertical groove, the metal barrier contacts the epitaxial layer in a horizontal structure, and contacts the epitaxial layer in a vertical structure to form a Schottky junction;

[0010] The sidewall of the arc-shaped groove is bent outward into an arc shape, an arc-shaped groove oxide layer is arranged on the inner wall surface of the arc-shaped groove, a polysilicon filler is arranged in the arc-shaped groove, and the metal barrier is connected to the polysilicon filler.

[0011] Further, the epitaxial layer includes a lightly doped N-type epitaxial layer and a heavily doped epitaxial layer, and the heavily doped epitaxial layer is located on the surface of the lightly doped N-type epitaxial layer;

[0012] The substrate layer is a heavily doped N-type substrate layer, and the polysilicon filler is a heavily doped polysilicon filler;

[0013] The top of the arc-shaped trench is located in the heavily doped epitaxial layer, and the bottom of the arc-shaped trench is located in the lightly doped N-type epitaxial layer.

[0014] Furthermore, there are multiple arc-shaped grooves, the structure and depth of each arc-shaped groove are consistent, and the distance between two adjacent arc-shaped grooves is not less than 30 nm.

[0015] Furthermore, the arc-shaped groove is an arc-shaped groove structure formed by anisotropically etching the groove and then adopting an isotropic etching method, and the depth of the isotropic etching is 0.3-1 um.

[0016] Furthermore, the distance between the arc-shaped groove and the top silicon surface of the polysilicon filler is 0.5-3 um.

[0017] Furthermore, the arc-shaped trench oxide layer is formed by a gate oxidation process to form a thickness of

[0018] Furthermore, the polysilicon filler is formed by polysilicon deposition and reverse etching, and the polysilicon deposition thickness is

[0019] Furthermore, the doping concentration of the heavily doped epitaxial layer is 1×10 16 cm -3 ~5×10 16 cm -3 , the doping elements are phosphorus or arsenic.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention proposes a Schottky diode device with ultra-low leakage, in which the metal barrier not only contacts the epitaxial layer in a planar position, but also contacts the epitaxial layer in a vertical structure to form a Schottky junction, with a larger junction area, which can effectively reduce the on-state voltage drop of the device; the feature of the present invention is the use of an arc-shaped groove structure, which has a stronger shielding effect than the traditional right-angle groove structure when the device is turned off, reduces the height of the barrier on the device surface, and can effectively reduce the leakage current of the Schottky diode. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of the structure of a Schottky diode device with ultra-low leakage in one embodiment of the present invention;

[0023] Figure 2 It is a schematic diagram of the structure of a traditional trench Schottky diode;

[0024] Figure 3 A schematic diagram of the structure of a Schottky diode device with ultra-low leakage in another embodiment of the present invention;

[0025] Figure 4 It is a comparison diagram of the reverse electric field between the conventional trench Schottky diode simulated in the embodiment of the present invention and the trench Schottky diode proposed in the present invention.

[0026] The reference numerals are as follows:

[0027] 101 - heavily doped N-type substrate layer, 102 - lightly doped N-type epitaxial layer, 103 - heavily doped polysilicon filler, 104 - heavily doped epitaxial layer, 201 - arc-shaped trench oxide layer, 301 - metal barrier. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the embodiments described below are part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0029] Therefore, the detailed description of the embodiments of the present application provided below in conjunction with the accompanying drawings is intended to represent only selected embodiments of the present application, and is not intended to limit the scope of protection claimed in the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0030] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or can communicate with each other; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0031] Example 1

[0032] This embodiment provides a Schottky diode device with ultra-low leakage, including a substrate layer and an epitaxial layer. The epitaxial layer is located on the surface of the substrate layer, an arc-shaped groove is provided in the epitaxial layer, the top of the arc-shaped groove is at a certain distance from the surface of the epitaxial layer, a vertical groove extending to the surface of the epitaxial layer is provided in the epitaxial layer located at the top of the arc-shaped groove, and a metal barrier 301 is provided on the surface of the epitaxial layer and in the vertical groove, and the metal barrier 301 contacts the epitaxial layer in the horizontal structure and contacts the epitaxial layer in the vertical structure to form a Schottky junction. The metal barrier 301 is the metal anode of the device.

[0033] The sidewall of the arc-shaped trench is bent outward into an arc shape, an arc-shaped trench oxide layer 201 is provided on the inner wall surface of the arc-shaped trench, polysilicon filling is provided in the arc-shaped trench, and the metal barrier 301 is connected to the polysilicon filling.

[0034] like Figure 1 As shown, in this embodiment, the epitaxial layer is a lightly doped N-type epitaxial layer 102 , the substrate layer is a heavily doped N-type substrate layer 101 , and the polysilicon filler is a heavily doped polysilicon filler 103 .

[0035] The ultra-low leakage Schottky diode device provided by the present invention has a metal anode in contact with the lightly doped N-type epitaxial layer 102 in both the plane and the vertical plane to form a Schottky contact, and the metal anode is connected to the heavily doped polysilicon filler 103. The arc-shaped groove of the ultra-low leakage Schottky diode device has a certain depth from the silicon surface, and there is a layer of vertical groove structure above the arc-shaped groove. This vertical interface contacts the metal barrier 301 on the surface, which can effectively increase the Schottky contact conduction area of ​​the device, reduce the increase in the channel resistance caused by the lateral extension of the arc-shaped groove, and reduce the forward channel voltage drop of the device as a whole.

[0036] Optionally, there are multiple arc-shaped grooves, the structure and depth of each arc-shaped groove are consistent, and the distance between two adjacent arc-shaped grooves is not less than 30 nm.

[0037] The shielding effect of the arc-shaped groove structure with ultra-low leakage Schottky diode device proposed by the present invention is related to the size of the cell. Under a certain amount of isotropic corrosion, the smaller the device cell is, the smaller the distance between the arc-shaped grooves of adjacent cells is, the stronger the pinch-off effect is, the stronger the shielding ability is, and the lower the leakage current of the device is, but at the same time it will increase the voltage drop of the device. The distance between the arc-shaped grooves of adjacent cells can be up to 30nm, which has a super strong shielding effect on leakage.

[0038] Optionally, the arc-shaped groove is an arc-shaped groove structure formed by anisotropically etching the groove and then adopting an isotropic etching method, and the depth of the isotropic etching is 0.3-1 um.

[0039] Optionally, the distance between the arc-shaped trench and the top silicon surface of the polysilicon filling is 0.5 to 3 um. Figure 2 The vertical groove structure shown in the figure, the arc groove structure in the device provided by the present invention has a stronger shielding effect on the plane than the traditional vertical groove structure, and has a very low leakage current. In the reverse cutoff state of the device, the arc structure has a double truncation effect on the vertical electric field, and the arc top shoulder and the arc bottom of the arc structure have a shielding effect on the vertical electric field. By simulating the silicon plane longitudinal electric field structure of the two device structures, it can be seen that the arc structure can effectively reduce the surface electric field, thereby reducing the leakage current of the device.

[0040] Optionally, the arc-shaped trench oxide layer is formed by a gate oxidation process to form a thickness of

[0041] Optionally, the polysilicon filler is formed by polysilicon deposition and reverse etching, and the polysilicon deposition thickness is

[0043] Example 2

[0044] like Figure 3As shown, this embodiment provides a Schottky diode device with ultra-low leakage. The difference between this device and Embodiment 1 is that the epitaxial layer includes a lightly doped N-type epitaxial layer 102 and a heavily doped epitaxial layer 104. The heavily doped epitaxial layer 104 is located on the surface of the lightly doped N-type epitaxial layer 102. The top of the arc-shaped groove is located in the heavily doped epitaxial layer 104, and the bottom of the arc-shaped groove is located in the lightly doped N-type epitaxial layer 102. The doping concentration of the heavily doped epitaxial layer 104 is 1×10 16 cm -3 ~5×10 16 cm -3 , the doping elements are phosphorus or arsenic, and this heavily doped epitaxial layer 104104 can effectively reduce the on-state voltage drop of the device.

[0045] like Figure 4 As shown, the arc groove structure proposed in the present invention is compared through device simulation. Compared with the traditional structure, under the same on-state voltage drop, the device leakage current can be reduced by 60%; under small cell size shielding, the device leakage current can be reduced by 90%. Under small current conditions, the on-state voltage drop of the arc groove structure is equivalent to that of the traditional structure, which can effectively reduce the device leakage current.

[0046] In summary, the present invention provides a Schottky diode device with ultra-low leakage, in which the metal barrier not only contacts the epitaxial layer in a planar position, but also contacts the epitaxial layer in a vertical structure to form a Schottky junction, with a larger junction area, which can effectively reduce the on-state voltage drop of the device; the device adopts an arc-shaped groove structure. Compared with the traditional right-angle groove structure, when the device is turned off, the arc-shaped groove structure has a stronger shielding effect, reduces the height of the device surface barrier, and can effectively reduce the leakage current of the Schottky diode.

[0047] The above is only the best specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application shall be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A Schottky diode device having ultra-low leakage, characterized in that: including a substrate layer and an epitaxial layer; The epitaxial layer is located on the surface of the substrate layer, at least one arc-shaped groove is arranged in the epitaxial layer, the top of the arc-shaped groove is at a first distance from the surface of the epitaxial layer, a vertical groove extending to the surface of the epitaxial layer is arranged in the epitaxial layer located at the top of the arc-shaped groove, a metal barrier is arranged on the surface of the epitaxial layer and in the vertical groove, the metal barrier contacts the epitaxial layer in a horizontal structure, and contacts the epitaxial layer in a vertical structure to form a Schottky junction; The sidewall of the arc-shaped groove is bent outward into an arc shape, an arc-shaped groove oxide layer is arranged on the inner wall surface of the arc-shaped groove, a polysilicon filler is arranged in the arc-shaped groove, and the metal barrier is connected to the polysilicon filler.

2. The ultra-low leakage Schottky diode device according to claim 1, characterized in that: The epitaxial layer includes a lightly doped N-type epitaxial layer and a heavily doped epitaxial layer, and the heavily doped epitaxial layer is located on the surface of the lightly doped N-type epitaxial layer; The substrate layer is a heavily doped N-type substrate layer, and the polysilicon filler is a heavily doped polysilicon filler; The top of the arc-shaped trench is located in the heavily doped epitaxial layer, and the bottom of the arc-shaped trench is located in the lightly doped N-type epitaxial layer.

3. The ultra-low leakage Schottky diode device according to claim 1, characterized in that: There are multiple arc-shaped grooves, the structure and depth of each arc-shaped groove are consistent, and the distance between two adjacent arc-shaped grooves is not less than 30nm.

4. The ultra-low leakage Schottky diode device according to any one of claims 1 to 3, characterized in that: The arc-shaped groove is an arc-shaped groove structure formed by anisotropically etching the groove and then adopting an isotropic etching method, and the depth of the isotropic etching is 0.3-1um.

5. The ultra-low leakage Schottky diode device according to claim 4, characterized in that: The distance between the arc-shaped groove and the top silicon surface of the polysilicon filler is 0.5-3 um.

6. The ultra-low leakage Schottky diode device according to claim 4, characterized in that: The arc-shaped trench oxide layer is formed by a gate oxidation process to form a thickness of 7. The ultra-low leakage Schottky diode device according to claim 4, characterized in that: The polysilicon filler is formed by polysilicon deposition and reverse etching, and the polysilicon deposition thickness is 8. The ultra-low leakage Schottky diode device according to claim 2, characterized in that: The doping concentration of the heavily doped epitaxial layer is 1×10 16 cm -3 ~5×10 16 cm -3 , the doping elements are phosphorus or arsenic.

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