阅读说明：本技术 一种集成续流二极管的GaN HEMT器件 (GaN HEMT device integrated with freewheeling diode ) 是由 罗小蓉 廖德尊 张�成 邓思宇 魏杰 贾艳江 孙涛 郗路凡 于 2021-08-30 设计创作，主要内容包括：本发明属于功率半导体技术领域,涉及一种集成续流二极管的GaN HMET器件。本发明主要特征在于：器件正向导通时,肖特基二极管处于关断状态,一方面利用肖特基金属与半导体之间的功函数差,耗尽阳极区域的二维电子气,另一方面利用阳极区域部分保留的介质层,降低肖特基二极管关断时的泄漏电流；器件反向续流时,肖特基阳极侧壁与二维电子气(2DEG)直接接触,有利于降低反向传导损耗；绝缘栅极结构允许器件在具有较厚势垒层的情况下,实现增强型HEMT,有利于降低正向导通电阻以及增强器件的栅控能力；集成的肖特基二极管与GaN HEMT在漏极一侧共享漂移区,相较于并联二极管实现续流,有利于减小器件面积和寄生参数以及降低正向传导与反向传导时的导通电阻。(The invention belongs to the technical field of power semiconductors, and relates to a GaN HMET device integrated with a freewheeling diode. The invention is mainly characterized in that: when the device is conducted in the forward direction, the Schottky diode is in a turn-off state, on one hand, the two-dimensional electron gas in the anode region is exhausted by utilizing the work function difference between the Schottky metal and the semiconductor, and on the other hand, the leakage current when the Schottky diode is turned off is reduced by utilizing the dielectric layer reserved in the anode region; when the device reversely flows current, the side wall of the Schottky anode is directly contacted with two-dimensional electron gas (2DEG), which is beneficial to reducing reverse conduction loss; the insulated gate structure allows the device to realize an enhanced HEMT under the condition of a thicker barrier layer, and is beneficial to reducing the forward on-resistance and enhancing the gate control capability of the device; the integrated Schottky diode and the GaN HEMT share the drift region on one side of the drain electrode, and compared with a parallel diode, the integrated Schottky diode and the GaN HEMT realize follow current, and are beneficial to reducing the area and parasitic parameters of a device and reducing the on-resistance during forward conduction and reverse conduction.)

1. A GaN HEMT device integrated with a freewheeling diode comprises a substrate layer (1), a GaN buffer layer (2), a GaN channel layer (3), a barrier layer (4) and a passivation layer (5) which are sequentially stacked from bottom to top along the vertical direction of the device;

the device is characterized in that a first conductive material (6) and a source end structure are respectively arranged at two ends above the device; the first conductive material (6) penetrates through the passivation layer (5) and extends into the upper layer of the barrier layer (4), and the upper surface of the first conductive material (6) leads out a drain electrode and is used as a cathode of the integrated freewheeling diode;

defining the direction of a source end structure of the device pointing to the first conductive material (6) as a transverse direction of the device, defining the direction perpendicular to the transverse direction of the device and the vertical direction of the device as a longitudinal direction of the device, and sequentially including a first groove (9), an insulated gate structure, a second groove (10), a second conductive material (7) and a third groove (11) along the longitudinal direction of the device; the bottom parts of the first groove (9), the second groove (10) and the third groove (11) penetrate through the barrier layer (4) and then extend into the upper layer of the GaN channel layer (3), and dielectric layers (13) are arranged at the bottom parts and the side surfaces of the first groove (9), the second groove (10) and the third groove (11); the insulated gate structure comprises a P-type GaN layer (12) and a fourth conductive material (14), the bottom of the P-type GaN layer (12) is in surface contact with the upper surface of the barrier layer (4), the outer surface of the P-type GaN layer (12) is wrapped by the fourth conductive material (14), the fourth conductive material (14) is isolated from the P-type GaN layer (12) through a dielectric layer (13), and the fourth conductive material (14) further extends to the bottoms of the first groove (9) and the second groove (10) along the side walls of the first groove (9) and the second groove (10); the third conductive material (8) arranged in parallel with the P-type GaN layer (12) is further arranged along the transverse direction of the device, a space is formed between the P-type GaN layer (12) and the third conductive material (8), the P-type GaN layer (12) is located at one end close to the first conductive material (6), and the edges of the two ends of the P-type GaN layer (12) and the third conductive material (8) are flush with the edge of the first groove (9) and the edge of the second groove (10) respectively; a second conductive material (7) is arranged above the barrier layer (4) between the second groove (10) and the third groove (11), the barrier layer (4) and the second conductive material (7) are isolated by a dielectric layer (13) at one side close to the passivation layer (5) along the transverse direction of the device, the barrier layer (4) at the other side is contacted with the second conductive material (7), the second conductive material (7) also extends to the bottoms of the second groove (10) and the third groove (11) along the side walls of the second groove (10) and the third groove (11), the second conductive material (7) contacted with the barrier layer (4) is contacted with the side walls of the second groove (10) and the third groove (11), and the second conductive material (7) isolated from the barrier layer (4) by the dielectric layer (13) is isolated from the side walls of the second groove (10) and the third groove (11) by the dielectric layer (13), and the second conductive material (7) in contact with the barrier layer (4) is in contact with the GaN channel layer (3);

an integrated freewheeling diode anode is led out of the upper surface of the second conductive material (7); the third conductive material (8) penetrates through the passivation layer (5) and extends into the upper layer of the barrier layer (4), and a source electrode is led out from the upper surface of the third conductive material; the first conductive material (6) and the third conductive material (8) form ohmic contact with the barrier layer (4); the second conductive material (7) forms a Schottky contact with the barrier layer (4) and the GaN channel layer (3).

2. The GaN HEMT device of claim 1, wherein the fourth conductive material (14) extends in the lateral direction of the device to one side of the first conductive material (6) and covers part of the passivation layer (5) to form a gate field plate (15), and the gate field plate (15) is spaced apart from the first conductive material (6).

3. The GaN HEMT device integrating the free-wheeling diode as claimed in claim 1 or 2, wherein the barrier layer (4) is made of one or more of AlN, AlGaN, InGaN and InAlN.

Technical Field

The invention belongs to the technical field of power semiconductors, and relates to a GaN HEMT device integrated with a freewheeling diode.

Background

Compared with the first-generation semiconductor material Si, the third-generation wide bandgap semiconductor material GaN has more excellent material physical characteristics, and the physical parameters such as the forbidden band width, the electron mobility, the electron saturation rate, the critical breakdown electric field, the thermal conductivity and the high/low frequency Baliga excellent value are far higher than those of the Si material. Currently, P-GaN gate power HEMTs are commercialized and have excellent performance.

However, since the P-GaN gate power HEMT does not have a body diode, the reverse turn-on voltage of the HEMT depends on the threshold voltage (V)_th) And off-state gate bias voltage (V)_GS). In many power switching circuits, such as inverters and DC-DC converters, the power transistor is typically connected in anti-parallel with a freewheeling diode so as not to disturb the inductive load current when the transistor is not yet conducting, in which case the circuit achieves reverse current conduction through the freewheeling diode. However, deploying external diodes not only increases cost, but also introduces additional parasitic inductance and capacitance. Another solution to this problem is to integrate a planar schottky diode on the HEMT, but the main disadvantage of this approach is that the planar schottky diode has a large reverse leakage current, which may be several orders of magnitude higher than the leakage current when the HEMT is off-state.

In addition, P-GaN gate devices have a trade-off between achieving normally-off functionality and low on-resistance. On the one hand, this is due to the thinner barrier layer required for the two-dimensional electron gas (2DEG) in the P-GaN depletion channel, which increases the on-resistance. On the other hand, it is impossible to fully restore the conductivity of the channel under the P-GaN gate by applying a positive gate bias voltage, resulting in the P-GaN region still being less conductive than the other regions of the channel. Therefore, shorter P-GaN and thicker barrier layers are required to reduce on-resistance. However, this makes it difficult to achieve the normally-off function of the device. The three-grid structure forms a fin-shaped structure by etching the area below the grid, two-dimensional electron gas in the grid area is exhausted by utilizing the work function difference between grid metal and a semiconductor, so that the positive threshold voltage of the device is realized, and meanwhile, a thick barrier layer is still used in a drift area, so that the low on-resistance is kept in the non-etched area. However, the realization of the positive threshold voltage of the device only by relying on the tri-gate structure requires the width of the fin structure to be very small, which brings difficulty to the realization of the process.

Disclosure of Invention

The invention provides a GaN HEMT device integrated with a freewheel diode based on the application requirement of the HEMT device;

the technical scheme of the invention is as follows:

a GaN HEMT device integrated with a freewheeling diode comprises a substrate layer 1, a GaN buffer layer 2, a GaN channel layer 3, a barrier layer 4 and a passivation layer 5 which are sequentially stacked from bottom to top along the vertical direction of the device;

the two ends above the device are respectively provided with a first conductive material 6 and a source end structure; the first conductive material 6 penetrates through the passivation layer 5 and extends into the upper layer of the barrier layer 4, and the upper surface of the first conductive material 6 leads out a drain electrode and is used as a cathode of the integrated freewheeling diode;

defining the direction of the source end structure of the device pointing to the first conductive material 6 as the transverse direction of the device, defining the direction perpendicular to the transverse direction of the device and the vertical direction of the device as the longitudinal direction of the device, and along the longitudinal direction of the device, the source end structure sequentially comprises a first groove 9, an insulated gate structure, a second groove 10, a second conductive material 7 and a third groove 11; the bottoms of the first groove 9, the second groove 10 and the third groove 11 penetrate through the barrier layer 4 and then extend into the upper layer of the GaN channel layer 3, and the bottoms and the side faces of the first groove 9, the second groove 10 and the third groove 11 are provided with dielectric layers 13; the insulated gate structure comprises a P-type GaN layer 12 and a fourth conducting material 14, the bottom of the P-type GaN layer 12 is in contact with the barrier layer 4, the outer surface of the P-type GaN layer 12 is wrapped by the fourth conducting material 14, the fourth conducting material 14 is isolated from the P-type GaN layer 12 through a dielectric layer 13, and the fourth conducting material 14 further extends to the bottoms of the first groove 9 and the second groove 10 along the side walls of the first groove 9 and the second groove 10; the third conductive material 8 which is arranged in parallel with the P-type GaN layer 12 is further arranged along the transverse direction of the device, a space is formed between the P-type GaN layer 12 and the third conductive material 8, the P-type GaN layer 12 is located at one end close to the first conductive material 6, and edges of two ends of the P-type GaN layer 12 and the third conductive material 8 are respectively flush with the edge of the first groove 9 and the edge of the second groove 10; the second conducting material 7 is arranged above the barrier layer 4 between the second groove 10 and the third groove 11, the barrier layer 4 and the second conducting material 7 are isolated by a dielectric layer 13 on one side close to the passivation layer 5 along the transverse direction of the device, the barrier layer 4 on the other side is contacted with the second conducting material 7, the second conducting material 7 further extends to the bottoms of the second groove 10 and the third groove 11 along the side walls of the second groove 10 and the third groove 11, the second conducting material 7 contacted with the barrier layer 4 is contacted with the side walls of the second groove 10 and the third groove 11, the second conducting material 7 isolated from the barrier layer 4 by the dielectric layer 13 is isolated from the side walls of the second groove 10 and the third groove 11, and the second conducting material 7 contacted with the barrier layer 4 is contacted with the GaN 3;

an integrated freewheeling diode anode is led out of the upper surface of the second conductive material 7, the third conductive material 8 penetrates through the passivation layer 5 and extends into the upper layer of the barrier layer 4, and a source electrode is led out of the upper surface of the third conductive material; the first conductive material 6 and the third conductive material 8 form ohmic contacts with the barrier layer 4; the second conductive material 7 forms a schottky contact with the barrier layer 4 and the GaN channel layer 3.

Further, the barrier layer 4 is made of one or a combination of more of AlN, AlGaN, InGaN, and InAlN;

the invention has the beneficial effect that the high reverse turn-on voltage of the GaN HEMT is strongly dependent on the threshold voltage (V) when the GaN HEMT is reversely conducted_th) And off-state gate bias voltage (V)_GS) The device realizes reverse follow current through an integrated Schottky diode; when the device is in forward conduction, the Schottky diode is in an off state, and one side is in an on stateTwo-dimensional electron gas in an anode region is exhausted by utilizing the work function difference between the Schottky metal and the semiconductor, and leakage current when the Schottky diode is turned off is reduced by utilizing a dielectric layer reserved in the anode region; when the device reversely flows current, the side wall of the Schottky anode is directly contacted with two-dimensional electron gas (2DEG), which is beneficial to reducing reverse conduction loss; the insulated gate structure allows the device to realize an enhanced HEMT under the condition of a thicker barrier layer, and is beneficial to reducing the forward on-resistance and enhancing the gate control capability of the device; the integrated Schottky diode and the GaN HEMT share a drift region on one side of the drain electrode, and compared with a scheme of realizing follow current by parallel diodes, the integrated Schottky diode and the GaN HEMT are beneficial to reducing the area and parasitic parameters of a device and reducing the on-resistance during forward conduction and reverse conduction;

drawings

FIG. 1 is a schematic three-dimensional structure of example 1;

FIG. 2 is a top view of the structure of example 1;

FIG. 3 is a cross-sectional view along AA' of the structure of example 1;

FIG. 4 is a cross-sectional view along BB' of the structure of example 1;

FIG. 5 is a sectional view of the structure of example 1 taken along line CC';

FIG. 6 is a cross-sectional view of the structure of example 1 taken along DD';

FIG. 7 is a schematic three-dimensional structure of example 2;

Detailed Description

The technical scheme of the invention is described in detail in the following with reference to the accompanying drawings and embodiments:

example 1

As shown in fig. 1, the HEMT device of this example includes a substrate layer 1, a GaN buffer layer 2, a GaN channel layer 3, a barrier layer 4, and a passivation layer 5, which are sequentially stacked from bottom to top in the vertical direction of the device;

the two ends above the device are respectively provided with a first conductive material 6 and a source end structure; the first conductive material 6 penetrates through the passivation layer 5 and extends into the upper layer of the barrier layer 4, and the upper surface of the first conductive material 6 leads out a drain electrode and is used as a cathode of the integrated freewheeling diode;

defining the direction of the source end structure of the device pointing to the first conductive material 6 as the transverse direction of the device, defining the direction perpendicular to the transverse direction of the device and the vertical direction of the device as the longitudinal direction of the device, and along the longitudinal direction of the device, the source end structure sequentially comprises a first groove 9, an insulated gate structure, a second groove 10, a second conductive material 7 and a third groove 11; the bottoms of the first groove 9, the second groove 10 and the third groove 11 penetrate through the barrier layer 4 and then extend into the upper layer of the GaN channel layer 3, and the bottoms and the side faces of the first groove 9, the second groove 10 and the third groove 11 are provided with dielectric layers 13; the insulated gate structure comprises a P-type GaN layer 12 and a fourth conducting material 14, the bottom of the P-type GaN layer 12 is in contact with the barrier layer 4, the outer surface of the P-type GaN layer 12 is wrapped by the fourth conducting material 14, the fourth conducting material 14 is isolated from the P-type GaN layer 12 through a dielectric layer 13, and the fourth conducting material 14 further extends to the bottoms of the first groove 9 and the second groove 10 along the side walls of the first groove 9 and the second groove 10; the third conductive material 8 which is arranged in parallel with the P-type GaN layer 12 is further arranged along the transverse direction of the device, a space is formed between the P-type GaN layer 12 and the third conductive material 8, the P-type GaN layer 12 is located at one end close to the first conductive material 6, and edges of two ends of the P-type GaN layer 12 and the third conductive material 8 are respectively flush with the edge of the first groove 9 and the edge of the second groove 10; the second conductive material 7 is arranged above the barrier layer 4 between the second groove 10 and the third groove 11, the barrier layer 4 and the second conductive material 7 are isolated by a dielectric layer 13 on one side close to the passivation layer 5 along the transverse direction of the device, the barrier layer 4 on the other side is contacted with the second conductive material 7, the second conductive material 7 also extends to the bottoms of the second groove 10 and the third groove 11 along the side walls of the second groove 10 and the third groove 11, and the second conductive material 7 contacted with the barrier layer 4 is contacted with the side walls of the second groove 10 and the third groove 11;

an integrated freewheeling diode anode is led out of the upper surface of the second conductive material 7, the third conductive material 8 penetrates through the passivation layer 5 and extends into the upper layer of the barrier layer 4, and a source electrode is led out of the upper surface of the third conductive material; the first conductive material 6 and the third conductive material 8 form ohmic contacts with the barrier layer 4; the second conductive material 7 forms a schottky contact with the barrier layer 4 and the GaN channel layer 3.

The working mechanism of this example: when the voltage of the grid electrode, the source electrode and the Schottky anode is 0V, and a certain positive voltage is applied to the drain electrode, two-dimensional electron gas in a region below the grid electrode is exhausted by P-GaN and the work function difference between grid electrode metal and a semiconductor, and the HEMT and the Schottky diode are in a turn-off state; when the voltage of the grid and the drain is 0V and a certain positive voltage is applied to the Schottky anode, the Schottky diode is in a conducting state;

the GaN HMET integrated with the freewheeling diode has low-loss reverse conduction capability and low leakage current; the invention has the advantages of high threshold voltage, small on-resistance, high switching speed and the like.

Example 2

The difference between this example and embodiment 1 is that, in this example, the fourth conductive material 14 extends toward the first conductive material 6 along the device lateral direction and covers the passivation layer 5 to form a gate field plate 15, and the gate field plate 15 has a gap from the first conductive material 6; compared with embodiment 1, the advantage of this embodiment is that the gate field plate 15 further optimizes the electric field distribution of the device during voltage withstanding, which is beneficial to improving the breakdown voltage of the device.