A curved field plate structure based on HEMT device and a preparation method thereof

Abstract

The present disclosure provides a curved field plate structure based on a HEMT device, comprising a gate, a source and a drain, the gate being located between the source and the drain, characterized in that a curved field plate structure is formed between the gate and the drain, the curved surface of which is perpendicular to the growth direction of the device, and by optimizing the field plate structure, the peak electric field of the HEMT device can be effectively suppressed, and by arranging the optimized field plate structure in the groove, the distance between the field plate and the channel carriers is shortened, which can further effectively suppress the peak electric field of the HEMT device. The present disclosure also provides a preparation method of the curved field plate structure based on the HEMT device.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor devices, specifically to a curved field plate structure based on HEMT devices and its fabrication method. Background Technology

[0002] GaN HEMT (High Electron Mobility Transistor) devices, with their unique material properties, have become core components for fabricating high-frequency, high-voltage power amplifiers. Currently, low-frequency GaN devices are already in large-scale use, and research on GaN devices has entered the millimeter-wave band. With the further expansion of device applications, higher demands are being placed on device performance. In particular, as devices enter the millimeter-wave band, the source-drain spacing is further shortened, and the increase in the peak electric field at the gate leads to a decrease in operating voltage and an increase in leakage current, severely limiting the high-voltage, high-power applications of these devices.

[0003] Conventional methods for suppressing electric field strength include introducing field plate structures and adding passivation layers. Among these, field plate structures are highly effective in suppressing electric field strength, a fact verified by experiments, and various field plate structures are used in low-frequency devices to improve their high-voltage, high-power characteristics. However, for millimeter-wave devices, while introducing field plate structures can indeed reduce electric field strength, it also comes with the disadvantage of increased parasitic capacitance, severely affecting the device's frequency characteristics and hindering the realization of high-frequency, high-power devices. Therefore, optimizing the field plate structure of millimeter-wave devices to suppress the electric field while minimizing its impact on the device's frequency characteristics is crucial. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this disclosure provides a curved field plate structure based on HEMT devices and its fabrication method. By optimizing the field plate structure, the peak electric field of HEMT devices can be effectively suppressed. Furthermore, by setting the optimized field plate structure in the groove, the distance between the field plate and the channel carriers is shortened, which can further effectively suppress the peak electric field of HEMT devices.

[0005] One aspect of this disclosure provides a curved field plate structure based on a HEMT device, comprising: a gate, a source, and a drain, wherein the gate is located between the source and the drain, characterized in that a curved field plate structure is formed between the gate and the drain, the curved surface of which is perpendicular to the device growth direction.

[0006] Furthermore, a passivation layer is grown between the source and drain, and a curved field plate structure is formed on the passivation layer.

[0007] Furthermore, the passivation layer includes a groove, in which a curved field plate structure is formed, and the height of the curved field plate structure is greater than the depth of the groove.

[0008] Furthermore, the curved field plate structure is composed of multiple continuous curved field plates, forming an S-shaped structure.

[0009] Furthermore, the width of the curved surface of the curved field plate structure is less than half the distance between the gate and the drain.

[0010] Furthermore, the curved surface width of the curved field plate structure is 0.2μm to 0.4μm, and the curved surface angle is 1° to 180°.

[0011] Furthermore, the passivation layer has a thickness of 120 nm and a groove depth of 0–80 nm.

[0012] Furthermore, the curved field plate structure is connected to the source or gate via leads or without bias.

[0013] Another aspect of this disclosure provides a method for fabricating a curved field plate structure based on a HEMT device, comprising: S1, forming a source, a gate, and a drain in sequence by evaporating metal, wherein the gate is located between the source and the drain; S2, forming a curved field plate structure between the gate and the drain by evaporating metal, wherein the curved surface is perpendicular to the device growth direction.

[0014] This disclosure provides a curved field plate structure for HEMT devices and its fabrication method. By setting a curved field plate structure between the gate and drain, the electric field strength of the entire device can be effectively suppressed, thereby further improving the breakdown voltage of the device, i.e., increasing the operating voltage of the device and increasing its output power. In addition, the curved field plate structure can also be set in the passivation layer or in a groove above the passivation layer, which can further effectively suppress the electric field strength of the entire device while ensuring that a small parasitic capacitance is introduced into the device. Attached Figure Description

[0015] To gain a more complete understanding of this disclosure and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, wherein:

[0016] Figure 1A A perspective view of a curved field plate structure based on a HEMT device according to an embodiment of the present disclosure is schematically shown;

[0017] Figure 1B A schematic front view of a curved field plate structure based on a HEMT device according to an embodiment of the present disclosure is shown.

[0018] Figure 2 A schematic top view of a curved field plate structure based on a HEMT device according to an embodiment of the present disclosure is shown.

[0019] Figure 3 A schematic front view of a curved field plate structure based on a HEMT device according to another embodiment of the present disclosure is shown.

[0020] Figure 4 A schematic front view of a curved field plate structure based on a HEMT device according to another embodiment of the present disclosure is shown.

[0021] Figure 5 The diagram schematically illustrates a comparison of the electric field intensity distribution of a curved field plate structure based on a HEMT device according to an embodiment of the present disclosure.

[0022] Figure 6 The schematic diagrams show top views of comparative examples 1 and 2 of a straight field plate structure based on HEMT devices;

[0023] Figure 7 A comparative diagram illustrating the parasitic capacitance distribution of a curved field plate structure based on a HEMT device according to an embodiment of the present disclosure is shown schematically.

[0024] Figure 8 The diagram illustrates a comparison of the electric field intensity distribution of a curved field plate structure based on HEMT devices at different groove depths.

[0025] Figure 9 The flowchart illustrates a method for fabricating a curved field plate structure based on a HEMT device according to an embodiment of the present disclosure. Detailed Implementation

[0026] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0027] It should be understood that when an element (such as a layer, film, region, or substrate) is described as being "on" another element, the element may be directly on the other element, or there may be an intermediate element present. Furthermore, in the specification and claims, when an element is described as being "connected" to another element, the element may be "directly connected" to the other element, or "connected" to the other element via a third element.

[0028] Example 1

[0029] Figure 1A and Figure 1B A perspective view and a front view of a curved field plate structure based on a HEMT device according to an embodiment of the present disclosure are schematically shown.

[0030] like Figure 1A and Figure 1BAs shown, the device includes a substrate 1, a nucleation layer 2, a first semiconductor layer 3, an insertion layer 4, a second semiconductor layer 5, and a cap layer 6 stacked sequentially from bottom to top. It also includes a gate 9, a source 7, a drain 8, and a curved field plate structure 10. The gate 9, source 7, drain 8, and curved field plate structure 10 are located above the cap layer 6. The gate 9 is located between the source 7 and the drain 8, and the curved field plate structure 10 is located between the gate 9 and the drain 8.

[0031] The substrate 1 is SiC, but it can also be single-crystal silicon, gallium nitride, or sapphire; the nucleation layer 2 is an AlN layer with a thickness of 2nm, which is used to improve the nucleation quality of the first semiconductor layer 3; the first semiconductor layer 3 is a GaN layer with a thickness of 2.5μm; the insertion layer 4 is an AlN layer with a thickness of 1nm, which is used to improve the thresholding capability of the high-density two-dimensional electron gas (2-DEG); the second semiconductor layer 5 is an AlGaN layer with a thickness of 20nm, and the band gap width of the material of the second semiconductor layer 5 is greater than the band gap width of the material of the first semiconductor layer 3, forming a heterojunction with the first semiconductor layer 3; the cap layer 6 is a GaN layer with a thickness of 1nm, which is used to protect the interface of the second semiconductor layer 5; the source 7 and drain 8 are formed by high-temperature alloying of titanium, aluminum, nickel, and gold layers; the gate 9 is formed by stacking nickel and gold layers; and the curved field plate structure 10 is formed by high-temperature alloying of nickel and gold layers. In addition, the multiple-cycle device structure forms isolation between devices through N2 injection, so that the devices do not affect each other.

[0032] In this embodiment, the distance between the source 7 and the drain 8 is 2.4 μm, the distance between the source 7 and the gate 9 is 0.8 μm, and the distance between the gate 9 and the drain 8 is 1.4 μm; the gate 9 has a vertical width of 0.2 μm, a height of 450 nm, and a horizontal width of 0.6 μm, and it is T-shaped; the distance between the gate 9 and the curved field plate structure 10 is 0.3 μm, the curved surface width of the curved field plate structure 10 is 0.2 μm, the height is 300 nm, and its bending angle is 180°.

[0033] Figure 2 A schematic top view of a curved field plate structure based on a HEMT device according to an embodiment of the present disclosure is shown, which can be seen to be composed of multiple continuous curved field plates, forming a type of S-structure.

[0034] In some embodiments of this disclosure, based on the size design of the gate 9, source 7 and drain 8, in order to achieve a better field strength suppression effect of the device, the curved surface angle of the curved field plate structure 10 is in the range of 1° to 180°, and the curved surface width is designed according to the spacing of the gate 9, source 7 and drain 8, that is, its curved surface width is less than half of the spacing between the gate 9 and drain 8. In the embodiments of this disclosure, the preferred range of the curved surface width of the curved field plate structure is 0.2μm to 0.4μm.

[0035] Furthermore, depending on the needs of actual applications, the surface width and surface angle of the curved field plate structure are not limited to the numerical ranges listed in the embodiments of this disclosure. They are designed according to the changes in the device structure size in order to achieve a better device electric field strength suppression effect.

[0036] Example 2

[0037] Figure 3 A schematic front view of a curved field plate structure based on a HEMT device according to another embodiment of the present disclosure is shown.

[0038] like Figure 3 As shown, the difference between this embodiment and Embodiment 1 is that:

[0039] A passivation layer 11 is grown above the surface between the source 7 and the drain 8. The curved field plate structure 10 is disposed on the passivation layer and is also located between the gate 9 and the drain 8.

[0040] The passivation layer 11 is a SiN layer with a thickness ranging from 110nm to 140nm. In this embodiment, the passivation layer 11 has a thickness of 120nm. It can also be a multilayer structure, such as SiNx / SiO2, SiNx / SiO2 / SiONx, etc. The passivation layer 11 is used to suppress the current collapse effect of the device and protect the device.

[0041] Example 3

[0042] Figure 4 A schematic front view of a curved field plate structure based on a HEMT device according to another embodiment of the present disclosure is shown.

[0043] like Figure 4 As shown, the difference between this embodiment and Embodiment 2 is that:

[0044] A groove is etched above the passivation layer 11 between the gate 9 and the drain 8, and the curved field plate structure 10 is disposed in the groove.

[0045] The depth of the groove is less than or equal to the thickness of the passivation layer 11. That is, when the thickness of the passivation layer 11 is 110nm to 140nm, the optimal range of the groove depth is 0 to 80nm. The width of the groove is less than the spacing between the gate 9 and the drain 8. The width of the groove is greater than the curved surface width of the curved field plate structure. The width of the groove is preferably 0.4μm to 0.8μm. The curved field plate structure 10 disposed in the groove forms an air gap with both sides of the passivation layer 11.

[0046] In this embodiment, the curved field plate structure 10 is connected to the source 7 via leads. Simulation software is used to simulate and calculate the electric field intensity and parasitic capacitance under the gate of the device structure. The device is set to be biased in the off state, i.e., Vgs = -6V and Vds = 100V, where Vgs is the voltage between the gate and the source and Vds is the voltage between the source and the drain. The electric field intensity distribution curve at 1nm under the gate of the device is obtained.

[0047] Figure 5 The diagram schematically illustrates a comparison of the electric field intensity distribution of a curved field plate structure based on a HEMT device according to an embodiment of the present disclosure.

[0048] like Figure 5 As shown, this is a comparison diagram of the HEMT device with no field plate structure, a linear field plate structure, and a curved field plate structure. Comparative Examples 1 and 2 are top views of the linear field plate structure. Figure 6 As shown, the width of the straight field plate structure 12 and the surface width of the curved field plate structure 10 are both 0.2 μm. The bending angle of the curved field plate structure is 180°, the groove width is 0.4 μm, and the groove depth is 80 nm. From Figure 5 It can be seen that the peak electric field at the gate pin of this HEMT device without a field plate structure is 3.23 MV / cm. 2 The peak electric field at the gate pin of the device in Comparative Examples 1 and 2 is 2.602 MV / cm, respectively. 2 2.634MV / cm 2 and 2.608MV / cm 2 As can be seen, setting a field plate structure in a HEMT device can effectively suppress the peak electric field of the device. Furthermore, the gate electric field strength of the device in this embodiment is smaller than the average peak value of the gate electric field in Comparative Examples 1 and 2. This means that the curved field plate structure 10 has a higher suppression effect on the peak electric field of the gate foot compared to the straight field plate structure 12. The curved field plate structure 10 in this embodiment can also weaken the influence of right-angle structures on the gate electric field. In addition, placing the curved field plate structure 10 in the groove on the passivation layer 11 shortens the distance between it and the channel carriers, further effectively suppressing the gate electric field strength.

[0049] Figure 7 A comparative diagram illustrating the parasitic capacitance distribution of a curved field plate structure in a HEMT device according to an embodiment of this disclosure is shown schematically. With the drain-gate voltage Vds set to 10V, the variation of parasitic capacitance under gate bias for different field plate structures is calculated through simulation. Figure 7As shown, the parasitic capacitance of the HEMT device increases after the field plate structure is set. As the gate-source bias voltage increases, the parasitic capacitance introduced by the field plate structure increases, and the parasitic capacitance increases as the distance between the field plate structure and the gate decreases.

[0050] Figure 8 The diagram schematically illustrates a comparison of the electric field intensity distribution of curved field plate structures based on HEMT devices at different groove depths. For example... Figure 7 As shown, the groove depths D1, D2, and D3 are 0 nm, 80 nm, and 120 nm, respectively. With the increase of the groove etching depth, the gate foot electric field strength is further effectively reduced, and the suppression effect of the gate foot electric field strength varies at different distances. In addition, the edge electric field of the curved field plate structure increases with the increase of the groove etching depth. Considering the influence of both, the groove etching depth is preferably less than or equal to 80 nm.

[0051] In some embodiments of this disclosure, the curved field plate structure 10 is connected to the gate 9 via leads, or it may be without bias. The connection relationship is adjusted according to actual needs. Its fabrication and testing principles are the same as in Embodiment 3, and will not be repeated here. Connecting the curved field plate structure 10 with the source 7 or gate 9 via leads or without bias results in different effects on suppressing the gate electric field strength and the magnitude of the introduced parasitic capacitance. Simulation calculations show that connecting the curved field plate structure 10 to the gate 9 via leads is more effective in suppressing the gate electric field strength than connecting it to the source 7, but the introduced parasitic capacitance is relatively larger. Without bias, the effect on suppressing the gate electric field strength is less effective, and the introduced parasitic capacitance is smaller than when bias is added. Therefore, in practical applications, the placement of the curved field plate structure 10 and the addition of bias can be adjusted according to actual needs.

[0052] Example 4

[0053] Figure 9 A flowchart illustrating a method for fabricating a curved field plate structure based on a HEMT device according to an embodiment of the present disclosure is shown.

[0054] like Figure 9 As shown, the fabrication method includes: S1, forming a source, a gate, and a drain by evaporating metal in sequence, with the gate located between the source and the drain; S2, forming a curved field plate structure between the gate and the drain by evaporating metal, with the curved surface perpendicular to the device growth direction.

[0055] In this embodiment, the gate is formed by stacking nickel and gold layers, the source and drain are formed by stacking titanium, aluminum, nickel, and gold layers, and the field plate is formed by stacking nickel and gold layers. The distance between the source and drain is 2.4 μm, the distance between the source and gate is 0.8 μm, and the distance between the gate and drain is 1.4 μm, forming a T-shape. The gate has a vertical width of 0.2 μm, a height of 450 nm, a horizontal width of 0.6 μm, a distance of 0.3 μm between the gate metal and the curved field plate, a curved width of 0.2 μm, a height of 300 nm, and a bending angle of 180°.

[0056] S1 includes: S11, growing a first semiconductor layer and a second semiconductor layer sequentially on a substrate; S12, forming a source, a gate, and a drain on the second semiconductor layer by evaporating metal, with the gate located between the source and the drain. The bandgap width of the material of the second semiconductor layer is greater than the bandgap width of the material of the first semiconductor layer, and it forms a heterojunction with the first semiconductor layer.

[0057] In some embodiments of this disclosure, S1 further includes: sequentially growing a nucleation layer, an insertion layer, and a cap layer on a substrate; the nucleation layer is grown between the substrate and the first semiconductor layer to improve the nucleation quality of the first semiconductor layer 3; the insertion layer is grown between the first semiconductor layer and the second semiconductor layer to improve the thresholding capability of the high-density two-dimensional electron gas (2-DEG); and the cap layer is grown on the second semiconductor layer to protect the interface of the second semiconductor layer 5.

[0058] Those skilled in the art will understand that the features described in the various embodiments and / or claims of this disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure can be combined and / or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0059] Although this disclosure has been shown and described with reference to specific exemplary embodiments thereof, those skilled in the art will understand that various changes in form and detail may be made to this disclosure without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents. Therefore, the scope of this disclosure should not be limited to the above embodiments, but should be defined not only by the appended claims, but also by their equivalents.

Claims

1. A curved field plate structure based on a HEMT device, comprising a gate, a source, and a drain, wherein the gate is located between the source and the drain, characterized in that, A curved field plate structure is formed between the gate and the drain. The curved field plate structure extends in a direction parallel to the source and the drain. The curved surface of the curved field plate structure is perpendicular to the device growth direction. A passivation layer is grown between the source and the drain, and the curved field plate structure is formed on the passivation layer; The passivation layer includes a groove, the curved field plate structure is formed in the groove, and the height of the curved field plate structure is greater than the depth of the groove; The curved field plate structure is composed of multiple continuous curved field plates, forming an S-shaped structure; The width of the curved surface of the curved field plate structure is less than half the distance between the gate and the drain. The curved surface width of the curved field plate structure is 0.

2. m ~0.4 m, with a surface angle of 1° to 180°; The passivation layer has a thickness of 120 nm and a groove depth of 0~80 nm.

2. The curved field plate structure based on HEMT devices according to claim 1, characterized in that, The curved field plate structure is connected to the source or the gate via leads or without bias.

3. A method for fabricating a curved field plate structure based on a HEMT device, used to fabricate the curved field plate structure based on a HEMT device as described in claim 1 or 2, characterized in that, include: S1, a source, a gate, and a drain are formed sequentially by evaporating metal, with the gate located between the source and the drain; S2, a curved field plate structure is formed between the gate and the drain by evaporating metal, and the curved surface is perpendicular to the device growth direction.

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