Schottky diode and preparation method thereof

Abstract

The invention provides a Schottky diode and a preparation method thereof, and the preparation method comprises the steps: providing a first conductive type substrate on which a first conductive type epitaxial layer grows, and forming a patterned first hard mask layer, forming a first active injection region of a second conductive type, a first terminal injection region of the second conductive type and a first transition injection region of the second conductive type on the upper surface layer of the epitaxial layer based on the first hard mask layer, and forming a first side wall to obtain a second hard mask layer, forming a second active injection region of a second conductive type, a second terminal injection region of the second conductive type and a second transition injection region of the second conductive type in the epitaxial layer based on the second hard mask layer, forming a field oxide layer on the terminal region of the epitaxial layer, and sequentially forming a conductive metal layer and a conductive functional layer on the cellular region of the epitaxial layer. According to the preparation method of the Schottky diode, the silicon carbide Schottky barrier diode with low break-over voltage, low leakage current and high extreme stress reliability can be realized at the same time.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor integrated circuit manufacturing technology, and relates to a Schottky diode and its preparation method. Background Technology

[0002] Silicon carbide-Schottky barrier diodes (SiC-SBDs) are playing an increasingly crucial role in modern electronics and power systems due to their superior electrical characteristics. Compared to traditional silicon (Si) devices, SiC SBDs offer higher operating temperatures, lower forward voltage drops, and faster switching speeds. These features make SiC SBDs suitable for applications in high-efficiency, high-frequency, and high-temperature environments.

[0003] In SiC-SBD devices, the design of heavily doped P-wells is crucial. If the area of ​​the heavily doped P-wells is small and the junction depth is shallow, the on-state voltage of the SiC-SBD will decrease. However, when the SiC-SBD device is in the blocking state, the leakage current will increase, and its shock resistance under extreme stress (such as avalanche and surge) will be significantly reduced. If the area of ​​the heavily doped P-wells is large and the junction depth is deep, the heavily doped P-wells will have a strong shielding effect on the electric field of the Schottky metal interface, reducing the leakage current and improving its extreme stress reliability. However, due to the reduced Schottky metal area and increased diffusion resistance, the on-state voltage will increase. Therefore, current technology struggles to achieve a silicon carbide Schottky barrier diode that simultaneously possesses low on-state voltage, low leakage current, and high extreme stress reliability.

[0004] Therefore, how to provide a Schottky diode and its fabrication method to achieve a silicon carbide Schottky barrier diode with low on-state voltage, low leakage current and high extreme stress reliability without increasing the fabrication cost of the device has become an important problem that needs to be solved by those skilled in the art.

[0005] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this application and facilitating understanding by those skilled in the art. It should not be assumed that these technical solutions are known to those skilled in the art simply because they have been described in the background section of this application. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a Schottky diode and its fabrication method, so as to solve the problem that it is difficult to realize silicon carbide Schottky barrier diodes with low on-state voltage, low leakage current and high extreme stress reliability in the prior art.

[0007] To achieve the above and other related objectives, the present invention provides a method for fabricating a Schottky diode, comprising the following steps:

[0008] A substrate of a first conductivity type is provided, and an epitaxial layer of the first conductivity type is grown on the substrate. The epitaxial layer includes a cell region and a terminal region, and the doping concentration of the epitaxial layer is less than the doping concentration of the substrate.

[0009] A patterned first hard mask layer is formed on the epitaxial layer. The first hard mask layer has a first opening, a second opening, and a third opening that respectively expose the cell region, the terminal region, and the boundary region between the cell region and the terminal region.

[0010] Ion implantation is performed on the epitaxial layer based on the first hard mask layer to form a first active implantation region of the second conductivity type, a first terminal implantation region of the second conductivity type, and a first transition implantation region of the second conductivity type on the upper surface of the epitaxial layer. The first active implantation region is located in the cell region, the first terminal implantation region is located in the terminal region, and the first transition implantation region is located in the boundary region between the cell region and the terminal region.

[0011] A first sidewall is formed on the sidewalls of the first opening, the second opening, and the third opening to obtain a second hard mask layer;

[0012] Ion implantation is performed on the epitaxial layer based on the second hard mask layer to form a second active implantation region of the second conductivity type, a second terminal implantation region of the second conductivity type, and a second transition implantation region of the second conductivity type in the epitaxial layer. The second active implantation region extends downward from the bottom surface of the first active implantation region, the second terminal implantation region extends downward from the bottom surface of the first terminal implantation region, and the second transition implantation region extends downward from the bottom surface of the first transition implantation region. The doping concentration of the second active implantation region is less than that of the first active implantation region, the doping concentration of the second terminal implantation region is less than that of the first terminal implantation region, and the doping concentration of the second transition implantation region is less than that of the first transition implantation region.

[0013] Remove the second hard mask layer to form a field oxide layer on the terminal region;

[0014] A conductive metal layer and a conductive functional layer are sequentially formed on the cell region. The conductive metal layer includes a first portion that is in ohmic contact with the first active implantation region and a second portion that is in Schottky contact with the epitaxial layer.

[0015] Optionally, the doping concentration range of the first active implantation region, the first terminal implantation region, and the first transition implantation region is the same, and the doping concentration range is 1E19 cm⁻¹.-3 ~1E20 cm -3 .

[0016] Optionally, the following steps are also included:

[0017] An electrode metal layer is formed, which covers the field oxide layer and the conductive functional layer;

[0018] A passivation layer is formed on the electrode metal layer, the passivation layer exposing the electrode leads of the electrode metal layer, and the electrode leads are located above the cell region;

[0019] An insulating layer is formed on the electrode metal layer, the insulating layer encapsulates the passivation layer and exposes the electrode lead-out portion.

[0020] Optionally, in the X direction, the width of the first terminal injection region is smaller than the width of the first active injection region, and the width of the first active injection region is smaller than the width of the first transition injection region.

[0021] Optionally, in the X direction, the width of the second active injection region is smaller than the width of the first active injection region, the width of the second terminal injection region is smaller than the width of the first terminal injection region, and the width of the second transition injection region is smaller than the width of the first transition injection region.

[0022] Optionally, after forming the second active injection region, the second terminal injection region, and the second transition injection region, the following steps are further included:

[0023] A second sidewall is formed on the outer wall of the first sidewall;

[0024] Ion implantation is performed on the epitaxial layer based on the second hard mask layer with the second sidewall to form a third active implantation region of the second conductivity type, a third terminal implantation region of the second conductivity type, and a third transition implantation region of the second conductivity type in the epitaxial layer. The third active implantation region extends downward from the bottom surface of the second active implantation region, the third terminal implantation region extends downward from the bottom surface of the second terminal implantation region, and the third transition implantation region extends downward from the bottom surface of the second transition implantation region. The doping concentration of the third active implantation region is less than that of the second active implantation region, the doping concentration of the third terminal implantation region is less than that of the second terminal implantation region, and the doping concentration of the third transition implantation region is less than that of the second transition implantation region.

[0025] Optionally, in the X direction, the width of the third active injection region is smaller than the width of the second active injection region, the width of the third terminal injection region is smaller than the width of the second terminal injection region, and the width of the third transition injection region is smaller than the width of the second transition injection region.

[0026] The present invention also provides a Schottky diode, comprising:

[0027] A first conductivity type substrate is provided on the substrate, the epitaxial layer of the first conductivity type is provided, the epitaxial layer includes a cell region and a terminal region, and the doping concentration of the epitaxial layer is less than the doping concentration of the substrate;

[0028] A first active injection region, a first terminal injection region, and a first transition injection region of a second conductivity type are disposed at intervals on the side of the epitaxial layer away from the substrate and extend along the direction of the epitaxial layer toward the substrate. The first active injection region is located in the cell region, the first terminal injection region is located in the terminal region, and the first transition injection region is located in the boundary region between the cell region and the terminal region.

[0029] A second active implantation region, a second terminal implantation region, and a second transition implantation region of a second conductivity type are disposed at intervals in the epitaxial layer. The second active implantation region extends downward from the bottom surface of the first active implantation region, the second terminal implantation region extends downward from the bottom surface of the first terminal implantation region, and the second transition implantation region extends downward from the bottom surface of the first transition implantation region. The doping concentration of the second active implantation region is less than that of the first active implantation region, the doping concentration of the second terminal implantation region is less than that of the first terminal implantation region, and the doping concentration of the second transition implantation region is less than that of the first transition implantation region.

[0030] A field oxide layer is located on the terminal region;

[0031] A conductive metal layer and a conductive functional layer are stacked on the cell region from bottom to top. The conductive metal layer includes a first portion that is in ohmic contact with the first active injection region and a second portion that is in Schottky contact with the epitaxial layer.

[0032] Optionally, it further includes an electrode metal layer, a passivation layer, and an insulating layer. The electrode metal layer covers the field oxide layer and the conductive functional layer. The passivation layer is located on the electrode metal layer and exposes the electrode leads of the electrode metal layer. The electrode leads are located above the cell region. The insulating layer is located on the electrode metal layer to enclose the passivation layer and expose the electrode leads.

[0033] Optionally, the epitaxial layer further includes a third active implantation region of the second conductivity type, a third terminal implantation region of the second conductivity type, and a third transition implantation region of the second conductivity type. The third active implantation region extends downward from the bottom surface of the second active implantation region, the third terminal implantation region extends downward from the bottom surface of the second terminal implantation region, and the third transition implantation region extends downward from the bottom surface of the second transition implantation region. The doping concentration of the third active implantation region is less than that of the second active implantation region, the doping concentration of the third terminal implantation region is less than that of the second terminal implantation region, and the doping concentration of the third transition implantation region is less than that of the second transition implantation region.

[0034] As described above, the method for fabricating a Schottky diode according to the present invention includes the following steps: providing a substrate of a first conductivity type; growing an epitaxial layer of the first conductivity type on the substrate, the epitaxial layer including a cell region and a termination region, and the doping concentration of the epitaxial layer being less than the doping concentration of the substrate; forming a patterned first hard mask layer on the epitaxial layer, the first hard mask layer having a first opening, a second opening, and a third opening respectively exposing the cell region, the termination region, and the boundary region between the cell region and the termination region; performing ion implantation on the epitaxial layer based on the first hard mask layer to form a first active implantation region of a second conductivity type, a first termination implantation region of a second conductivity type, and a first transition implantation region of a second conductivity type on the upper surface layer of the epitaxial layer, the first active implantation region being located in the cell region, the first termination implantation region being located in the termination region, and the first transition implantation region being located in the boundary region between the cell region and the termination region; forming a first sidewall on the sidewall of the first opening, the second opening, and the third opening to obtain a second... A hard mask layer is used; based on the second hard mask layer, ion implantation is performed on the epitaxial layer to form a second active implantation region of the second conductivity type, a second terminal implantation region of the second conductivity type, and a second transition implantation region of the second conductivity type in the epitaxial layer. The second active implantation region extends downward from the bottom surface of the first active implantation region, the second terminal implantation region extends downward from the bottom surface of the first terminal implantation region, and the second transition implantation region extends downward from the bottom surface of the first transition implantation region. The doping concentration of the second active implantation region is less than that of the first active implantation region, the doping concentration of the second terminal implantation region is less than that of the first terminal implantation region, and the doping concentration of the second transition implantation region is less than that of the first transition implantation region. The second hard mask layer is removed to form a field oxide layer on the terminal region. A conductive metal layer and a conductive functional layer are sequentially formed on the cell region. The conductive metal layer includes a first portion that is in ohmic contact with the first active implantation region and a second portion that is in Schottky contact with the epitaxial layer. The Schottky diode fabrication method of the present invention, by introducing a second active injection region, a second terminal injection region and a second transition injection region, can realize a silicon carbide Schottky barrier diode with low on-state voltage, low leakage current and high extreme stress reliability at the same time. It significantly improves the trade-off between on-state voltage, leakage current and extreme stress reliability, and does not require the addition of a new mask, thus not increasing the fabrication cost of the device. Attached Figure Description

[0035] Figure 1 The diagram shows a schematic of the structure of a heavily doped N-type substrate in the fabrication process of a silicon carbide Schottky barrier diode.

[0036] Figure 2 The diagram shows the structure obtained after forming a P-type active injection region, a P-type terminal injection region, and a P-type transition injection region in the fabrication process of a silicon carbide Schottky barrier diode.

[0037] Figure 3The diagram shows a schematic of the structure obtained after forming a field oxide layer in the fabrication process of a silicon carbide Schottky barrier diode.

[0038] Figure 4 The diagram shows the structure obtained after forming a titanium metal layer and a titanium nitride layer in the fabrication process of a silicon carbide Schottky barrier diode.

[0039] Figure 5 The diagram shows the structure obtained after forming an aluminum metal layer in the fabrication process of a silicon carbide Schottky barrier diode.

[0040] Figure 6 This diagram illustrates the structure obtained after forming a passivation layer and a polyimide layer in the fabrication process of a silicon carbide Schottky barrier diode.

[0041] Figure 7 The diagram shown is a process flow chart of the method for fabricating the Schottky diode of the present invention.

[0042] Figure 8 The diagram shows a schematic of the first conductivity type substrate in the method for fabricating a Schottky diode according to the present invention.

[0043] Figure 9 The diagram shows the structure obtained after forming a patterned first hard mask layer, a first active injection region of a second conductivity type, a first terminal injection region of a second conductivity type, and a first transition injection region of a second conductivity type in the fabrication method of the Schottky diode of the present invention.

[0044] Figure 10 Displayed as Figure 9 Top view of the structure shown.

[0045] Figure 11 The diagram shows the structure obtained after forming a first sidewall, a second active injection region of a second conductivity type, a second terminal injection region of a second conductivity type, and a second transition injection region of a second conductivity type in the fabrication method of the Schottky diode of the present invention.

[0046] Figure 12 The diagram shows a schematic of the structure obtained after forming a second sidewall, a third active injection region of a second conductivity type, a third terminal injection region of a second conductivity type, and a third transition injection region of a second conductivity type in the fabrication method of the Schottky diode of the present invention.

[0047] Figure 13 The diagram shown is a schematic diagram of the structure obtained after forming a field oxide layer in the fabrication method of the Schottky diode of the present invention.

[0048] Figure 14 The diagram shown is a schematic diagram of the structure obtained after forming a conductive metal layer and a conductive functional layer in the fabrication method of the Schottky diode of the present invention.

[0049] Figure 15 The diagram shown is a schematic diagram of the structure obtained after forming the electrode metal layer in the preparation method of the Schottky diode of the present invention.

[0050] Figure 16 The diagram shown is a schematic diagram of the structure obtained after forming a passivation layer and an insulating layer in the fabrication method of the Schottky diode of the present invention.

[0051] Explanation of reference numerals in the attached figures

[0052] 101 Heavily doped N-type substrate 102 N-type drift zone 103 Hard mask layer 104、204 First opening 105、205 Second opening 106、206 Third opening 107 P-type active injection region 108 P-type terminal injection area 109 P-type transition injection region 110、218 field oxide layer 111 Titanium metal layer 112 Titanium nitride layer 113 Aluminum metal layer 114、222 passivation layer 115 polyimide layer 201 substrate 202 Epitaxial layer 203 First hard mask layer 207 First active injection region 208 First terminal injection area 209 First transition injection zone 210 First side wall 211 Second active injection region 212 Second terminal injection area 213 Second transition injection zone 214 Second side wall 215 Third active injection region 216 Third terminal injection area 217 Third transition injection zone 219 conductive metal layer 220 conductive functional layer 221 Electrode metal layer 221a Electrode lead-out section 223 Insulation layer I, III Cellular region II, IV Terminal area W1 Width of the first active injection region W2 Width of the first terminal injection area W3 Width of the first transition injection region W4 Width of the second active injection region W5 Width of the second terminal injection area W6 Width of the second transition injection region W7 Width of the third active injection region W8 Width of the third terminal injection area W9 Width of the third transition injection region S1~S7 step Detailed Implementation

[0053] Please see Figures 1 to 6 This demonstrates the steps involved in the fabrication process of a silicon carbide Schottky barrier diode:

[0054] (1) Please refer to Figure 1 A heavily doped N-type substrate 101 is provided, and an N-type drift region 102 is epitaxially grown on the heavily doped N-type substrate 101. The N-type drift region 102 includes a cell region I and a terminal region II.

[0055] (2) Please refer to Figure 2 An oxide layer is deposited on the N-type drift region 102 and etched to form a hard mask layer 103. The hard mask layer 103 has a first opening 104, a second opening 105, and a third opening 106 that expose the cell region I, the terminal region II, and the boundary region between the cell region I and the terminal region II, respectively. Ion implantation is performed on the N-type drift region 102 based on the hard mask layer 103 to form a P-type active implantation region 107, a P-type terminal implantation region 108, and a P-type transition implantation region 109 on the upper surface of the epitaxial layer. The P-type active implantation region 107, the P-type terminal implantation region 108, and the P-type transition implantation region 109 have the same doping concentration range, which is 1E19 cm⁻¹. -3 ~1E20 cm -3 .

[0056] (3) Please refer to Figure 3 Remove the mask layer to form a field oxide layer 110 on the terminal region II.

[0057] (4) Please refer to Figure 4 A titanium metal layer 111 and a titanium nitride layer 112 are sequentially formed on the cell region I. Rapid heat treatment causes the titanium metal layer 111 to form an ohmic contact with the P-type active injection region 107 and a Schottky contact with the N-type drift region 102.

[0058] (5) Please refer to Figure 5An aluminum metal layer 113 is formed and etched, the aluminum metal layer 113 covering the field oxide layer 110 and the titanium nitride layer 112.

[0059] (6) Please refer to Figure 6 A passivation layer 114 is formed on the aluminum metal layer 113 and the passivation layer 114 is etched, exposing the electrode leads of the aluminum metal layer 113. The electrode leads are located above the cell region I. A polyimide layer 115 is formed on the aluminum metal layer 113 and the aluminum metal layer 113 is etched, so that the polyimide layer 115 encapsulates the passivation layer 114 and exposes the electrode leads.

[0060] The above-mentioned fabrication processes for silicon carbide Schottky barrier diodes cannot effectively improve the trade-off between turn-on voltage, leakage current, and extreme stress reliability; that is, they cannot achieve a silicon carbide Schottky barrier diode that simultaneously possesses low turn-on voltage, low leakage current, and high extreme stress reliability. To address this, this application proposes a method for fabricating a Schottky diode that, by introducing a second active injection region, a second terminal injection region, and a second transition injection region, can achieve a silicon carbide Schottky barrier diode that simultaneously possesses low turn-on voltage, low leakage current, and high extreme stress reliability, without requiring additional photomasks and without increasing the device fabrication cost.

[0061] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0062] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, whole, step, or component, but does not exclude the presence or addition of one or more other features, wholes, steps, or components.

[0063] Features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0064] In the detailed description of embodiments of the present invention, for ease of explanation, the schematic diagrams illustrating the device structure may be partially enlarged without adhering to the general scale, and the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. Furthermore, in actual manufacturing, the three-dimensional spatial dimensions of width, depth, and height should be included.

[0065] For ease of description, spatial relation terms such as “below,” “under,” “lower than,” “below,” “above,” and “upper” may be used herein to describe the relationship between one element or feature shown in the accompanying drawings and other elements or features. It will be understood that these spatial relation terms are intended to include directions other than those depicted in the drawings for devices in use or operation. Furthermore, when a layer is referred to as being “between” two layers, it may be the only layer between the two layers, or there may be one or more layers in between.

[0066] In the context of this application, the structure described above the first feature may include embodiments in which the first and second features are in direct contact, or embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0067] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0068] Please see Figure 7 The diagram shows a process flow chart of the method for fabricating a Schottky diode according to the present invention, which includes at least the following steps:

[0069] S1: Provide a substrate of a first conductivity type, grow an epitaxial layer of the first conductivity type on the substrate, the epitaxial layer including a cell region and a terminal region, and the doping concentration of the epitaxial layer is less than the doping concentration of the substrate;

[0070] S2: A patterned first hard mask layer is formed on the epitaxial layer, wherein the first hard mask layer has a first opening, a second opening and a third opening that respectively expose the cell region, the terminal region and the boundary region between the cell region and the terminal region;

[0071] S3: Ion implantation is performed on the epitaxial layer based on the first hard mask layer to form a first active implantation region of the second conductivity type, a first terminal implantation region of the second conductivity type, and a first transition implantation region of the second conductivity type on the upper surface of the epitaxial layer. The first active implantation region is located in the cell region, the first terminal implantation region is located in the terminal region, and the first transition implantation region is located in the boundary region between the cell region and the terminal region.

[0072] S4: Form a first sidewall on the sidewalls of the first opening, the second opening and the third opening to obtain a second hard mask layer;

[0073] S5: Ion implantation is performed on the epitaxial layer based on the second hard mask layer to form a second active implantation region of the second conductivity type, a second terminal implantation region of the second conductivity type, and a second transition implantation region of the second conductivity type in the epitaxial layer. The second active implantation region extends downward from the bottom surface of the first active implantation region, the second terminal implantation region extends downward from the bottom surface of the first terminal implantation region, and the second transition implantation region extends downward from the bottom surface of the first transition implantation region. The doping concentration of the second active implantation region is less than the doping concentration of the first active implantation region, the doping concentration of the second terminal implantation region is less than the doping concentration of the first terminal implantation region, and the doping concentration of the second transition implantation region is less than the doping concentration of the first transition implantation region.

[0074] S6: Remove the second hard mask layer to form a field oxide layer on the terminal region;

[0075] S7: A conductive metal layer and a conductive functional layer are sequentially formed on the cell region. The conductive metal layer includes a first portion that is in ohmic contact with the first active implantation region and a second portion that is in Schottky contact with the epitaxial layer.

[0076] The following section, using a structural diagram, details the specific implementation methods for each of the above steps.

[0077] Please refer to the following first. Figure 8 Step S1 is executed: a first conductivity type substrate 201 is provided, and a first conductivity type epitaxial layer 202 is grown on the substrate 201. The epitaxial layer 202 includes a cell region III and a terminal region IV, and the doping concentration of the epitaxial layer 202 is less than the doping concentration of the substrate 201.

[0078] As an example, the first conductivity type is N-type and the second conductivity type is P-type. In this embodiment, the substrate 201 is a heavily doped N-type substrate, and the epitaxial layer 202 is an N-type epitaxial layer 202 to form an N-type drift region.

[0079] Please see again Figure 9 Step S2: A patterned first hard mask layer 203 is formed on the epitaxial layer 202. The first hard mask layer 203 has a first opening 204, a second opening 205, and a third opening 206 that respectively expose the cell region III, the terminal region IV, and the boundary region between the cell region III and the terminal region IV.

[0080] Specifically, forming the patterned first hard mask layer 203 includes the following steps:

[0081] (1) A first oxide layer is deposited on the epitaxial layer 202;

[0082] (2) Etch the first oxide layer to obtain the patterned first hard mask layer 203.

[0083] Please see again Figure 9 and Figure 10 Step S3: Ion implantation is performed on the epitaxial layer 202 based on the first hard mask layer 203 to form a first active implantation region 207 of the second conductivity type, a first terminal implantation region 208 of the second conductivity type, and a first transition implantation region 209 of the second conductivity type on the upper surface of the epitaxial layer 202. The first active implantation region 207 is located in the cell region III, the first terminal implantation region 208 is located in the terminal region IV, and the first transition implantation region 209 is located in the boundary region between the cell region III and the terminal region IV. Figure 9 The diagram shows the structure obtained after forming a patterned first hard mask layer 203, a first active injection region 297, a first terminal injection region 208, and a first transition injection region 209. Figure 10 Displayed as Figure 9 Top view of the structure shown ( Figure 9 for Figure 10 (Cross-section along the AA' direction).

[0084] As an example, the first active implantation region 207, the first terminal implantation region 208, and the first transition implantation region 209 have the same doping concentration range, which is 1E19 cm⁻¹. -3 ~1E20 cm -3 .

[0085] As an example, the ion type of the ion implantation includes aluminum ions. In this embodiment, a high dose of aluminum ions is implanted into the epitaxial layer 202 to form the first active implantation region 207, the first terminal implantation region 208, and the first transition implantation region 209.

[0086] As an example, in the X direction, the width W1 of the first terminal injection region 208 is smaller than the width W2 of the first active injection region 207, and the width W2 of the first active injection region 207 is smaller than the width W3 of the first transition injection region 209.

[0087] Please see again Figure 11 Step S4: Form a first sidewall on the sidewalls of the first opening 204, the second opening 205 and the third opening 206 to obtain a second hard mask layer.

[0088] Specifically, forming the first sidewall includes the following steps:

[0089] (1) A second oxide layer of predetermined thickness is deposited isotropically within the first opening 204, the second opening 205 and the third opening 206;

[0090] (2) The second oxide layer is anisotropically etched to obtain the first sidewall.

[0091] Specifically, the second hard mask layer is obtained by forming the first sidewall, without the need to add a new mask, so the fabrication cost of the device remains basically unchanged.

[0092] Please see again Figure 11 Step S5: Ion implantation is performed on the epitaxial layer 202 based on the second hard mask layer to form a second active implantation region 211 of the second conductivity type, a second terminal implantation region 212 of the second conductivity type, and a second transition implantation region 213 of the second conductivity type in the epitaxial layer 202. The second active implantation region 211 extends downward from the bottom surface of the first active implantation region 207, the second terminal implantation region 212 extends downward from the bottom surface of the first terminal implantation region 208, and the second transition implantation region 213 extends downward from the bottom surface of the first transition implantation region 209. The doping concentration of the second active implantation region 211 is less than the doping concentration of the first active implantation region 207, the doping concentration of the second terminal implantation region 212 is less than the doping concentration of the first terminal implantation region 208, and the doping concentration of the second transition implantation region 213 is less than the doping concentration of the first transition implantation region 209.

[0093] Specifically, by introducing the second active injection region 211, the second terminal injection region 212, and the second transition injection region 213, the electric field at the Schottky metal interface can be effectively reduced, thereby reducing leakage current. In particular, the presence of the second active injection region 211, the second terminal injection region 212, and the second transition injection region 213 can effectively discharge avalanche current and improve avalanche tolerance when the device is in an avalanche state; and can increase the PN junction area when the device is in a surge state, allowing the device to enter the bipolar conduction state earlier and improving current conduction capability, thereby enhancing the device's resistance to extreme stress impacts.

[0094] In addition, the introduction of the second active injection region 211, the second terminal injection region 212, and the second transition injection region 213 can effectively reduce the thickness of the drift region. Since the doping concentration of the second active injection region 211 is less than that of the first active injection region 207, the doping concentration of the second terminal injection region 212 is less than that of the first terminal injection region 208, and the doping concentration of the second transition injection region 213 is less than that of the first transition injection region 209, the electric field decreases more slowly in the lightly doped injection region. The on-state voltage of the device will only increase slightly, and the breakdown voltage can still meet the application requirements.

[0095] As an example, the ion type for ion implantation includes aluminum ions. In this embodiment, aluminum ions are implanted into the epitaxial layer 202 at high energy to form the second active implantation region 211, the second terminal implantation region 212, and the second transition implantation region 213. In this embodiment, the second active implantation region 211, the second terminal implantation region 212, and the second transition implantation region 213 have the same doping concentration, which is 1E17 cm⁻¹. -3 .

[0096] As an example, in the X direction, the width W4 of the second active injection region 211 is smaller than the width W5 of the first active injection region 207, the width W5 of the second terminal injection region 212 is smaller than the width W6 of the first terminal injection region 208, and the width W6 of the second transition injection region 213 is smaller than the width W3 of the first transition injection region 209.

[0097] For example, please refer to Figure 12 After forming the second active injection region 211, the second terminal injection region 212, and the second transition injection region 213, the method further includes the following steps:

[0098] (1) A second sidewall 214 is formed on the outer wall of the first sidewall;

[0099] (2) Ion implantation is performed on the epitaxial layer 202 based on the second hard mask layer with the second sidewall 214 to form a third active implantation region 215 of the second conductivity type, a third terminal implantation region 216 of the second conductivity type, and a third transition implantation region 217 of the second conductivity type in the epitaxial layer 202. The third active implantation region 215 extends downward from the bottom surface of the second active implantation region 211, the third terminal implantation region 216 extends downward from the bottom surface of the second terminal implantation region 212, and the third transition implantation region 217 extends downward from the bottom surface of the second transition implantation region 213. The doping concentration of the third active implantation region 215 is less than the doping concentration of the second active implantation region 211, the doping concentration of the third terminal implantation region 216 is less than the doping concentration of the second terminal implantation region 212, and the doping concentration of the third transition implantation region 217 is less than the doping concentration of the second transition implantation region 213.

[0100] Specifically, the ion type for ion implantation includes aluminum ions. In this embodiment, aluminum ions are implanted into the epitaxial layer 202 at a high energy of megaelectron volts (MeV) to form the third active implantation region 215, the third terminal implantation region 216, and the third transition implantation region 217. In this embodiment, the third active implantation region 215, the third terminal implantation region 216, and the third transition implantation region 217 have the same doping concentration, which is 1E16 cm⁻¹. -3 .

[0101] As an example, in the X direction, the width W7 of the third active injection region 215 is smaller than the width W5 of the second active injection region 211, the width W8 of the third terminal injection region 216 is smaller than the width W5 of the second terminal injection region 212, and the width W9 of the third transition injection region 217 is smaller than the width W6 of the second transition injection region 213.

[0102] Please see again Figure 13 Step S6: Remove the second hard mask layer to form a field oxide layer 218 on the terminal region IV.

[0103] Specifically, forming the field oxide layer 218 includes the following steps:

[0104] (1) A third oxide layer is formed on the epitaxial layer 202;

[0105] (2) Etch the third oxide layer to expose the cell region III and part of the terminal region IV, and obtain the field oxide layer 218.

[0106] Please see again Figure 14Step S7: Sequentially form a conductive metal layer 219 and a conductive functional layer 220 on the cell region III. The conductive metal layer 219 includes a first portion that is in ohmic contact with the first active injection region 207 and a second portion that is in Schottky contact with the epitaxial layer 202.

[0107] As an example, the conductive metal layer 219 is made of titanium, and the conductive functional layer 220 is made of titanium nitride. The conductive metal layer 219 forms an ohmic contact with the contact surface of the first active injection region 207, and forms a Schottky contact with the contact surface of the epitaxial layer 202 outside the first active injection region 207 in the cell region III.

[0108] As an example, after forming the conductive metal layer 219 and the conductive functional layer 220 on the cell region III, a rapid thermal treatment step is also included to promote the formation of ohmic and Schottky contacts.

[0109] As an example, the following steps are also included:

[0110] (1) Please refer to Figure 15 An electrode metal layer 221 is formed, which covers the field oxide layer 218 and the conductive functional layer 220.

[0111] (2) Please refer to Figure 16 A passivation layer 222 is formed on the electrode metal layer 221, and the passivation layer 222 exposes the electrode lead-out portion 221a of the electrode metal layer 221, which is located above the cell region III.

[0112] (3) Please refer to the following: Figure 16 An insulating layer 223 is formed on the electrode metal layer 221, the insulating layer 223 encapsulates the passivation layer 222 and exposes the electrode lead-out portion 221a.

[0113] Specifically, the electrode metal layer 221 is made of aluminum, and the passivation layer 222 is made of polyimide.

[0114] Thus, a Schottky diode is fabricated, comprising a substrate of a first conductivity type 201, a first active implantation region 207 of a second conductivity type, a first terminal implantation region 208 of a second conductivity type, a first transition implantation region 209 of a second conductivity type, a second active implantation region 211 of a second conductivity type, a second terminal implantation region 212 of a second conductivity type, a second transition implantation region 213 of a second conductivity type, a field oxide layer 218, a conductive metal layer 219, and a conductive functional layer 220. The substrate 201 is provided with an epitaxial layer 202 of a first conductivity type, the epitaxial layer 202 comprising a cell region III and a terminal region IV, and the doping concentration of the epitaxial layer 202 is less than the doping concentration of the substrate 201.

[0115] Specifically, the first active injection region 207 of the second conductivity type, the first terminal injection region 208 of the second conductivity type, and the first transition injection region 209 of the second conductivity type are spaced apart on the side of the epitaxial layer 202 away from the substrate 201 and extend along the direction of the epitaxial layer 202 toward the substrate 201. The first active injection region 207 is located in the cell region III, the first terminal injection region 208 is located in the terminal region IV, and the first transition injection region 209 is located in the boundary region between the cell region III and the terminal region IV.

[0116] Specifically, the second active injection region 211, the second terminal injection region 212, and the second transition injection region 213 of the second conductivity type are spaced apart in the epitaxial layer 202. The second active injection region 211 extends downward from the bottom surface of the first active injection region 207, the second terminal injection region 212 extends downward from the bottom surface of the first terminal injection region 208, and the second transition injection region 213 extends downward from the bottom surface of the first transition injection region 209. The doping concentration of the second active injection region 211 is less than the doping concentration of the first active injection region 207, the doping concentration of the second terminal injection region 212 is less than the doping concentration of the first terminal injection region 208, and the doping concentration of the second transition injection region 213 is less than the doping concentration of the first transition injection region 209.

[0117] Specifically, the field oxide layer 218 is located on the terminal region IV, the conductive metal layer 219 and the conductive functional layer 220 are stacked on the cell region III from bottom to top, and the conductive metal layer 219 includes a first portion that is in ohmic contact with the first active implantation region 207 and a second portion that is in Schottky contact with the epitaxial layer 202.

[0118] As an example, the system also includes an electrode metal layer 221, a passivation layer 222, and an insulating layer 223. The electrode metal layer 221 covers the field oxide layer 218 and the conductive functional layer 220. The passivation layer 222 is located on the electrode metal layer 221 and exposes the electrode lead-out portion 221a of the electrode metal layer 221. The electrode lead-out portion 221a is located above the cell region III. The insulating layer 223 is located on the electrode metal layer 221 to enclose the passivation layer 222 and expose the electrode lead-out portion 221a.

[0119] As an example, the epitaxial layer 202 further includes a third active implantation region 215 of the second conductivity type, a third terminal implantation region 216 of the second conductivity type, and a third transition implantation region 217 of the second conductivity type. The third active implantation region 215 extends downward from the bottom surface of the second active implantation region 211, the third terminal implantation region 216 extends downward from the bottom surface of the second terminal implantation region 212, and the third transition implantation region 217 extends downward from the bottom surface of the second transition implantation region 213. The doping concentration of the third active implantation region 215 is less than the doping concentration of the second active implantation region 211, the doping concentration of the third terminal implantation region 216 is less than the doping concentration of the second terminal implantation region 212, and the doping concentration of the third transition implantation region 217 is less than the doping concentration of the second transition implantation region 213.

[0120] In summary, the method for fabricating a Schottky diode according to the present invention includes the following steps: providing a substrate of a first conductivity type; growing an epitaxial layer of the first conductivity type on the substrate, the epitaxial layer including a cell region and a termination region, and the doping concentration of the epitaxial layer being less than the doping concentration of the substrate; forming a patterned first hard mask layer on the epitaxial layer, the first hard mask layer having a first opening, a second opening, and a third opening respectively exposing the cell region, the termination region, and the boundary region between the cell region and the termination region; performing ion implantation on the epitaxial layer based on the first hard mask layer to form a first active implantation region of a second conductivity type, a first termination implantation region of a second conductivity type, and a first transition implantation region of a second conductivity type on the upper surface layer of the epitaxial layer, the first active implantation region being located in the cell region, the first termination implantation region being located in the termination region, and the first transition implantation region being located in the boundary region between the cell region and the termination region; forming a first sidewall on the sidewall of the first opening, the second opening, and the third opening to obtain a second... A hard mask layer is used; based on the second hard mask layer, ion implantation is performed on the epitaxial layer to form a second active implantation region of the second conductivity type, a second terminal implantation region of the second conductivity type, and a second transition implantation region of the second conductivity type in the epitaxial layer. The second active implantation region extends downward from the bottom surface of the first active implantation region, the second terminal implantation region extends downward from the bottom surface of the first terminal implantation region, and the second transition implantation region extends downward from the bottom surface of the first transition implantation region. The doping concentration of the second active implantation region is less than that of the first active implantation region, the doping concentration of the second terminal implantation region is less than that of the first terminal implantation region, and the doping concentration of the second transition implantation region is less than that of the first transition implantation region. The second hard mask layer is removed to form a field oxide layer on the terminal region. A conductive metal layer and a conductive functional layer are sequentially formed on the cell region. The conductive metal layer includes a first portion that is in ohmic contact with the first active implantation region and a second portion that is in Schottky contact with the epitaxial layer. The Schottky diode fabrication method of the present invention, by introducing a second active injection region, a second terminal injection region, and a second transition injection region, enables the fabrication of a silicon carbide Schottky barrier diode that simultaneously possesses low on-state voltage, low leakage current, and high extreme stress reliability, without requiring additional photomasks and without increasing the device fabrication cost. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has high industrial applicability.

[0121] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method of fabricating a Schottky diode, characterized by, Includes the following steps: A substrate of a first conductivity type is provided, and an epitaxial layer of the first conductivity type is grown on the substrate. The epitaxial layer includes a cell region and a terminal region, and the doping concentration of the epitaxial layer is less than the doping concentration of the substrate. A patterned first hard mask layer is formed on the epitaxial layer. The first hard mask layer has a first opening, a second opening, and a third opening that respectively expose the cell region, the terminal region, and the boundary region between the cell region and the terminal region. Ion implantation is performed on the epitaxial layer based on the first hard mask layer to form a first active implantation region of the second conductivity type, a first terminal implantation region of the second conductivity type, and a first transition implantation region of the second conductivity type on the upper surface of the epitaxial layer. The first active implantation region is located in the cell region, the first terminal implantation region is located in the terminal region, and the first transition implantation region is located in the boundary region between the cell region and the terminal region. A first sidewall is formed on the sidewalls of the first opening, the second opening, and the third opening to obtain a second hard mask layer; Ion implantation is performed on the epitaxial layer based on the second hard mask layer to form a second active implantation region of the second conductivity type, a second terminal implantation region of the second conductivity type, and a second transition implantation region of the second conductivity type in the epitaxial layer. The second active implantation region extends downward from the bottom surface of the first active implantation region, the second terminal implantation region extends downward from the bottom surface of the first terminal implantation region, and the second transition implantation region extends downward from the bottom surface of the first transition implantation region. The doping concentration of the second active implantation region is less than that of the first active implantation region, the doping concentration of the second terminal implantation region is less than that of the first terminal implantation region, and the doping concentration of the second transition implantation region is less than that of the first transition implantation region. Remove the second hard mask layer to form a field oxide layer on the terminal region; A conductive metal layer and a conductive functional layer are sequentially formed on the cell region. The conductive metal layer includes a first portion that is in ohmic contact with the first active implantation region and a second portion that is in Schottky contact with the epitaxial layer.

2. The method of claim 1, wherein: The first active implant region, the first termination implant region, and the first transition implant region have a same doping concentration range, the doping concentration range being 1E19 cm -3 1E20 cm -3 .

3. The method of claim 1, wherein the metal layer is formed by a method selected from the group consisting of sputtering, vacuum deposition, and plating. It also includes the following steps: An electrode metal layer is formed, which covers the field oxide layer and the conductive functional layer; A passivation layer is formed on the electrode metal layer, the passivation layer exposing the electrode leads of the electrode metal layer, and the electrode leads are located above the cell region; An insulating layer is formed on the electrode metal layer, the insulating layer encapsulates the passivation layer and exposes the electrode lead-out portion.

4. The method of claim 1, wherein: In the X direction, the width of the first terminal injection region is smaller than the width of the first active injection region, and the width of the first active injection region is smaller than the width of the first transition injection region.

5. The method of claim 1, wherein: In the X direction, the width of the second active injection region is smaller than the width of the first active injection region, the width of the second terminal injection region is smaller than the width of the first terminal injection region, and the width of the second transition injection region is smaller than the width of the first transition injection region.

6. The method for fabricating a Schottky diode according to claim 1, characterized in that, After forming the second active injection region, the second terminal injection region, and the second transition injection region, the following steps are also included: A second sidewall is formed on the outer wall of the first sidewall; Ion implantation is performed on the epitaxial layer based on the second hard mask layer with the second sidewall to form a third active implantation region of the second conductivity type, a third terminal implantation region of the second conductivity type, and a third transition implantation region of the second conductivity type in the epitaxial layer. The third active implantation region extends downward from the bottom surface of the second active implantation region, the third terminal implantation region extends downward from the bottom surface of the second terminal implantation region, and the third transition implantation region extends downward from the bottom surface of the second transition implantation region. The doping concentration of the third active implantation region is less than that of the second active implantation region, the doping concentration of the third terminal implantation region is less than that of the second terminal implantation region, and the doping concentration of the third transition implantation region is less than that of the second transition implantation region.

7. The method for fabricating a Schottky diode according to claim 6, characterized in that: In the X direction, the width of the third active injection region is smaller than the width of the second active injection region, the width of the third terminal injection region is smaller than the width of the second terminal injection region, and the width of the third transition injection region is smaller than the width of the second transition injection region.

8. A Schottky diode, characterized in that, include: A first conductivity type substrate is provided on the substrate, the epitaxial layer of the first conductivity type is provided, the epitaxial layer includes a cell region and a terminal region, and the doping concentration of the epitaxial layer is less than the doping concentration of the substrate; A first active injection region, a first terminal injection region, and a first transition injection region of a second conductivity type are disposed at intervals on the side of the epitaxial layer away from the substrate and extend along the direction of the epitaxial layer toward the substrate. The first active injection region is located in the cell region, the first terminal injection region is located in the terminal region, and the first transition injection region is located in the boundary region between the cell region and the terminal region. A second active implantation region, a second terminal implantation region, and a second transition implantation region of a second conductivity type are disposed at intervals in the epitaxial layer. The second active implantation region extends downward from the bottom surface of the first active implantation region, the second terminal implantation region extends downward from the bottom surface of the first terminal implantation region, and the second transition implantation region extends downward from the bottom surface of the first transition implantation region. The doping concentration of the second active implantation region is less than that of the first active implantation region, the doping concentration of the second terminal implantation region is less than that of the first terminal implantation region, and the doping concentration of the second transition implantation region is less than that of the first transition implantation region. A field oxide layer is located on the terminal region; A conductive metal layer and a conductive functional layer are stacked on the cell region from bottom to top. The conductive metal layer includes a first portion that is in ohmic contact with the first active injection region and a second portion that is in Schottky contact with the epitaxial layer.

9. The Schottky diode according to claim 8, characterized in that: It also includes an electrode metal layer, a passivation layer, and an insulating layer. The electrode metal layer covers the field oxide layer and the conductive functional layer. The passivation layer is located on the electrode metal layer and exposes the electrode leads of the electrode metal layer. The electrode leads are located above the cell region. The insulating layer is located on the electrode metal layer to wrap the passivation layer and expose the electrode leads.

10. The Schottky diode according to claim 8, characterized in that: The epitaxial layer further includes a third active implantation region of the second conductivity type, a third terminal implantation region of the second conductivity type, and a third transition implantation region of the second conductivity type. The third active implantation region extends downward from the bottom surface of the second active implantation region, the third terminal implantation region extends downward from the bottom surface of the second terminal implantation region, and the third transition implantation region extends downward from the bottom surface of the second transition implantation region. The doping concentration of the third active implantation region is less than that of the second active implantation region, the doping concentration of the third terminal implantation region is less than that of the second terminal implantation region, and the doping concentration of the third transition implantation region is less than that of the second transition implantation region.

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