Semi-super-junction IGBT with anode provided with deep slowly-varying doped field stop layer and preparation method of semi-super-junction IGBT

Abstract

The invention relates to a power semiconductor technology, in particular to a semi-super-junction IGBT with an anode provided with a deep slowly-changing doped field stop layer and a preparation method thereof, and the IGBT comprises a front cathode grid-control MOS structure, a middle region semi-super-junction drift region structure and a back anode slowly-changing doped field stop layer; the back anode slowly-doped field cut-off layer sequentially comprises a second-type conductive layer, a first-type conductive layer and a back conductive layer from top to bottom, the doping type of the second-type conductive layer is different from that of the first-type conductive layer, and the doping concentration of the second-type conductive layer is slowly reduced from the surface of the anode to the interior of the anode. The doping depth is between 10 microns and 30 microns, and the doping concentration peak value is at the order of magnitude of 1e < 15 > cm <-3 >. According to the invention, the slowly doped field stop layer is introduced to the anode on the basis of the traditional carrier storage semi-super junction IGBT, so that the turn-off voltage overshoot of the semi-super junction IGBT is slowed down.

Description

Technical Field

[0001] The present invention relates to power semiconductor technology, and in particular to a semi-superjunction insulated gate bipolar transistor (IGBT) with an anode having a deep graded doped field stop layer and a preparation method thereof. Background Art

[0002] Semi-super-junction (SemiSJ) technology combines super-junction pillars and single impurity drift regions to form a semi-super-junction structure that meets the breakdown voltage requirements of high-voltage devices. It uses thinner super-junction pillars to achieve some characteristics of super-junction IGBTs, reduces the difficulty of process implementation of high-voltage super-junction devices, and achieves a certain compromise between process implementation difficulty and device performance. However, compared with typical single impurity drift region IGBTs, the high turn-off overshoot brought by the super-junction structure is one of the factors that affect its application reliability. Reducing the turn-off overshoot can improve the reliability of device applications. Summary of the invention

[0003] In order to reduce the turn-off voltage overshoot of the IGBT and better ensure the reliable application of the semi-super junction IGBT, the present invention proposes a semi-super junction IGBT with an anode having a deep graded doped field stop layer, including a front cathode gate-controlled MOS structure, a middle region semi-super junction drift region structure and a back anode graded doped field stop layer; the back anode graded doped field stop layer includes, from top to bottom, a second type conductive layer 12, a first type conductive layer 13, and a back conductive layer 14, wherein the second type conductive layer 12 and the first type conductive layer 13 have different doping types, and the doping concentration of the second type conductive layer 12 decreases slowly from the anode surface to the body, and the doping depth is between 10μm and 30μm, and the doping concentration peak is at e15cm -3 Magnitude.

[0004] Furthermore, the second type conductive layer 12 can achieve a gradual doping concentration distribution by single injection, and the formed doping concentration gradually decreases from the anode to the body.

[0005] Furthermore, the second type conductive layer 12 may be implanted multiple times to form a multi-peak gradually varying doping concentration distribution, wherein the energy of the implanted ions is different each time, and the concentrations may be the same or different.

[0006] Furthermore, the second type conductive layer 12 and the first type conductive layer 13 have different doping types.

[0007] Furthermore, the front cathode gate-controlled MOS structure includes a conductive layer 11, an insulating layer 6, and a first type doped conductive region 5. The first type doped conductive region 5 is divided into three parts, namely left, middle and right, by two second type heavily doped semiconductor layers 7 wrapped by the insulating layer 6. A first type impurity conductive region 9 and a second type impurity conductive region 10 are sequentially formed on the upper surface of the middle part by ion implantation; the first type doped conductive region 5 and the conductive layer 11 are isolated by the insulating layer 6.

[0008] Furthermore, the two second type heavily doped semiconductor layers 7 may be made of the same material or different materials, and the two second type heavily doped semiconductor layers 7 may have different potentials.

[0009] Furthermore, the structure of the semi-superjunction drift region in the middle region includes a second type doped conductive region 4, a superjunction drift region, and a single impurity drift region 1, and the superjunction drift region is composed of alternatingly arranged first type conductive regions 3 and second type conductive regions 2.

[0010] Furthermore, the lower portions of the two second type heavily doped semiconductor layers 7 wrapped by the insulating layer extend into the second type doped conductive region 4 , or extend into the second type conductive region 2 of the super junction drift region.

[0011] The present invention also provides a method for preparing a semi-superjunction IGBT having an anode with a deep graded doped field stop layer, which is used to prepare a semi-superjunction IGBT having an anode with a deep graded doped field stop layer, such as Figure 4 , specifically including the following preparation process:

[0012] First, a semi-superjunction drift region structure is formed in the middle region: a single impurity drift region 1 is formed by an epitaxial process, such as Figure 4 (1); then use multi-layer epitaxy or deep trench etching to form the second type conductive region 2 and the first type conductive region 3 corresponding to the super junction column region, such as Figure 4 (2); As an optional embodiment, in the process of preparing the intermediate drift region, you can choose Figure 5 (a), deep trench etching + poly backfill solution, you can also choose Figure 5 (b),Multilayer epitaxy scheme;

[0013] Then, a front cathode gate-controlled MOS structure is formed: a doped conductive region 4 and a first type doped conductive region 5 are formed by epitaxy, such as Figure 4 (3); then the impurity type of the first type doped conductive region 5 is changed by ion implantation, such as Figure 4 (4); and then forming a longitudinal deep groove portion in the insulating layer 6 by etching, such as Figure 4 (5); and then forming an insulating layer 6 by thermal growth, such as Figure 4(6); forming two second type heavily doped semiconductor layers 7 by deposition, such as Figure 4 (7); then the lateral region of the insulating layer 6 is supplemented by deposition, and then the first type impurity conductive region 9 and the second type impurity conductive region 10 are sequentially formed by ion implantation, such as Figure 4 (8); and then forming a conductive layer 11 by deposition, such as Figure 4 Middle (9);

[0014] Finally, a back anode graded doped field stop layer is formed: a back second type conductive layer 12 and a first type conductive layer 13 are formed by thinning, ion implantation, and thermal annealing. Figure 4 (10) to (11); and then forming a back conductive layer 14 by deposition, wherein the second type conductive layer 12 as a graded field stop layer can be realized by single or multiple heavy ion implantation, and the corresponding impurity diffusion depth is higher than that of the conventional non-graded field stop layer, such as Figure 4 The superjunction pillar realization process of the present invention can be multi-layer epitaxy or deep trench etching.

[0015] Furthermore, the back conductive layer 14 can be uniformly doped or non-uniformly doped, and can be realized by epitaxy or ion implantation heating annealing process.

[0016] The present invention reduces the turn-off voltage overshoot of the semi-super junction IGBT by introducing a gradually doped field stop layer at the anode on the basis of a conventional carrier storage semi-super junction IGBT; the gradually doped field stop layer at the anode of the present invention has a deeper doping depth and a lower peak doping concentration, and can be single-peak or multi-peak doping, and can be implemented by a single (single-peak) or multiple (multi-peak) high-energy particle injection process. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention provides a carrier storage type semi-super junction IGBT with an anode having a deep graded doped field stop layer;

[0018] Figure 2 This is a schematic diagram of the anode deep graded doping field stop layer of the present invention;

[0019] Figure 3 This is an application effect diagram of the anode deep graded doping field stop layer of the present invention;

[0020] Figure 4 Schematic diagram of the super junction process flow that can be adopted in the present invention;

[0021] Figure 5 is an embodiment to which the present invention relates;

[0022] Among them, 1. single impurity drift region; 2. second type conductive region; 3. first type conductive region; 4. second type doped conductive region; 5. first type doped conductive region; 6. insulating layer; 7. second type heavily doped semiconductor layer; 9. first type impurity conductive region; 10. second type impurity conductive region; 11. conductive layer; 12. second type conductive layer; 13. first type conductive layer; 14. back conductive layer. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] The present invention proposes a semi-superjunction IGBT with an anode having a deep graded doped field stop layer, comprising a front cathode gate-controlled MOS structure, a middle region semi-superjunction drift region structure and a back anode graded doped field stop layer; the back anode graded doped field stop layer comprises, from top to bottom, a second type conductive layer 12, a first type conductive layer 13, and a back conductive layer 14, wherein the second type conductive layer 12 and the first type conductive layer 13 have different doping types, the doping concentration of the second type conductive layer 12 decreases slowly from the anode surface to the body, and the doping depth is between 10 μm and 30 μm, and the doping concentration peak is at e15 cm -3 In the prior art, the doping depth of the field stop layer is generally less than 5 μm, and the doping concentration peak is e16 cm -3 The doping depth of the present invention is significantly higher than that of the conventional field stop layer, and the peak doping concentration of the present invention is significantly lower than that of the conventional field stop layer.

[0025] This embodiment provides Figure 1 A semi-super junction IGBT with an anode having a deep graded doped field stop layer is shown, comprising a front cathode gate-controlled MOS structure, a middle region semi-super junction drift region structure and a back anode graded doped field stop layer, wherein:

[0026] The front cathode gate-controlled MOS structure includes: a conductive layer 11, an insulating layer 6 connected to the conductive layer 11, two second-type heavily doped semiconductor layers 7 connected to the insulating layer 6 and wrapped by the insulating layer 6, a first-type doped conductive region 5 connected to the insulating layer 6, a first-type doped conductive region 5 connected to the conductive layer 11, the insulating layer 6, and the second-type doped conductive region 4, a first-type impurity conductive region 9 connected to the conductive layer 11, the insulating layer 6, and the first-type doped conductive region 5, and a second-type impurity conductive region 10; the first-type doped conductive region 5, the insulating layer 6, the second-type heavily doped semiconductor layer 7, the first-type impurity conductive region 9, the second-type impurity conductive region 10, and the conductive layer 11 together constitute a front MOS structure;

[0027] The structure of the semi-superjunction drift region in the middle region includes: a second type doped conductive region 4 connected to the first type doped conductive region 5, the upper surfaces of the alternately arranged first type conductive regions 3 and the second type conductive regions 2 connected to the lower surfaces of the second type doped conductive regions 4, and the lower surfaces of the alternately arranged first type conductive regions 3 and the second type conductive regions 2 connected to the upper surface of the first impurity conductive layer; wherein the second type doped conductive region 4 and the fifth conductive layer have different doping types, the first type conductive region 3 and the second type conductive region 2 have different doping types, and the second type doped conductive region 4 has a doping type of the first type. The first type conductive region 3 or the second type conductive region 2 is one of the doped conductive region 3 or the second type conductive region 2, and the second type doped conductive region 4 can be uniformly or non-uniformly doped; the second type doped conductive region 4 forms a carrier storage layer; the doping types of the first type conductive region 3 and the second type conductive region 2 are alternated in a periodic manner; the single impurity drift region 1 is a single impurity type drift region, which has the same doping type as the first type conductive region 3 or the second type conductive region 2; the above-mentioned single impurity drift region 1, the second type conductive region 2, the first type conductive region 3, and the second type doped conductive region 4 conductive layers together constitute a semi-superjunction withstand voltage drift region structure in the middle of the cell;

[0028] The back anode graded doped field stop layer structure includes a second type conductive layer 12 connected to the single impurity drift region 1, a first type conductive layer 13 connected to the second type conductive layer 12, and a fourteenth conductive layer 14 connected to the first type conductive layer 13; the second type conductive layer 12, the first type conductive layer 13, and the back conductive layer 14 together constitute a back deep graded doped field stop transparent collector structure, wherein the second type conductive layer 12 is a field stop layer with a graded doping concentration distribution, and compared with a traditional thin field stop layer, this graded field stop layer has a deeper doping depth and a lower doping concentration peak;

[0029] Among them, the periodic width corresponding to the cathode MOS structure composed of a single impurity drift region 1, a second type conductive region 2, a first type conductive region 3, a second type doped conductive region 4, a first type doped conductive region 5, and an insulating layer 6 is independent of the periodic width of the conductive region composed of a second heavily doped semiconductor layer 8 and a first type impurity conductive region 9, that is, the periodic widths of the two can be selected to be equal or unequal.

[0030] like Figure 2 (a) is a traditional thin field stop layer. The present invention provides two types of graded doping deep field stop layer structures, one of which is as follows Figure 2 (b) is a structure of a gradually doped deep field stop layer formed by a single injection, in which the doping concentration gradually decreases from the anode surface to the body, and the second is as shown in Figure 2 (c) shows a graded doped deep field stop layer structure formed by multiple implantations, in which the doping concentration changes from the anode surface to the body according to each implantation concentration.

[0031] In this embodiment, the first type conductive region 3, the first type doped conductive region 5, and the first type conductive layer 13 use the same doping type; the second type doped conductive region 4 structurally physically isolates the first type doped conductive region 5 from the alternatingly arranged first type conductive region 3 and second type conductive region 2, and the doping type of the second type doped conductive region 4 is different from the doping type of the first type doped conductive region 5.

[0032] In the present invention, the first type and the second type represent two different types of doping, which can be P-type doping, N-type doping or other mixed doping, and the first type and the second type of impurity types can be interchanged. Specifically, in the present invention, the first type conductive region 3, the first type doped conductive region 5, the first type impurity conductive region 9, and the first type conductive layer 13 adopt the first type of doping scheme; the second type conductive region 2, the second type doped conductive region 4, the second type heavily doped semiconductor layer 7, the second type impurity conductive region 10, and the second type conductive layer 12 adopt the second type of doping scheme.

[0033] Preferably, the periodic width corresponding to the cathode MOS structure composed of the first type doped conductive region 5, the insulating layer 6, the second type heavily doped semiconductor layer 7, the first type impurity conductive region 9, the second type impurity conductive region 10, and the conductive layer 11 is independent of the periodic width of the conductive layer composed of the second type conductive region 2 and the first type conductive region 3, and the parameters of the two can be selected to be equal or unequal.

[0034] Preferably, the two second type heavily doped semiconductor layers 7 in the present invention have different potentials but the same physical material.

[0035] Preferably, the bottom of the longitudinal groove structure of the insulating layer 6 extends to the second type doped conductive region 4 .

[0036] Unless otherwise specified, the conductive materials involved in each conductive structure of the present invention are semiconductors or metals, and the semiconductor material type can be single crystal silicon, polycrystalline silicon, silicon carbide or gallium nitride.

[0037] This embodiment provides a carrier storage type semi-super junction IGBT device with a deep graded doped field stop layer at the anode. In this embodiment, the conductive impurity of the device is single crystal silicon, the first type is P-type doping, and the second type is N-type doping. The entire cell includes a front cathode gate-controlled MOS structure, a middle area semi-super junction drift region structure, and a back anode field stop structure, wherein:

[0038] The front gate-controlled MOS structure includes: a metal conductive layer Metal, an insulating oxide layer Oxide connected to Metal, a heavily doped semiconductor layer Gate and Emitter connected to Oxide and wrapped by Oxide, a P-type doped conductive layer P-body connected to Oxide, an N-type heavily doped conductive layer N+ connected to Metal, Oxide, and P-body, a P-type heavily doped conductive layer P+ connected to the metal layer Metal, P-body, and N+, and Metal, Oxide, Gate, Emitter, P-body, N+, and P+ together constitute a front cathode gate-controlled MOS structure; Gate and Emitter in this embodiment indicate that the two have different potentials, but the two can have the same material; in addition, Gate, Emitter and the surrounding Oxide extend into the N-CS layer, and can also extend into the N-pillar;

[0039] The semi-superjunction drift region in the middle area includes: an N-type conductive layer N-CS connected to the P-body, forming a carrier storage layer; a P-type conductive layer P-pillar and an N-type conductive layer N-pillar connected to the N-CS and arranged alternately together form a superjunction drift region; an N-type conductive layer N-drift connected to the conductive layers P-pillar and N-pillar is a lightly doped region, forming a single impurity drift region; the above-mentioned N-CS, P-pillar, N-pillar, and N-drift conductive layers together constitute a semi-superjunction withstand voltage drift region in the middle of the cell; the superjunction drift region corresponding to the N-pillar and the P-pillar can be realized by a variety of processes, for example: multiple epitaxy combined with ion implantation, or deep trench etching combined with backfilling;

[0040] The back anode graded doped field stop layer includes: an N-type conductive layer N-buffer connected to N-drift, a P-type conductive layer P-collector connected to N-buffer, and a metal conductive layer Metal connected to P-collector; the above-mentioned N-buffer, P-collector, and Metal together constitute the field stop type transparent collector structure on the back; preferably, the back transparent anode is composed of an N-type field resistance layer and a P-type collector region, and both layers are formed by ion implantation.

[0041] The present invention introduces a slowly varying field stop layer with a deeper thickness and a lower peak doping concentration into the bottom single impurity doping layer of the semi-superjunction IGBT. This field stop layer distribution can make the electric field penetrate in advance, advance the start time of current drop, thereby extending the current drop time and slowing down the turn-off voltage overshoot. Figure 3 On the basis of ensuring the withstand voltage capability of the device, the turn-off voltage overshoot of the semi-super junction IGBT is significantly reduced compared with that of the device with a traditional thin non-gradually varying doped field stop layer.

[0042] In the description of the present invention, it is necessary to understand that the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inside", "outside", "front", "center", "both ends" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0043] In the present invention, unless otherwise clearly stipulated and limited, the terms such as "installation", "setting", "connection", "fixation" and "rotation" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, ordinary technicians in this field can understand the specific meanings of the above terms in the present invention according to the specific circumstances.

[0044] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A semi-superjunction IGBT having an anode with a deep graded doped field stop layer, comprising a front cathode gate-controlled MOS structure, a middle region semi-superjunction drift region structure and a back anode graded doped field stop layer; the back anode graded doped field stop layer comprises, from top to bottom, a second type conductive layer (12), a first type conductive layer (13), and a back conductive layer (14), wherein the second type conductive layer (12) and the first type conductive layer (13) have different doping types, and is characterized in that: The doping concentration of the second type conductive layer (12) decreases slowly from the surface of the anode to the body, and the doping depth is between 10 μm and 30 μm, and the doping concentration peak is at e15 cm -3 Magnitude.

2. A semi-superjunction IGBT having an anode with a deep graded doped field stop layer according to claim 1, characterized in that: The doping concentration distribution of the second type conductive layer (12) is gradually changed by single injection, and the formed doping concentration gradually decreases from the anode surface to the body.

3. A semi-superjunction IGBT having an anode with a deep graded doped field stop layer according to claim 1, characterized in that: The doping concentration distribution of the second type conductive layer (12) is gradually changed by multiple injections, each time the energy of the injected ions is different, each time the injected ions concentration is the same or different, and finally a deep gradually changing field stop layer with multiple doping concentration peaks is formed.

4. A semi-superjunction IGBT having an anode with a deep graded doped field stop layer according to claim 1, characterized in that: The second type conductive layer (12) and the first type conductive layer (13) have different doping types.

5. A semi-superjunction IGBT with an anode having a deep graded doped field stop layer according to claim 1, characterized in that: The front cathode gate-controlled MOS structure comprises a conductive layer (11), an insulating layer (6), and a first type doped conductive region (5); the first type doped conductive region (5) is divided into three parts, namely left, middle and right, by two second type heavily doped semiconductor layers (7) wrapped by the insulating layer (6); a first type heavily doped conductive region (9) and a second type heavily doped conductive region (10) are sequentially formed on the upper surface of the middle part by ion implantation; and the first type doped conductive region (5) and the conductive layer (11) are isolated by the insulating layer (6).

6. A semi-superjunction IGBT having an anode with a deep graded doped field stop layer according to claim 5, characterized in that: The two second type heavily doped semiconductor layers (7) are made of the same material or different materials, and the two second type heavily doped semiconductor layers (7) have different potentials.

7. A semi-super junction IGBT with an anode having a deep graded doped field stop layer according to claim 5, characterized in that: The intermediate region semi-super junction drift region structure comprises a second type doped conductive region (4), a super junction drift region, and a single impurity drift region (1), wherein the super junction drift region is composed of alternately arranged first type conductive regions (3) and second type conductive regions (2).

8. A semi-superjunction IGBT having an anode with a deep graded doped field stop layer according to claim 7, characterized in that: The lower parts of the two second type heavily doped semiconductor layers (7) wrapped by the insulating layer extend into the second type doped conductive region (4), or extend into the second type conductive region (2) of the super junction drift region.

9. A method for preparing a semi-superjunction IGBT having an anode with a deep graded doped field stop layer, characterized in that: Used to prepare a semi-super junction IGBT with an anode having a deep graded doped field stop layer as described in claim 1.

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