IGBT (Insulated Gate Bipolar Translator) cell with novel hole extraction structure

Abstract

The invention discloses an IGBT (Insulated Gate Bipolar Translator) cell with a novel hole extraction structure. Low-doped N-type buried layers and low-doped P-type buried layers which are alternately distributed are introduced to the two sides of a groove, and the concentration of the N-type buried layers and two adjacent P-type areas just form an accumulation type PMOS with the threshold voltage close to 0. When the device is turned off, the PMOS in the vertical direction is opened to form a vertical hole path, and all the P-type buried layers and the Pbody are connected. According to the channel, a relatively high potential barrier of a conventional IGBT hole extraction channel is converted into a plurality of relatively low potential barriers, so that the smoothness of the hole extraction channel in energy change is improved, and the extraction speed is increased. A plurality of P-type buried layers and inversion channels in the vertical direction form a comb-shaped hole extraction structure, the area of the structure is far larger than that of a traditional IGBT cellular structure, and the hole extraction rate is improved. Compared with a traditional IGBT cell, the IGBT cell is higher in turn-off speed and lower in turn-off loss.

Description

Technical Field

[0001] The invention relates to the technical field of power semiconductor devices, in particular to an IGBT cell with a novel hole extraction structure. Background Art

[0002] IGBT (Insulated Gate Bipolar Transistor) is a device that combines MOS voltage control and bipolar conduction modulation. It has the advantages of high input impedance, low control power, and simple drive circuit of MOSFET, and has the advantages of high current density, low saturation voltage drop, and strong current handling capability of bipolar power transistor. It is an ideal power device for applications requiring high voltage, high current, and high speed. It is currently widely used in transportation, power grid, consumer electronics and other fields.

[0003] As a bipolar device, IGBT has an obvious defect compared to unipolar devices such as MOSFET. In the on state, a large number of holes are injected into the drift region, resulting in the accumulation of a large number of unbalanced minority carriers in the drift region; at the moment of device shutdown, these unbalanced minority carriers do not have time to be extracted from the emitter, and can only disappear through slow recombination of electrons in the drift region, resulting in an obvious tail current in the shutdown process, increasing the shutdown time and shutdown loss. Therefore, the defect of IGBT in hole extraction ability is a key problem that must be solved in IGBT design. Summary of the invention

[0004] The present invention provides an IGBT cell with a novel hole extraction structure, the purpose of which is to solve the defects of the traditional IGBT cell structure, that is, the low hole extraction rate and long shutdown time when the hole extraction rate is turned off. There are two main reasons for the low hole extraction rate when the traditional IGBT cell structure is turned off. One is that the cross-sectional area of ​​the hole extraction path is small, and the other is that the potential barrier on the hole extraction path is high. The present invention will solve the defects of the traditional IGBT cell structure from these two aspects.

[0005] In the first aspect, an IGBT cell with a novel hole extraction structure is provided, comprising an emitter metal electrode and a collector metal electrode; a low-doped N-type drift region, a medium-doped P-type Pbody region, an oxide isolation layer and a P-type heavily doped collector electrode are arranged between the emitter metal electrode and the collector metal electrode; the oxide isolation layer is located between the medium-doped P-type Pbody region and the emitter metal electrode, and the P-type heavily doped collector electrode is located between the low-doped N-type drift region and the collector metal electrode;

[0006] On one side of the middle-doped P-type Pbody region close to the emitter metal electrode, an ohmic contact layer is formed by ion implantation in the middle-doped P-type Pbody region, the ohmic contact layer is in contact with both the oxide isolation layer and the emitter metal electrode; the ohmic contact layer includes a heavily doped N-type emitter and a heavily doped P-type Pbody ohmic contact region; in the ohmic contact layer, the heavily doped P-type Pbody ohmic contact region is located at the periphery of the heavily doped N-type emitter;

[0007] At least one group of buried layers is formed by ion implantation in the low-doped N-type drift region on a side away from the collector metal electrode, each group of buried layers includes a lightly doped N-type buried layer and a lightly doped P-type buried layer; when there are multiple groups of buried layers, the lightly doped N-type buried layers and the lightly doped P-type buried layers are alternately arranged; the buried layer farthest from the collector metal electrode in the low-doped N-type drift region is the lightly doped N-type buried layer;

[0008] The IGBT cell also includes a gate oxide layer and a polysilicon gate; a groove is etched in the low-doped N-type drift region and the medium-doped P-type Pbody region so that the groove passes through the heavily doped N-type emitter, the medium-doped P-type Pbody region, and all buried layers in the low-doped N-type drift region; the gate oxide layer is arranged on the inner wall of the groove and wrapped around the periphery of the polysilicon gate.

[0009] In combination with the first aspect, in certain implementations of the first aspect, when the number of buried layer groups is multiple, the doping concentration of the lightly doped P-type buried layer gradually decreases with the depth of the buried layer, and the doping concentration of the lightly doped P-type buried layer decreases linearly with the depth of the buried layer after taking the logarithm to the base 10.

[0010] In combination with the first aspect, in certain implementations of the first aspect, when the number of buried layer groups is multiple, the doping concentration of the lightly doped N-type buried layer does not change with the depth of the buried layer, and the doping concentration value of the lightly doped N-type buried layer is one to two orders of magnitude lower than the doping concentration of the low-doped N-type drift region.

[0011] In combination with the first aspect, in some implementations of the first aspect, the doping concentration of the low-doped N-type drift region is 10 13 cm -3 Up to 10 14 cm -3 between.

[0012] In combination with the first aspect, in some implementations of the first aspect, the doping concentration of the P-type Pbody region is 10 17 cm -3 Up to 10 18 cm -3 between.

[0013] In combination with the first aspect, in some implementations of the first aspect, the doping concentration of the heavily doped N-type emitter is 1020 cm -3 above.

[0014] In combination with the first aspect, in certain implementations of the first aspect, the doping concentration of the heavily doped P-type Pbody ohmic contact region is 10 20 cm -3 above.

[0015] In combination with the first aspect, in some implementations of the first aspect, the doping concentration of the lightly doped N-type buried layer is 10 13 cm -3 the following.

[0016] In combination with the first aspect, in some implementations of the first aspect, the doping concentration of the lightly doped P-type buried layer is 10 14 cm -3 Up to 10 17 cm -3 between.

[0017] In combination with the first aspect, in some implementations of the first aspect, the doping concentration of the P-type heavily doped collector is 10 19 cm -3 above.

[0018] In a second aspect, a method for manufacturing an IGBT cell as described in any one of the implementations of the first aspect is provided, comprising:

[0019] A low-doped N-type Si-based substrate is used as a low-doped N-type drift region, and ions are first implanted on the front side of the low-doped N-type drift region to form a medium-doped P-type Pbody region; then, ions are implanted within the corresponding depth range of the medium-doped P-type Pbody region to form a heavily doped N-type emitter and a heavily doped P-type Pbody ohmic contact region; then, a higher ion implantation energy is used to penetrate the medium-doped P-type Pbody region, and at least one group of buried layers (including a lightly doped N-type buried layer and a lightly doped P-type buried layer) are implanted below the medium-doped P-type Pbody region and in the low-doped N-type drift region, and the implantation order of the buried layers is from shallow to deep; then, a groove is etched to form a gate oxide layer and a polysilicon gate in the groove; then, an oxide insulating layer is formed on the upper surface of the cell, and ions are implanted on the back side to form a heavily doped collector, and metals are deposited on the upper and lower surfaces of the cell to form an emitter metal electrode and a collector metal electrode.

[0020] Compared with the prior art, the solution provided by the present invention includes at least the following beneficial technical effects:

[0021] The technical solution of the present invention is to deepen the groove depth of the IGBT, introduce a low-doped N-type buried layer and a low-doped P-type buried layer that are alternately distributed in the vertical direction on both sides of the groove, and the doping concentration of the N-type buried layer is just enough to form an accumulation-type PMOS with a threshold voltage close to 0 with the two adjacent P-type regions. When the device is turned off, the PMOS in the vertical direction is turned on to form a vertical hole path, which connects all the P-type buried layers and Pbody. Since the doping concentration of the P-type buried layer gradually decreases with the depth of the buried layer, the path converts a higher potential barrier of the traditional IGBT hole extraction path into several lower potential barriers, improves the smoothness of the hole extraction path in energy change, and improves the extraction speed. In addition, multiple P-type buried layers and inversion channels in the vertical direction form a comb-shaped hole extraction structure, the area of ​​which is much larger than that of the traditional IGBT cell structure, thereby improving the hole extraction rate. Compared with the traditional IGBT cell, the present invention has a faster turn-off speed and lower turn-off loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of an IGBT cell with a new hole extraction structure.

[0023] Figure 2 This is an embodiment of increasing the number of buried layers to n layers.

[0024] Figure 3 This is a schematic diagram of the doping distribution of a p-type buried layer with multiple groups of buried layers. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Figure 1 An IGBT cell with a novel hole extraction structure provided by the present invention is shown. The IGBT cell includes an emitter metal electrode 11 and a collector metal electrode 12. A low-doped N-type drift region 1, a medium-doped P-type Pbody region 2, an oxide isolation layer 9 and a P-type heavily doped collector 10 are arranged between the emitter metal electrode 11 and the collector metal electrode 12. The oxide isolation layer 9 is located between the medium-doped P-type Pbody region 2 and the emitter metal electrode 11, and the P-type heavily doped collector 10 is located between the low-doped N-type drift region 1 and the collector metal electrode 12.

[0027] On one side of the mid-doped P-type Pbody region 2 close to the emitter metal electrode 11, an ohmic contact layer is formed by ion implantation in the mid-doped P-type Pbody region 2, and the ohmic contact layer is in contact with both the oxide isolation layer 9 and the emitter metal electrode 11. The ohmic contact layer includes a heavily doped N-type emitter 3 and a heavily doped P-type Pbody ohmic contact region 4. In the ohmic contact layer, the heavily doped P-type Pbody ohmic contact region 4 is located at the periphery of the heavily doped N-type emitter 3.

[0028] At least one group of buried layers is formed by ion implantation in the low-doped N-type drift region 1 on the side away from the collector metal electrode 12, each group of buried layers includes a lightly doped N-type buried layer 5 and a lightly doped P-type buried layer 6. Figure 2 As shown, when the number of buried layer groups is n (n>1), lightly doped N-type buried layers 5 and lightly doped P-type buried layers 6 are arranged alternately. The buried layer farthest from the collector metal electrode 12 in the low-doped N-type drift region 1 is the lightly doped N-type buried layer 5.

[0029] The IGBT cell also includes a gate oxide layer 7 and a polysilicon gate 8. A trench is etched in the low-doped N-type drift region 1 and the medium-doped P-type Pbody region 2 so that the trench passes through the heavily doped N-type emitter 3, the medium-doped P-type Pbody region 2, and all buried layers in the low-doped N-type drift region 1. The gate oxide layer 7 is arranged on the inner wall of the trench and wrapped around the periphery of the polysilicon gate 8.

[0030] In some embodiments, Figure 3 As shown, the doping concentration of the lightly doped P-type buried layer 6 decreases gradually with the buried layer depth (the closer to the emitter metal electrode 11, the shallower the buried layer depth). After taking the logarithm of the buried layer doping concentration with base 10, its curve decreases approximately linearly.

[0031] In some embodiments, Figure 3 As shown, the doping concentration of the lightly doped N-type buried layer 5 does not vary with the depth of the buried layer, and its value is one to two orders of magnitude lower than the doping concentration of the low-doped N-type drift region 1 .

[0032] In some embodiments, the doping concentration of the low-doped N-type drift region 1 is between 10 13 cm -3 Up to 10 14 cm -3 between.

[0033] In some embodiments, the doping concentration of the P-type Pbody region 2 is 10 17 cm -3 Up to 10 18 cm -3 between.

[0034] In some embodiments, the doping concentration of the heavily doped N-type emitter 3 is 10 20 cm -3 above.

[0035] In some embodiments, the doping concentration of the heavily doped P-type Pbody ohmic contact region 4 is about 10 20 cm -3 above.

[0036] In some embodiments, the doping concentration of the lightly doped N-type buried layer 5 is about 10 13 cm -3 the following.

[0037] In some embodiments, the doping concentration of the lightly doped P-type buried layer 6 is about 10 14 cm -3 Up to 10 17 cm -3 between.

[0038] In some embodiments, the doping concentration of the P-type heavily doped collector 10 is about 10 19 cm -3 above.

[0039] The present invention also provides a method for manufacturing an IGBT cell with a novel hole extraction structure.

[0040] A low-doped N-type Si-based substrate is used as a low-doped N-type drift region 1, and ions are first implanted on the front side of the low-doped N-type drift region 1 to form a medium-doped P-type Pbody region 2; then, ions are implanted in the corresponding depth range of the medium-doped P-type Pbody region 2 to form a heavily doped N-type emitter 3 and a heavily doped P-type Pbody ohmic contact region 4; then, a higher ion implantation energy is used to penetrate the medium-doped P-type Pbody region 2, and at least one group of buried layers (including a lightly doped N-type buried layer 5 and a lightly doped P-type buried layer 6) are implanted below the medium-doped P-type Pbody region 2 and in the low-doped N-type drift region 1, and the implantation order of the buried layers is from shallow to deep; then, a trench is etched to form a gate oxide layer 7 and a polysilicon gate 8 in the trench; then, an oxide insulating layer 9 is formed on the upper surface of the cell, and ions are implanted on the back side to form a heavily doped collector 10, and metals are deposited on the upper and lower surfaces of the cell to form an emitter metal electrode 11 and a collector metal electrode 12.

[0041] The present invention improves the energy smoothness of the hole extraction path by optimizing the barrier distribution of the hole extraction path; at the same time, a comb-like structure with a larger extraction area is formed in the vertical direction, and the hole extraction rate is improved under the simultaneous action of the two aspects.

[0042] Although the present invention is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. An IGBT cell with a novel hole extraction structure, characterized in that: The invention comprises an emitter metal electrode (11) and a collector metal electrode (12); a low-doped N-type drift region (1), a medium-doped P-type Pbody region (2), an oxide isolation layer (9) and a P-type heavily doped collector electrode (10) are arranged between the emitter metal electrode (11) and the collector metal electrode (12); the oxide isolation layer (9) is located between the medium-doped P-type Pbody region (2) and the emitter metal electrode (11), and the P-type heavily doped collector electrode (10) is located between the low-doped N-type drift region (1) and the collector metal electrode (12); An ohmic contact layer is formed by ion implantation in the middle-doped P-type Pbody region (2) on a side close to the emitter metal electrode (11), wherein the ohmic contact layer is in contact with both the oxide isolation layer (9) and the emitter metal electrode (11); the ohmic contact layer comprises a heavily doped N-type emitter (3) and a heavily doped P-type Pbody ohmic contact region (4); in the ohmic contact layer, the heavily doped P-type Pbody ohmic contact region (4) is located at the periphery of the heavily doped N-type emitter (3); At least one group of buried layers is formed by ion implantation in the low-doped N-type drift region (1) on a side of the low-doped N-type drift region (1) away from the collector metal electrode (12), each group of buried layers comprising a lightly doped N-type buried layer (5) and a lightly doped P-type buried layer (6); when there are multiple groups of buried layers, the lightly doped N-type buried layers (5) and the lightly doped P-type buried layers (6) are alternately arranged; the buried layer farthest from the collector metal electrode (12) in the low-doped N-type drift region (1) is the lightly doped N-type buried layer (5); The IGBT cell also includes a gate oxide layer (7) and a polysilicon gate (8); a groove is etched in the low-doped N-type drift region (1) and the medium-doped P-type Pbody region (2) so that the groove passes through the heavily-doped N-type emitter (3), the medium-doped P-type Pbody region (2), and all buried layers in the low-doped N-type drift region (1); the gate oxide layer (7) is arranged on the inner wall of the groove and wrapped around the outer periphery of the polysilicon gate (8).

2. The IGBT cell according to claim 1, characterized in that: When there are multiple buried layer groups, the doping concentration of the lightly doped P-type buried layer (6) gradually decreases with the buried layer depth, and the doping concentration of the lightly doped P-type buried layer (6) is linearly decreased with the buried layer depth after taking the logarithm with base 10.

3. The IGBT cell according to claim 1 or 2, characterized in that: When there are multiple buried layer groups, the doping concentration of the lightly doped N-type buried layer (5) does not change with the buried layer depth, and the doping concentration of the lightly doped N-type buried layer (5) is one to two orders of magnitude lower than the doping concentration of the low-doped N-type drift region (1).

4. The IGBT cell according to claim 1, characterized in that: The doping concentration of the low-doped N-type drift region (1) is 10 13 cm -3 Up to 10 14 cm -3 between.

5. The IGBT cell according to claim 1, characterized in that: The doping concentration of the P-type Pbody region (2) is 10 17 cm -3 Up to 10 18 cm -3 between.

6. The IGBT cell according to claim 1, characterized in that: The doping concentration of the heavily doped N-type emitter (3) is 10 20 cm -3 above.

7. The IGBT cell according to claim 1, characterized in that: The doping concentration of the heavily doped P-type Pbody ohmic contact region (4) is 10 20 cm -3 above.

8. The IGBT cell according to claim 1, characterized in that: The doping concentration of the lightly doped N-type buried layer (5) is 10 13 cm -3 the following.

9. The IGBT cell according to claim 1, characterized in that: The doping concentration of the lightly doped P-type buried layer (6) is 10 14 cm -3 Up to 10 17 cm -3 between.

10. The IGBT cell according to claim 1, characterized in that: The doping concentration of the P-type heavily doped collector (10) is 10 19 cm -3 above.

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