Charge-compensated MOSFET with Gradient Epitaxial Distribution and its Manufacturing Method

Abstract

A charge-compensated MOSFET with a gradient epitaxial distribution and a method for manufacturing the same are disclosed. A vertical power semiconductor transistor device includes: a drain region of a first conductivity type; a body region of a second conductivity type; a drift region of a first conductivity type separating the body region from the drain region; a source region of a first conductivity type separated from the drift region by the body region; a gate trench extending through the source region and the body region and into the drift region, the gate trench including a gate electrode; and a field electrode in the gate trench or in a separated trench. The drift region has a generally linearly gradient first doping distribution increasing from the body region toward the bottom of the trench including the field electrode, and a gradient second doping distribution increasing at a rate greater than the first doping distribution from the ends of the first doping distribution toward the drain region.

Description

Background Technology

[0001] Some types of power MOSFETs (metal-oxide-semiconductor field-effect transistors) employ an insulating field plate structure in deep trenches, allowing for significantly higher doping levels in the mesa regions between the trenches due to lateral charge compensation. This facilitates low on-resistance. Importantly, it also maintains good switching characteristics, low switching losses, and good device durability simultaneously.

[0002] Therefore, there is a need for power MOSFET devices that optimize the parameters discussed above, as well as methods for manufacturing such power MOSFET devices. Summary of the Invention

[0003] According to an embodiment of a vertical power semiconductor transistor device, the vertical power semiconductor transistor device includes: a drain region of a first conductivity type; a body region of a second conductivity type opposite to the first conductivity type; a drift region of the first conductivity type separating the body region from the drain region; a source region of the first conductivity type separating the body region from the drift region; a gate trench extending through the source region and the body region and into the drift region, the gate trench including a gate electrode; and a field electrode in the gate trench or in a separated trench, wherein the drift region has a generally linearly gradient first doping distribution increasing from the body region toward the bottom of the trench including the field electrode, and a gradient second doping distribution increasing at a larger ratio than the first doping distribution toward the drain region.

[0004] According to an embodiment of a method for manufacturing a vertical power semiconductor transistor device, the method includes: forming a drain region of a first conductivity type, a drift region of a first conductivity type, a body region of a second conductivity type opposite to the first conductivity type and separated from the drain region by the drift region, and a source region of the first conductivity type and separated from the drift region by the body region; forming a gate trench extending through the source region and the body region and into the drift region, the gate trench including a gate electrode; forming a field electrode in the gate trench or in the separated trench; establishing a generally linearly gradient first doping distribution in the drift region and increasing from the body region toward the bottom of the trench including the field electrode; and establishing a gradient second doping distribution in the drift region and increasing from the end of the first doping distribution toward the drain region at a rate greater than that of the first doping distribution.

[0005] 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

[0006] The elements in the accompanying drawings are not necessarily proportional to each other. The same reference numerals indicate corresponding similar parts. Features of the various illustrated embodiments can be combined unless they are mutually exclusive. Embodiments are depicted in the accompanying drawings and described in detail below.

[0007] Figure 1A The figure shows a partial cross-sectional view of a vertical power semiconductor transistor device.

[0008] Figure 1B The illustration is in Figure 1A The image shows a partial top plan view of a vertical power semiconductor transistor device.

[0009] Figure 2A The illustration shows a partial cross-sectional view of another embodiment of a vertical power semiconductor transistor device.

[0010] Figure 2B The illustration is in Figure 2A The image shows a partial top plan view of a vertical power semiconductor transistor device.

[0011] Figures 3A to 3B The diagram shows the production process. Figures 1A to 1B and Figures 2A to 2B An example of a vertical power semiconductor transistor device is shown in the figure.

[0012] Figures 4A to 4B The diagram shows the production process. Figures 1A to 1B and Figures 2A to 2B Another embodiment of the vertical power semiconductor transistor device illustrated in the figure.

[0013] Figures 5A to 5B The diagram shows the production process. Figures 1A to 1B and Figures 2A to 2B Another embodiment of the vertical power semiconductor transistor device illustrated in the figure.

[0014] Figures 6A to 6C The diagram shows the production process. Figures 1A to 1B and Figures 2A to 2B Another embodiment of the vertical power semiconductor transistor device illustrated in the figure. Detailed Implementation

[0015] The described embodiments provide a vertical power semiconductor transistor device having a drift region having a generally linearly gradient first doping distribution increasing from the body region of the vertical power semiconductor transistor device toward the bottom of a trench including a field electrode, and a gradient second doping distribution increasing at a larger ratio from the ends of the first doping distribution toward the drain region of the vertical power semiconductor transistor device. Related methods for producing a vertical power semiconductor transistor device having such a gradient drift region are also described.

[0016] Optimizing the vertical doping distribution of the drift region in a vertical power semiconductor transistor device, as described herein, results in improved device performance with lower on-resistance. For example, because the generally linearly gradient first doping distribution of the drift region extends through the main portion of the device's compensation region, the field peak at the bulk junction is reduced compared to the case of a constant doping distribution, while still achieving a lower overall voltage drop over the mesa portions between adjacent trenches. The lower field peak is beneficial for reducing DIBL (drain-induced barrier leakage), which provides more margin regarding parasitic turn-on. Lower surface doping concentration significantly simplifies edge-termination design. The gradient second doping distribution of the drift region effectively forms or operates as a field-stop region, while allowing the electric field to extend in the event of avalanche events associated with a large generation of charge carriers, resulting in improved avalanche robustness while reducing voltage, and thus reducing the contribution to the overall on-resistance of the device. The electric field extends less into the drift region under normal operating conditions, which reduces the amount of excess charge carriers generated during bulk diode operation (which must be removed during commutation). Therefore, the reverse recovery charge is reduced, which in turn reduces switching losses. Reverse recovery also exhibits softer behavior and the device will generate substantially less electromagnetic interference, where softer switching corresponds to smaller dv / dt and di / dt. The reduced on-resistance of the device also reduces associated quality factors such as FOMg (quality factor of total gate charge), FOMgd (quality factor of gate-drain charge), and FOMoss (quality factor of output charge). The small-signal output capacitance (Coss) has a more linear shape, which helps reduce overshoot. Various embodiments of a vertical power semiconductor transistor device with a drift region having a generally linearly gradient (upper) first doping distribution and a gradient (lower) second doping distribution that increases at a larger rate than the first doping distribution are described below.

[0017] Figure 1A The figure shows a partial cross-sectional view of a vertical power semiconductor transistor device 100. Figure 1B The illustration is in Figure 1A The image shows a partial top plan view of a vertical power semiconductor transistor device 100. Figure 1A The partial cross-sectional view in the middle is along Figure 1B It was obtained from the line marked A-A'.

[0018] The vertical power semiconductor transistor device 100 includes a drain region 102 of a first conductivity type, a body region 104 of a second conductivity type opposite to the first conductivity type, a drift region 106 of the first conductivity type separating the body region 104 from the drain region 102, and a source region 108 of the first conductivity type separating the body region 104 from the drift region 106. In the case of an n-channel device, the first conductivity type is n-type and the second conductivity type is p-type. In the case of a p-channel device, the first conductivity type is p-type and the second conductivity type is n-type. This is only for ease of explanation. Figure 1A In the diagram, the first conductivity type is labeled as n-type (e.g., "n", "n"). + “n” ++ And the second conductivity type is labeled as p-type (e.g., "p", "p"). + ”). Figure 1A The markers "n" and "n" in the text + “n” ++ “p” and “p” + "Indicates a general relative dopant concentration relationship between different regions of the same doping type, and is not intended to limit with respect to a specific doping concentration, range, or distribution. For example, denoted as "n" + The region marked with "" indicates that it is more heavily doped compared to the region marked with "n", and is marked with "n" ++ The area marked "n" indicates that the area is different from the area marked "n". + The regions marked with "" or "n" are more heavily doped.

[0019] The gate trench 110 extends through the source region 108 and the body region 104 and enters the drift region 106. The gate trench 100 includes a gate electrode 112 insulated from the surrounding semiconductor material by a gate dielectric 114. The gate electrode 112 may be longitudinally grounded in a strip-like manner. Figure 1B The direction “x” in the middle extends and / or forms a grid section. Figure 1A and Figure 1B The directions “x” and “y” are lateral (horizontal) directions that are perpendicular to each other and parallel to the front main surface of device 100, while the direction “z” is a vertical direction that travels into the depth of device 100 and extends perpendicular to the front main surface of device 100.

[0020] The vertical power semiconductor transistor device 100 also includes a source electrode 116 for providing a source potential (“Source”) to the body region 104 and the source region 108 of the device 100. The body region 104 may include a heavily doped body contact region 118 to ensure an ohmic contact between the source electrode 116 and the body region 104. A drain electrode 120 located on opposite sides of the vertical power semiconductor transistor device 100 provides a drain potential (“Drain”) to the heavily doped drain region 102 of the device 100. With proper biasing of the source electrode 116, drain electrode 120, and gate electrode 112 of the device 100, a conductive channel region 122 appears in the body region 104.

[0021] According to Figure 1A and Figure 1B In the embodiment illustrated, the vertical power semiconductor transistor device 100 further includes a field electrode 124 disposed in the same trench 110 as the gate electrode 112. The field electrode 124 is insulated from the gate electrode 112 and the surrounding semiconductor material by a field dielectric 126, which may be the same material as the gate dielectric 114 or a different insulating material. The field electrode 124 may be biased at the source (S) potential, biased at another potential, or floated.

[0022] The drift region 106 of the vertical power semiconductor transistor device 100 has a generally linearly gradient (upper) first doping distribution (DP_drain1) that increases from the body region 104 toward the bottom 128 of the trench 110 including the field electrode 124. As used herein, the term "generally linearly gradient" generally means a slope ratio similar to a straight line. Thus, although the first doping distribution (DP_drain1) of the drift region 106 may have one or more localized nonlinear regions due to processing variations, material defects, etc., it generally increases like a straight line.

[0023] The drift region 106 also has a gradient (lower) second doping distribution (DP_drain2), which increases from the end of the first doping distribution toward the drain region 102 at a greater rate than the first doping distribution. Figure 1A The diagram also shows exemplary source doping profiles (DP_source), exemplary body doping profiles (DP_body), and exemplary drain doping profiles (DP_drain) to illustrate the general relative doping concentration differences between the doped device regions 102, 104, 106, and 108 of the vertical power semiconductor transistor device 100.

[0024] Figure 2A The figure shows a partial cross-sectional view of another embodiment of the vertical power semiconductor transistor device 200. Figure 2B The illustration is in Figure 2A Partial top plan view of the vertical power semiconductor transistor device 200 shown in the figure. Figure 2A The partial cross-sectional view in is along the line in Figure 2B It was obtained from the line marked B-B'.

[0025] exist Figures 2A to 2B The embodiments illustrated in the figure are Figures 1A to 1B The embodiment illustrated in the figure is similar. However, the difference is that the field electrode 124 is located in a different trench 202 than the gate electrode 112, and the field electrode 124 extends longitudinally ( Figure 2A In the direction 'z', it is needle-shaped. As used herein, the term "needle-shaped" describes an electrode structure having a small or narrow perimeter or width proportional to its height / depth in the semiconductor material, which is similar to... Figures 1A to 1B The electrode structure shown is the opposite of the strip shape, which is longer compared to its deeper sections. The gate trench 110 can be formed as a grid (e.g., as shown in...). Figure 2B (as shown in the diagram) or formed as strips (e.g., as in...) Figure 1B (As shown in the diagram). In either case, it is advantageous to use needle-shaped field plate grooves 202 because, compared with those in... Figure 1B The trench strip structure shown is larger than the remaining silicon mesa region 204 that surrounds each field plate trench 202 and is defined by the adjacent gate trench 110, enabling a lower on-resistance.

[0026] For in Figures 1A to 1B The vertical power semiconductor transistor device 100 shown in the figure and in Figures 2A to 2B In the power semiconductor transistor device 200 illustrated in the figure, the second doping distribution (DP_drain2) of the drift region 106 can generally be linearly gradual like the first doping distribution (DP_drain1), but increases with a greater slope compared to the generally linearly gradual first doping distribution.

[0027] For in Figures 1A to 1B The vertical power semiconductor transistor device 100 shown in the figure and in Figures 2A to 2B For both the power semiconductor transistor device 200 shown in the figure, the second doping distribution (DP_drain2) of the drift region 106 can be exponentially gradual.

[0028] For in Figures 1A to 1B The vertical power semiconductor transistor device 100 shown in the figure and in Figures 2A to 2BFor the power semiconductor transistor device 200 shown in the figure, the second doping distribution (DP_drain2) of the drift region 106 can increase from the first doping level L1 to the second doping level L2 adjacent to the drain region 102, which is 10 to 100 times larger than the first doping level L1.

[0029] The first doping level L1 and the second doping level L2 of the second doping distribution (DP_drain2) used for the drift region 106 can vary depending on the voltage level of devices 100 and 200. For example, in the case of a 100V device, the drift region 106 can have approximately 1e16 cm⁻¹. -3 The doping level L3 around the pn junction with a bulk region of 104 is increased to approximately 2.4 to 3e16 cm⁻¹. -3 The doping concentration in drift region 106 increases from level L1 to approximately (e.g., + / - 10%) 3e17cm at or near drain region 102. -3 Or a larger level L2. At or near the drain region at approximately 102 cm, around 3e17 cm. -3 The doping level L2 can be dominated by the n-type dopant diffused from the drain region 102. Generally, the doping levels L1, L2, and L3 in the drift region can vary according to different voltage levels, and can even vary within a single voltage level, depending on the optimization scheme applied. In one embodiment, the first doping level L1 is at 1e15 cm⁻¹. -3 and 1e17cm -3 Within the range between, and the second doping level L2 is at 1e17cm -3 and 1e19cm -3 Within the range between.

[0030] For in Figures 1A to 1B The vertical power semiconductor transistor device 100 shown in the figure and in Figures 2A to 2B With regard to the power semiconductor transistor device 200 illustrated in the figure, the first doping distribution (DP_drain1) of the drift region 106 may end at or near the level (T_end) corresponding to the bottom 128 of the trench 110 including the field electrode 124 within the drift region 106, and the second doping distribution (DP_drain2) of the drift region 106 may begin at or near the level (T_end).

[0031] For in Figures 1A to 1B The vertical power semiconductor transistor device 100 shown in the figure and in Figures 2A to 2BFor both the power semiconductor transistor device 200 illustrated in the figure, the first doping distribution (DP_drain1) of the drift region 106 can extend to at least 3 / 4 (three-quarters) of the depth (Depth_T) of the trench 110 / 202 including the field electrode 124 (Depth_DP_drift1).

[0032] For in Figures 1A to 1B The vertical power semiconductor transistor device 100 shown in the figure and in Figures 2A to 2B Regarding the power semiconductor transistor device 200 illustrated in the figure, the first doping distribution (DP_drain1) of the drift region 106 can be increased from the first doping level L3 adjacent to the body region 104 to the second doping level L4 of the second doping distribution (DP_drain2) adjacent to the drift region 106, and the second doping level L4 of the first doping distribution (DP_drain1) can be at least three times the first doping level L3 of the first doping distribution (DP_drain1).

[0033] The following describes production in Figures 1A to 1B and Figures 2A to 2B Examples of vertical power semiconductor transistor devices 100 and 200 illustrated in the figure.

[0034] Figures 3A to 3B The diagram shows the production process. Figures 1A to 1B and Figures 2A to 2B The illustration shows embodiments of vertical power semiconductor transistor devices 100 and 200. According to this embodiment, the drain region 102 is formed from a semiconductor substrate 300 of a first conductivity type. For example, the semiconductor substrate 300 may be a Si substrate.

[0035] Figure 3A A single epitaxial layer 302 grown on a semiconductor substrate 300 is shown. According to this embodiment, all device regions except the drain region 102 are to be formed in this single epitaxial layer 302. The single epitaxial layer 302 is doped during or after deposition to have a generally linearly graded first doping profile (DP_drift1) throughout it. For example, during the epitaxial deposition process, impurities such as trihydroarsine, phosphine, diborane, etc., can be added to the source gas in a controlled manner to produce a generally linearly graded first doping profile (DP_drift1) throughout the single epitaxial layer 302. The generally linearly graded first doping profile (DP_drift1) can alternatively be achieved after epitaxial growth, for example, by implantation or diffusion.

[0036] Figure 3BThe diagram illustrates the outward diffusion of a first conductivity type dopant 304 from the semiconductor substrate 300 into an adjacent single epitaxial layer 302. The outwardly diffused dopant 304 of the first conductivity type achieves a penetration depth (Pen_depth) within the single epitaxial layer 302, as measured from the semiconductor substrate 300. The penetration depth (Pen_depth) is less than the thickness of the final drift region 106. The outwardly diffused dopant 304 of the first conductivity type transforms a generally linearly gradient first dopant distribution (DP_drift1) into a gradient second dopant distribution (DP_drift2) at the penetration depth (Pen_depth). In one embodiment, the penetration depth (Pen_depth) and therefore the thickness of the portion of the final drift region 106 with the gradient second dopant distribution (DP_drift2) are in the range of approximately 3 to 4 μm. However, the portion of the final drift region 106 with the gradient second dopant distribution (DP_drift2) may be thinner than 3 μm or thicker than 4 μm.

[0037] The final drift region 106 has a generally linearly gradient (upper) first doping distribution (DP_drain1) established by the initial doping distribution of the single epitaxial layer 302, and a gradient (lower) second doping distribution (DP_drain2) established by the outward diffusion of a first conductivity type dopant 304 from the semiconductor substrate 300 to the adjacent single epitaxial layer 302. A second conductivity type body region 104 and a first conductivity type source region 108 are also formed in the single epitaxial layer 302 above the drift region 106. A gate trench 110 and field electrodes 124 in the gate trench 110 or in the separated trench 202 are also formed in the single epitaxial layer 302. Standard semiconductor processes such as photolithography, masking, etching, ion implantation, and annealing can be used to form the... Figures 1A to 1B and Figures 2A to 2B These regions are shown in the diagram for vertical power semiconductor transistor devices 100 and 200.

[0038] For example, a dopant of a second conductivity type can be implanted into a single epitaxial layer 302 to form a body region 104, and a dopant of a first conductivity type can be implanted into a single epitaxial layer 302 to form a source region 108. The single epitaxial layer 302 can be annealed at least once to electrically activate the dopant implanted into the single epitaxial layer 302 to form the body region 104, drift region 106, and source region 108 of the device 100 / 200. In one embodiment, a first conductivity type dopant 304 diffuses outward from the semiconductor substrate 300 into the adjacent single epitaxial layer 302 by a heat treatment 306 applied to activate the respective dopants of the body region 104 and source region 108. For ease of illustration, the body region 104, drift region 106, and source region 108, together with the trench structure, are... Figure 3B Omitted. However, in Figure 3B The diagram shows the doping concentration distribution (DP_body, DP_drift1, DP_drift2, DP_source) of the body region 104, drift region 106, and source region 108 relative to the positions of these regions in a single epitaxial layer 302.

[0039] Figures 4A to 4B The diagram shows the production process. Figures 1A to 1B and Figures 2A to 2B Another embodiment of the vertical power semiconductor transistor devices 100 and 200 illustrated in the figure. According to this embodiment, the drain region 102 is formed from a semiconductor substrate 400 of a first conductivity type (such as a suitably doped Si substrate).

[0040] Figure 4A A semiconductor substrate 400 is shown, doped with a first dopant n1 of a first conductivity type. The semiconductor substrate 400 is also provided with a second dopant n2 of the first conductivity type, which has a faster diffusion rate compared to the first dopant n1 of the first conductivity type. For example, when Si is the material of the substrate 400, the second dopant n2 of the first conductivity type can be phosphorus, and the first dopant n1 of the first conductivity type can be arsenic or antimony. The second dopant n2 of the first conductivity type can be implanted or diffused into the semiconductor substrate 400, for example, at the epitaxial growth side 402 of the substrate 400.

[0041] Figure 4B This illustrates a single epitaxial layer 404 grown on the epitaxial growth side 402 of the semiconductor substrate 400. (As shown above...) Figures 3A to 3B As explained therein, a single epitaxial layer 404 is formed through which a first doping distribution (DP_drift1) with a generally linear gradient is present, and all device regions except the drain region 102 will be formed in the single epitaxial layer 404.

[0042] Figure 4B The diagram also illustrates the outward diffusion of a first conductivity type dopant 406 from the epitaxial growth side 402 of the semiconductor substrate 400 to the adjacent single epitaxial layer 404. Due to the diffusion rate difference explained above, more second conductivity type dopant n2 diffuses outward from the semiconductor substrate 400 into the adjacent single epitaxial layer 404 compared to the first conductivity type dopant n1. The outwardly diffused first conductivity type dopant 406 reaches a penetration depth (Pen_depth) within the single epitaxial layer 404 and transforms the generally linearly gradient first dopant distribution (DP_drift1) into a gradient second dopant distribution (DP_drift2) at the penetration depth (Pen_depth), as shown above. Figures 3A to 3B As explained in the relevant text.

[0043] The final drift region 106 has a generally linearly gradient (upper) first doping distribution (DP_drain1) established by the initial doping distribution of a single epitaxial layer 404, and a gradient (lower) second doping distribution (DP_drain2) established by the outward diffusion of a first conductivity type dopant 406 from the semiconductor substrate 400 to the adjacent single epitaxial layer 402. As described above... Figures 3A to 3B As explained in relation to this, through a heat treatment 408 applied to the respective dopants of the body region 104 and source region 108 of the activating device 100 / 200, a first conductivity type dopant 406 can diffuse outward from the semiconductor substrate 400 into an adjacent single epitaxial layer 404. For ease of illustration, the body region 104, drift region 106, and source region 108, together with the trench structure, are... Figure 4B The text is omitted. However, in... Figure 4B The diagram shows the doping concentration distribution (DP_body, DP_drift1, DP_drift2, DP_source) of the body region 104, drift region 106, and source region 108 relative to the positions of these regions in a single epitaxial layer 404.

[0044] Figures 5A to 5B The diagram shows the production process. Figures 1A to 1B and Figures 2A to 2B Another embodiment of the vertical power semiconductor transistor devices 100 and 200 illustrated in the figure. According to this embodiment, the drain region 102 is formed from a semiconductor substrate 500 of a first conductivity type (such as a suitably doped Si substrate).

[0045] Figure 5A A first epitaxial layer 502 grown on a semiconductor substrate 500 is shown. The first epitaxial layer 502 is doped during or after deposition to have a gradient (lower) second doping profile (DP_drift2) for the final drift region 106. For example, during the epitaxial deposition process, impurities such as trihydroarsine, phosphine, diborane, etc., can be added to the source gas in a controlled manner to produce a gradient second doping profile (DP_drift2) within the first epitaxial layer 502. The gradient second doping profile (DP_drift2) can alternatively be achieved after epitaxial growth, for example, by implantation or diffusion.

[0046] Figure 5BA second epitaxial layer 504 grown on the first epitaxial layer 502 is shown. The second epitaxial layer 504 is doped during or after deposition to have a generally linearly graded (upper) first doping distribution (DP_drain1) for the final drift region 106. For example, during the epitaxial deposition process, impurities such as trihydroarsine, phosphine, diborane, etc., can be added to the source gas in a controlled manner to produce a generally linearly graded first doping distribution (DP_drift1) within the second epitaxial layer 504. The generally linearly graded first doping distribution (DP_drift1) can alternatively be achieved after epitaxial growth, for example, by implantation or diffusion.

[0047] In one embodiment, the first epitaxial layer 502 is thinner than the second epitaxial layer 504. The thickness of the combination of the first epitaxial layer 502 and the second epitaxial layer 504 can be selected based on the blocking voltage requirements for device 100 / 200. A body region 104 of a second conductivity type and a source region 108 of a first conductivity type are formed in the second epitaxial layer 504 above the drift region 106. A gate trench 110 and a field electrode 124 in the gate trench 110 or in a separate trench 202 are also formed in the second epitaxial layer 504 and can extend into the first epitaxial layer 502. Standard semiconductor processes such as photolithography, masking, etching, ion implantation, annealing, etc., can be used to form the first epitaxial layer 504. Figures 1A to 1B and Figures 2A to 2B These regions are shown in the diagram of vertical power semiconductor transistor devices 100 and 200. For ease of explanation, the body region 104, drift region 106, and source region 108, along with the trench structure, are described from... Figure 5B Omitted in .

[0048] Figures 6A to 6B The diagram shows the production process. Figures 1A to 1B and Figures 2A to 2B Another embodiment of the vertical power semiconductor transistor devices 100 and 200 illustrated in the figure. According to this embodiment, the drain region 102 is formed from a semiconductor substrate 600 of a first conductivity type (such as, for example, a suitably doped Si substrate).

[0049] Figure 6A A first epitaxial layer 602 grown on a semiconductor substrate 600 is shown. The first epitaxial layer 602 is doped during or after deposition to have a first constant doping profile (DP_const1). For example, during the epitaxial deposition process, impurities such as trihydroarsine, phosphine, diborane, etc., can be added to the source gas in a controlled manner to produce the first constant doping profile (DP_const1) within the first epitaxial layer 602. Alternatively, the first constant doping profile (DP_const1) can be achieved after epitaxial growth, for example, by implantation or diffusion.

[0050] Figure 6B A second epitaxial layer 604 grown on a first epitaxial layer 602 is shown. The second epitaxial layer 604 is doped during or after deposition to have a second constant doping profile (DP_const2) and a lower average doping concentration compared to the first epitaxial layer 602. For example, during the epitaxial deposition process, impurities such as trihydroarsine, phosphine, diborane, etc., can be added to the source gas in a controlled manner to produce a second constant doping profile (DP_const2) within the second epitaxial layer 604. Alternatively, the second constant doping profile (DP_const2) can be achieved after epitaxial growth, for example, by implantation or diffusion.

[0051] Figure 6C This illustrates how a dopant of a first conductivity type diffuses outward from the semiconductor substrate 600 into the adjacent first epitaxial layer 602. For example, as shown above... Figure 3B As explained relevantly, through a subsequent heat treatment 608 applied during the formation of the body region 104 and the source region 108, a dopant of the first conductivity type can diffuse outward from the semiconductor substrate 600 into the adjacent first epitaxial layer 602. In another example, as described above... Figure 4B As explained accordingly, the semiconductor substrate 600 may be doped with a first dopant of a first conductivity type and provided with a second dopant of the first conductivity type that has a faster diffusion rate compared to the first dopant. A subsequent heat treatment 608 causes the second dopant of the first conductivity type to diffuse outward from the semiconductor substrate 600 into the first epitaxial layer 602. In each case, the outward diffusion of the first conductivity type dopant transforms the first constant doping distribution (DP_const1) into a gradient second doping distribution (DP_drain2) in the first epitaxial layer 602.

[0052] The heat treatment 608 applied during the formation of the body region 104 and the source region 108, along with the associated diffusion treatment, also transforms the second constant doping distribution (DP_const2) in the second epitaxial layer 604 into a generally linearly gradient first doping distribution (DP_drain1) in the drift region segment 606 of the second epitaxial layer 604. The body region 104 and the source region 108 are formed in the second epitaxial layer 604 above the drift region segment 606. The gate trench 110 and the field electrode 124 in the gate trench 110 or in the separated trench 202 are also formed in the second epitaxial layer 604 and can extend into the first epitaxial layer 602. Standard semiconductor processes such as photolithography, masking, etching, ion implantation, annealing, etc., can be used to form the second epitaxial layer 604. Figures 1A to 1B and Figures 2A to 2BThese regions are shown in the diagram of vertical power semiconductor transistor devices 100 and 200. For ease of explanation, the body region 104, drift region 106, and source region 108, along with the trench structure, are described from... Figure 6B The text is omitted. However, in... Figure 6B The diagram shows the doping concentration distribution (DP_body, DP_drift1, DP_drift2, DP_source) of the body region 104, drift region 106, and source region 108 relative to the positions of these regions in the first epitaxial layer 602 and the second epitaxial layer 604.

[0053] While this disclosure is not limited thereto, the examples numbered below illustrate one or more aspects of this disclosure.

[0054] Example 1. A vertical power semiconductor transistor device, comprising: a drain region of a first conductivity type; a body region of a second conductivity type opposite to the first conductivity type; a drift region of the first conductivity type separating the body region from the drain region; a source region of the first conductivity type separated from the drift region by the body region; a gate trench extending through the source region and the body region and into the drift region, the gate trench including a gate electrode; and a field electrode in the gate trench or in a separated trench, wherein the drift region has a generally linearly gradient first doping distribution increasing from the body region toward the bottom of the trench including the field electrode, and a gradient second doping distribution increasing at a larger ratio from the ends of the first doping distribution toward the drain region.

[0055] Example 2. A vertical power semiconductor transistor device according to Example 1, wherein the second doping distribution is generally linearly graded and increases with a greater slope compared to the generally linearly graded first doping distribution.

[0056] Example 3. A vertical power semiconductor transistor device according to Example 1, wherein the second doping distribution is exponentially gradual.

[0057] Example 4. A vertical power semiconductor transistor device according to any one of Examples 1 to 3, wherein the second doping distribution increases from a first doping level adjacent to the first doping distribution to a second doping level adjacent to the drain region, and wherein the second doping level is in the range of 10 to 100 times the first doping level.

[0058] Example 5. A vertical power semiconductor transistor device according to Example 4, wherein the vertical power semiconductor transistor device is rated for 100V, wherein the first doping level is 2.4e16cm. -3 and 3e16cm -3 Within the range between, and where the second doping level is approximately 3e17cm. -3Or larger.

[0059] Example 6. A vertical power semiconductor transistor device according to any one of Examples 1 to 5, wherein a first doping distribution ends at or near a horizontal level corresponding to the bottom of a trench including a field electrode within a drift region, and a second doping distribution begins at or near said horizontal level.

[0060] Example 7. A vertical power semiconductor transistor device according to any one of Examples 1 to 6, wherein the field electrode is in a trench different from the gate electrode, and wherein the field electrode is needle-shaped in its longitudinal extension.

[0061] Example 8. A vertical power semiconductor transistor device according to any one of Examples 1 to 7, wherein a first doping distribution of the drift region extends to a depth of at least 3 / 4 of the depth of the trench including the field electrode.

[0062] Example 9. A vertical power semiconductor transistor device according to any one of Examples 1 to 8, wherein a first doping distribution increases from a first doping level adjacent to a body region to a second doping level adjacent to a second doping distribution, and wherein the second doping level is at least three times the first doping level.

[0063] Example 10. A vertical power semiconductor transistor device according to any one of Examples 1 to 9, wherein the drain region is formed from a semiconductor substrate of a first conductivity type, wherein the drift region, the body region, and the source region are formed in a single epitaxial layer grown on the semiconductor substrate, wherein the semiconductor substrate is doped with a first dopant of the first conductivity type, wherein a second doping distribution for the drift region is generated by a second dopant of the first conductivity type diffusing outward from the semiconductor substrate, and wherein the second dopant has a faster diffusion rate than the first dopant.

[0064] Example 11. A vertical power semiconductor transistor device according to any one of Examples 1 to 9, wherein the drain region is formed of a semiconductor substrate of a first conductivity type, wherein a second doping distribution for the drift region exists in a first epitaxial layer grown on the semiconductor substrate, wherein the first doping distribution for the drift region exists in a second epitaxial layer grown on the first epitaxial layer, and wherein, in the drift region, the first epitaxial layer is thinner than the second epitaxial layer and has a higher average doping concentration.

[0065] Example 12. A method of manufacturing a vertical power semiconductor transistor device, the method comprising: forming a drain region of a first conductivity type, a drift region of a first conductivity type, a body region of a second conductivity type opposite to the first conductivity type and separated from the drain region by the drift region, and a source region of the first conductivity type and separated from the drift region by the body region; forming a gate trench extending through the source region and the body region and into the drift region, the gate trench including a gate electrode; forming a field electrode in the gate trench or in the separated trench; establishing a generally linearly gradient first doping distribution in the drift region and increasing from the body region toward the bottom of the trench including the field electrode; and establishing a gradient second doping distribution in the drift region and increasing at a rate greater than that of the first doping distribution from the ends of the first doping distribution toward the drain region.

[0066] Example 13. According to the method of Example 12, wherein the second doping distribution is generally linearly graded and increases with a greater slope compared to the generally linearly graded first doping distribution, or wherein the second doping distribution is exponentially graded.

[0067] Example 14. The method according to Example 12 or 13, wherein the drain region is formed of a semiconductor substrate of a first conductivity type, and wherein establishing a gradient second doping distribution in the drift region comprises: growing a single epitaxial layer on the semiconductor substrate having a generally linearly gradient first doping distribution therethrough; and diffusing a dopant of the first conductivity type outward from the semiconductor substrate into an adjacent single epitaxial layer, the outwardly diffused dopant of the first conductivity type reaching a penetration depth in the single epitaxial layer as measured from the semiconductor substrate, and the penetration depth being less than the thickness of the drift region, the outwardly diffused dopant of the first conductivity type transforming the generally linearly gradient first doping distribution into a gradient second doping distribution in terms of penetration depth.

[0068] Example 15. According to the method of Example 14, a dopant of a first conductivity type diffuses outward from the semiconductor substrate into a single adjacent epitaxial layer by heat treatment applied during the formation of the body region and the source region.

[0069] Example 16. The method of Example 14, wherein a semiconductor substrate is doped with a first dopant of a first conductivity type, and wherein the diffusion of the first conductivity type dopant from the semiconductor substrate outward into an adjacent single epitaxial layer comprises: providing a second dopant of the first conductivity type in the semiconductor substrate, the second dopant having a faster diffusion rate compared to the first dopant; and applying a heat treatment after providing the second dopant and after growing the single epitaxial layer, the heat treatment causing the second dopant of the first conductivity type to diffuse outward from the semiconductor substrate into the adjacent single epitaxial layer to a penetration depth.

[0070] Example 17. The method according to Example 12 or 13, wherein the drain region is formed from a semiconductor substrate of a first conductivity type, and wherein establishing a gradient second doping distribution in the drift region comprises: growing a first epitaxial layer on the semiconductor substrate, the first epitaxial layer having a gradient second doping distribution; and growing a second epitaxial layer on the first epitaxial layer, the second epitaxial layer having a generally linearly gradient first doping distribution, wherein the first epitaxial layer is thinner than the second epitaxial layer.

[0071] Example 18. The method according to Example 12 or 13, wherein the drain region is formed from a semiconductor substrate of a first conductivity type, and wherein establishing a gradient second doping distribution in the drift region comprises: growing a first epitaxial layer on the semiconductor substrate, the first epitaxial layer having a first constant doping distribution; growing a second epitaxial layer on the first epitaxial layer, the second epitaxial layer having a second constant doping distribution and having a lower average doping concentration compared to the first epitaxial layer; causing a dopant of the first conductivity type to diffuse outward from the semiconductor substrate into an adjacent first epitaxial layer, the outwardly diffused dopant of the first conductivity type converting the first constant doping distribution into a gradient second doping distribution in the first epitaxial layer; and converting the second constant doping distribution into a generally linearly gradient first doping distribution in the drift region segment of the second epitaxial layer by heat treatment applied during the formation of the body region and the source region.

[0072] Example 19. According to the method of Example 18, a dopant of a first conductivity type diffuses outward from the semiconductor substrate into an adjacent first epitaxial layer by heat treatment applied during the formation of the body region and the source region.

[0073] Example 20. The method of Example 18, wherein a semiconductor substrate is doped with a first dopant of a first conductivity type, and wherein causing the first conductivity type dopant to diffuse outward from the semiconductor substrate into an adjacent first epitaxial layer comprises: providing a second dopant of the first conductivity type in the semiconductor substrate, the second dopant having a faster diffusion rate compared to the first dopant; and applying a heat treatment after providing the second dopant and after growing the first epitaxial layer, the heat treatment causing the second dopant of the first conductivity type to diffuse outward from the semiconductor substrate into the first epitaxial layer.

[0074] Terms such as "first" and "second" are used to describe various elements, sections, and segments, and are not intended to be restrictive. Throughout the description, the same terms refer to the same elements.

[0075] As used herein, the terms “having,” “containing,” “including,” and “including” are open-ended terms that indicate the presence of the stated element or feature but do not exclude additional elements or features. The quantifiers “a,” “one,” and the pronoun “the” are intended to include both plural and singular forms unless the context clearly indicates otherwise.

[0076] It should be understood that, unless otherwise specifically indicated, the features of the various embodiments described herein can be combined with each other.

[0077] 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 by the claims and their equivalents.

Claims

1. A vertical power semiconductor transistor device, comprising: Drain region of the first conductivity type; A body region of a second conductivity type, opposite to the first conductivity type; The first conductivity type and the drift region that separates the body region from the drain region; The first type of conductivity source region, which is separated from the drift region by the body region; A gate trench extending through the source region and the body region and into the drift region, the gate trench including a gate electrode; and Field electrodes in the gate trench or in separate trenches, The drift region has a generally linearly gradient first doping distribution that increases from the body region toward the bottom of the trench including the field electrode, and a gradient second doping distribution that increases at a larger ratio than the first doping distribution toward the drain region. The first doping distribution ends at or near the level corresponding to the bottom of the trench including the field electrode within the drift region, and the second doping distribution begins at or near the level, or the first doping distribution in the drift region extends to at least 3 / 4 of the depth of the trench including the field electrode.

2. The vertical power semiconductor transistor device according to claim 1, wherein, The second doping distribution is generally linearly gradual and increases with a greater slope compared to the generally linearly gradual first doping distribution.

3. The vertical power semiconductor transistor device according to claim 1, wherein, The second doping distribution is exponentially gradual.

4. The vertical power semiconductor transistor device according to claim 1, wherein, The second doping distribution increases from a first doping level adjacent to the first doping distribution to a second doping level adjacent to the drain region, wherein the second doping level is in the range of 10 to 100 times the first doping level.

5. The vertical power semiconductor transistor device according to claim 4, wherein, The vertical power semiconductor transistor device is rated for 100V, wherein the first doping level is 2.4e16cm. -3 and 3e16cm -3 Within the range between, and where the second doping level is 3e17cm. -3 Or larger.

6. The vertical power semiconductor transistor device according to claim 1, wherein, The field electrode is in a trench different from the gate electrode, and wherein the field electrode is needle-shaped in its longitudinal extension.

7. The vertical power semiconductor transistor device according to claim 1, wherein, The first doping distribution increases from a first doping level adjacent to the bulk region to a second doping level adjacent to the second doping distribution, wherein the second doping level is at least three times the first doping level.

8. The vertical power semiconductor transistor device according to claim 1, wherein, The drain region is formed from a semiconductor substrate of a first conductivity type, wherein the drift region, the body region, and the source region are formed in a single epitaxial layer grown on the semiconductor substrate, wherein the semiconductor substrate is doped with a first dopant of the first conductivity type, wherein a second doping distribution for the drift region is generated by a second dopant of the first conductivity type diffusing outward from the semiconductor substrate, and wherein the second dopant has a faster diffusion rate than the first dopant.

9. The vertical power semiconductor transistor device according to claim 1, wherein, The drain region is formed from a semiconductor substrate of a first conductivity type, wherein a second doping distribution for the drift region exists in a first epitaxial layer grown on the semiconductor substrate, wherein the first doping distribution for the drift region exists in a second epitaxial layer grown on the first epitaxial layer, and wherein, in the drift region, the first epitaxial layer is thinner than the second epitaxial layer and has a higher average doping concentration.

10. A method for producing a vertical power semiconductor transistor device, the method comprising: A drain region of the first conductivity type, a drift region of the first conductivity type, a body region of the second conductivity type opposite to the first conductivity type and separated from the drain region by the drift region, and a source region of the first conductivity type and separated from the drift region by the body region; A gate trench is formed that extends through the source region and the body region and into the drift region, the gate trench including the gate electrode; Field electrodes are formed in the gate trench or in separate trenches; A generally linearly gradient first doping distribution is established in the drift region and increases from the bulk region toward the bottom of the trench including the field electrode; as well as A second doping distribution is established in the drift region and increases at a greater rate than the first doping distribution from the end of the first doping distribution toward the drain region. The first doping distribution ends at or near the level corresponding to the bottom of the trench including the field electrode within the drift region, and the second doping distribution begins at or near the level, or the first doping distribution in the drift region extends to at least 3 / 4 of the depth of the trench including the field electrode.

11. The method according to claim 10, wherein, The second doping distribution is generally linearly gradual and increases with a greater slope compared to the generally linearly gradual first doping distribution, or the second doping distribution is exponentially gradual.

12. The method according to claim 10, wherein, The drain region is formed from a semiconductor substrate of a first conductivity type, and wherein establishing a gradient second doping distribution in the drift region includes: A single epitaxial layer is grown on a semiconductor substrate, the single epitaxial layer having a generally linearly graded first doping distribution throughout it; and A dopant of a first conductivity type diffuses outward from the semiconductor substrate into a single adjacent epitaxial layer, the outward diffusion of the first conductivity type dopant reaching a penetration depth within the single epitaxial layer as measured from the semiconductor substrate, and this penetration depth is less than the thickness of the drift region, the outward diffusion of the first conductivity type dopant transforms a generally linearly gradient first doping distribution into a gradient second doping distribution in the penetration depth.

13. The method according to claim 12, wherein, Through heat treatment applied during the formation of the bulk region and source region, dopants of the first conductivity type diffuse outward from the semiconductor substrate into a single adjacent epitaxial layer.

14. The method of claim 12, wherein, A semiconductor substrate is doped with a first dopant of a first conductivity type, wherein the dopant of the first conductivity type diffuses outward from the semiconductor substrate into a neighboring single epitaxial layer, comprising: A second dopant of a first conductivity type is provided in a semiconductor substrate, the second dopant having a faster diffusion rate compared to the first dopant; and After the second dopant is provided and after the growth of a single epitaxial layer, a heat treatment is applied that causes the second dopant of the first conductivity type to diffuse outward from the semiconductor substrate into the adjacent single epitaxial layer to achieve a penetration depth.

15. The method according to claim 10, wherein, The drain region is formed from a semiconductor substrate of a first conductivity type, and wherein establishing a gradient second doping distribution in the drift region includes: A first epitaxial layer is grown on a semiconductor substrate, the first epitaxial layer having a gradient second doping distribution; and A second epitaxial layer is grown on the first epitaxial layer, the second epitaxial layer having a generally linearly graded first doping distribution. The first epitaxial layer is thinner than the second epitaxial layer.

16. The method of claim 10, wherein, The drain region is formed from a semiconductor substrate of a first conductivity type, and wherein establishing a gradient second doping distribution in the drift region includes: A first epitaxial layer is grown on a semiconductor substrate, the first epitaxial layer having a first constant doping distribution; A second epitaxial layer is grown on the first epitaxial layer. The second epitaxial layer has a second constant doping distribution and a lower average doping concentration compared with the first epitaxial layer. A dopant of a first conductivity type diffuses outward from the semiconductor substrate into an adjacent first epitaxial layer, and the outward diffusion of the dopant of the first conductivity type transforms a first constant doping distribution into a gradual second doping distribution in the first epitaxial layer; and By applying heat treatment during the formation of the body region and the source region, the second constant doping distribution is transformed into a first doping distribution that is generally linearly gradual in the drift region segment of the second epitaxial layer.

17. The method according to claim 16, wherein, Through heat treatment applied during the formation of the body region and the source region, a dopant of the first conductivity type diffuses outward from the semiconductor substrate into the adjacent first epitaxial layer.

18. The method according to claim 16, wherein, A semiconductor substrate is doped with a first dopant of a first conductivity type, and wherein diffusing the first conductivity type dopant from the semiconductor substrate outward into an adjacent first epitaxial layer comprises: providing a second dopant of the first conductivity type in the semiconductor substrate, the second dopant having a faster diffusion rate than the first dopant; and After the second dopant is provided and after the first epitaxial layer is grown, a heat treatment is applied, which causes the second dopant of the first conductivity type to diffuse outward from the semiconductor substrate into the first epitaxial layer.

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