Quasi-vertical Schottky barrier diode with common cathode low K dielectric layer and separate field plate structure

Abstract

The invention relates to a quasi-vertical Schottky barrier diode with a common cathode low K dielectric layer and a separate field plate structure. The diode is characterized in that a substrate is covered with an N + current expansion layer, one side of the N + current expansion layer is covered with an N-drift layer, the N-drift layer is in a step shape facing the inner side, separation field plate dielectric layers are distributed on the upper surface of the N-drift layer in a matrix mode, and Schottky contact electrodes cover the separation field plate dielectric layers and the upper surface of the N-drift layer where intervals of the separation field plate dielectric layers are located; the low K dielectric layer is located at the position of the first step of the supplemented N-drift layer; the dielectric layer covers the side wall and extends to the surface of the low K dielectric layer; and the ohmic contact electrode sequentially covers the upper surface of the low K dielectric layer, the upper surface and the side wall of the dielectric layer and the upper surface of the exposed part of the N + current expansion layer. The method is high in operability, low in cost, simple and reliable in process and suitable for industrial application and popularization.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power electronics, in particular to a quasi-vertical Schottky barrier diode structure with a common cathode low K dielectric layer and a separate field plate structure and a preparation method. BACKGROUND

[0002] As an indispensable part of modern industry and daily life, the performance of power electronics directly affects the efficiency of energy conversion and the reliability of the system. With the increasing stringent requirements of energy efficiency standards and the emphasis on environmental protection, wide bandgap semiconductor materials have attracted widespread attention due to their excellent performance at high temperature, high voltage and high frequency. Wide bandgap semiconductor materials such as SiC, GaN and Ga2O3 have become a new direction for the development of power electronics due to their high breakdown voltage, low conduction loss and excellent thermal stability.

[0003] Under this background, GaN Schottky barrier diodes have become a hot research object in the field of power electronics due to their low on-resistance and high switching rate. They show great potential in improving energy conversion efficiency, reducing device size and reducing heat dissipation requirements. However, traditional GaN Schottky barrier diodes are prone to high leakage current due to the reduction of the barrier caused by the mirror force when facing high reverse voltage, which limits their performance in high voltage applications.

[0004] To solve this problem, researchers have proposed trench junction barrier Schottky diodes (TJBS) and trench MOS barrier Schottky diodes (TMBS) architectures. The composite structure diode combines the characteristics of PN junction or MOS structure and Schottky junction, realizes the charge coupling effect in the reverse bias state, effectively suppresses the strong electric field effect of the Schottky contact interface, and thus improves the breakdown voltage. In order to further reduce the manufacturing cost of the device, GaN epitaxy technology based on silicon and sapphire substrates gradually dominates; however, the P-type doping efficiency of GaN material is low, which cannot effectively realize the electric field coupling effect, so the local strong field effect still exists, which seriously affects the breakdown voltage of the quasi-vertical Schottky barrier diode (QV-SBD). At the same time, the body defects generated in the heteroepitaxy process and the sidewall defects caused by etching seriously non-radiative recombine, which increases the leakage current in the off-state, leading to premature breakdown of the device, reducing the Baliga figure of merit (BFOM).

[0005] In order to improve the breakdown voltage, the researchers put forward a kind of quasi-vertical structure GaN-based SBD with recessed anode and its preparation method (CN202410323798.7), which regulates the potential distribution through the recessed anode and the side wall field plate structure, thereby reducing the metal / semiconductor interface electric field strength, reducing the reverse leakage current and improving the breakdown voltage. However, the technical scheme only focuses on the electric field regulation and breakdown voltage of the power semiconductor device, while the present invention can not only realize the function of CN202410323798.7, but also can inhibit the diffusion effect of non-equilibrium electrons to the mesa sidewall defect area, solve the problem of sidewall defect induced non-radiative recombination caused by mesa etching process, so as to reduce the leakage current under off state. SUMMARY

[0006] The purpose of the present application is to solve the problems existing in the quasi-vertical Schottky barrier diode (QV-SBD) structure and technology, and to provide a quasi-vertical Schottky barrier diode structure with a common cathode low K dielectric layer and a separate field plate structure. The device structure has a separate field plate under the Schottky contact, and a low K dielectric layer at the anode edge, which is connected with the cathode. The separate field plate can make the electric field uniformly distributed, reduce the maximum electric field strength, and realize the effect of improving the breakdown voltage. At the same time, the low K dielectric layer connected with the cathode can limit the diffusion of electrons to the sidewall defect by modulating the band effect, reduce the defect induced non-radiative recombination rate, reduce the leakage current under off state, and solve the problem of early breakdown of power electronic devices. The method of the present application has strong operability, low cost, simple and reliable process, and is suitable for industrial use.

[0007] The technical solution adopted by the present application to solve the technical problem is: A quasi-vertical Schottky barrier diode with a common cathode low K dielectric layer and a separate field plate structure, the composition of the diode comprises: A substrate is covered with N + A current spreading layer, N + One side of the current spreading layer is covered with N - A drift layer, N - The drift layer is a step shape towards the inside, and the upper surface matrix of the drift layer is distributed with a separate field plate dielectric layer, and a Schottky contact electrode is covered on the separate field plate dielectric layer 107 and the N - Drift layer upper surface; The low K dielectric layer is located at the position of the first step of the N - Drift layer; + The dielectric layer is located on the current spreading layer and covers the N -The side wall of the step portion of the drift layer and the side wall of the upper low K dielectric layer, and extending to the surface of the low K dielectric layer; the ohmic contact electrode covers the upper surface of the low K dielectric layer, the upper surface and side wall of the dielectric layer in turn, and the N + The upper surface of the current spreading layer exposed portion; The projected area of the low K dielectric layer is 5 ~ 40 % of the total N - The projected area of the drift layer is 5 ~ 40 % of the total N The projected area of the discrete field plate dielectric layer is N - The projected area of the drift layer is 10 ~ 90 % of the total N The N - The projected area of the drift layer is N + The projected area of the current spreading layer 102 is 60 ~ 80 % of the total N The substrate material is Si, SiC, GaN or Ga2O3, and the material thickness is 50 μm~ 500 μm; The N + The current spreading layer and the N - The material of the drift layer 104 can be Si, SiC, GaN or Ga2O3; The N + The material of the current spreading layer is GaN; the thickness is 1 μm ~ 3 μm; the doping concentration is 1.0 x10 18 cm -3 ~ 5.0 x 10 19 cm -3 ; The N - The material of the drift layer is GaN; the thickness is 5 μm~ 15 μm; the doping concentration is 1.0 x10 15 cm -3 ~ 8.0 x 10 16 cm -3 ; The material of the dielectric layer is SiO2, SiN, Al2O3 or HfO2, and the thickness is higher than N - The thickness of the drift layer is 0.1 μm~ 5 μm; The material of the low K dielectric layer is SiO2, Spin-On Glass (SOG) or Si3N4, and the dielectric constant is less than that of GaN; the thickness is 0.5 μm~ 10 μm; The material of the discrete field plate dielectric layer is SiO2, SiN, Al2O3 or HfO2, and the thickness is 0.05 μm~ 3 μm; The metal of the Schottky contact electrode is Ni / Au; The ohmic contact electrode metal is Ti / Au.

[0008] The ohmic contact electrode on the upper surface of the low K dielectric layer is connected with the N + The ohmic contact electrode of the current spreading layer is connected in common; The raw materials involved in the above-mentioned quasi-vertical Schottky barrier diode device with a common-cathode low K dielectric layer and a separate field plate structure can be obtained through general channels, and the operation process in the preparation method is possessed by the person skilled in the art.

[0009] The substantial features of the present application are: The present application is based on the structure innovation of the traditional quasi-vertical Schottky barrier diode, a plurality of separate field plates are arranged below the Schottky contact, a low K dielectric layer is arranged at the edge of the sidewall close to the cathode, and the low K dielectric layer is connected in common with the cathode. The device structure can reduce the defect-induced leakage current under forward bias, and can also reduce the reverse bias leakage current and has a higher breakdown voltage under reverse bias.

[0010] The separate field plates below the Schottky contact and the low K dielectric layer connected in common with the cathode are important features of the device of the present application.

[0011] When the device is in forward bias, the low K dielectric layer plays a role in modulating the energy band, limiting the diffusion of electrons to the sidewall, thereby effectively reducing the forward leakage current caused by the sidewall defects of the traditional quasi-vertical Schottky barrier diode, and the low K dielectric layer is connected in common with the cathode, avoiding the formation of a channel below the dielectric layer and thus increasing the forward leakage current; when the device is reversely biased, the separate field plate structure can significantly reduce the strong electric field at the Au-semiconductor contact interface, thereby greatly reducing the leakage current caused by the Schottky barrier reduction effect depending on the strong electric field at the interface and the trap-assisted tunneling current, and further improving the breakdown voltage of the device.

[0012] The beneficial effects of the present application are: Compared with the prior art, the present application has the following outstanding substantial features and significant progress: 1) The present application designs a quasi-vertical Schottky barrier diode with a common-cathode low K dielectric layer and a separate field plate structure, when the device is in forward bias, the low K dielectric layer plays a role in modulating the energy band, limiting the diffusion of electrons to the sidewall, thereby effectively reducing the forward leakage current caused by the sidewall defects of the traditional quasi-vertical Schottky barrier diode, and the low K dielectric layer is connected in common with the cathode, avoiding the formation of a channel below the dielectric layer, thereby increasing the forward leakage current, compared with the traditional QV-SBD architecture, the leakage current is reduced from 1 × 10 -3 A / cm 2 to 1 × 10 -5 A / cm2 .

[0013] 2) The present application designs a quasi-vertical Schottky barrier diode with a common cathode low-K dielectric layer and a separate field plate structure. Compared with the traditional quasi-vertical Schottky barrier diode, the separate field plate structure can significantly reduce the strong electric field at the metal / semiconductor contact interface when the device is applied with a reverse bias, thereby greatly suppressing the mirror force and reducing the carrier tunneling effect induced by the metal / semiconductor interface defects, and significantly improving the breakdown voltage of the device. Compared with the traditional QV-SBD architecture, the breakdown voltage is increased from 265V to 770V.

[0014] 3) The quasi-vertical Schottky barrier diode with a common cathode low-K dielectric layer and a separate field plate structure designed by the present application has flexible design parameters and can meet different requirements. 4) The present application significantly reduces the forward leakage current: as described in Example 1, the forward leakage current of the structure described in the present application is 1 × 10 -5 A / cm 2 at a forward voltage of 0.4V, proving the inhibitory effect of the common cathode low-K dielectric layer structure on the sidewall leakage. At the same time, it can also improve the breakdown voltage of the device: as described in Example 1, when the reverse leakage current reaches 0.1 A / cm 2 is used as the breakdown standard of the device, the structure of the present application can reach 770V, which is about 3.5 times higher than the traditional vertical SBD (breakdown voltage about 225V), proving the improvement effect of the separate field plate on the reverse characteristics. In addition, it can also suppress the local strong electric field: as described in Example 1, comparing the difference in lateral electric field between the traditional structure and the structure of the present application when the reverse voltage is 200V, the lateral electric field distribution at the Schottky junction of the structure of the present application is more uniform, especially at the sidewall edge where breakdown is prone to occur, the electric field strength is effectively reduced, indicating that the separate field plate can well optimize the electric field distribution and uniform the electric field.

[0015] In summary, the method of the present application has strong operability and can adjust the spacing and materials according to different device performance requirements, has low cost, simple and reliable process, and is suitable for industrial popularization and use. BRIEF DESCRIPTION OF DRAWINGS

[0016] The present application will be further described below in conjunction with the drawings.

[0017] Figure 1 is a schematic diagram of a standard quasi-vertical Schottky diode (QV-SBD) device structure in the prior art.

[0018] Figure 2A schematic diagram of the device structure of the quasi-vertical Schottky barrier diode with a common cathode low K dielectric layer and a separate field plate structure in Example 1.

[0019] Figure 3 A forward current-voltage (I-V) characteristic curve map of the structure of the quasi-vertical Schottky barrier diode with a common cathode low K dielectric layer and a separate field plate structure in Example 1.

[0020] Figure 4 A reverse I-V characteristic curve map of the structure of the quasi-vertical Schottky barrier diode with a common cathode low K dielectric layer and a separate field plate structure in Example 1.

[0021] Figure 5 A lateral electric field strength map of the structure of the quasi-vertical Schottky barrier diode with a common cathode low K dielectric layer and a separate field plate structure in Example 1 at a reverse voltage of 200 V, taken at the Schottky junction.

[0022] wherein, 101 - substrate; 102 - N + current spreading layer; 103 - ohmic contact electrode; 104 - N - drift layer; 105 - dielectric layer; 106 - low K dielectric layer; 107 - separate field plate dielectric layer; 108 - Schottky contact electrode. DETAILED DESCRIPTION

[0023] The application is further described below in conjunction with the embodiments and the accompanying drawings, which serve as a limitation to the scope of protection claimed by the present application.

[0024] A standard quasi-vertical Schottky diode device structure in the prior art is shown in Figure 1 . The device structure sequentially includes, in the direction of epitaxial growth: a substrate 101, a N + current spreading layer 102, an ohmic contact electrode 103, a N - drift layer 104, and a Schottky contact electrode 108. The quasi-vertical structure is prone to electric field crowding at the Schottky contact interface, particularly at the contact edge, and thus the strong electric field described above is likely to cause premature breakdown of the device, making it difficult to be applied to a medium-high voltage operating environment; and the leakage current of the device when not turned on in the forward direction caused by surface defects and side wall defects will affect the rectification characteristics of the device.

[0025] A structure of a quasi-vertical Schottky barrier diode with a common cathode low K dielectric layer and a separate field plate structure according to the present application is shown in Figure 2 . The device structure sequentially includes, in the direction of epitaxial growth: a substrate 101 covered with a N + current spreading layer 102, a N +One side of the current spreading layer 102 is covered with N - drift layer 104, N - The drift layer 104 is stepped towards the inner side, and its upper surface is matrix-distributed with strip-shaped discrete field plate dielectric layer 107, and Schottky contact electrode 108 covers the discrete field plate dielectric layer 107 and the N - upper surface of the drift layer 104; low K dielectric layer 106 is located in the N - position of the first step of the drift layer 104 (i.e. the upper surface of the low K dielectric layer 106 and the N - upper surface of the drift layer 104 on the outer side is flush, and the projection of the low K dielectric layer 106 overlaps with the N - projection of the stepped part of the drift layer 104); dielectric layer 105 is located in the N + current spreading layer 102, and covers the N - side wall of the stepped part of the drift layer 104 and the side wall of the upper low K dielectric layer 106, and its height is higher than the upper surface of the low K dielectric layer 106 (4 μm higher), and extends to the surface of the low K dielectric layer 106 (5 μm extended); ohmic contact electrode 103 covers the upper surface of the low K dielectric layer 106, the upper surface and side wall of the dielectric layer 105, and the N + upper surface of the exposed part of the current spreading layer 102; low K dielectric layer 106 projection area is the total N - 5 ~ 40 % of the area of the drift layer 104; discrete field plate dielectric layer 107 projection area is N - 10 ~ 90 % of the upper surface area of the drift layer 104; the N - projection area of the drift layer 104 is N + 60 ~ 80% of the projection area of the substrate; the material of the substrate 101 is Si, SiC, GaN or Ga2O3, and the material thickness is 50 μm ~ 500 μm; the N + material of the current spreading layer 102 is GaN, and the material thickness is 1 μm ~ 3 μm, and the doping concentration is 1.0x10 18 cm -3 ~ 5.0 x 10 19 cm -3 ; the N - material of the drift layer 104 is GaN, and the material thickness is 5 μm ~ 15 μm, and the doping concentration is 1.0x10 15 cm-3 8.0 x 10 16 cm -3 ; The material of the dielectric layer 105 is not unique, and can be SiO2, SiN, Al2O3, HfO2, etc. The thickness of the dielectric layer 105 is higher than that of the N - The thickness of the drift layer 104 is 0.1 μm~ 5 μm; The low K dielectric layer 106 is etched from the N - The low K dielectric layer 106 is etched from the N The material of the low K dielectric layer 106 is not unique, and can be SiO2, Spin-On Glass (SOG), Si3N4, etc. The dielectric constant of the material is less than that of GaN; The material of the dielectric layer 105 is not unique, and can be SiO2, SiN, Al2O3, HfO2, etc. The thickness of the dielectric layer 105 is higher than that of the N The metal of the Schottky contact electrode 108 is Ni / Au; The metal of the ohmic contact electrode 103 is Ti / Au. The ohmic contact electrode 103 on the upper surface of the low K dielectric layer 106 is in ohmic contact with the N + The ohmic contact electrode 103 of the current spreading layer 102 is in ohmic contact; The thickness of the Ni metal of the Schottky contact electrode 108 is 20 nm ~ 60 nm, and the thickness of the Au metal of the Schottky contact electrode 108 is 80 nm ~ 260 nm; The thickness of the Ti metal of the ohmic contact electrode 103 is 40 nm ~ 120 nm, and the thickness of the Au metal of the ohmic contact electrode 103 is 80 nm ~ 260 nm.

[0026] The device structure of the quasi-vertical Schottky barrier diode with a low K dielectric layer and a separate field plate structure is prepared as follows: Firstly, the substrate 101 is subjected to high-temperature heat treatment at 950 ℃ in a MOCVD (metal organic chemical vapor deposition) reaction furnace to remove impurities adhered to the surface of the substrate 101; Secondly, the N + The current spreading layer 102 and the N - The drift layer 104 are epitaxially grown on the surface of the substrate 101 in the MOCVD reaction furnace, and the temperature is 1050 ℃ and the pressure is 120 mbar; Thirdly, the N -SiO2 is grown on the surface of the drift layer 104, photoresist is coated on the SiO2, and after the photoresist is exposed, developed and other photoetching steps, the SiO2 is etched to form a pattern. The patterned SiO2 is used as a mask layer, and finally part of the N + The current spreading layer 102; In the fifth step, the N + The current spreading layer 102 and the N - Photoresist is coated on the surface of the drift layer 104, and after the photoresist is exposed, developed and other photoetching steps, the drift layer 104 is patterned. Finally, the N - The drift layer 104 side wall is etched to remove part of the GaN; In the sixth step, the N + The current spreading layer 102 and the N - Low K dielectric is grown on the surface of the drift layer 104, photoresist is coated on the low K dielectric, and after the photoresist is exposed, developed and other photoetching steps, the low K dielectric is etched to form a low K dielectric layer 106 (the thickness of the low K dielectric layer 106 is equal to the thickness of the N - The drift layer 104 side wall is etched to remove part of the GaN; In the seventh step, the N + The current spreading layer 102, the N - The drift layer 104 and the low K dielectric layer 106 are grown on the surface of the field plate dielectric and coated with photoresist, and after the photoresist is exposed, developed and other photoetching steps, the field plate dielectric is formed. Finally, the photoresist is removed to form a discrete field plate dielectric layer 107; In the eighth step, the N + The current spreading layer 102, the N - The drift layer 104, the low K dielectric layer 106 and the discrete field plate dielectric layer 107 are grown on the surface of the dielectric and coated with photoresist, and after the photoresist is exposed, developed and other photoetching steps, the dielectric layer is formed. Finally, the photoresist is removed to form a dielectric layer 105; In the ninth step, the N + The current spreading layer 102, the N - Photoresist is coated on the surface of the drift layer 104, the low K dielectric layer 106, the discrete field plate dielectric layer 107 and the dielectric layer 105, and after the photoresist is exposed, developed and other photoetching steps, the low K dielectric layer 106 is etched on the surface of the N + The current spreading layer 102 is etched to form an ohmic contact window; In the tenth step, an ohmic contact electrode 103 is evaporated at the position of the ohmic contact window formed in the ninth step; In the eleventh step, the N + The current spreading layer 102, the N - Photoresist is coated on the surface of the drift layer 104, the low K dielectric layer 106 and the discrete field plate dielectric layer 107 and the dielectric layer 105, and after the photoresist is exposed, developed and other photoetching steps, the N -A Schottky contact window is formed on the upper surface of the drift layer 104 and the upper surface of the discrete field plate dielectric layer 107; In the twelfth step, a Schottky contact electrode 108 is evaporated at the position of the Schottky contact window formed in the eleventh step. Thus, the structure of the quasi-vertical Schottky barrier diode with a common cathode low K dielectric layer and a discrete field plate structure is obtained.

[0027] Embodiment 1 This embodiment adopts a structure of a quasi-vertical Schottky barrier diode with a common cathode low K dielectric layer and a discrete field plate structure as shown in the figure. Figure 2 The device structure includes, in sequence along the epitaxial growth direction: a substrate 101, an N + current spreading layer 102, an ohmic contact electrode 103, an N - drift layer 104, a dielectric layer 105, a low K dielectric layer 106, a discrete field plate dielectric layer 107, and a Schottky contact electrode 108. - The sidewall of the N - drift layer 104 is the low K dielectric layer 106, and the projected area of the low K dielectric layer 106 is 7% of the total area of the upper surface of the N - drift layer 104, and the shadow projected by the low K dielectric layer 106 coincides with the first step of the N - drift layer 104; the N - drift layer 104 has the discrete field plate dielectric layer 107 on the upper surface, and the projected area of the discrete field plate dielectric layer 107 is 50% of the total area of the upper surface of the N - drift layer 104; the N + current spreading layer 102, the dielectric layer 105, and the low K dielectric layer 106 are covered with the Schottky contact electrode 107.

[0028] The projected area of the N - drift layer 104 is 80% of the projected area of the substrate; + The material of the substrate 101 is GaN, and the material thickness is 50 μm (this device is circular with Lac=30 μm); The material of the N + current spreading layer 102 is GaN, and the material thickness is 1 μm, and the doping concentration is 5.0 x10 18 cm -3 ; The material of the N - drift layer 104 is GaN, and the material thickness is 8 μm, and the doping concentration is 6.0 x10​15 cm -3 ; The material of the medium layer 105 is Al2O3, and the thickness of the medium layer 105 above the surface of the low K medium layer 106 is 4 μm; The low K medium layer 106 is etched from N - The sidewall of the drift layer 104 is then grown with a low K medium layer, and the thickness of the low K medium layer is 2 μm; The material of the low K medium layer 106 is SiO2; The material of the discrete field plate medium layer 107 is SiO2, and the thickness of the discrete field plate medium layer 107 is 1 μm; The metal of the Schottky contact electrode 108 is Ni / Au; The metal of the ohmic contact electrode 103 is Ti / Au; the ohmic contact electrode 103 on the surface of the low K medium layer 106 is connected with the N + The ohmic contact electrode 103 of the current spreading layer 102 is connected in common; The thickness of the metal Ni of the Schottky contact electrode 108 is 50 nm, and the thickness of the metal Au of the Schottky contact electrode 108 is 220 nm; The thickness of the metal Ti of the ohmic contact electrode 103 is 30 nm, and the thickness of the metal Au of the ohmic contact electrode 103 is 200 nm.

[0029] The following forward I-V curve, reverse I-V curve, and electric field distribution curve are from the power device simulation software simapsys.

[0030] Figure 3 The forward I-V characteristic graph of the quasi-vertical Schottky barrier diode device with a common-cathode low K medium layer and a discrete field plate structure in the embodiment 1 of the application is shown in the figure, wherein the gray line is the forward I-V curve of the device structure of the application. From the I-V curve, it can be seen that the structure of the application has a smaller leakage current when the device is not turned on, for example, when the forward voltage is 0.4 V, the forward current density is 1 × 10 F A / cm -5 . V 2 .

[0031] Figure 4 The reverse I-V characteristic curve of the quasi-vertical Schottky barrier diode device with a common-cathode low K medium layer and a discrete field plate structure in the embodiment 1 of the application is shown in the figure, and the I-V curve obviously shows that the structure of the application has a larger breakdown voltage, for example, when the reverse leakage current is 0.1 A / cm 2Time (the breakdown standard of power device is: the current value reaches 0.1 A / cm after taking log value of reverse leakage current 2 For breakdown point), the breakdown voltage value of the structure of the application is 770 V, while the breakdown voltage value of the traditional quasi-vertical Schottky diode under the same leakage current level is 265 V.

[0032] Figure 5 For example 1, the quasi-vertical Schottky barrier diode device with common cathode low K dielectric layer and separate field plate structure of the application intercepts the lateral electric field intensity distribution at the Schottky junction under the reverse voltage of 200 V. It is illustrated that the electric field intensity distribution at the Schottky junction of the structure of the application is more uniform, especially the electric field at the side wall is reduced, compared with the traditional quasi-vertical Schottky diode.

[0033] Example 2: This embodiment adopts a structure of quasi-vertical Schottky barrier diode with common cathode low K dielectric layer and separate field plate structure as shown in Figure 2 The device structure includes, in sequence along the epitaxial growth direction: substrate 101, N + current spreading layer 102, ohmic contact electrode 103, N - drift layer 104, dielectric layer 105, low K dielectric layer 106, separate field plate dielectric layer 107 and Schottky contact electrode 108, wherein, N - drift layer 104 side wall is low K dielectric layer 106, the projection area of low K dielectric layer 106 is 7% of the total N - drift layer 104 upper surface area and the shadow projected by low K dielectric layer 106 is coincident with N - drift layer 104 first step projection; N - drift layer 104 has separate field plate dielectric layer 107, the projection area of separate field plate dielectric layer 107 is 50% of the total N - drift layer 104 upper surface area; N - drift layer 104 and separate field plate dielectric layer 107 are covered with Schottky contact electrode 108; dielectric layer 105 is deposited on the side wall, and ohmic contact electrode 103 is located on N + current spreading layer 102, dielectric layer 105 and low K dielectric layer 106.

[0034] The projection area of N - drift layer 104 is N + substrate projection area is 80%; The material of substrate 101 is GaN, and the material thickness is 50 μm; (this device is circular Lac=30um); The projection area of N +The current spreading layer 102 is made of GaN with a thickness of 1 μm and a doping concentration of 5.0 x 10⁻⁶. 18 cm -3 ; The N - The drift layer 104 is made of GaN, with a thickness of 8 μm and a doping concentration of 6.0 x 10⁻⁶. 15 cm -3 ; The dielectric layer 105 is made of Al2O3 and has a thickness of 4 μm above the upper surface of the low K dielectric layer 106. The low K dielectric layer 106 is formed by etching N - The drift layer 104 was then grown with a low-K medium, and the thickness was 4 μm. The material of the low K dielectric layer 106 is Si3N4; The material of the split-field plate dielectric layer 107 is HfO2, and the thickness of the split-field plate dielectric layer 107 is 1 μm; The Schottky contact electrode 108 is made of Ni / Au metal; The ohmic contact electrode 103 is made of Ti / Au metal; the ohmic contact electrode 103 on the upper surface of the low K dielectric layer 106 is connected to the N... + The ohmic contact electrode 103 of the current spreading layer 102 is shared; The thickness of the Schottky contact electrode 108 metallic Ni is 50 nm, and the thickness of the Schottky contact electrode 108 metallic Au is 220 nm. The thickness of the ohmic contact electrode 103 metal Ti is 30 nm, and the thickness of the ohmic contact electrode 103 metal Au is 200 nm.

[0035] Example 3: This embodiment employs a quasi-vertical Schottky barrier diode structure with a common cathode low-K dielectric layer and a split-field plate structure, as shown below. Figure 2 As shown, the device structure, along the epitaxial growth direction, includes, in sequence: substrate 101, N... + Current spreading layer 102, ohmic contact electrode 103, N - Drift layer 104, dielectric layer 105, low K dielectric layer 106, field separation plate dielectric layer 107, and Schottky contact electrode 108, wherein N - The sidewalls of drift layer 104 are low-K dielectric layer 106, and the projected area of ​​low-K dielectric layer 106 is the total N. - The shadow projected by the drift layer 104 and the N of the low K dielectric layer 106, which accounts for 7% of the surface area of ​​the drift layer 104. -The projection of the first step of the drift layer 104 coincides with N - The projection area of the discrete field plate dielectric layer 107 on the drift layer 104 is the whole N - 50% of the surface area of the drift layer 104; N - The drift layer 104 and the discrete field plate dielectric layer 107 are covered with the Schottky contact electrode 108; the dielectric layer 105 is deposited on the sidewall, and the ohmic contact electrode 103 is located on N + The current spreading layer 102, the dielectric layer 105 and the low K dielectric layer 106.

[0036] The projection area of the N - The projection area of the drift layer 104 is N + 80% of the projection area of the substrate; The material of the substrate 101 is GaN, and the material thickness is 50 μm; (the device is circular, Lac=30um) The projection area of the N + The material of the current spreading layer 102 is GaN, the material thickness is 1 μm, and the doping concentration is 5.0 x10 18 cm -3 ; The projection area of the N - The material of the drift layer 104 is GaN, the material thickness is 10 μm, and the doping concentration is 6.0 x10 15 cm -3 ; The material of the dielectric layer 105 is Al2O3, and the thickness above the upper surface of the low K dielectric layer 106 is 4 μm; The low K dielectric layer 106 is obtained by etching N - The sidewall of the drift layer 104 is then grown with the low K dielectric layer, and the thickness is 5 μm; The material of the low K dielectric layer 106 is SOG; The material of the discrete field plate dielectric layer 107 is HfO2, and the thickness of the discrete field plate dielectric layer 107 is 3 μm; The metal of the Schottky contact electrode 108 is Ni / Au; The metal of the ohmic contact electrode 103 is Ti / Au; the ohmic contact electrode 103 on the upper surface of the low K dielectric layer 106 and N + The ohmic contact electrode 103 of the current spreading layer 102 is connected in common; The thickness of the metal Ni of the Schottky contact electrode 108 is 50 nm, and the thickness of the metal Au of the Schottky contact electrode 108 is 220 nm; The thickness of the ohmic contact electrode 103 metal Ti is 30 nm, and the thickness of the ohmic contact electrode 103 metal Au is 200 nm.

[0037] Embodiment 2 and Embodiment 3 change the low K field plate material and the discrete field plate material involved in the patent, which shows the wide applicability and performance scalability of the application, Embodiment 2 replaces the low K dielectric layer material from SiO2 to Si3N4, and replaces the discrete field plate dielectric from SiO2 to HfO2 with a higher dielectric constant, aiming to prove that the core innovation of the application does not depend on a certain specific dielectric material. The core of Embodiment 3 is to expand the size of the device in the longitudinal direction, thereby proving that the patent can achieve better parameter indicators by optimizing parameters, representing the potential of the application to develop in the direction of high voltage and high performance, and selecting mature and low-cost SOG on the dielectric material to further reduce the manufacturing cost of the device.

[0038] From the above embodiments, it can be seen that the application cooperatively solves two main problems of QV-SBD: sidewall defect-induced non-radiative recombination and low breakdown voltage. The application uses a low-k dielectric (106) located in the mesa sidewall region of the N-drift layer (104), and forms a common contact with the cathode metal (103) of the device; the common low-k dielectric (106) and the cathode metal (103) are at the same potential, thereby raising the energy level of the N-drift layer (104) in the sidewall region, limiting the effect of lateral diffusion of electrons, and reducing the leakage current. In order to improve the breakdown voltage, the application uses a plurality of discrete field plates (107), which are located at the interface between the N-drift layer (104) and the Schottky metal (anode metal 108); the multi-field plate structure can effectively make the peak electric field under the metal / semiconductor contact more uniform, suppress the local strong field, significantly weaken the mirror force strength, and reduce the metal / semiconductor interface defect-assisted carrier tunneling process.

[0039] Therefore, the composite structure of the discrete multi-field plate and the common cathode low-k dielectric layer reduces the local strong field at the metal / semiconductor interface, improves the breakdown voltage, and solves the problem of large sidewall defect-induced leakage current caused by etching process, so that the quasi-vertical Schottky diode exhibits excellent performance in both forward and reverse working states, and solves the long-standing difficult problem of being difficult to balance.

[0040] The remaining matters of the application are known technologies.

[0041] The above only describes the preferred embodiments of the application, and is not intended to limit the application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application should be included in the protection scope of the application.

Claims

1. A quasi-vertical Schottky barrier diode having a common cathode low K dielectric layer and a separate field plate structure, characterized by, The diode comprises the following components: N + current spreading layer, N + one side of the current spreading layer is covered with N - drift layer, N - the drift layer is stepped towards the inner side, and its upper surface is distributed with discrete field plate dielectric layers, and Schottky contact electrodes are covered on the discrete field plate dielectric layers and the N - upper surface of the drift layer; low K dielectric layer is located on the filled N - the position of the first step of the drift layer; the dielectric layer is located on the N + the current spreading layer, and covers the N - the sidewall of the step portion of the drift layer and the sidewall of the upper low K dielectric layer, and extends to the surface of the low K dielectric layer; the ohmic contact electrode covers the upper surface of the low K dielectric layer, the upper surface and the sidewall of the dielectric layer, and the N + the upper surface of the exposed portion of the current spreading layer.

2. The Quasi-vertical Schottky Barrier Diode with a common cathode low K dielectric layer and a separate field plate structure of claim 1, wherein, Low K dielectric layer projected area is all N - 5 ~ 40 % of the drift layer area; The projection area of the discrete field plate dielectric layer is N - 10 ~ 90 % of the upper surface area of the drift layer The N - The projected area of the drift layer is N + The current spreading layer 102 projects an area of 60 ~ 80%.

3. The Quasi-vertical Schottky Barrier Diode with a common cathode low K dielectric layer and a separate field plate structure of claim 1, wherein, The material of the low K dielectric layer is SiO2, Spin-On Glass (SOG) or Si3N4, and the dielectric constant is less than that of GaN; the thickness is 0.5-10 μm; The material of the discrete field plate dielectric layer is SiO2, SiN, Al2O3 or HfO2, and the thickness is 0.05-3 μm.

4. The Quasi-vertical Schottky Barrier Diode with a common cathode low K dielectric layer and discrete field plate structure of claim 1, wherein, The N + The current spreading layer and the N - The drift layer material is Si, SiC, GaN or Ga2O3. The N + The material of the current spreading layer is GaN. The thickness is 1-3 μm; doping concentration of 1.0 x 10 18 cm -3 -5.0 x 10 19 cm -3 ; The N - The material of the drift layer is GaN; the thickness is 5 μm~ 15 μm; the doping concentration is 1.0 x10 15 cm -3 ~ 8.0 x10 16 cm -3 .

5. The Quasi-vertical Schottky Barrier Diode with a common cathode low K dielectric layer and discrete field plate structure of claim 1 wherein, The substrate material is Si, SiC, GaN or Ga2O3, and the material thickness is 50-500 μm; The material of the medium layer is SiO2, SiN, Al2O3 or HfO2, and the thickness is higher than N - The thickness of the drift layer is 0.1 μm~ 5 μm.

6. The Quasi-vertical Schottky Barrier Diode with a common cathode low K dielectric layer and discrete field plate structure of claim 1, wherein, The metal of the Schottky contact electrode is Ni / Au; The metal of the ohmic contact electrode is Ti / Au.

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