阅读说明：本技术 一种GaN基增强型垂直HEMT器件及其制备方法 (GaN-based enhanced vertical HEMT device and preparation method thereof ) 是由 李祥东 韩占飞 刘苏杭 张进成 郝跃 于 2021-06-17 设计创作，主要内容包括：本发明提供了一种GaN基增强型垂直HEMT器件及其制备方法,GaN基增强型垂直HEMT器件的结构从下至上依次包括漏极、衬底、漂移区、垂直沟道阻挡层、沟道层、势垒层、钝化层、沟槽栅和源极。GaN沟道层和其上侧的AlGaN势垒层以及其下方的Al-(x)Ga-(1-x)N垂直沟道阻挡层形成双异质结结构,该结构通过GaN/AlGaN异质结构在垂直沟道方向形成势垒层,从而在关态条件下阻断载流子在垂直方向的输运,进而关断沟道,实现增强型特性。该结构可有效避免传统的Mg掺杂的p-GaN阻挡层带来的负面影响,设计的器件具有低导通电阻、高漏极电流密度和高阈值电压的显著特性。(The invention provides a GaN-based enhanced vertical HEMT device and a preparation method thereof. GaN channel layer, AlGaN barrier layer on upper side of GaN channel layer, and Al below GaN channel layer x Ga 1‑x The N vertical channel barrier layer forms a double heterojunction structure, and the barrier layer is formed in the vertical channel direction through the GaN/AlGaN heterostructure, so that the transport of a current carrier in the vertical direction is blocked under the off-state condition, and the current carrier is further turned offChannel, enabling enhanced features. The structure can effectively avoid the negative influence caused by the traditional Mg-doped p-GaN barrier layer, and the designed device has the remarkable characteristics of low on-resistance, high drain current density and high threshold voltage.)

1. A GaN-based enhanced vertical HEMT device, comprising: the trench gate structure comprises a drain electrode (1), a substrate (2), a drift region (3), a vertical channel barrier layer (4), a channel layer (5), a trench gate (6), a barrier layer (7), a passivation layer (8) and a source electrode (9), wherein the trench gate (6) comprises trench gate metal (61) and trench gate dielectric (62), the trench gate metal is surrounded by the trench gate dielectric (62), the trench gate dielectric (62) is connected with the passivation layer (8), the drain electrode (1), the substrate (2), the drift region (3) and the vertical channel barrier layer (4) are contacted with each other from bottom to top in sequence, the trench gate (6) is a trench gate, a trench opening range from the barrier layer (7) to the bottom end of the vertical channel barrier layer (4) from top to bottom in the center position of the barrier layer (7), the passivation layer (8) is positioned on the barrier layer (7) and is contacted with the upper surface of the barrier layer (7), the passivation layer (8) is overlapped with the edge of the barrier layer (7), the cross section of the source electrode (9) is in an inverted C shape, the source electrode (9) is located on the passivation layer (8), the edges of the passivation layer (8) and the barrier layer (7) are correspondingly contacted with the edge of the source electrode (9), the channel layer (5), the barrier layer (7) on the upper side of the channel layer and the vertical channel barrier layer (4) below the channel layer form a double heterojunction structure, and the source electrode (9) penetrates through the barrier layer (7) and the channel layer (5) to form ohmic contact.

2. The device according to claim 1, wherein the trench gate dielectric (62) is the same material as the passivation layer (8), and the trench gate dielectric (62) is 100nm thick SiN or SiO₂。

3. Device according to claim 1, characterized in that the barrier layer (7) is Al with a thickness of 30nm_xGa_1-xN; wherein x is 0.1 to 0.5.

4. The device of claim 1, wherein the channel layer is GaN having a thickness of 50-500 nm.

5. The device according to claim 1, wherein the drift region (3) is n-GaN with a thickness of 500 to 5000 nm.

6. Device according to claim 1, characterized in that the material of the substrate (2) is n⁺-GaN。

7. The device according to claim 1, wherein the vertical channel stop layer (4) is Al with a thickness of 50-300 nm_xGa_1-xN, wherein the content of x is 2-30%.

8. A preparation method of a GaN-based enhanced vertical HEMT device is characterized by comprising the following steps:

step 1: at n⁺-epitaxially growing an n-GaN drift region on a GaN substrate;

step 2: epitaxially growing Al on n-GaN drift region_xGa_1-xN is vertical to the channel barrier layer;

and step 3: epitaxially growing an intrinsic GaN channel layer on the surface of the vertical channel barrier layer;

and 4, step 4: epitaxially growing an AlGaN barrier layer on the surface of the intrinsic GaN channel layer;

and 5: etching a groove on the surface of the AlGaN barrier layer, wherein the groove ranges from the barrier layer to the bottom end of the vertical channel barrier layer from top to bottom, and penetrates through the channel layer;

step 6: SiN or SiO is deposited on the AlGaN barrier layer and the surface of the groove₂As a trench gate dielectric connected to the passivation layer;

and 7: depositing metal in the groove to form a gate electrode;

and 8: epitaxially growing SiN or SiO on the surface of the groove₂A passivation layer;

and step 9: performing medium hole opening etching and AlGaN etching on a preset ohmic region on the surface of the passivation layer until reaching the GaN channel layer, and forming an etched shallow groove in the GaN channel layer;

step 10: performing source metal deposition and annealing in the ohmic region to form ohmic contact between the GaN channel layer and the deposited metal;

step 11: at said n⁺-etching the back side of the GaN substrate to form a drain region, depositing metal for ohmic contact in the drain region, and annealing to form a drain electrode.

Technical Field

The invention belongs to the technical field of semiconductor devices, and particularly relates to a GaN-based enhanced vertical HEMT device and a preparation method thereof.

Background

The wide bandgap semiconductor material plays an increasingly important role in the high-frequency high-power field and the photoelectric field by virtue of the advantages of large bandgap, high bonding energy and the like. The GaN High Electron Mobility Transistor (HEMT) with a transverse structure is a main structure in the application field of power devices, and the core of the HEMT is an AlGaN/GaN heterojunction. Compared with the traditional GaN transverse device, the GaN-based vertical power field effect transistor has the advantages of high area efficiency, lower thermal resistance, easier packaging, small electric field edge effect, lower on-resistance and the like.

To mitigate the current collapse effect and improve the reliability of the device, the high field region of GaN-based vertical HEMTs is typically embedded in the device body to avoid surface arcing at the gate edge. Current Aperture Vertical Electron Transistors (CAVETs) and trench gate Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) are two common GaN-based vertical field effect transistors. Both of these conventional GaN vertical field effect transistors need to use Mg-doped p-GaN as their channel barrier layer or barrier layer. Two methods are generally used in fabricating the p-GaN layer, the first is etching followed by regrowth, and the second is Mg ion implantation. The two methods have the disadvantages of large etching damage, extremely complex process, low Mg activation rate and high introduced defect state, so that a high-performance and high-reliability GaN vertical device is difficult to manufacture.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a GaN-based enhanced vertical HEMT device and a preparation method thereof. The technical problem to be solved by the invention is realized by the following technical scheme:

in a first aspect, the present invention provides a GaN-based enhancement type vertical HEMT device comprising: the drain electrode 1, the substrate 2, the drift region 3, the vertical channel barrier layer 4, the channel layer 5, the trench gate 6, the barrier layer 7, the passivation layer 8 and the source electrode 9, wherein the trench gate 6 comprises trench gate metal 61 and trench gate dielectric 62, the trench gate dielectric 62 surrounds the trench gate metal, the trench gate dielectric 62 is connected with the passivation layer 8, the drain electrode 1, the substrate 2, the drift region 3 and the vertical channel barrier layer 4 are sequentially contacted from bottom to top, the trench gate 6 is a trench gate, starting from the central position of the barrier layer 7, the trench extends from the barrier layer 7 to the bottom end of the vertical channel barrier layer 4 from top to bottom, the passivation layer 8 is positioned on the barrier layer 7 and is contacted with the upper surface of the barrier layer 7, the passivation layer 8 is superposed with the edge of the barrier layer 7, the cross section of the source electrode 9 is inverted C-shaped, the source electrode 9 is positioned on the passivation layer 8, the edges of the passivation layer 8 and the barrier layer 7 are respectively contacted with the edge of the source electrode 9, the channel layer 5 and the barrier layer 7 on its upper side and the vertical channel barrier layer 4 below it form a double heterojunction structure, and the source 9 forms an ohmic contact through the barrier layer 7 and the channel layer 5.

Optionally, the material of the trench gate dielectric 62 is the same as that of the passivation layer 8, and the trench gate dielectric 62 is SiN or SiO with a thickness of 100nm₂。

Optionally, the barrier layer 7 is 30nm thick Al_xGa_1-xN; wherein x is 0.1 to 0.5.

Wherein the channel layer is GaN with the thickness of 50-500 nm.

Wherein, the drift region 3 is n-GaN with the thickness of 500-5000 nm.

Wherein the substrate 2 is made of n⁺-GaN。

Wherein the vertical channel barrier layer 4 is Al with a thickness of 50-300 nm_xGa_1-xN, wherein the content of x is 2-30%.

In a second aspect, the invention provides a method for manufacturing a GaN-based enhanced vertical HEMT device, comprising:

step 1: at n⁺-epitaxially growing an n-GaN drift region on a GaN substrate;

step 2: epitaxially growing Al on n-GaN drift region_xGa_1-xN is vertical to the channel barrier layer;

and step 3: epitaxially growing an intrinsic GaN channel layer on the surface of the vertical channel barrier layer;

and 4, step 4: epitaxially growing an AlGaN barrier layer on the surface of the intrinsic GaN channel layer;

and 5: etching a groove on the surface of the AlGaN barrier layer, wherein the groove ranges from the barrier layer to the bottom end of the vertical channel barrier layer from top to bottom, and penetrates through the channel layer;

step 6: depositing SiN or SiO on the AlGaN barrier layer and the surface of the groove₂As a trench gate dielectric connected to the passivation layer;

and 7: depositing metal in the groove to form a gate electrode;

and 8: epitaxially growing SiN or SiO on the surface of the trench₂A passivation layer;

and step 9: performing medium open pore etching and AlGaN etching in a preset ohmic region on the surface of the passivation layer until reaching the GaN channel layer, and forming an etched shallow groove in the GaN channel layer;

step 10: performing source metal deposition and annealing in the ohmic region to form ohmic contact between the GaN channel layer and the deposited metal;

step 11: at n⁺-etching the back side of the GaN substrate to form a drain region, depositing metal for ohmic contact in the drain region, and annealing to form a drain electrode.

The invention provides a GaN-based enhanced vertical HEMT device and a preparation method thereof. Device GaN channel layer, AlGaN barrier layer on upper side of device GaN channel layer and Al below device GaN channel layer_xGa_1-xThe N vertical channel barrier layer forms a double heterojunction structure, and the barrier layer is formed in the vertical channel direction through the vertical GaN/AlGaN heterostructure, so that the transport of a current carrier in the vertical direction is blocked under the off-state condition, the channel is further cut off, and the enhancement characteristic is realized. The structure can effectively avoid the negative influence caused by the traditional Mg-doped p-GaN barrier layer, and the designed device has low resistance (R)_on) High drain current density and high threshold voltage (V)_th>3V).

The invention provides a preparation method of a GaN-based enhanced vertical HEMT device, which comprises the steps of growing Al above a drift region in sequence_xGa_1-xThe N vertical channel barrier layer, the GaN channel layer and the AlGaN barrier layer form a double heterojunction structure. Compared with the traditional p-GaN enhanced HEMT device, the invention adopts Al_xGa_1-xThe N replaces the traditional unstable Mg-doped p-GaN to serve as a vertical channel barrier layer, a series of problems caused by the Mg-doped p-GaN barrier layer are avoided, and meanwhile, the drain current density and the forward threshold voltage are effectively improved. And the source electrode penetrates through the barrier layer through the groove to form ohmic contact with the channel layer, so that the advantage of high mobility of two-dimensional electron gas can be fully utilized, and the on-resistance of the source electrode is reduced. Meanwhile, the process of the invention is simpler and is compatible with the traditional GaN HEMT process.

The present invention will be described in further detail with reference to the accompanying drawings and examples.

Drawings

Fig. 1 is a schematic structural diagram of a GaN-based enhancement type vertical HEMT device according to an embodiment of the present invention;

FIG. 2 is a graph of transfer characteristics of a GaN-based enhanced vertical HEMT device provided by the present invention;

FIG. 3 is a graph of the output characteristics of a GaN-based enhanced vertical HEMT device provided by the present invention;

fig. 4 is a flowchart of a method for manufacturing a GaN-based enhancement type vertical HEMT device according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention are not limited thereto.

As shown in fig. 1, the present invention provides a GaN-based enhancement type vertical HEMT device comprising: the drain electrode 1, the substrate 2, the drift region 3, the vertical channel barrier layer 4, the channel layer 5, the trench gate 6, the barrier layer 7, the passivation layer 8 and the source electrode 9, wherein the trench gate 6 comprises trench gate metal 61 and trench gate dielectric 62, the trench gate dielectric 62 surrounds the trench gate metal, the trench gate dielectric 62 is connected with the passivation layer 8, the drain electrode 1, the substrate 2, the drift region 3 and the vertical channel barrier layer 4 are contacted with each other from bottom to top in sequence, the trench gate 6 is a trench gate, starting from the central position of the barrier layer 7, the trench extends from the barrier layer 7 to the bottom end of the vertical channel barrier layer 4 from the top to the bottom, the passivation layer 8 is positioned on the barrier layer 7 and is contacted with the upper surface of the barrier layer 7, the passivation layer 8 is superposed with the left and right edges of the barrier layer 7, the cross section of the source electrode 9 is in an inverted C shape, the source electrode 9 is positioned on the passivation layer 8, and the edges of the passivation layer 8 and the barrier layer 7 are respectively contacted with the edge of the source electrode 9, the channel layer forms a double heterojunction structure with the barrier layer 7 on its upper side and the vertical channel barrier layer 4 below it, and the source 9 forms an ohmic contact through the barrier layer 7 and the channel layer 5.

As an optional embodiment of the present invention, the material of the trench gate dielectric 62 is the same as that of the passivation layer 8, and the trench gate dielectric 62 is SiN or SiO with a thickness of 100nm₂。

As an alternative embodiment of the invention, the barrier layer 7 is Al with a thickness of 30nm_xGa_1-xN; wherein x is 0.1 to 0.5.

In an optional embodiment of the present invention, the channel layer is GaN with a thickness of 50 to 500 nm.

As an optional implementation mode of the invention, the drift region 3 is n-GaN with the thickness of 500-5000 nm.

As an alternative embodiment of the present invention, the substrate 2 is made of n⁺-GaN。

As an alternative embodiment of the present invention, the length of the source electrode 9, the distance between the source electrode 9 and the trench gate 6, and the trench gate width are set to 0.5, 1.1, and 0.8 μm, respectively.

As an optional embodiment of the present invention, the vertical channel stop layer 4 is Al with a thickness of 50 to 300nm_xGa_1-xN, wherein the content of x is 2-30%.

Referring to fig. 2 and 3, fig. 2 is a graph of transfer characteristics of the GaN-based enhancement type vertical HEMT device of the present invention, with V on the horizontal axis_DSThe vertical axis is the z-transfer characteristic, and the curve condition is V_DS＝10V，V_th5.4V. FIG. 3 is a graph of output characteristics, V, of a GaN-based enhanced vertical HEMT device provided in the present invention_GS＝0～9V。

The invention provides a GaN-based enhanced vertical HEMT device which sequentially comprises a drain electrode, a substrate, a drift region and a GaN-based enhanced vertical HEMT device,Vertical channel barrier layer, channel layer, barrier layer, passivation layer, trench gate and source. The device GaN channel layer, the AlGaN barrier layer on the upper side of the device GaN channel layer and the Al below the device GaN channel layer_xGa_1-xThe N vertical channel barrier layer forms a double heterojunction structure, and the barrier layer is formed in the vertical channel direction through the vertical GaN/AlGaN heterostructure, so that the transport of a current carrier in the vertical direction is blocked under the off-state condition, the channel is further cut off, and the enhancement characteristic is realized. The structure can effectively avoid the negative influence caused by the traditional Mg-doped p-GaN barrier layer, and the designed device has low resistance (R)_on) High drain current density and high threshold voltage (V)_th>3V).

As shown in fig. 4, the method for manufacturing a double-heterojunction-based trench-gate enhanced vertical HEMT device provided by the present invention comprises:

step 1: at n⁺-epitaxially growing an n-GaN drift region on a GaN substrate;

step 2: epitaxially growing Al on n-GaN drift region_xGa_1-xN is vertical to the channel barrier layer;

and step 3: epitaxially growing an intrinsic GaN channel layer on the surface of the vertical channel barrier layer;

and 4, step 4: epitaxially growing an AlGaN barrier layer on the surface of the intrinsic GaN channel layer;

and 5: etching a groove on the AlGaN barrier layer (the surface of the AlGaN barrier layer, wherein the groove ranges from the barrier layer to the bottom end of the vertical channel barrier layer from top to bottom through the channel layer;

step 6: SiN or SiO is deposited on the AlGaN barrier layer and the surface of the groove₂As a trench gate dielectric connected to the passivation layer;

and 7: depositing metal in the groove to form a gate electrode;

and 8: epitaxially growing SiN or SiO on the surface of the groove₂A passivation layer;

and step 9: performing medium hole opening etching and AlGaN etching on a preset ohmic region on the surface of the passivation layer until reaching the GaN channel layer, and forming an etched shallow groove in the GaN channel layer;

step 10: performing source metal deposition and annealing in the ohmic region to form ohmic contact between the GaN channel layer and the deposited metal;

step 11: at said n⁺-etching the back side of the GaN substrate to form a drain region, depositing metal for ohmic contact in the drain region, and annealing to form a drain electrode.

The preparation method provided by the invention grows Al above the drift region in sequence_xGa_1-xThe N vertical channel barrier layer, the GaN channel layer and the AlGaN barrier layer form a double heterojunction structure. Compared with the traditional p-GaN enhanced HEMT device, the invention adopts Al_xGa_1-xThe N replaces the traditional unstable Mg-doped p-GaN to serve as a vertical channel barrier layer, a series of problems caused by the Mg-doped p-GaN barrier layer are avoided, and meanwhile, the drain current density and the forward threshold voltage are effectively improved. And the source electrode penetrates through the barrier layer through the groove to form ohmic contact with the channel layer, so that the advantage of high mobility of two-dimensional electron gas can be fully utilized, and the on-resistance of the source electrode is reduced. Meanwhile, the process of the invention is simpler and is compatible with the traditional GaN HEMT process.

The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.