阅读说明：本技术 一种提高反向恢复鲁棒性的快恢复自举二极管
(Fast recovery bootstrap diode for improving reverse recovery robustness
) 是由 祝靖
邹艳勤
李少红
孙伟锋
时龙兴 于 2019-10-31 设计创作，主要内容包括：一种提高反向恢复鲁棒性的快恢复自举二极管，包括P型衬底，在P型衬底上设有N型漂移区，在N型漂移区的表面设有二氧化硅氧化层，在P型衬底与N型漂移区之间设有第一N型重掺杂区，在N型漂移区的表面设有P型重掺杂阳极区、P型轻掺杂阳极区、N型轻掺杂阴极区及N型重掺杂阴极区，在N型漂移区的表面并处于N型重掺杂阴极区的外侧以及N型重掺杂阴极区与P型轻掺杂阳极区之间的区域设有氧化层，在P型重掺杂阳极区、N型重掺杂阴极区及P型衬底上分别连接有阳极金属、阴极金属及衬底金属，其特征在于，在P型轻掺杂阳极区的表面并位于P型重掺杂阳极区的外侧设有相互电连接的第一P型重掺杂区、N型重掺杂区和第二P型重掺杂区。(A fast recovery bootstrap diode for improving reverse recovery robustness comprises a P-type substrate, an N-type drift region is arranged on the P-type substrate, a silicon dioxide oxide layer is arranged on the surface of the N-type drift region, a first N-type heavily doped region is arranged between the P-type substrate and the N-type drift region, a P-type heavily doped anode region, a P-type lightly doped anode region, an N-type lightly doped cathode region and an N-type heavily doped cathode region are arranged on the surface of the N-type drift region, oxide layers are arranged on the surface of the N-type drift region and at the outer side of the N-type heavily doped cathode region and in the region between the N-type heavily doped cathode region and the P-type lightly doped anode region, anode heavily doped region, N-type heavily doped cathode region and P-type substrate are respectively connected with anode metal, cathode metal and substrate metal, and the fast recovery bootstrap diode is characterized in that a first P-type heavily doped region, a first N-type heavily doped region, an N-type heavily doped region and a second P-type heavily doped region.)
1. A fast recovery bootstrap diode for improving reverse recovery robustness comprises a P-type substrate (1), wherein an N-type drift region (2) is arranged on the P-type substrate (1), a silicon dioxide oxidation layer (7) is arranged on the surface of the N-type drift region (2), a first N-type heavily doped region (3) is arranged between the P-type substrate (1) and the N-type drift region (2), a P-type lightly doped anode region (10) serving as an anode region and an N-type lightly doped cathode region (8) and an N-type heavily doped cathode region (9) which are located on the outer side of the anode region and serve as a cathode region are arranged on the surface of the N-type drift region (2), the N-type heavily doped cathode region (9) is arranged in the N-type lightly doped cathode region (8), a P-type heavily doped anode region (11) is arranged on the surface of the P-type lightly doped anode region (10), and the surface of the N-type drift region (2) is located on the outer side of the N-type heavily doped cathode region (9) and the N-type heavily doped cathode region ( An oxide layer (6) is arranged in a region among the anode regions (10), and anode metal (anode), cathode metal (cathode) and substrate metal (sub) are respectively connected to the P-type heavily doped anode region (11), the N-type heavily doped cathode region (9) and the P-type substrate (1), and the solar cell is characterized in that a first P-type heavily doped region (14), an N-type heavily doped region (15) and a second P-type heavily doped region (16) which are electrically connected with each other are arranged on the surface of the P-type lightly doped anode region (10) and located on the outer side of the P-type heavily doped anode region (11).
2. The fast recovery bootstrap diode of improvement reverse recovery robustness of claim 1, characterized in that, first heavily doped P-type region (14), heavily doped N-type region (15) and second heavily doped P-type region (16) are electrically connected to each other through the floating metal electrode (13) disposed in the silicon dioxide oxide layer (7).
3. The fast recovery bootstrap diode of improving the robustness of reverse recovery of claim 1, characterized in that, there is a P-type dynamic field limiting ring (12) on the surface of the P-type lightly doped anode region (10) and between the first heavily doped P-type region (14) and the heavily doped P-type anode region (11).
4. The fast recovery bootstrap diode of improving the robustness of reverse recovery of claim 1, characterized in that, within the N-type drift region (2) and below the N-type heavily doped cathode region (9), there is a second N-type heavily doped region (17) and the second N-type heavily doped region (17) falls on the first N-type heavily doped region (3).
5. The fast recovery bootstrap diode of improving reverse recovery robustness of claim 1, characterized in that, there is a first P type heavily doped substrate region (4) in the P type substrate (1) and the first P type heavily doped substrate region (4) extends into the N type drift region (2), there is a second P type heavily doped substrate region (5) connected on the first P type heavily doped substrate region (4) and the second P type heavily doped substrate region (5) extends and is connected to the substrate metal (sub) to realize the connection of the P type substrate (1) and the substrate metal (sub).
6. The fast recovery bootstrap diode as claimed in claim 3, 4 or 5, wherein the doping concentration range of the P-type dynamic field limiting ring (12), the first heavily doped P-type region (14) and the second heavily doped P-type region (16) is 1.8e 14-2.3 e14cm-2。
7. The fast recovery bootstrap diode of claim 1 characterized in that, the concentration range of the N-type heavily doped region (15) is 0.8e15 ~ 1.1e15cm-2。
8. The fast recovery bootstrap diode of claim 4 characterized in that, the length of the second N-type heavily doped region (17) ranges from 9 to 9.5 μm, the doping concentration ranges from 22e15 to 33e15cm-2。
Technical Field
The invention mainly relates to the technical field of power semiconductor devices, in particular to a fast recovery bootstrap diode for improving reverse recovery robustness.
Background
Compared with Si MOSFETs, the GaN FETs have higher conversion efficiency, power density, switching frequency, on-resistance under the same withstand voltage and small device volume, and the characteristics of the GaN FETs meet the requirements of next-generation semiconductor power devices on high power, high efficiency, high frequency, high speed, high reliability and small volume, thereby ensuring that the GaN FETs have very wide prospects and markets in the future power electronic application field. However, there are some factors that need special attention, for example, the upper limit of the gate-source voltage V must be setGS(MAX)And strictly controlling to avoid damaging the grid electrodes of the GaN FETs power tubes. Therefore, the bootstrap circuit usually adopts a clamp design, so as to achieve the purpose of controlling the gate-source voltage. In addition, in order to adapt to the switching frequency of GaN FETs, the bootstrap diode (hereinafter BSD) in the circuit must have fast turn-on and turn-off capability, i.e. lower forward turn-on voltage VFAnd a shorter reverse recovery time. Meanwhile, in order to improve the energy efficiency and reliability of the system, the reverse recovery tail current of the BSD must be reduced and the reverse recovery robustness thereof must be improved.
In a high-voltage and high-current circuit, the traditional BSD has good reverse voltage resistance and very low forward conducting voltage VFA large forward conduction current will occur. Therefore, the total amount of minority carriers stored in the intrinsic region is large in the forward conduction period of the conventional BSD, so that the extraction speed of minority carriers in the intrinsic region is low in the reverse recovery period, a serious tail current exists, the reverse recovery time is long, the power consumption of a system circuit is seriously increased, and the improvement of the system operating frequency is limited. In addition, during the reverse recovery period, a situation of high voltage and large current exists at the same time, current accumulation is easy to occur on the anode and the cathode, a current spike is formed, a peak electric field appears on the surfaces of the anode and the cathode, double-side dynamic avalanche is caused, thermal failure occurs, and the reliability of the system is seriously influenced.
Therefore, the temperature of the molten metal is controlled,in reducing the forward conduction voltage VFThe premise of reducing the reverse recovery time and the tailing current during BSD reverse recovery is favorable for ensuring the effectiveness of the system, and the improvement of the reverse recovery robustness is favorable for ensuring the reliability of the system by reducing the peak electric fields of the anode and the cathode, which has important significance for the development and design of power integrated circuits.
Disclosure of Invention
The invention provides a fast recovery bootstrap diode for improving the reverse recovery robustness, aiming at the problems, not only improves the reverse recovery robustness of the bootstrap diode, but also reduces the forward conduction voltage VFEffectively reducing the reverse recovery time and reducing the reverse recovery tail current.
The technical scheme of the invention is as follows:
a fast recovery bootstrap diode for improving reverse recovery robustness comprises a P-type substrate, wherein an N-type drift region is arranged on the P-type substrate, a silicon dioxide oxide layer is arranged on the surface of the N-type drift region, a first N-type heavily doped region is arranged between the P-type substrate and the N-type drift region, a P-type lightly doped anode region serving as an anode region, an N-type lightly doped cathode region and an N-type heavily doped cathode region are arranged on the surface of the N-type drift region, the N-type lightly doped cathode region and the N-type heavily doped cathode region are positioned on the outer side of the anode region and serve as cathode regions, the N-type heavily doped cathode region is arranged in the N-type lightly doped cathode region, a P-type heavily doped anode region, an N-type heavily doped cathode region and a P-type substrate are respectively connected with an anode metal (anode) and a cathode metal (anode) and an oxide layer, The cathode metal (cathode) and the substrate metal (sub) are characterized in that a first P-type heavily doped region, an N-type heavily doped region and a second P-type heavily doped region which are electrically connected with each other are arranged on the surface of the P-type lightly doped anode region and positioned on the outer side of the P-type heavily doped anode region.
Compared with the prior art, the structure of the invention has the following advantages:
1. according to the invention, the first P-type heavily doped region 14, the N-type heavily doped region 15 and the second P-type heavily doped region 16 which are mutually connected through the floating metal electrode 13 are respectively added on two sides of the tail end of the P-type lightly doped anode region 10, and partial holes stored in the drift region 2 can be compounded with electrons at the N-type heavily doped region 15, so that the extraction speed of the holes in the drift region 2 is accelerated, and the reverse recovery time is reduced. During the reverse recovery period, when the cathode is connected with a high potential and the anode and the substrate are both connected with a low potential, the P-type lightly doped anode region 10, the P-type heavily doped anode region 11, the first P-type heavily doped region 14, the N-type heavily doped region 15 and the second P-type heavily doped region 16 which are connected with each other through the floating metal electrode 13 are all at a low potential, holes stored in the drift region 2 flow out of the body through the P-type lightly doped anode region 10, due to the heavily N-doped region 15 in the P-type lightly doped anode region 10, part of the holes stored in the drift region 2 will recombine with electrons there, as shown in fig. 4, part of the holes flow into the heavily N-doped region 15, which increases the extraction rate of the excess carriers on the anode side and greatly reduces the reverse recovery time, as shown in fig. 7, at the same di/dt-50A/mus, the inventive structure has a shorter reverse recovery time.
2. According to the invention, the P-type dynamic field limiting ring 12, the first P-type heavily doped region 14, the N-type heavily doped region 15 and the second P-type heavily doped region 16 which are mutually connected through the floating metal electrode 13 are respectively added on two sides of the tail end of the P-type lightly doped anode region 10, so that the accumulation of electric field lines at the anode heavily doped region 11 is avoided, the peak electric field at the anode side is effectively alleviated, and the reverse recovery robustness is improved. When the P-type dynamic field limiting ring 12 is not added, electric field lines may be concentrated at the outermost P-type heavily doped anode region 11, which causes the peak electric field at that position to be too high, as shown by a point a in fig. 5. When the P-type dynamic field limiting ring 12 is added, the boundary of the depletion layer is widened by reasonably adjusting the concentration of the P-type dynamic field limiting ring 12, electric field lines cannot be gathered at the outermost P-type heavily doped anode region 11, meanwhile, because part of the current path flows through the N-type heavily doped region 15, the gathering of current at the anode heavily doped region 11 can also be avoided, and thus the peak electric field at the anode side is effectively alleviated, as shown in fig. 5, the peak electric field a is alleviated into three lower peak electric fields a1, a2 and A3. The reduction of the peak electric field at the anode side can effectively improve the reverse recovery robustness of the diode, as shown in fig. 6, the reverse recovery failure occurs in the traditional structure at a low di/dt of-120A/mus, the structure of the invention still does not fail at a low di/dt of-250A/mus, the reverse recovery robustness of the structure of the invention can be improved by two times compared with the traditional structure, and the reliability of the device is greatly improved.
3. According to the invention, by reasonably adjusting the position of the second N-type heavily doped region 17 in the drift region 2, the extraction path of the cavity in the drift region 2 is effectively shortened during reverse recovery, and the trailing current of the reverse recovery is reduced, so that rapid recovery is realized. The second N-type heavily doped region 17 is located right below the N-type lightly doped cathode region 8, and during reverse recovery, due to the existence of the second N-type heavily doped region 17, holes almost flow between the second N-type heavily doped region 17 and the N-type lightly doped cathode region 8, as shown in fig. 4, the extraction path of the holes is effectively shortened, and the reverse recovery trailing current is reduced, as shown in fig. 7, the trailing current of the structure is obviously reduced, so that rapid recovery is realized. In addition, as almost no current flows in the N-type lightly doped cathode region 8, current spikes are avoided, and thus the peak electric field of the cathode side is effectively reduced, as shown in fig. 5, the peak electric field of the cathode side of the structure of the present invention is effectively suppressed compared with the B point of the conventional structure, which can effectively improve the reverse recovery robustness of the diode and improve the reliability of the device.
4. According to the invention, the concentration of the second N-type heavily doped region 17 in the drift region 2 is reasonably adjusted, so that the on-resistance of the drift region is effectively reduced during the forward conduction period, and the forward conduction capability of the device is improved. According to the structure, the second N-type heavily doped regions 17 are respectively added on two sides of the tail end of the first N-type heavily doped region 3, the concentration of the second N-type heavily doped regions 17 is far higher than that of the drift region 2, so that the overall concentration of the drift region 2 is increased, the on-resistance is greatly reduced during forward conduction, the forward conduction capability of a device can be effectively improved, and as shown in fig. 3, the structure has lower forward conduction voltage drop under the same current density.
Drawings
Fig. 1 is a view illustrating a structure of a conventional BSD.
Fig. 2 is a block diagram of the present invention.
Fig. 3 shows the forward conduction characteristic curves of the structure of the present invention and the conventional BSD structure.
Fig. 4 shows the extraction path of minority carriers in the drift region during reverse recovery for the inventive structure and the conventional BSD structure.
Fig. 5 shows the electric field distribution at 49 μm along the same section Y during reverse recovery for the inventive structure and the conventional BSD structure.
FIG. 6 shows the reverse recovery characteristics of the inventive structure and the conventional BSD structure at different di/dt.
FIG. 7 shows the reverse recovery characteristics of the inventive structure and the conventional BSD structure at the same di/dt.
Detailed Description
The invention is described in detail below with reference to the accompanying drawings:
a fast recovery bootstrap diode for improving reverse recovery robustness comprises a P-type substrate 1, an N-type drift region 2 is arranged on the P-type substrate 1, a silicon dioxide oxidation layer 7 is arranged on the surface of the N-type drift region 2, a first N-type heavily doped region 3 is arranged between the P-type substrate 1 and the N-type drift region 2, a P-type lightly doped anode region 10 serving as an anode region, an N-type lightly doped cathode region 8 and an N-type heavily doped cathode region 9 which are positioned on the outer side of the anode region and serve as a cathode region are arranged on the surface of the N-type drift region 2, the N-type heavily doped cathode region 9 is arranged in the N-type lightly doped cathode region 8, a P-type heavily doped anode region 11 is arranged on the surface of the P-type lightly doped anode region 10, an oxidation layer 6 is arranged on the surface of the N-type drift region 2 and on the outer side of the N-type heavily doped cathode region 9 and in the region between the N-type heavily doped cathode, the P-type heavily doped anode region 11, the N-type heavily doped cathode region 9 and the P-type substrate 1 are respectively connected with anode metal (anode), cathode metal (cathode) and substrate metal (sub), and the P-type heavily doped anode region is characterized in that a first P-type heavily doped region 14, an N-type heavily doped region 15 and a second P-type heavily doped region 16 which are electrically connected with each other are arranged on the surface of the P-type lightly doped anode region 10 and positioned on the outer side of the P-type heavily doped anode region 11.
The first heavily doped P-type region 14, the heavily doped N-type region 15, and the heavily doped second P-type region 16 of the present embodiment are electrically connected to each other through a floating metal electrode 13 disposed in the silicon dioxide oxide layer 7.
In this embodiment, a P-type dynamic field limiting ring 12 is disposed on the surface of the P-type lightly doped anode region 10 and between the first P-type heavily doped region 14 and the P-type heavily doped anode region 11.
In the embodiment, a second N-type heavily doped region 17 is arranged in the N-type drift region 2 and below the N-type heavily doped cathode region 9, and the second N-type heavily doped region 17 falls on the first N-type heavily doped region 3.
In the embodiment, a first P-type heavily doped substrate region 4 is arranged in a P-type substrate 1, the first P-type heavily doped substrate region 4 extends into an N-type drift region 2, a second P-type heavily doped substrate region 5 is connected to the first P-type heavily doped substrate region 4, and the second P-type heavily doped substrate region 5 extends and is connected to a substrate metal (sub), so that the connection between the P-type substrate 1 and the substrate metal (sub) is realized.
The doping concentration ranges of the P-type dynamic field limiting ring 12, the first P-type heavily doped region 14 and the second P-type heavily doped region 16 are 1.8e 14-2.3 e14cm-2。
The concentration range of the N-type heavily doped region 15 is 0.8e 15-1.1 e15cm-2。
The length range of the second N-type heavily doped region 17 is 9-9.5 mu m, and the doping concentration range is 2.2e 15-3.3 e15cm-2。
The invention is further described below with reference to the accompanying drawings.
The working principle of the invention is as follows:
when the conventional BSD device changes from the forward conducting state to the reverse blocking state, a reverse recovery process is performed, which can be divided into four stages, as shown in fig. 5. At the stage t 0-t 1, the device is still in the stage of continuous current, at this time, a PN junction formed by the P-type lightly doped anode region 10 and the N-type region formed by the drift region 2, the N-type lightly doped cathode region 8 and the N-type heavily doped cathode region 9 is in forward bias, and the forward current flowing through the BSD begins to be reduced to 0 by a fixed di/dt value; at the stage t 1-t 2, under the action of reverse voltage, charges stored in the diode before start to be swept out, because a depletion layer at the PN junction is not formed yet, the swept-out excessive charges continue to maintain reverse current, the current starts to increase in a reverse direction at a di/dt rate, and at the moment, the diode does not bear the reverse voltage yet; at the stage t 2-t 3, the plasma concentration at the PN junction is already attenuated to 0, a depletion layer is formed, and the diode starts to bear reverse voltage. As the reverse voltage increases sharply, the rate of reverse increase di/dt of the reverse recovery current begins to gradually decrease to 0 and the reverse recovery current reaches the reverse maximum value, Irrm. In the stage from t3 to t4, carriers diffusing to the depletion layer start to continue to maintain reverse current, because plasma is always dissipated, and the excessive charge concentration gradient at the edge of the space charge region is gradually reduced, the reverse current is gradually reduced to 0 from t3 at the rate of negative di/dt, during the process, high voltage and large current simultaneously occur in the device, the current is easy to appear sharply at the anode and the cathode, and the electric field at the surface of the anode and the cathode is increased, as shown in fig. 5, the conventional structure has peak electric fields of a and B at the anode and the cathode, so that double-sided dynamic avalanche failure is caused, as shown in fig. 6, the reverse recovery failure phenomenon occurs at di/dt-120A/μ s in the conventional structure. When the device is in the forward conducting state, because a large number of holes are stored in the drift region 2, these excess carriers must first be swept out when the device is turned off, increasing the reverse recovery time of the device.
The structure of the invention is that a P-type dynamic field limiting ring 12, a first P-type heavily doped region 14, an N-type heavily doped region 15 and a second P-type heavily doped region 16 which are mutually connected through a floating metal electrode 13 are respectively added on two sides of the tail end of a P-type lightly doped anode region 10. In addition, the structure of the invention is additionally provided with a second N type heavily doped region 17 at two sides of the tail end of the first N type heavily doped region 3 respectively. When the structure is in forward conduction, the substrate and the cathode end of the device are both connected with a low potential, and the anode end is connected with a high potential. According to the structure, the second N-type heavily doped regions 17 are respectively added on two sides of the tail end of the first N-type heavily doped region 3, the concentration of the second N-type heavily doped regions 17 is far higher than that of the drift region 2, so that the overall concentration of the drift region 2 is increased, the on-resistance is greatly reduced during forward conduction, the forward conduction capability of a device can be effectively improved, and as shown in fig. 3, the structure has lower forward conduction voltage drop under the same current density. When the structure of the invention is in reverse blocking, the cathode end of the device is connected with high potential, the anode end and the substrate are both connected with low potential, and at the moment, the diode firstly undergoes a reverse recovery process. At this time, minority carriers stored in the drift region during the forward conduction period respectively flow out through the anode and the substrate, and due to the existence of the second N-type heavily doped region 17, holes almost flow from between the second N-type heavily doped region 17 and the N-type lightly doped cathode region 8 to the anode region, so that the extraction path of the holes is effectively shortened, and meanwhile, the current path flowing to the substrate region is also shortened, as shown in fig. 4, the reverse recovery tail current is reduced, as shown in fig. 7. In addition, as almost no current flows in the N-type lightly doped cathode region 8, current spikes are avoided, and thus the peak electric field of the cathode side is effectively reduced, as shown in fig. 5, the peak electric field of the cathode side of the structure of the present invention is effectively suppressed at the point B in comparison with the conventional structure, the reverse recovery robustness of the diode is effectively improved, and the reliability of the device is improved. When the cathode is connected with a high potential, and the anode and the substrate are connected with a low potential, the P-type lightly doped anode region 10, the P-type heavily doped anode region 11, the P-type dynamic field limiting ring 12, and the first P-type heavily doped region 14, the N-type heavily doped region 15 and the second P-type heavily doped region 16 which are connected with each other through the floating metal electrode 13 are all at a low potential, holes stored in the drift region 2 can flow out of the body through the P-type lightly doped anode region 10, because of the existence of the N-type heavily doped region 15 in the P-type lightly doped anode region 10, part of the holes stored in the drift region 2 can be compounded with electrons at the position, as shown in fig. 4, part of the holes flow into the N-type heavily doped region 15, the extraction speed of surplus carriers at the anode side is increased, and the reverse recovery time is greatly reduced, as shown in fig. 7, under the same di/dt value, the structure of. When the P-type dynamic field limiting ring 12 is added, the boundary of the depletion layer is widened by reasonably adjusting the concentration of the P-type dynamic field limiting ring 12, electric field lines cannot be gathered at the P-type heavily doped anode region 11 at the outermost side, and meanwhile, because part of the current path flows through the N-type heavily doped region 15, the gathering of current at the anode heavily doped region 11 can also be avoided, so that the peak electric field at the anode side is effectively alleviated, and as shown in fig. 5, the peak electric field a is alleviated into three lower peak electric fields a1, a2 and A3. The reduction of the peak electric field at the anode side can effectively improve the reverse recovery robustness of the diode, as shown in fig. 6, the reverse recovery failure occurs in the traditional structure at a low di/dt value, the reverse recovery robustness of the structure of the invention can be improved by more than two times compared with the traditional structure, and the reliability of the device is greatly improved.
Therefore, the structure can improve the forward conduction capability of the device in the forward conduction period, can effectively reduce peak electric fields of the anode side and the cathode side in the reverse recovery period, avoids reverse recovery failure, improves the reverse recovery robustness, and can effectively reduce trailing current and reverse recovery time so as to realize quick recovery.
