阅读说明：本技术 一种沟槽栅igbt半导体器件及其制备方法 (Trench gate IGBT semiconductor device and preparation method thereof ) 是由 不公告发明人 于 2019-10-22 设计创作，主要内容包括：本发明提供了一种沟槽栅IGBT半导体器件及其制作方法,半导体器件包括半导体衬底和位于半导体衬底表面内的沟槽栅结构和虚设沟槽栅结构；其中,虚设沟槽栅结构位于两个沟槽栅结构之间,沟槽栅结构包括覆盖在沟槽内表面上和上表面的氧化层及填充在沟槽中的多晶硅；虚设沟槽栅之间为埋入的P型基区,虚设沟槽栅结构包括掺杂区,掺杂区位于P型基区表面并且直接连接到发射极电极；在P型掺杂区下表面形成n型空穴阻挡层。本发明通过n型空穴阻挡层位于虚设沟槽栅的P基区下方,以避免空穴流向发射极；这种结构将空穴存储在虚拟沟槽栅单元下,在不牺牲任何IGBT性能的情况下,寄生电容会显著降低,进而缩短逆变器的死区时间。(The invention provides a trench gate IGBT semiconductor device and a manufacturing method thereof, wherein the semiconductor device comprises a semiconductor substrate, a trench gate structure and a virtual trench gate structure, wherein the trench gate structure and the virtual trench gate structure are positioned in the surface of the semiconductor substrate; the dummy trench gate structure is positioned between the two trench gate structures, and each trench gate structure comprises an oxide layer covering the inner surface and the upper surface of each trench and polycrystalline silicon filled in the trench; a buried P-type base region is arranged between the dummy trench gates, the dummy trench gate structure comprises a doping region, and the doping region is positioned on the surface of the P-type base region and is directly connected to an emitter electrode; and forming an n-type hole blocking layer on the lower surface of the P-type doped region. According to the invention, the n-type hole blocking layer is positioned below the P base region of the dummy trench gate, so that holes are prevented from flowing to the emitter; the structure stores holes under the virtual trench gate unit, and under the condition of not sacrificing the performance of any IGBT, the parasitic capacitance can be obviously reduced, so that the dead time of the inverter is shortened.)

1. A trench gate IGBT semiconductor device, comprising: the semiconductor device comprises a semiconductor substrate, and a trench gate structure and a dummy trench gate structure which are positioned in the surface of the semiconductor substrate; the dummy trench gate structure is positioned between the two trench gate structures, and each trench gate structure comprises an oxide layer covering the inner surface and the upper surface of each trench and polycrystalline silicon filled in the trench; the semiconductor substrate comprises an n-type doped region and a P-type doped region positioned above a bottom layer; the P-type doped region is divided into a plurality of interval regions by the trench gate structure and the dummy trench gate structure, the P-type doped region between the dummy trench gates forms a P-type base region, the dummy trench gate structure comprises a doped region, and the doped region is positioned on the surface of the P-type base region and is directly connected to the emitter electrode; and forming an n-type hole blocking layer on the lower surface of the P-type doped region.

2. The trench gate IGBT semiconductor device according to claim 1, wherein the n-type doped region is formed by n-type doping the semiconductor substrate, and the P-type doped region is formed by injecting P-type impurities into the surface of the semiconductor substrate.

3. The trench gate IGBT semiconductor device according to claim 2, wherein the P-type doped region spacing region between the trench gate structure and the dummy trench gate structure comprises an n + -type doped region and a P + -type doped region, the P + -type doped region is arranged side by side with the n + -type doped region and the n + -type doped region is arranged at two sides of the P + -type doped region; the n + type doping region is arranged in the surface part of the spacing region, the side walls of the n + type doping region and the p type base region are both in contact with the outer surface of the side wall of the groove, and the n + type doping region is electrically coupled with the emitter electrode.

4. The trench gate IGBT semiconductor device according to claim 1, wherein the trench gate structures and the dummy trench gate structures are arranged at intervals.

5. The trench gate IGBT semiconductor device according to claim 1, wherein the dummy trench gate comprises an oxide layer covering the inner surface of the dummy trench and polysilicon filled in the trench.

6. The trench gate IGBT semiconductor device of claim 1, wherein the dummy trench gate polysilicon is connected to an emitter electrode.

7. The trench gate IGBT semiconductor device of claim 1, wherein the dummy trench gates are shorted to each other.

8. A preparation method of a trench gate IGBT semiconductor device is characterized by comprising the following steps: the preparation method of the trench gate IGBT semiconductor device according to claims 1-7 comprises the following steps:

forming a P base, carrying out groove dry etching, forming a grid oxide and depositing a doped polysilicon grid; forming an additional groove by Reactive Ion Etching (RIE), wherein the width and the depth of the additional groove are about 2500-3500A and 5 mu m respectively, and then completely depositing oxide in the groove by using high-density plasma (HDP); then, chemical mechanical polishing is performed, an n + emission region is formed by ion implantation, and an insulating film is deposited.

Technical Field

The invention belongs to the technical field of power semiconductors, and particularly relates to a trench gate IGBT semiconductor device and a preparation method of the semiconductor device.

Background

The IGBT is a composite full-control voltage-driven power semiconductor device consisting of a BJT (bipolar junction transistor) and an MOS (insulated gate field effect transistor), and has the advantages of both high input impedance of the MOSFET and low conduction voltage drop of the GTR. Turning on the IGBT by providing a transistor base current; conversely, if a reverse gate voltage is applied, the channel is eliminated and the IGBT is turned off by the reverse gate current. The IGBT integrates the advantages of small GTR on-state voltage drop, large current-carrying density, high withstand voltage, small power MOSFET driving power, high switching speed, high input impedance and good thermal stability, and is popular among people. The development success of the inverter provides favorable conditions for improving the performance of power electronic devices, particularly for miniaturization, high efficiency and low noise of the inverter, so that the inverter can be used for locomotives and trains, electric automobile trains and hybrid electric automobiles. The growth in the area of renewable energy sources such as solar and wind power has led to a demand for high power IGBTs.

When the IGBT is used as an electric energy conversion device such as an inverter and the like, an important parameter influencing the use of the IGBT is dead time, and if the dead time is set to be too small, bridge circuits are directly connected, so that a device is short-circuited and fails; the dead time is set too much, which causes signal waveform distortion, the output efficiency is seriously reduced, and the stability of the induction motor is also adversely affected.

Taking a two-level half-bridge inverter unit as an example, as shown in fig. 1(a), control signals of an upper transistor and a lower transistor of the same bridge arm are a pair of complementary signals, in actual operation, due to existence of turn-off time of the IGBT, a certain delay exists from gate turn-off of a T1 transistor to collector turn-off of a collector current, in this period of delay, since a T2 transistor starts to be turned on, a bridge circuit is easily connected directly, a large loop current spike is caused, and then a large voltage spike is generated at two ends of the IGBT through a loop stray inductance LS, once a rated blocking voltage of the IGBT is exceeded, the IGBT is subjected to avalanche breakdown and fails, and a fault of the whole device is caused. Therefore, a certain delay, called dead time, must be added between the complementary control signals of the switches of the same bridge arm in an electric energy conversion device such as an inverter

tdead, such that one tube on the same bridge arm is completely off and the other tube is not yet on during that time. This avoids the occurrence of bridge-through.

Therefore, it is necessary to shorten the dead time of the inverter as much as possible without bridge breakdown, and to ensure the safety and stability of the system and high conversion efficiency.

Disclosure of Invention

The invention aims to solve the technical problem of how to shorten the dead time of an inverter as much as possible without bridge circuit breakdown on the premise of ensuring the safety and stability of a system and the conversion efficiency, and provides a trench gate IGBT semiconductor device and a preparation method thereof.

In one aspect, the present invention provides a trench gate IGBT semiconductor device, comprising: the semiconductor device comprises a semiconductor substrate, and a trench gate structure and a dummy trench gate structure which are positioned in the surface of the semiconductor substrate; the dummy trench gate structure is positioned between the two trench gate structures, and each trench gate structure comprises an oxide layer covering the inner surface and the upper surface of each trench and polycrystalline silicon filled in the trench; the semiconductor substrate comprises an n-type doped region and a P-type doped region positioned above a bottom layer; the P-type doped region is divided into a plurality of spaced regions by the trench gate structure and the dummy trench gate structure,

the P-type doped region between the dummy trench gates forms a P-type base region, the dummy trench gate structure comprises a doped region, and the doped region is positioned on the surface of the P-type base region and is directly connected to an emitter electrode; and forming an n-type hole blocking layer on the lower surface of the P-type doped region.

Further, the semiconductor substrate comprises an n-type doped region and a P-type doped region located above the bottom layer, the n-type doped region is formed by conducting n-type doping on the semiconductor substrate, and the P-type doped region is formed by injecting P-type impurities into the surface of the semiconductor substrate.

Furthermore, the P-type doped region is divided into a plurality of interval regions by the trench gate structure and the dummy trench gate structure, and the interval region of the P-type doped region between the trench gate structure and the dummy trench gate structure comprises an n + -type doped region and a P + -type doped region, wherein the P + -type doped region and the n + -type doped region are arranged side by side and the n + -type doped region is arranged at two sides of the P + -type doped region; the n + type doping region is arranged in the surface part of the spacing region, the side walls of the n + type doping region and the p type base region are both in contact with the outer surface of the side wall of the groove, and the n + type doping region is electrically coupled with the emitter electrode.

Furthermore, the trench gate structures and the dummy trench gate structures are multiple and arranged at intervals.

Further, the dummy trench gate comprises an oxide layer covering the inner surface of the dummy trench and polysilicon filled in the trench. Further, the dummy trench gate polysilicon is connected to the emitter electrode.

Further, the gates between the dummy trench gates are shorted.

The beneficial technical effects are as follows:

according to the invention, the n-type hole blocking layer is positioned below the P base region of the dummy trench gate, so that holes are prevented from flowing to the emitter; the structure stores holes under the dummy trench gate unit, so that the parasitic capacitance can be remarkably reduced under the condition of not sacrificing the performance of any IGBT, and further the dead time of the inverter is shortened;

the polycrystalline silicon grid electrode and the emitter electrode of the dummy trench gate are short-circuited, so that the parasitic oxide capacitance is remarkably reduced; but in this case the P-collector holes can easily flow to the emitter electrode.

Drawings

Fig. 1 is a schematic diagram of a two-level half-bridge inverter unit, wherein 1(a) is a circuit diagram of the two-level half-bridge inverter unit, and 1(b) is an IGBT control signal waveform;

FIG. 2 is a schematic cross-sectional structure diagram of a conventional trench gate IGBT;

FIG. 3 is a component of the parasitic capacitance of a conventional trench gate IGBT;

fig. 4 is a schematic structural diagram of a trench gate IGBT semiconductor device according to an embodiment of the present invention;

fig. 5 is a schematic diagram of a method for manufacturing a trench gate IGBT semiconductor device according to an embodiment of the present invention;

the labels in the figure are: 1, emitter metal; 2, SiO2 layer; 3, a P-type doped region; 4: a trench gate structure; 5: an oxide layer; 6, n + type doping area; 7, P + type doped region; 8: an n-type drift layer; 9: an n-type buffer layer; 10: a P collector electrode; 11: a collector metal; 12: a dummy trench; 13: a P-type doped region; 14: an n-type hole blocking layer; 16: an emitter short-circuit region; 17-dummy trench gate; 202: and doping the region.

Detailed Description

The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

Taking a two-level half-bridge inverter unit as an example, as shown in fig. 1(a), control signals of an upper transistor and a lower transistor of the same bridge arm are a pair of complementary signals, in actual operation, due to existence of turn-off time of the IGBT, a certain delay exists from gate turn-off of a T1 transistor to collector turn-off of a collector current, in this period of delay, since a T2 transistor starts to be turned on, a bridge circuit is easily connected directly, a large loop current spike is caused, and then a large voltage spike is generated at two ends of the IGBT through a loop stray inductance LS, once a rated blocking voltage of the IGBT is exceeded, the IGBT is subjected to avalanche breakdown and fails, and a fault of the whole device is caused. Therefore, a certain delay, called as a dead time tdead, must be added between the complementary control signals of the switches of the same bridge arm in the power conversion device such as the inverter, so that one tube of the same bridge arm is completely turned off and the other tube is not turned on in the time. This avoids the occurrence of bridge-through. Fig. 1(b) is a schematic diagram of waveforms of switching control of the inverter unit after a certain time delay is added, wherein the upper diagram is waveforms of VGE1 and IC1 when the T1 transistor is turned off, and the lower diagram is waveforms of VGE2 and IC2 when the T2 transistor is turned on. The T1 tube turn-off time toff is divided into two parts, turn-off delay time td (off), namely, the time from the grid voltage dropping to 90% of the maximum value to the collector current dropping to 90% of the maximum value; the collector current fall time tf, i.e. the time for the collector current to fall from 90% of the maximum value to 10% of the maximum value. td (on) is the turn-on delay time of the T2 tube, defined as the time from a gate voltage of 0 to a collector current of 10% of the maximum value. As can be seen from fig. 1(b), if the delay time of the two-transistor switching pulse is less than the difference between toff and td (on), the two-transistor through can be avoided without considering the driving delay. If the influence of the drive delay is added, the minimum delay time or dead time of the two-tube control signal is

tdead＝(toff－td(on)+tPDD－Max－tPDD－Min)r，(1)

Toff and td (on) as mentioned above, tPDD-Max and tPDD-Min are respectively the maximum and minimum output delays of the IGBT driving circuit, and r is a safety factor introduced by considering influence factors such as process dispersibility, and generally takes 1.2-1.5, but this cannot accurately reflect the rule that the dead time is influenced by the device working conditions. As can be seen from the formula (1), the calculation of the dead time is closely related to the turn-on and turn-off processes of the IGBT. Therefore, the reasonable setting of the dead time firstly needs to analyze the switching mechanism of the IGBT, find out the main factors influencing the switching time of the IGBT and further obtain the influence of the factors on the setting of the dead time.

FIG. 2 is a schematic cross-sectional structure diagram of a conventional trench gate IGBT; to avoid bridge breakdown and ensure that the system is stable and efficient, the switching time of igbt, which is mainly td (off) and td (on), must be reduced, and the delay time is caused by parasitic capacitance, cge, cgc and cae, as shown in fig. 3. Fig. 3 shows the parasitic capacitance component of the dashed frame portion in fig. 2, and reduction qge and qgc are necessary from the viewpoint of the gate charge characteristic of fig. 3, which means that the parasitic capacitances cgc and cge should be mainly reduced. Fig. 3 shows the composition of the conventional IGBT structure and parasitic capacitances, cies, coes and crs.

Therefore, the present invention primarily considers reducing the parasitic capacitance, and the embodiment is shown in fig. 4. The invention will be further explained with reference to the drawings.