High voltage diode with trench-modified current path on soi substrate

Abstract

The present invention is entitled "High Voltage Diode with Trench-Improved Current Path on SOI Substrate." A semiconductor device can include a silicon-on-insulator (SOI) substrate and a diode formed on the SOI substrate, the diode including a cathode region and an anode region. The semiconductor device can include at least one breakdown voltage trench disposed at an edge of the cathode region and between the cathode region and the anode region.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Patent Application No. 16 / 450,298, filed June 24, 2019, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This specification relates to diodes used in silicon-on-insulator (SOI) devices. Background Technology

[0004] A diode's breakdown voltage (BV) (where a large reverse current flows when the diode is reverse-biased) is a fundamental diode characteristic that governs the potential applications of a diode. For example, it might be desirable to use the diode as a blocking diode or for electrostatic discharge (ESD) protection. Among these and similar capabilities, it might be desirable to ensure that the maximum reverse voltage occurring at the diode is less than the diode's breakdown voltage.

[0005] In silicon-on-insulator (SOI) technology, bulk silicon is covered by an insulator, which in turn covers another silicon layer on which devices and other structures are formed. SOI technology has several known advantages associated with the miniaturization of circuits and devices. For example, isolating the circuit from the bulk silicon through the intervening insulator results in lower parasitic capacitance, lower leakage current, and higher power efficiency.

[0006] It is also desirable to form different types of circuits on a single SOI substrate in order to further pursue miniaturization, increase circuit speed and reliability, facilitate interconnection between circuits, and make associated manufacturing processes more efficient and cost-effective. For example, logic circuits, analog circuits, and power circuits can be included on a single SOI substrate.

[0007] While techniques exist for isolating such circuits from each other on an SOI substrate, the presence of power circuitry specifically necessitates the inclusion of high (breakdown) voltage diodes. However, conventional techniques do not provide a practical way to form diodes with sufficiently high BV for use in isolation circuitry on an SOI substrate. Summary of the Invention

[0008] According to one general aspect, a semiconductor device includes a silicon-on-insulator (SOI) substrate and a diode formed on the SOI substrate, the diode including a cathode region and an anode region. The semiconductor device may include at least one breakdown voltage trench disposed at an edge of the cathode region and located between the cathode region and the anode region.

[0009] According to another general aspect, a semiconductor device can include a substrate and a diode formed in the substrate, the diode including a cathode region and an anode region. The semiconductor device can include at least one trench insulator adjacent to the cathode region, the at least one trench insulator defining a diode current path around the at least one trench insulator, the diode current path traversing the substrate between the cathode region and the anode region.

[0010] According to another general aspect, a method of fabricating a semiconductor device can include forming a silicon-on-insulator (SOI) substrate, and forming a breakdown voltage trench in the SOI substrate. The method can also include forming a diode in the SOI, including forming a cathode region of the diode adjacent to the breakdown voltage trench, where the breakdown voltage trench is located between the cathode region and an anode region.

[0011] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF DRAWINGS

[0012] FIG. 1A A simplified cross-section of a high voltage diode with trench modifications to the current path is shown, in accordance with some example implementations.

[0013] FIG. 1B A more detailed example implementation of a cross-section of FIG. 1A is shown.

[0014] FIG. 2 A top view of an example high voltage diode of FIG. 1B is shown.

[0015] FIG. 3 A relationship between the structure, breakdown voltage, and electric field distribution of a high voltage diode of FIG. 1B and FIG. 2 is shown.

[0016] FIG. 4 A cross-section of a second example implementation of a high voltage diode of FIG. 1A is shown.

[0017] FIG. 5A A simplified cross-section of another example implementation of a high voltage diode is shown, in which vertical field plates are used for increased breakdown voltage.

[0018] FIG. 5B A more detailed example implementation of a simplified cross-section of FIG. 5A is shown.

[0019] FIG. 6 A top view of example implementations of FIG. 5B and FIG. 6 is shown.

[0020] FIG. 7 The structure, breakdown voltage, and electric field distribution of an exemplary implementation of FIG. 5B and FIG. 6 are shown.

[0021] FIG. 8 Additional exemplary relationships between the structure, breakdown voltage, and electric field distribution of an exemplary implementation of FIG. 5B and FIG. 6 are shown.

[0022] FIG. 9 A fourth exemplary implementation of a high voltage diode is shown.

[0023] FIG. 10 A fifth exemplary implementation of a high voltage diode is shown.

[0024] FIG. 11 A flowchart showing exemplary processing operations for forming FIG. 4 the various faces of an exemplary implementation of

[0025] FIG. 12 A structure for the first example of operations in the flowchart is shown. FIG. 11

[0026] A structure for the second example of operations in the flowchart is shown. FIG. 13 FIG. 11 A structure for the third example of operations in the flowchart is shown.

[0027] FIG. 14 FIG. 11 A structure for the fourth example of operations in the flowchart is shown.

[0028] FIG. 15 A structure for the fifth example of operations in the flowchart is shown. FIG. 11

[0029] A structure for the sixth example of operations in the flowchart is shown. FIG. 16 FIG. 11 A structure for the seventh example of operations in the flowchart is shown.

[0030] FIG. 17 FIG. 11 A structure for the eighth example of operations in the flowchart is shown. DETAILED DESCRIPTION

[0031] ​​​​As detailed below, embodiments include a compact high-voltage diode located on a silicon-on-insulator (SOI) substrate that utilizes cathode-adjacent trenches to improve the current path of the diode and increase its breakdown voltage under reverse current conditions. The compact high-voltage diode can be manufactured inexpensively by incorporating other types of trenches (e.g., isolation trenches) formed on the SOI substrate. Therefore, reliable diode performance can be obtained.

[0032] FIG. 1A A simplified cross-section of a high-voltage diode 100A with a trench-modified current path 136 according to some exemplary specific implementations is shown. FIG. 1B It shows FIG. 1A A more detailed exemplary embodiment of the cross-section. For clarity, FIG. 1A and FIG. 1B Consistent numbering (i.e., similar labels indicate similar elements).

[0033] exist FIG. 1A In a simplified example, diode 100a includes a cathode 116 and an anode 118 formed in a silicon-on-insulator (SOI) layer 108. As mentioned above, and as can be discussed below... FIG. 2 As seen in the top view, diode 100a can be isolated from other circuits by an isolation trench, referred to as deep trench isolation (DTI) structure 126. Specifically, for example, DTI 126 can be designed to isolate diode 100a from high-voltage power circuitry also formed in SOI 108.

[0034] Nevertheless, in various application scenarios, including unexpected short circuits, electrostatic discharge events, and other faults, diode 100a may be exposed to large reverse voltages and may need to withstand associated large breakdown voltages (BV). In conventional diodes, reverse current flow is governed by the electric field in the cathode region (and the associated lateral doping profile), and specifically by, for example, the field located in the N-th cathode region. well The critical electric field is controlled at the edge of the cathode region and at the PN junction with the p-type SOI layer. Therefore, the marginal increase in BV can be achieved by increasing the lateral distance or spacing between the cathode and anode regions in a conventional diode.

[0035] However, in FIG. 1A In this context, the breakdown voltage trench (BVT) 134 improves the electric field distribution in the region of the cathode 116 and the associated reverse current path 136 between the cathode 116 and the anode 118. Specifically, as shown, the BVT 134 causes the current path 136 to be at least quasi-vertical, for example, at least partially traveling in the direction of the insulator on which the SOI layer 108 is formed (not shown). FIG. 1A In the middle; shown asFIG. 1B In other words, the BVT 134 is formed to a depth that extends beyond the cathode 116 but does not reach the bottom of the SOI layer 108, such that at least a portion of the SOI layer 108 is available for the trench- improved current path 136 to flow therethrough between the cathode 116 and the anode 118.

[0036] Accordingly, the lateral portion of the PN junction between the conventional cathode region and the adjacent P-type SOI layer, just mentioned, can be eliminated by including the BVT 134. For example, the example of FIG. 4B, FIG. 3 The example of FIG. 4B shows an electric field having a static potential that is strongest in the region of the cathode 116 and weakens vertically along the length of the BVT 134, which is consistent with the illustrated flow of the trench-improved current path 136.

[0037] FIG. 1A The simplified example of FIG. 4B shows a single BVT 134 having the illustrated width and depth, but in various other implementations, these and other BVT parameters can be varied. For example, multiple BVTs can be included, as shown in FIG. 5, FIG. 7 and FIG. 9 The width of each BVT can be varied, as shown in FIG. 5, FIG. 10 and the depth of the BVT 134 can also be varied. In addition, the spacing between multiple BVTs, as well as the spacing between the anode 118 and the BVT 134 closest to the anode 118, can be varied.

[0038] As detailed below, appropriate design choices with respect to the above-mentioned (and similar) parameters enable a certain degree of control over the resulting breakdown voltage. For example, a conventional SOI diode without the BVT 134 can be rated for a breakdown voltage in the range of 90V. By adding the BVT 134, the diode 100a can have a breakdown voltage in the range of at least 140V, enabling an operating range of, for example, 120V. As mentioned above, and as described and shown in detail below, variations in the design parameters associated with the BVT 134 (e.g., variations in the number, width, or spacing of the BVTs) also enable the BV to be further increased.

[0039] Advantageously, the BVT 134 can be formed using a processing flow that is similar to the processing flow used to form the DTI 126. In some examples, as shown in the example of FIG. 4B, the BVT 134 can be formed in the same processing step as the DTI 126 by varying certain processing parameters (e.g., the size of the mask openings). Accordingly, the various benefits of the BVT 134 described herein can be obtained in a cost-effective, reliable, and efficient manner. FIG. 11 to FIG. 16

[0040] Other design variations are also possible. For example, as relative to the example of FIG. 5, the BVT 134 can be formed to a depth that extends beyond the cathode 116 but does not reach the bottom of the SOI layer 108, such that at least a portion of the SOI layer 108 is available for the trench-improved current path 136 to flow therethrough between the cathode 116 and the anode 118.​FIG. 4 As shown and described, BVT 134 can be formed with an internal air gap. Also, relative to... FIG. 4 The description and illustration show that an additional N-type layer can be disposed in the P-type anode (and electrically shorted to the P-type anode) to convert the diode into a BJT diode, such that the N-layer forms the collector of a lateral NPN BJT, wherein the original cathode acts as the emitter, the original P-type anode acts as the base, and the newly added N-type layer acts as the collector.

[0041] exist FIG. 1B In a more detailed example, diode 100b is shown to be formed using a bulk Si substrate 102 having an insulating layer 104 formed thereon. For example, the bulk silicon substrate 102 may have P+ type doping, while layer 104 may be formed using an oxide or other suitable insulator and may be referred to as a buried oxide or BOX.

[0042] An anti-reverse gate layer (ABG layer) 106 may be formed on the BOX layer 104. The ABG layer may also have a P+ type doping concentration and is known to be used to shield the diode 100b and other circuitry formed on the SOI 108 from the potential of the substrate 102.

[0043] SOI layer 108 may represent a P-type silicon layer formed on layers 102, 104, and 106, in which various devices and circuit elements can be formed, including diodes 100A and 100B. Specifically, as shown in the figure, cathode 116 may include N-type layer 110 (e.g., N... well or N well / N resurf It can be formed within the SOI layer 108. N-type contact layer (N...) imp 112 may be formed in N-type region 110, and metal contacts (e.g., silicides) 114 may be formed on N-type contact layer 112. Therefore, as shown, regions / layers 110, 112, and 114 can be understood as representing cathodes 116 of diodes 100a and 100b.

[0044] The anode 118 of diodes 100A and 100B can be electrically connected to a P-type contact layer (e.g., P...). imp The metal contact 120 of 121 is formed or may include the metal contact, thereby providing contact with the P-type anode region 122 (e.g., P...). well Electrical contacts. Shallow trench isolation (STI) region 124 (e.g., suitable oxide) may be formed adjacent to P-type contact layer 121 and P-type anode region 122.

[0045] In addition, FIG. 1BIn the diagram, the deep trench isolation (DTI) region 126 is shown to isolate the aforementioned structures of diodes 100a and 100b (including cathode 116 and anode 118) from other circuit elements or other areas that may be formed on or within the SOI layer 108. Similar to STI 124, DTI 126 can be formed using a suitable oxide. In some embodiments, DTI 126 may have a polysilicon layer formed therein.

[0046] To illustrate the function and purpose of DTI 126, the outer recessed area 133 is shown as including a P-type area 130, a shallow trench isolation area 132, a P-type contact layer 131, and a metal contact 128. For description FIG. 1B It should be understood that the external recess 133 and the elements shown therein are merely for illustrating the isolation function of the DTI 126, and therefore will not be described in detail herein.

[0047] exist FIG. 1B In the example above, according to the text above... FIG. 1A As described, BVT 134 can be configured to improve the current path 136 of diode 100b between cathode 116 and anode 118. Specifically, BVT 134 redirects current flow, causing the current path 136 to extend primarily in a substantially vertical direction, i.e., in the direction toward BOX layer 104.

[0048] As mentioned above, in contrast to FIG. 1A As mentioned, various design parameters of the BVT 134 can be correlated with variations in the breakdown voltage of the diode 100b. For example, the breakdown voltage can depend on the relative width of the BV trench 134 and the spacing between the BVT 134 and the anode 118. In specific implementations that include multiple BVT 134s (e.g., Figure 5, ...), ... FIG. 7 , FIG. 9 The resulting breakdown voltage can vary depending on factors such as the total number of included BVTs and the degree of spacing between them. Like STI 124 and DTI 126, BVT 134 can be formed using suitable oxides. In some exemplary embodiments shown and described below, BVT 134 may be formed with an air gap included therein.

[0049] FIG. 2 for FIG. 1B A top view of diode 100b. As shown, BVT 134 can be configured to surround cathode 116 in the region between cathode 116 and anode 118. Also shown, diode 100b can be isolated from other circuit elements via DTI 126.

[0050] FIG. 3 It shows the usual with FIG. 1Bcorresponding simplified diode 300. As shown, diode 300 includes a bulk silicon layer 302, a BOX layer 304, and an ABG layer 306. An SOI layer 308 has a BVT 334 formed therein that separates a cathode region 310 from an anode region 322. As shown, BVT 334 is adjacent to an edge of cathode region 310 and extends vertically in the direction of BOX 304.

[0051] Also in FIG. 3 , a spacing L b between BVT 334 and anode region 322 is shown. b As mentioned above, and as shown with respect to graph 314, the breakdown voltage of diode 300 can vary according to spacing L b .

[0052] In a conventional SOI diode without a BVT 334, the breakdown voltage is typically limited by the lateral doping profile of the diode cathode region. That is, in a conventional diode, the radius of curvature of the cathode region as created by diffusion / implantation will dictate the electric field strength at the point of curvature, and breakdown typically occurs in the region that first reaches the breakdown field.

[0053] As mentioned above, conventional approaches can attempt to enhance the breakdown voltage of an SOI diode by increasing the spacing between the cathode region and the anode region. Thus, in a conventional scenario, it is difficult to form a compact diode because limiting the cathode / anode spacing will also decrease the breakdown voltage of the diode. Additionally, even in scenarios where the cathode / anode spacing can be increased, the associated breakdown voltage increase experiences a point of diminishing returns such that even relatively large cathode / anode spacings result in a breakdown voltage of, for example, less than 100 volts, such as approximately 90 volts.

[0054] In contrast, as shown in graph 314 of FIG. 3 , the inclusion of BVT 334 causes the breakdown voltage of diode 300 to increase across a range of spacings L b , for example, ranging from 2 microns to 8 microns. As shown, a high breakdown voltage occurs even at relatively small spacings L b , allowing for a compact configuration of diode 300. For example, FIG. 3 , the breakdown voltage can increase to approximately 140 V, or in a range of, for example, 130 V to 150 V, allowing for a compact diode configuration to have a reliable breakdown voltage in the range below 140 V, for example, for a 120 V operating scenario.

[0055] Additionally, in FIG. 4 , the impact ionization graph 320 shows that for the shown BV and corresponding L bThe impact ionization at the breakdown point (as shown in graph 324, where the associated electric field reaches a critical value and avalanche breakdown occurs) is strongest in the region below the cathode region 310 and extends at least semi-vertically toward the BOX layer 304. Similarly, the electrostatic potential 324, as shown by field line 326, is strongest in the region of the cathode region 316 and extends at least semi-vertically in the direction of the BOX layer 304.

[0056] FIG. 1B It shows FIG. 4 An alternative exemplary implementation of diode 100b. FIG. 1B In the diagram, diode 400 is shown as a bipolar junction transistor (BJT) diode 400a (i.e., a diode connected to a BJT), which has a corresponding structure 400b.

[0057] Many structural elements of diode 400b are similar to FIG. 4 The diode 100b is numbered accordingly. Thus, for example, diode 400b includes a bulk silicon substrate 402, a BOX layer 404, and an ABG layer 406. The silicon layer 408 has a cathode region 410 formed therein, wherein an N-type contact layer 412 is electrically connected to a metal contact 414, thereby forming a cathode 416.

[0058] In addition, FIG. 1B In the anode 118, there are metal contacts 420, a P-type contact layer 421, and an N-type contact layer 423. As further shown, N... well Area 425 includes P well In anode region 422. STI region 424 is adjacent to anode 118, for example, adjacent to P-type contact layer 421, as shown. DTI 432 isolates diode 400B from outer pit 433. Therefore, as mentioned above, diode 400b forms a quasi-vertical diode, which, with FIG. 4 Compared to the implementation scheme, it may have, for example, improved forward current.

[0059] exist FIG. 3 In the example, BVT 434 is shown adjacent to the N-type cathode region 410. BVT 434 is used in conjunction with the regions already shown above relative to Figures 1 to 12. FIG. 4 The same or similar purpose, but in which it is FIG. 4 In the case of diode 400B, for example, BVT 434 enables vertical or quasi-vertical current flow in diode 400B and the associated increase in breakdown voltage.

[0060] FIG. 5AIt is also shown that BVT 434 can be implemented as an air gap BVT 436 in an alternative embodiment. That is, as shown, BVT 434 can be formed with an air gap 437 formed therein. Of course, other variations of BVT 434 can also be implemented, some of which are described herein, including varying the width of BVT 434 and / or including multiple instances of BVT 434 / 436.

[0061] FIG. 5B A simplified cross-section of another example implementation of a high voltage diode is shown, in which vertical field plates 535 are used for increased breakdown voltage. FIG. 5A A more detailed example implementation of a simplified cross-section of FIG. 4 is shown. As with the above FIG. 5A , FIG. 5B and FIG. 1A many of the elements of FIG. 1B and FIG. 5A are the same or similar to corresponding elements in and are numbered consistently where possible.

[0062] In FIG. 1A , diode 500a is shown as including multiple BVTs 534a, 534b, 534c, and 534d. As mentioned above, and as described and shown in more detail below, including multiple BVTs can have an enhanced effect with respect to increasing the BV of diode 500a as compared to a single BVT 134 of FIG. 1B and FIG. 7 .

[0063] In addition, as also mentioned, vertical field plates 535 can further enhance the BV of diode 500a. As shown, vertical field plates 535 include DTI 538 and a cathode connection region 539. Region 537 of SOI layer 108 is thus isolated by DTI 538 and existing DTI 526, and is referred to herein as a trench isolation region 537.

[0064] By connecting cathode connection region 539 to cathode 516 using a metal connection 541, it can be observed that vertical field plates 535 provide a well, such as a P-type epitaxy (PEPI) well. As shown below with respect to FIG. 3 , vertical field plates 535 positively improve the electric field distribution as compared to example electric field distribution 326 of FIG. 5B . Thus, the vertical face of current 536 is enhanced, and the BV of diode 500a is increased. For example, the BV of diode 500b can be in the range of, for example, 240 V.

[0065] In FIG. 5A , diode 500b is shown as including bulk silicon 502, BOX layer 504, ABG layer 506, and SOI 508. Similarly, cathode Nwell Region 510 is shown as having a contact layer 512 formed therein. A metal contact 514 is electrically connected to the metal contact layer 512, thereby forming a cathode 516. An anode 518 is shown as including a metal contact 520 electrically connected to a metal contact layer 521, which itself is formed within a region 522. Also in FIG. 5, a DTI 526 is shown as isolating the diode 500B from an outer recess 533.

[0066] As in the simplified example of FIG. 5B , FIG. 5B includes multiple BVTs 534a, 534b, 534c, 534d. The diode 500b also shows a more detailed example of a vertical field plate 535. In particular, in FIG. 5B , a cathode connection region is shown as including a metal contact 540, a shallow trench isolation structure 542, a metal contact layer 543, and a P well region 544. However, other suitable configurations of the cathode connection region 539 can be used, e.g., structures that are readily formed as a whole in the context of the manufacturing processes required for the diode 500b and that achieve the required electrical connection to the cathode 116.

[0067] In various implementations of the example structure of FIG. 6 , one or more of the BVTs 534a-534d can be implemented using an air gap BVT 534e, where, as shown and as mentioned above, the BVT 534e can be formed with an air gap included therein. Similarly, one or more of the deep trenches 526, 538, e.g., either or both, can be formed with polysilicon material included therein. If such DTI polysilicon is included, it can be left floating as a dielectric material.

[0068] FIG. 5B is a top view of an example implementation of FIG. 7 . As shown, a vertical field plate 535 can be formed, where the deep trench 538 and the deep trench isolation structure 526 are configured and implemented to provide the isolation of the vertical field plate 535. As shown and described, a metal connection 538 can be used to connect the vertical field plate 535 to the cathode 516.

[0069] FIG. 5B shows examples of various implementations of the diode 500b of FIG. 7 . In particular, FIG. 7 shows design choice variations made with respect to the number and spacing of the BVTs 534. For example, FIG. 7 shows a first example implementation 702, where two BVTs 534a, 534b are included, with the spacing between them denoted as L cImplementation 704 includes an additional BVT 534c, and implementation 706 includes BVTs 534a-534d.

[0070] Graph 708 illustrates an exemplary relationship between breakdown voltage and BVT-to-BVT spacing L c for implementations 702, 704, 706. As shown in graph 708, generally, increasing the number of BVTs is associated with increasing the total breakdown voltage. For relatively small spacing L c , it can be advantageous to include additional BVTs. For a given number of BVTs, this implies a smaller cathode-to-anode spacing. For example, L c may be in a range of, for example, 1-3 microns. The resulting / corresponding breakdown voltage can be in a range of, for example, 140-190 V.

[0071] As mentioned above, FIG. 7 It is also shown that breakdown voltage is related to or defined by the vertical electric field of a given termination. For example, FIG. 3 Collision ionization 704A is shown, in contrast to collision ionization 320 of FIG. 8 , showing an enhanced vertical face. Similarly, electrostatic potential 704B is shown as having an enhanced vertical face and distribution due to the inclusion of BVTs 534A, 534B, 534C.

[0072] FIG. 6 Another exemplary implementation and associated effects are shown with respect to vertical field plate 535. As shown in this example, diode 800 is formed on SOI layer 802 and BOX 804, and includes two BVTs 834a, 834b, and vertical field plate 835 connected to cathode 816. DTI 838 isolates the pockets of vertical field plate 535, as described above with respect to FIGS. 5 and FIG. 8 As mentioned above, DTI 838 can include undoped polysilicon 839.

[0073] Graph 804 illustrates an exemplary relationship between a number of included BVTs (e.g., 2, 3, or 4 BVTs) and corresponding breakdown voltage. As shown, for a given set of design choices / parameters, some implementations can have a maximum BV with two BVTs, and can experience a decrease or negative improvement by including additional BVTs. In the example of graph 804, for a given L c of 3 microns, the BV can be in a range of, for example, 220-280 V. For example, for 3 or 4 BVTs, the BV can be in a range of about 220-240 V, while 2 BVTs can have a BV in a range of, for example, 260-270 V in this example.

[0074] Additionally, inFIG. 7 In the graph 800a, the direction of the electric field is shown by arrow 840, which is influenced by the vertical field plate 835. FIG. 7 The vertical direction shown in 704a is changed to more diagonal directions. For a more vertical electric field, such as... FIG. 8 As shown in Figure 704a, the breakdown voltage can be limited by the thickness of the SOI layer. However, for more diagonal directions or orientations of the electric field generated by the vertical field plate 835, a higher breakdown voltage can be achieved for the corresponding / same SOI thickness. Figure 800b shows the corresponding electric field distribution. As can be observed in Figure 800b, the electrostatic potentials 842 and 844 are essentially the same, and the vertical plane of the electric field and the associated current are enhanced. In general, FIG. 5A It shows FIG. 5B and FIG. 9 Exemplary specific implementations (including vertical field plates 535 / 835) provide elimination of the gate-controlled diode, which would otherwise be caused by N. well / Pepi PN junction in N well It is formed on the side opposite to BVT 534a.

[0075] FIG. 9 A fourth exemplary embodiment of a high-voltage diode is shown. FIG. 1B In the diagram, diode 900 is shown as a bipolar junction transistor (BJT) diode 900a (i.e., a diode connected to a BJT), which has a corresponding structure 900b. Many structural elements of diode 900b are similar to... FIG. 4 , FIG. 5B and FIG. 9 The diodes are 100B, 400B, and 500B, and are numbered accordingly; therefore, for the sake of simplicity, they are no longer referred to as such. FIG. 9 repeat.

[0076] Also in FIG. 4 In, similar to FIG. 5B The anode 918 includes a metal contact 920, a P-type contact layer 921, and an N-type contact layer 923. As further shown, N... well Area 925 includes P well In the anode region 922. Therefore, as mentioned above, diode 900b forms a quasi-vertical diode, which, together with... FIG. 10 Compared to the implementation scheme, it may have, for example, improved forward current.

[0077] FIG. 10 A fifth exemplary embodiment of a high-voltage diode is shown. Specifically, FIG. 10An exemplary diode (shown as circuit element 1000a and having structure 1000b) is illustrated, wherein the BVT 1034 is wider than the various BVT implementations shown above (e.g., 134, 434, 534). Increasing the width of the BVT 1034 provides another design parameter for adjusting the breakdown voltage of diode 1000b to the desired range. FIG. 10 In the example, BVT 1034 extends through the entire distance between the trap regions of cathode 1016 and anode 1018, and is the edge adjacent to each trap region in the trap region.

[0078] In addition, FIG. 4 The diagram illustrates an alternative embodiment in which the diode-connected BJT 1000c is implemented by replacing anode 1018 with alternative anode 1018d to form the anode of the BJT base-collector configuration corresponding to circuit symbol 1000c. FIG. 9 and FIG. 11 As in the exemplary specific implementation, implementing the anode 1018 as the base-collector 1018d anode of the BJT achieves the various advantages mentioned above, such as a larger forward current range.

[0079] FIG. 4 To illustrate the formation FIG. 4 Each aspect of the exemplary specific implementation (and using relative to) FIG. 11 A flowchart of an exemplary processing operation (using the same reference numerals). For example... FIG. 12 to FIG. 17 As shown, each operation 1102 to 1112 is related to the subsequent... FIG. 11 One of them corresponds to the other. FIG. 12 In the example, an SOI stack (1102) is formed, as shown. FIG. 13 As shown. For example, the bulk Si layer 102, BOX layer 104, ABG layer 106 and SOI layer (e.g., p-EPI layer) 108 can be formed in successive steps.

[0080] The deep trench isolation structure and the desired BVT(1104) can then be formed together in a single step, such as FIG. 14 As shown. For example, etching can be used to form trenches, and the trench depth can be controlled by modulating the etching rate using the trench width. Therefore, combining processes that already require deep trench formation / isolation to form one or more BVTs is simple, fast, and inexpensive.

[0081] Then a shallow trench isolation (STI) structure (1106) can be formed, such as FIG. 11 As shown. For example, in FIG. 11In the example of FIG. 11, assume that the CMOS (complementary metal-oxide semiconductor) process is followed, and that the STI structures can be formed as part of that process flow. In such a context, the STI structures are typically formed, for example, to avoid leakage current of undesired parasitic BJTs that would otherwise be formed at the PN junctions.

[0082] Additionally, in FIG. 15 , various wells (1108) can be implanted, such as FIG. 16 For example, a combination of CMOS wells (N well and P well ) and medium voltage wells (N resurf and P field ) can be implanted. More generally, the techniques described herein can be used in implementations having, for example, only CMOS wells, as well as any combination of CMOS wells and relatively higher voltage wells.

[0083] Source and drain implants can then be formed, for example, as part of the CMOS process mentioned above, to form ohmic contacts with the wells (1110), as shown in FIG. 17 Finally, a module can be formed to provide low resistance contacts (and to short the intermediate N well 425 in the anode 118), as shown in ​

[0084] It should be understood that the various parameter values and ranges provided above are provided by way of example only, and are not limiting or exhaustive. For example, although not discussed in detail above, in some examples, the width of the vertical field plate can be in the range of 3 to 10 microns. The distance between the BVT and the DTI can be, for example, in the range of 2 to 5 microns. The width of the BVT can be, for example, in the range of 0.3 to 3 microns. The extension of the BVT beyond the bottom of the cathode region can be at least about 20% of the depth of the cathode region. The spacing between the BVTs can be in the range of 2 to 5 microns. Further, when three or more BVTs are included, the spacing between each successive pair of BVTs need not be equal.

[0085] ​In example implementations, a semiconductor device includes a silicon-on-insulator (SOI) substrate; a diode formed on the SOI substrate, the diode including a cathode region and an anode region; and at least one breakdown voltage trench disposed at an edge of the cathode region and between the cathode region and the anode region. A vertical field plate can be disposed at an edge of the cathode region opposite the at least one breakdown voltage trench, and the vertical field plate can be electrically connected to the cathode region. The vertical field plate can include a first deep trench isolation structure adjacent to the cathode region, the first deep trench isolation structure forming a pit with a second deep trench isolation structure that isolates the diode from at least one other circuit element formed in the SOI substrate, wherein an epitaxial material of the SOI substrate is held at the same potential as the cathode region. The at least one breakdown voltage trench can include at least two breakdown voltage trenches, including a first breakdown voltage trench at the edge of the cathode region and a second breakdown voltage trench between the first breakdown voltage trench and the anode region. The second breakdown voltage trench can then be adjacent to the anode region and extend beyond the anode region in a direction of an insulator of the SOI substrate.

[0086] In example implementations, a semiconductor device can include a substrate; a diode formed in the substrate, the diode including a cathode region and an anode region; and at least one trench insulator adjacent to the cathode region, the at least one trench insulator defining a diode current path around the at least one trench insulator that traverses the substrate between the cathode region and the anode region. The diode current path can be a reverse current that occurs at a breakdown voltage of the diode. The anode region can include a region of an opposite doping type shorted to an anode of the diode, the anode acting as a base of a lateral bipolar junction transistor (BJT), while the region of the opposite doping type acts as a collector of the lateral BJT. A vertical field plate can be disposed at an edge of the cathode region opposite an edge of the cathode region adjacent to the at least one trench insulator, and the vertical field plate can be electrically connected to the cathode region. The vertical field plate can include a first deep trench isolation structure adjacent to the cathode region, the first deep trench isolation structure forming a pit with a second deep trench isolation structure that isolates the diode from at least one other circuit element formed in the SOI substrate, wherein an epitaxial material of the SOI substrate is held at the same potential as the cathode region. The at least one trench insulator can include at least two trench insulators, including a first trench insulator at the edge of the cathode region and a second trench insulator between the first trench insulator and the anode region. The substrate can then include a silicon-on-insulator (SOI) substrate, and the second trench insulator can be adjacent to the anode region and extend beyond the anode region in a direction of an insulator of the SOI substrate.

[0087] It will be understood that, in the foregoing description, when an element such as a layer, region, substrate or component is referred to as being on another element, connected to another element, electrically connected to another element, coupled to another element, or electrically coupled to another element, it can be directly on, connected to, electrically connected to, or coupled to the other element, or one or more intervening elements can also be present. In contrast, when an element is referred to as being directly on, directly connected to, or directly coupled to another element, there are no intervening elements or layers present. While the terms directly on, directly connected to, or directly coupled to may not be used in the detailed description throughout the specification, elements described as directly on, directly connected to, or directly coupled to an element can be referred to in this manner. The claims of the present application, if any, can be amended to recite example relationships described in the specification or shown in the drawings.

[0088] As used in this specification and claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Spatially relative terms, such as "above," "on," "over," "under," "beneath," "below," "lower," "upper," "primarily," "secondarily," "left," "right," "vertical," "horizontal," and the like, merely describe the relative position or orientation in use or operation of a device and do not connote or require a specific orientation in the drawings. In some embodiments, the relative terms above and below can include vertically above and vertically below, respectively. In some embodiments, the term adjacent can include laterally adjacent or horizontally adjacent.

[0089] Some embodiments can be implemented using various semiconductor processing and / or packaging techniques. Some embodiments can be implemented using various types of semiconductor processing techniques associated with semiconductor substrates including, but not limited to, for example, silicon (Si), gallium arsenide (GaAs), gallium nitride (GaN), silicon carbide (SiC), etc.

[0090] While certain features of described implementations have been illustrated as described herein, many modifications, substitutions, changes, and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the scope of the implementations. It should be understood that they have been presented by way of example only, not limitation, and various changes in form and details can be made. Any portion of the apparatus and / or methods described herein can be combined in any combination, except mutually exclusive combinations. The implementations described herein can include various combinations and / or sub-combinations of the functions, components and / or features of the different implementations described.

Claims

1. A semiconductor device, comprising: a silicon-on-insulator (SOI) substrate on an insulating layer, the SOI substrate having a first conductivity type; a diode formed on the SOI substrate, the diode including a cathode region having a second conductivity type and an anode region having the first conductivity type; and at least one breakdown voltage trench disposed at an edge of the cathode region, wherein the at least one breakdown voltage trench is adjacent to the cathode region and extends beyond the cathode region in a direction of an insulator of the SOI substrate, and wherein the at least one breakdown voltage trench is configured to modify a reverse current path between the cathode region and the anode region and cause the reverse current path to travel at least quasi-vertically and at least partially in the direction.

2. The semiconductor device of claim 1, wherein, The at least one breakdown voltage trench extends in the direction of the insulator and causes a current path through the SOI substrate between the cathode region and the anode region.

3. The semiconductor device of claim 1, wherein, The at least one breakdown voltage trench includes at least two breakdown voltage trenches, including a first breakdown voltage trench at the edge of the cathode region and a second breakdown voltage trench between the first breakdown voltage trench and the anode region.

4. The semiconductor device of claim 1, wherein, The anode region includes a region of an opposite doping type shorted to an anode of the diode including the anode region, the anode acting as a base of a lateral bipolar junction transistor (BJT), the region of the opposite doping type acting as a collector of the lateral BJT.

5. The semiconductor device of claim 1, wherein, The at least one breakdown voltage trench includes an insulating material having an air gap formed therein.

6. The semiconductor device of claim 1, further comprising a vertical field plate disposed at an edge of the cathode region opposite the at least one breakdown voltage trench.

7. A semiconductor device, comprising: a substrate having a first conductivity type; a diode formed in the substrate, the diode including a cathode region having a second conductivity type and an anode region having the first conductivity type; and at least one trench insulator adjacent to the cathode region, the at least one trench insulator defining a diode current path around the at least one trench insulator, the diode current path traversing the substrate between the cathode region and the anode region, wherein the substrate includes a silicon-on-insulator (SOI) substrate, and further wherein the at least one trench insulator extends beyond the cathode region in a direction of an insulator of the SOI substrate, and wherein the at least one trench insulator is configured to modify a reverse current path between the cathode region and the anode region and cause the reverse current path to travel at least quasi-vertically and at least partially in the direction.

8. The semiconductor device of claim 7, wherein, The at least one trench insulator includes at least two trench insulators, including a first trench insulator at an edge of the cathode region and a second trench insulator between the first trench insulator and the anode region.

9. A method of fabricating a semiconductor device, comprising: A silicon-on-insulator (SOI) substrate is formed on an insulating layer, the SOI substrate having a first conductivity type; A breakdown voltage trench is formed in the SOI substrate; as well as A diode is formed in the SOI substrate, including a cathode region having a second conductivity type and an anode region having a first conductivity type adjacent to the breakdown voltage trench, wherein the breakdown voltage trench extends beyond the cathode region in the direction of the insulator of the SOI substrate, and wherein the breakdown voltage trench is configured to modify the reverse current path between the cathode region and the anode region and cause the reverse current path to be at least quasi-vertical and at least partially travel in the direction.

10. The method of claim 9, further comprising: A deep trench isolation (DTI) structure is formed in the SOI substrate at a certain location to isolate the diode from at least one other circuit element formed in the SOI substrate. The formation of the breakdown voltage trench and the formation of the DTI structure are performed during the trench etching process.

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