semiconductor devices

Abstract

A semiconductor device is disclosed. In an embodiment, a semiconductor device is provided, comprising a main transistor having a load path, a sensing transistor for sensing a main current flowing in the load path of the main transistor, and at least one bypass diode structure for protecting the sensing transistor. The at least one bypass diode structure is electrically coupled in parallel with the sensing transistor.

Description

Background Technology

[0001] Transistors used in power applications are typically fabricated using silicon (Si) semiconductor materials. Common transistor devices used in power applications include Si CoolMOS® transistors, Si power MOSFETs, and Si insulated-gate bipolar transistors (IGBTs).

[0002] For some power applications, it is desirable to measure the current in the power supply to provide, for example, fault detection and / or protection, current-mode controlled voltage regulation, or current control. A system for measuring the current in a power supply uses a field-effect transistor (FET), commonly referred to as a sensing field-effect transistor. The sensing FET is a small FET separate from the main power FET. The sensing FET is generally configured to generate a voltage corresponding to the current in the main FET to provide current sensing and can be integrated into the same semiconductor body as the main FET.

[0003] US 2017 / 0322239 A1 discloses an example of a vertical trench semiconductor device having a split gate structure, the vertical trench semiconductor device including a main field-effect transistor and a current-sensing field-effect transistor configured to generate a voltage corresponding to the drain-source current of the main field-effect transistor.

[0004] However, further improvements in providing more accurate and reliable current sensing in transistor devices that include current sensing functionality are desirable. Summary of the Invention

[0005] In some embodiments, the semiconductor device includes a main transistor having a load path, a sensing transistor for sensing a main current flowing in the load path of the main transistor, and at least one bypass diode structure for protecting the sensing transistor. The at least one bypass diode structure is electrically coupled in parallel with the sensing transistor.

[0006] In some embodiments, the main transistor includes a main drain, a main source, and a main gate, and the sensing transistor includes a sensing drain, a sensing source, and a sensing gate, wherein the main drain and the sensing drain are electrically coupled to each other, and the main gate and the sensing gate are electrically coupled to each other.

[0007] In some embodiments, the at least one bypass diode structure is electrically coupled between the sensing drain and the sensing source.

[0008] In some embodiments, the main transistor includes a plurality of main transistor units, each main transistor unit including a main trench and a main mesa, each main trench including a main gate electrode, and each main mesa including a main source region disposed on a main body region, and the sensing transistor includes a plurality of sensing transistor units, each sensing transistor unit including a sensing trench and a sensing mesa, each sensing trench including a sensing gate electrode, and each sensing mesa including a sensing source region disposed on a sensing body region, wherein the sensing source region is electrically isolated from the main source region.

[0009] In some embodiments, the bypass diode structure includes a plurality of bypass diode trenches and a plurality of bypass diode mesa, each bypass diode mesa including a bypass body region coupled to a sensing source region of a sensing transistor, wherein the bypass body region extends to the upper surface of the bypass diode mesa.

[0010] In some embodiments, the bypass body region and the sensing source region are electrically coupled to a common metal layer through one or more conductive vias.

[0011] In some embodiments, the contact area between the bypass body region and the common metal layer is greater than the contact area between the source sensing region and the common metal layer.

[0012] In some embodiments, the sensing trench and the bypass diode trench form a common trench, and the sensing mesa and the bypass diode mesa form a common mesa.

[0013] In some embodiments, elongated conductive vias are located in a common mesa, in a sensing source region, and in a bypass body region, to electrically couple the bypass body region and the sensing source region to a common metal layer.

[0014] In some embodiments, the elongated conductive via extends laterally to a distance of at least 10 μm within the bypass body region.

[0015] In some embodiments, the sensing trench extends to the gate wiring, and the gate electrode of the sensing trench is coupled to the gate wiring.

[0016] In some embodiments, the bypass diode structure is arranged laterally between the sensing transistor and the gate wiring.

[0017] In some embodiments, a common metal layer forms a source sensing wiring that extends laterally between the sensing transistor and the sensing pad, and electrically couples the sensing source region and the bypass body region to the sensing pad.

[0018] In some embodiments, at least one bypass diode structure is arranged below the sensing source wiring and / or at least one bypass diode structure is arranged below the sensing pad.

[0019] In some embodiments, each of the main trench and the sensing trench further includes a field plate electrically isolated from the first electrode.

[0020] Those skilled in the art will recognize the additional features and advantages upon reading the following detailed description and reviewing the accompanying drawings. Attached Figure Description

[0021] The elements in the accompanying drawings are not necessarily proportional to each other. The same reference numerals refer to corresponding similar parts. Features of the various illustrated embodiments can be combined unless they are mutually exclusive. Exemplary embodiments are depicted in the accompanying drawings, and exemplary embodiments are described in detail below.

[0022] Figure 1 The diagram illustrates a circuit diagram provided by a semiconductor device according to an embodiment, the semiconductor device including a main transistor, a sensing transistor, and a bypass diode structure.

[0023] Figure 2 Illustration provided Figure 1 The diagram shows a schematic of the semiconductor device used in the circuit.

[0024] Figure 3 The diagram shows a top view of a semiconductor device with a main transistor, a sensing transistor, and two bypass diodes.

[0025] Figure 4 Illustration Figure 4 An enlarged plan view of the first part of the semiconductor device, illustrating the structure of the sensing transistor and the first bypass diode.

[0026] Figure 5 The diagram follows Figure 4 The image shows a cross-sectional view of the sensing transistor of line AA.

[0027] Figure 6 The diagram follows Figure 4 The image shows a cross-sectional view of the main transistor of line BB.

[0028] Figure 7 The diagram follows Figure 4 The image shows a cross-sectional view of the bypass diode structure of line CC.

[0029] Figure 8 Illustration Figure 3 An enlarged view of the second part of the semiconductor device, and the structure of the second bypass diode is illustrated. Detailed Implementation

[0030] In the following detailed description, reference is made to the accompanying drawings, which form a part herein, and which illustrate by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terms such as "top," "bottom," "front," "rear," "front portion," "tail," etc., are used to refer to the orientation of the described figures(s). Because the components of the embodiments may be positioned in multiple different orientations, the directional terms are for illustrative purposes and are by no means limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the invention. The following detailed description of the invention should not be considered limiting in any way, and the scope of the invention is defined by the appended claims.

[0031] Several exemplary embodiments will now be explained. In this context, the same structural features in the various figures are identified by the same or similar reference numerals. In the context of this description, "lateral" or "lateral direction" should be understood to mean a direction or extension generally parallel to the lateral extension of the semiconductor material or semiconductor carrier. Thus, the lateral direction generally extends parallel to these surfaces or sides. In contrast, the term "vertical" or "vertical direction" is understood to mean a direction generally perpendicular to these surfaces or sides and therefore perpendicular to the lateral direction. Thus, the vertical direction travels in the thickness direction of the semiconductor material or semiconductor carrier.

[0032] As used in this specification, when an element such as a layer, region, or substrate is referred to as being "on" or "extending" to another element, it may be directly on or directly extended to the other element, or there may be intermediate elements. In contrast, when an element is referred to as being "directly on" or "directly extended" to another element, there are no intermediate elements.

[0033] As used in this specification, when an element is referred to as "connected" or "coupled" to another element, it can be directly connected or coupled to other elements, or there may be intermediate elements. Conversely, when an element is referred to as "directly connected" or "directly coupled" to another element, there are no intermediate elements.

[0034] Some applications, such as high-performance synchronous buck converters in server applications, require highly accurate monitoring of the output current, such as better than 2% accuracy over a wide load range, because the detected signal is used for system control, such as optimizing the computing power of the CPU connected to the output in the case of server applications.

[0035] Ideally, losses should be as low as possible to minimize temperature and energy consumption, making solutions such as external shunt resistors or increasing the impedance of inductors in the output path to improve measurement accuracy insufficient. Instead, the current signal is supplied directly from the integrated buck converter ("power stage"). This can be achieved by using a current mirror integrated into one or more power MOSFETs within the power stage. The control circuitry for the current mirror can be integrated into the driver IC of the power stage.

[0036] A current mirror on a power transistor, such as a power MOSFET, can include an embedded sensing transistor coupled in parallel with a power switch (i.e., the main transistor carrying the load path of the power stage). Typically, in the current mirror, both the main transistor and the sensing transistor share the same drain and gate potentials. The source potential of the main transistor is sensed at a representative location, reproduced by circuitry in the (driver) IC, and applied to the source terminal of the sensing transistor. In equilibrium, the potentials are matched, and ideally, the currents in both the power MOSFET and the sensing MOSFET are scaled across the active region. Because the sensing transistor is substantially smaller laterally than the power transistor in size, the sensed current is smaller and can be measured within the IC. The voltage or current signal, linearly scaled by the load current, is placed at the output pin of the integrated power stage for further processing on the application board.

[0037] Because the sensing transistor is coupled in parallel with the load path, it incurs some losses, which are also scaled by area. Therefore, the sensing transistor should ideally be as small as possible, which also helps keep the IC size small, as it must handle relatively low currents. A typical range is on the order of 1:40000, that is, IA in the main transistor. L A load current of 40A generates I in the sensing transistor. S =1mA sensing current. Abbreviation KILIS (K=I L / I S () is sometimes used for current ratio. In this example, KILIS = 40000.

[0038] Due to the small size of the sensing transistor (typically less than 100 μm) 2 It has been observed that sensing transistors can spuriously turn on under high drain-to-source voltages. Such conditions can lead to thermal carrier stress that potentially alters the characteristics of the sensing transistor, resulting in errors in current measurements. Furthermore, due to its small size, the sensing transistor is relatively sensitive to ESD events if exposed to external forces.

[0039] To mitigate or even overcome these problems, the embodiments described herein provide a semiconductor device including a main transistor, a sensing transistor, and at least one bypass diode structure for protecting the sensing transistor. The purpose of including one or more bypass diode structures is to improve tolerance to unwanted turn-on and ESD events affecting the sensing transistor.

[0040] In some embodiments, at least one diode structure is coupled in parallel with the sensing transistor. This diode structure has properties as similar as possible to the sensing transistor but without a MOSFET channel. This one or more additional diode structures firstly provide a bypass for unwanted charges to avoid spurious turn-on, and secondly provide additional regions in parallel with the sensing transistor to improve avalanche tolerance and thus also improve ESD ratings.

[0041] Figure 1 The diagram illustrates a circuit provided by a semiconductor device 10 according to an embodiment. The semiconductor device 10 includes a main transistor 11, a sensing transistor 12, and a bypass diode structure 13. Figure 2 Illustration provided Figure 1 The diagram shows a schematic of the semiconductor device 10 in the circuit shown in the figure.

[0042] The main transistor 11 provides a power switch for switching the load and has a load path 14. The sensing transistor 12 is used to sense the main current I flowing in the load path 14 of the main transistor 11. main The sensing transistor 12 is not connected in the load path 14, but is connected in parallel with the load path 14. The diode structure 13 is electrically coupled in parallel with the sensing transistor 12 and provides a bypass diode structure for protecting the sensing transistor 12.

[0043] The main transistor 11 includes a main drain 15, a main source 16, and a main gate 17. The sensing transistor 12 includes a sensing drain 18, a sensing source 19, and a sensing gate 20. The main drain 15 and the sensing drain 18 are electrically coupled to each other and to the same drain potential D, and the main gate 17 and the sensing gate 20 are electrically coupled to each other and to the same gate potential G. The main source 16 and the sensing source 19 are separate and electrically isolated from each other so that the sensing transistor 12 can provide current sensing to the main transistor 11. A bypass diode structure 13 is electrically coupled between the sensing drain 18 and the sensing source 19, thereby connecting the bypass diode 13 in parallel with the sensing transistor 12. In particular, the cathode 21 of the diode 13 is coupled to the sensing drain 18, and the anode 22 of the diode 13 is connected to the sensing source 19. The cathode 21, the sensing drain 18, and the main drain 15 of the diode structure 13 are all coupled to a common drain potential D. In some embodiments, two or more bypass diode structures are provided, each of which is coupled in parallel with the sensing transistor 12.

[0044] like Figure 2 As schematically indicated, the sensing transistor 12 and one or more bypass diode structures 13 may be integrated together with the main transistor 11 into a common semiconductor body 23 to form a semiconductor device 10. Each of the main transistor device 11 and the sensing transistor device 12 may be a vertical transistor device, such as a vertical MOSFET device, wherein terminals for the main source 16, the main gate 17, the sensing source 19, and the sensing gate 20 are arranged on a first surface 24 of the semiconductor body 23, and a common drain terminal 26 coupled to the main drain 15 and the sensing drain 18 is located on opposite second surfaces 25 of the semiconductor body 23, such that the main transistor 11 and the sensing transistor 12 have a vertical drift path.

[0045] One or more bypass diode structures 13 may have a transistor structure in which the gate is electrically coupled to the source to form the anode of the diode. Such a structure is commonly referred to as a gating MOSFET.

[0046] In some embodiments, the sensing transistor 12 is designed with design rules similar to those of the much larger power transistor 11, such that the sensing transistor 12 matches the characteristics of the power transistor 11 and forms a good current mirror. The bypass diode structure 13 may also be designed with similar design rules for the main transistor 11 and the sensing transistor 12, and may be provided by, for example, a gating transistor structure. In other embodiments, one or more bypass diode structures may comprise pn diodes.

[0047] Semiconductor device 10 may include a plurality of transistor units. A majority of these units are used to form a main transistor 11, and a small portion of these transistor units may be used to form a sensing transistor 12 and a bypass diode structure 13. The transistor structure of the transistor units may be a trench transistor structure, whereby the trenches may be columnar or elongated, for example, strip-like. In embodiments of semiconductor device 10 comprising a main transistor 11, a sensing transistor 12, and at least one bypass diode structure 13 based on an elongated trench transistor structure, the main transistor 11, the sensing transistor 12, and at least one bypass diode structure 13 may be formed laterally adjacent to each other in different regions of one or more common elongated trenches.

[0048] Figure 3 The figure shows a top view of a semiconductor device 30, which includes a main transistor device 31, a sensing transistor 32, a first bypass diode structure 33, and a second bypass diode structure 34, which are connected to form a semiconductor device 30. Figure 1The circuit is illustrated in the figure. However, semiconductor device 30 may include fewer or more than two bypass diode structures that may have the same or different structures. In some embodiments, semiconductor device 30 may include a single bypass diode structure and may include a first diode structure 33 or a second diode structure 34 depending on the functionality required for a particular application.

[0049] The main transistor 31 includes a main source, a main gate, and a main drain, and the sensing transistor 32 includes a sensing source, a sensing drain, and a sensing gate, which are not located in... Figure 3 The semiconductor device 30 is shown in a top view.

[0050] The main transistor 31 includes a source pad 35 coupled to the main source of the semiconductor device 30 and a gate pad 36 disposed on the upper surface 37. The gate pad 36 is electrically coupled to the main gate and the sensing gate and is disposed in a corner of the upper surface 37, extending into gate wirings 38, 39 extending in the outer peripheral regions of three adjacent sides of the first surface 37. The gate pad 36 and the gate wirings 38, 39 are spaced apart from and electrically insulated from the source pad 35. The gate pad 36 and the gate wirings 38, 39 are electrically coupled to the main gate of the main transistor 31 and the sensing gate of the sensing transistor 32.

[0051] The source pad 35 covers most of the first surface 37 and includes a gap or cutout 40 extending from one side toward the center of the first surface 37, so that the source pad 35 can be considered to have a U-shape. The sensing transistor 32 and the first bypass diode structure 33 are arranged in the cutout 40 toward the center of the first surface 37 and spaced apart from the source pad 35.

[0052] A sensing pad 41 is also disposed on the first surface 37 of the semiconductor device 30, and located in the corner of the first surface 37 opposite to the gate pad 36. The sensing pad 41 is electrically connected to the source sensing of the sensing transistor 32 via a sensing wiring 42. The sensing wiring 42 extends substantially parallel to the gate wiring 38 and then perpendicular to the gate wiring 38 into a notch 40 to electrically couple the sensing pad 41 to the source sensing of the sensing transistor 32. A first bypass diode structure 33 is electrically coupled in parallel with the sensing transistor 32, such that one terminal (particularly the anode) of the bypass diode structure 33 is electrically coupled to the sensing wiring 42, and thus to the sensing source of the sensing transistor.

[0053] The second bypass diode structure 34 is located below the sensing pad 41 and includes an anode electrically coupled to the sensing pad 41. The sensing pad 41 and sensing wiring 42 are electrically isolated from the source pad 35 and from the gate pad 36 and gate wirings 38, 39.

[0054] The layout of the main source pad 35, sensing pad 41, gate pad 36, sensing wiring 42, and gate wirings 38 and 39 on the first surface 37 is not limited to [specific details]. Figure 3 The layout shown in the diagram can be adapted to other arrangements. For example, the sense pad 41 and the gate pad 36 can be arranged diagonally at opposite corners of the first surface 37.

[0055] Figure 4 Illustration Figure 3 An enlarged plan view of the first portion of the semiconductor device, including an enlarged plan view of the sensing transistor 32 and the first bypass diode structure 33 located in the cutout 40 in the source pad 35. Figure 5 The diagram follows Figure 4 The image shows a cross-sectional view of line AA and a cross-sectional view of sensing transistor 32. Figure 6 The diagram follows Figure 4 The image shows a cross-sectional view of line BB and a cross-sectional view of the main transistor 31. Figure 7 The diagram follows Figure 4 The figure shows a cross-sectional view of line CC and a cross-sectional view of the first bypass diode structure 33.

[0056] As discussed above, the main transistor 31 and the sensing transistor 32 are typically formed using the same design rules, resulting in identical structures for the main transistor unit and the sensing transistor unit. One or both of the bypass diode structures 33 and 34 can also be formed using these same design rules. (Refer to...) Figures 3 to 7 In the description, the same reference symbols will be used for features found in all of the main transistor 31, the sensing transistor 32, and the bypass diode structures 33 and 34, whereby elements of the sensing transistor 32 are indicated by superscript apostrophe "'" and elements of the bypass diode structure 33 are indicated by superscript double apostrophe """.

[0057] In some embodiments, the main transistor 31 and the sensing transistor 32 are trench transistor devices, wherein each trench 43 is elongated and has a strip shape or bar shape in a plan view, as shown in Figure 4 As can be seen in the enlarged plan view. Each elongated groove 43 defines a common elongated platform 44 and is separated from each other by it.

[0058] The main transistor 31 includes multiple main transistor units, each main transistor unit including a main trench 43 and a main mesa 44, as shown in... Figure 6 As can be seen in the image. Each main trench 43 includes a main gate electrode 45, and each main mesa 44 includes a main source region 46 disposed on a main body region 47 disposed on a drift region 48.

[0059] Similarly, the sensing transistor 32 includes a plurality of sensing transistor units, each sensing transistor unit including a sensing trench 43' and a sensing mesa 44', as shown in Figure 6 As can be seen in the image. The bypass diode structure 33 also includes multiple bypass diode trenches 43" and bypass diode mesa 44", as shown in... Figure 7 You can see that in the image.

[0060] In reference Figures 3 to 7 In the described embodiment, the main transistor 31, the sensing transistor 32, and the first bypass diode structure 33 are formed in different lateral regions of the common trench 43 defining the common mesa 44.

[0061] As in Figure 4 As can be seen in the top view, the first bypass diode structure 33 is positioned laterally adjacent to the sensing transistor 32. The sensing transistor 32 and the first bypass diode structure 33 are located below the end of the source sensing wiring 42 within the cutout 40 of the source pad 35.

[0062] Figure 5 The diagram follows Figure 4 The diagram shows a cross-sectional view of line AA as indicated in the figure, and also illustrates a cross-sectional view of sensing transistor 32. Figure 5 The illustration shows two sensing grooves 43' separated by a sensing platform 44'. In, for example... Figures 3 to 7 In some embodiments illustrated in the figure, the sensing trench 43' and sensing mesa 44' are elongated and have a strip-like shape in plan view. Each sensing trench 43' includes a sensing gate electrode 45', and each sensing mesa 44' includes a sensing source region 46' disposed on a sensing body region 47', which in turn is disposed on a drift region 48. The drift region 48 includes a first conductivity type, the sensing body region 47' includes a second conductivity type opposite to the first conductivity type, and the sensing source region 46' includes the first conductivity type. The first conductivity type may be n-type, and the second conductivity type may be p-type, or vice versa. The sensing source region 46' is more heavily doped than the drift region 48.

[0063] Figure 6 The diagram follows Figure 4 The diagram shows a cross-sectional view of line BB and a cross-sectional view of the main transistor 31. Figure 6 The diagram illustrates two main channels 43 separated by the main platform 44. Sensing channel 43' and the main channels 43 form a single common channel, and sensing platform 44' and the main platform 44 form a single common platform, as shown in... Figure 4 You can see that in the top view.

[0064] Each main trench 43 includes a main gate electrode 45, and each main mesa 44 includes a main source region 46 disposed on a main body region 47, which is further disposed on a drift region 48. The main body region 47' includes a second conductivity type, and the sensing source region 46 includes a first conductivity type. The main gate electrode 45 and the sensing gate electrode 45' are coupled to each other and coupled to a gate pad 36 by means of one or both of gate wirings 38, 39. The main drain and the sensing drain are coupled to a common drain disposed on a second surface of the semiconductor body, which in Figures 5 to 7 It cannot be seen in the cross-sectional view.

[0065] Although the cross-sectional view of the main transistor device 31 corresponds to Figure 5 The figure shows a cross-sectional view of the sensing transistor 32, but the source sensing region 46' of the sensing transistor 32 is electrically isolated from the source sensing region 46 of the main transistor 31, so that the sensing transistor 32 can detect the current flowing in the load path of the main transistor 31.

[0066] In some embodiments, the sensing trench 43' and the main trench 43 include field plates 49, 49' positioned toward the bottom of the trenches 43, 43' and spaced apart from and electrically isolated from gate electrodes 45, 45' disposed toward the top of the trenches 43, 43'. The trenches 43, 43' are padded with insulating materials 50, 50', which electrically insulate the field plates 49, 49' from the drift region 48 and from the gate electrodes 45, 45'. The gate electrodes 45, 45' are electrically insulated from the body region 47, 47' and the source region 46, 46' by insulating layers 51, 51' that act as gate oxides and padded the sidewalls of the trenches. Figure 5 The location of the main transistor 31 shown in the diagram and in Figure 6 At the location of the sensing transistor 32 shown in the figure, trenches 43, 43' and gate electrodes 45, 45' are covered with electrically insulating layers 52, 52' (Note: 52 and 52' are not shown in the figure).

[0067] As in Figure 5 As can be seen, a contact in the form of a conductive via 53 is located in the sensing mesa 44'. The conductive via 53 extends through the sensing source region 46' into the sensing body region 47 and has a substrate located within the sensing body region 47. The conductive via 53 is electrically coupled to an upper conductive layer 54, which may include one or more metal layers. The conductive layer 54 may include two or more metal layers and may be formed by sensing wiring 42. The conductive via 53 is not connected to the main source 46 of the main transistor 31.

[0068] As in Figure 6As can be seen, the main source electrode 46 and the main body 47 are electrically connected to the conductive layer 57 through the conductive via 58. The conductive layer 57 may include one or more metal layers and may be formed from the source pad 35. Since the main source electrode 46 is not electrically connected to the sensing source electrode 46', the conductive layer 57 is electrically isolated from the conductive layer 54. Since the main source electrode 46 is not electrically connected to the sensing source electrode 46', the conductive via 58 is also electrically isolated from the conductive via 53.

[0069] Figure 7 The diagram follows Figure 4 The diagram illustrates a cross-sectional view of line CC, and thus a cross-sectional view of the first bypass diode structure 33. The first bypass diode structure 33 includes a plurality of bypass diode trenches 43" and bypass diode mesa 44". The bypass diode trenches 43" form a common trench with the sensing trench 43' and the main trench 43, and the bypass diode mesa 44" forms a common mesa 44 with the sensing mesa 44' and the main mesa 44, as shown in... Figure 4 As can be seen in the top view. The bypass diode structure 33 is arranged laterally adjacent to and adjacent to the sensing transistor 32, and is arranged between the sensing transistor 32 and the sensing wiring 42.

[0070] Each bypass diode mesa 44" includes a bypass body region 56 located on a drift region 48. The bypass body region 56 extends to a first surface 37, such that the first bypass diode structure 33 does not include a source region located on the body region 56. The bypass body region 56 is electrically coupled to a sensing source region 46' of a sensing transistor 32. The bypass body region 56 and the sensing source region 46' of the sensing transistor 32 are electrically coupled to each other through one or more conductive vias 53 and a metal layer 54.

[0071] As discussed above, the bypass diode structure 33 can be formed together with the sensing transistor 32 and the main transistor 31 in the lateral portion of the common trench and common mesa. Figure 4 As can be seen in the top view, the first bypass diode structure 33 is arranged laterally adjacent to and adjacent to the sensing transistor 32. Therefore, a conductive via 53 extends along a common trench 43 from the region in which the sensing transistor 32 is formed to the region in which the bypass diode structure 33 is formed, and a metal layer 54 extends from the bypass diode structure 33 to the sensing transistor 32, thus enabling the same common conductive via 53 and the same common metal layer 54 to electrically connect the body region 56 of the bypass diode structure 33 to the source region 46 of the sensing transistor structure 32.

[0072] The location and lateral shape (especially the length) of the elongated conductive via 53 can be selected to provide a desired contact area between the bypass body region 56 and the common metal layer 54, and also to provide a desired contact area between the source sensing region 46 and the common metal layer 54. In some embodiments, the contact area between the bypass body region 56 and the common metal layer 54 is larger than the contact area between the source sensing region 46 and the common metal layer 54.

[0073] In some embodiments, the elongated conductive via 53 extends laterally from the sensing source transistor 32 to a distance of at least 10 μm in the bypass body region 56, that is, from the outer periphery of the sensing source region 46 to the bypass body region 56 by at least 10 μm. This distance provides a contact area between the bypass body region 56 and the metal layer 54, which is not only larger than the contact area between the sensing source region 4 and the metal layer 54, but also larger than the typical contact area between the mesa of the transistor device and the overlying metal layer.

[0074] In some embodiments, a common trench 43 extends to and lies beneath the gate wiring 38, such that the gate electrode 45' of the sensing trench 43' and the gate electrode 45 in the main trench 43 can be electrically coupled to the gate wiring 38. For example, a vertical contact may extend between the gate wiring 38 and each gate electrode 45 in the trench 43. Figures 3 to 7 In the common trench embodiment illustrated in the figure, the gate electrode 45' in the sensing trench 43' and the gate electrode 45 in the main trench 43 can be formed by a single common conductive electrode.

[0075] As in Figure 7 As can be seen, each bypass diode trench 43" includes a first electrode 55. This first electrode 55 forms a common electrode with the sensing gate electrode 45' and the main gate electrode 45. The first electrode 55 enables the sensing gate electrode 45' and the main gate electrode 45 to be connected to the gate wiring 38.

[0076] In some embodiments, the common metal layer 54 is formed on Figure 3 The diagram shows a source sensing wiring 42 that extends laterally between the sensing transistor 32 and the sensing pad 41 and above the first bypass diode structure 33. The source sensing wiring 42 electrically couples the source sensing region 46 and the bypass body region 56 of the bypass diode structure 33 to the sensing pad 41.

[0077] Figure 8 The diagram shows a top view of the second bypass diode structure 34 arranged below the sensing pad 41. The structure of the second bypass diode structure 34 can be substantially the same as... Figure 7 The first bypass diode 33 shown in the diagram has the same structure.

[0078] The second bypass diode 34 includes a plurality of bypass diode trenches 143 and a plurality of bypass diode mesa 144, each extending between two adjacent bypass diode trenches 143. The bypass diode trenches 143 and bypass diode mesa 144 may be elongated, as in... Figure 8 As seen in the image. The bypass diode trench 143 can form a common trench with the main trench 43 of the main transistor 31, and the bypass diode mesa 144 can form a common mesa with the main mesa 44 of the main transistor 31. However, these bypass trenches 143 and mesa 144 do not form common trenches and mesas with the sensing transistor, respectively. The body region of the second bypass diode 34 is electrically coupled to the sensing pad 41 through an elongated contact 153 extending between the body region in the mesa 144 and the sensing pad 41 above it, as shown. Figure 8 As shown in the image.

[0079] The second bypass diode 34 is electrically coupled in parallel with the sensing transistor 32 because the body region of the second bypass diode 34 is electrically coupled to the sensing pad 41, the sensing source region 46' of the sensing transistor 32 is also coupled to the sensing pad 41, and the cathode of the second bypass structure 34 is also coupled to the sensing drain of the sensing transistor 32 and the main drain of the main transistor on the lower surface of the semiconductor body 23. Therefore, the second bypass diode structure 34 is also coupled in parallel with the first bypass diode structure 33.

[0080] In the second bypass diode, the gate electrode 145, which can be disposed in the bypass diode trench 143, is electrically coupled to the upper sensing pad 41 via a contact 155—the contact 155 being arranged laterally adjacent to the end of the contact 153 that electrically couples the body region to the sensing pad 41—to form a gated MOS structure. The second bypass diode structure 34 may also include a source region on top of the body region, which is also coupled to the upper sensing pad 41 via an elongated contact 153.

[0081] In summary, a bypass is provided for unwanted charges to avoid spurious switching of the sensing transistor. Additionally, avalanche tolerance and ESD rating are improved due to the additional area of ​​the bypass diode(s) coupled in parallel with the sensing transistor. The body region of the bypass diode contacts the sensing wiring that forms a connection to the source of the sensing transistor. Displacement current is bypassed, thus preventing the sensing transistor from turning on during rapid VDS rises. In an avalanche / ESD event, most of the current will flow through the bypass diode because its area is much larger than that of the sensing transistor.

[0082] A bypass diode structure coupled in parallel with the sensing transistor has properties as similar as possible to the sensing transistor but without a MOSFET channel. Because the connection region is similar to the sensing transistor, unwanted charges will not flow into the sensing transistor, thus protecting it from environmental influences. This can be achieved by designing a laterally larger sensing transistor with contacts to the metal on top, but only implanting source doping in a smaller region of this larger sensing transistor where the desired KILIS ratio is required. The remainder of the larger sensing transistor does not include a source region but only a body region, providing the bypass diode structure. This structure allows for the formation of identical gate-drain capacitance, gate-body capacitance, and drain-body capacitance, and allows for the connection of pn diodes.

[0083] By providing extended contacts within the mesa extending from the sensing transistor to the bypass diode structure, a bypass function for displacement current during rapid voltage changes is provided. The minimum length of the extended mesa contact can be 10 μm. Additionally, in the event of an ESD event, a larger area can be used for the resulting avalanche current, reducing the current density in the sensing transistor.

[0084] Figure 7 The bypass diode structure illustrated in the diagram provides diodes with the same breakdown voltage and can be located at different positions on the semiconductor device, such as under the sensing pads used to connect the sensing transistor to the lead frame or bonding wire, for example in... Figure 8 As shown in the diagram. In this case, the bypass diode structure maintains its bypass function against ESD events. Furthermore, if the impedance between the bypass diode and the sensing transistor is large enough, the voltage drop across the series impedance will reduce the current density in the sensing transistor region during an ESD event, further protecting the sensing element.

[0085] A current-mirror power stage with an exposed sensing transistor (i.e., an externally accessible sensing transistor) is provided, offering improved ESD tolerance. Such a current-mirror power stage can be provided in a QFN package. At least one bypass diode connected in parallel with the sensing transistor is used to improve ESD and avalanche tolerance and to prevent displacement current from charging the sensing transistor. Additionally, spurious turn-on of the sensing transistor is avoided, thus improving long-term current sensing accuracy. As a result, current measurements in the power stage are more reliable. This allows applications using such components, such as computer systems, to operate closer to their thermal limits.

[0086] For ease of description, spatially relative terms such as "below," "under," "lower part," "above," and "upper part" are used to explain the positioning of one element relative to a second element. These terms are intended to cover different orientations of the device other than those depicted in the figures. Furthermore, terms such as "first," "second," etc., are also used to describe various elements, areas, sections, etc., without any intention of limitation. The same terms are used throughout to refer to the same element.

[0087] As used herein, the terms "having," "comprising," "including," and "including" are open-ended terms that indicate the presence of a stated element or feature but do not exclude additional elements or features. The quantifiers "a," "an," and the pronoun "the" are intended to include both plural and singular forms unless the context clearly indicates otherwise. It is to be understood that, unless otherwise specifically indicated, features of the various embodiments described herein can be combined with each other.

[0088] While specific embodiments have been illustrated and described herein, those skilled in the art will appreciate that various substitutions and / or equivalent implementations may be made in place of the specific embodiments shown and described without departing from the scope of the invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that the invention be limited only to the claims and their equivalents.

Claims

1. A semiconductor device, comprising: a main transistor having a load path, wherein the main transistor comprises a plurality of main transistor cells, each main transistor cell comprising a main trench and a main mesa, each main trench comprising a main gate electrode, and each main mesa comprising a main source region disposed on a main body region; a sense transistor for sensing a main current flowing in the load path of the main transistor, wherein the sense transistor comprises a plurality of sense transistor cells, each sense transistor cell comprising a sense trench and a sense mesa, each sense trench comprising a sense gate electrode, and each sense mesa comprising a sense source region disposed on a sense body region, wherein the sense source region is electrically isolated from the main source region; at least one bypass diode structure for protecting the sense transistor, wherein the bypass diode structure comprises a plurality of bypass diode trenches and a plurality of bypass diode mesas, each bypass diode mesa comprising a bypass body region coupled to the sense source region of the sense transistor, wherein the bypass body region extends to an upper surface of the bypass diode mesa, wherein the at least one bypass diode structure is electrically coupled in parallel to the sense transistor, characterized in that the sense trench and the bypass diode trench form a common trench, and the sense mesa and the bypass diode mesa form a common mesa.

2. The semiconductor device of claim 1, wherein the main transistor comprises a main drain, a main source, and a main gate, and the sense transistor comprises a sense drain, a sense source, and a sense gate, wherein the main drain and the sense drain are electrically coupled to each other, and the main gate and the sense gate are electrically coupled to each other.

3. The semiconductor device of claim 2, wherein the at least one bypass diode structure is electrically coupled between the sense drain and the sense source.

4. The semiconductor device of one of claims 1 to 3, wherein the bypass body region and the sense source region are electrically coupled to a common metal layer by one or more conductive vias.

5. The semiconductor device of claim 4, wherein a contact area between the bypass body region and the common metal layer is larger than a contact area between the sense source region and the common metal layer.

6. The semiconductor device of one of claims 1 to 3, wherein an elongated conductive via is located in the common mesa and in the sense source region and in the bypass body region to electrically couple the sense source region and the bypass body region to the common metal layer.

7. The semiconductor device of claim 6, wherein the elongated conductive via extends in a lateral direction into the bypass body region by a distance of at least 10 pm.

8. The semiconductor device of one of claims 1 to 3, wherein the sense trench extends to a gate wiring and the sense gate electrode of the sense trench is coupled to the gate wiring.

9. The semiconductor device of claim 8, wherein the bypass diode structure is disposed in a lateral direction between the sense transistor and the gate wiring.

10. The semiconductor device of claim 4, wherein the common metal layer forms a source sense wiring extending in a lateral direction between the sense transistor and a sense pad, and electrically couples the sense source region and the bypass body region to the sense pad.

11. The semiconductor device of claim 10, wherein at least one bypass diode structure is disposed under a source sense wire, and / or at least one bypass diode structure is disposed under a sense pad.

12. The semiconductor device of one of claims 1 to 3, wherein each of the main trench and the sense trench further comprises a field plate electrically isolated from the main gate electrode and the sense gate electrode.

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