Preparation method of multi-channel Fin HEMT device with three-dimensional T-shaped gate

Abstract

The invention discloses a preparation method of a multi-channel Fin HEMT device with a three-dimensional T-shaped gate, relates to the technical field of semiconductors, and develops a T-shaped gate overall process scheme suitable for a high-depth side wall structure of a multi-channel radio frequency device aiming at the high-depth side wall structure of the multi-channel radio frequency device. An I-type gate is innovatively manufactured firstly to form good side wall contact, and then a three-step process of a conventional T-type gate, namely passivation layer deposition, gate groove etching and gate metal preparation, is completed on the I-type gate, so that the process difficulty of the three-dimensional T-type gate is reduced. The method provided by the invention solves the problem of poor contact between the gate metal and the Fin side wall caused by incomplete etching in the preparation process of the T-shaped gate of the multi-channel Fin HEMT device, and realizes effective gate control of the gate on the whole device, thereby really realizing the multi-channel radio frequency device with the three-dimensional T-shaped gate structure.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and particularly relates to a preparation method of a multi-channel Fin HEMT device with a three-dimensional T-shaped gate. Background Art

[0002] With the development of semiconductor technology, radio frequency transistors made of heterojunction materials (such as GaN, GaAs) are widely used in circuit modules and devices of radio frequency systems. Compared with traditional single-channel radio frequency transistors, multi-heterojunction materials form multiple two-dimensional electron gas channels through the stacking of several heterojunctions, and have a higher two-dimensional electron gas density. Therefore, multi-channel devices can adapt to higher power requirements compared with single-channel devices; at the same time, multi-channel devices have lower switching losses, can improve the efficiency of the devices, and thus can improve the linearity and efficiency of the entire radio frequency system and reduce power consumption.

[0003] As the requirement for the operating frequency of devices is getting higher and higher, an effective way to increase the cut-off frequency f T is to reduce the gate length. However, reducing the gate length will increase the gate resistance, cause a decrease in the device gain, and inhibit the f max of the device, and will also cause a decrease in the power gain of the device. Therefore, high-frequency and high-performance devices usually adopt the T-shaped gate process. The T-shaped gate refers to a T-shaped gate electrode with a mushroom-shaped cross-section. The smaller gate foot ensures that the device can operate under high-frequency conditions, and the larger gate cap width can increase the gate cross-sectional area, effectively reduce the gate resistance, and improve the power gain of the device.

[0004] Therefore, the T-shaped gate process manufacturing flow of passivation layer deposition, gate trench etching, and gate metal fabrication has been widely used in the fabrication of high-performance radio frequency devices. However, for multi-channel materials (such as AlGaN / GaN), due to the existence of multiple parallel 2DEG (two-dimensional electron gas) conductive channels, in order to obtain good gate control ability, the gate needs to be etched into a three-dimensional Fin array shape first and then the gate metal is fabricated, so that the gate metal wraps the top and two sides of the channels, thereby achieving effective control of multiple conductive channels. The groove depth in the Fin array is usually relatively deep. At this time, if the above-mentioned conventional T-shaped gate process is continued, during the gate trench etching process, due to the existence of non-ideal factors such as etching load effect, the passivation layer at the bottom of the groove cannot be completely removed, resulting in the inability of the gate metal fabricated in the next step to achieve good contact with the channel surface, as Figure 2 shown, and further resulting in the inability of the device to obtain effective gate control ability.

[0005] Based on this, for multi-channel materials, due to the particularity of their material structures, the T-gate process of conventional RF devices is not well applicable. In the existing reported technologies, there is no solution to implement the T-gate process on devices with relatively deep Fin sidewalls. A superlattice field-effect transistor (SLCFET) proposed by a company in the United States has achieved a T-gate on a 6-channel AlGaN / GaN. The SLCFET device is compatible with the existing conventional T-gate process by reducing the thickness of a single heterojunction channel, but reducing the thickness of the heterojunction will directly lead to a deterioration in the breakdown voltage characteristics of the device and a decrease in the breakdown voltage, making it inapplicable to high-voltage application scenarios with high microwave power. Summary of the Invention

[0006] To solve the above problems existing in the prior art, the present invention provides a method for fabricating a multi-channel Fin HEMT device with a three-dimensional T-gate. The technical problems to be solved by the present invention are achieved through the following technical solutions:

[0007] The present invention provides a method for fabricating a multi-channel Fin HEMT device with a three-dimensional T-gate, including:

[0008] Step 1: Prepare a substrate layer, a buffer layer, and a multi-channel heterojunction stacked from bottom to top;

[0009] Step 2: Prepare ohmic metal electrodes on both sides of the multi-channel heterojunction to form a source electrode and a drain electrode;

[0010] Step 3: Etch the multi-channel heterojunction to form a Fin structure;

[0011] Step 4: Prepare a first layer of gate metal on the top and two side surfaces of the Fin structure to form a three-dimensional I-gate that wraps the top and two side surfaces of the multi-channel heterojunction;

[0012] Step 5: Prepare a passivation layer on the surface of the device, and etch the passivation layer on the upper surfaces of the source electrode and the drain electrode and the three-dimensional I-gate region;

[0013] Step 6: Prepare a second layer of gate metal on the surface of the three-dimensional I-gate to form a gate cap, and the gate cap and the three-dimensional I-gate form a three-dimensional T-gate.

[0014] In an embodiment of the present invention, the substrate layer is a Si substrate, a sapphire substrate, or a SiC substrate; the buffer layer is a GaN buffer layer; the multi-channel heterojunction is a multi-channel AlGaN / GaN heterojunction, a multi-channel AlN / GaN heterojunction, or a multi-channel InGaN / GaN heterojunction.

[0015] In one embodiment of the present invention, step 2 includes: etching the multi-channel heterojunctions on both sides of the device, forming an ohmic region on the buffer layer, preparing an ohmic metal electrode in contact with the multi-channel heterojunction in the ohmic region, and forming a source electrode and a drain electrode.

[0016] In one embodiment of the present invention, step 3 includes: defining the Fin region by electron beam lithography, and etching to form a Fin structure through an etching process.

[0017] In one embodiment of the present invention, after forming the Fin structure, it further includes: preparing a gate dielectric layer on the device surface.

[0018] In one embodiment of the present invention, the material of the gate dielectric layer is Al2O3 or SiN.

[0019] In one embodiment of the present invention, the material of the passivation layer is SiN.

[0020] In one embodiment of the present invention, both the first layer of gate metal and the second layer of gate metal are Ni / Au / Ti laminated metals.

[0021] In one embodiment of the present invention, the width of the second layer of gate metal exceeds the width of the first layer of gate metal.

[0022] The present invention provides a multi-channel Fin HEMT device with a three-dimensional T-shaped gate, which is prepared by using the preparation method described in any one of the above embodiments.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. The preparation method of the multi-channel Fin HEMT device with a three-dimensional T-shaped gate according to the present invention develops a T-shaped gate overall process scheme suitable for the high-depth sidewall structure of multi-channel radio frequency devices. It innovatively first makes an I-shaped gate to form good sidewall contact, and then completes the three-step process of a conventional T-shaped gate on the I-shaped gate, namely passivation layer deposition, gate trench etching, and gate metal preparation, reducing the process difficulty of the three-dimensional T-shaped gate. The method of the present invention solves the problem of poor contact between the gate metal and the Fin sidewall due to incomplete etching during the preparation of the T-shaped gate of the multi-channel Fin HEMT device, realizes effective gate control of the entire device by the gate, and thus truly realizes a multi-channel radio frequency device with a three-dimensional T-shaped gate structure.

[0025] 2. The preparation method of the multi-channel Fin HEMT device with a three-dimensional T-shaped gate according to the present invention, compared with the existing method of reducing the heterojunction thickness, can be compatible with multi-channel materials of different thicknesses and different numbers of heterojunctions, and the finally realized device has better breakdown characteristics.

[0026] The above description is only an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of the present invention more obvious and understandable, the following preferred embodiments are specifically given and described in detail in conjunction with the accompanying drawings. Description of the Drawings

[0027] Figure 1 is a flowchart of a method for fabricating a multi-channel Fin HEMT device with a three-dimensional T-shaped gate according to an embodiment of the present invention;

[0028] Figure 2 is a schematic diagram of problems existing in the existing fabrication process according to an embodiment of the present invention;

[0029] Figures 3 - 11 The figure is a process flowchart of a method for fabricating a multi-channel Fin HEMT device with a three-dimensional T-shaped gate according to an embodiment of the present invention.

[0030] Figure 12 is a schematic diagram of a multi-channel Fin HEMT device with a three-dimensional T-shaped gate according to an embodiment of the present invention. Detailed Description of the Embodiment

[0031] In order to further elaborate on the technical means and effects adopted by the present invention to achieve the intended invention purpose, the following provides a detailed description of a method for fabricating a multi-channel Fin HEMT device with a three-dimensional T-shaped gate according to the present invention in conjunction with the accompanying drawings and specific embodiments.

[0032] The foregoing and other technical contents, features and effects of the present invention will be clearly presented in the following detailed description in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and specific understanding of the technical means and effects adopted by the present invention to achieve the intended purpose can be obtained. However, the accompanying drawings are only for reference and illustration, and are not used to limit the technical solution of the present invention.

[0033] First, an embodiment of the present invention provides a method for fabricating a multi-channel Fin HEMT device with a three-dimensional T-shaped gate. Please refer to Figure 1 , Figure 1 is a flowchart of a method for fabricating a multi-channel Fin HEMT device with a three-dimensional T-shaped gate according to an embodiment of the present invention. As Figure 1 shown, the method for fabricating a multi-channel Fin HEMT device with a three-dimensional T-shaped gate in this embodiment includes the following steps:

[0034] Step 1: Prepare a substrate layer, a buffer layer, and a multi-channel heterojunction stacked from bottom to top.

[0035] Optionally, the substrate layer is a Si substrate, a sapphire substrate or a SiC substrate; the buffer layer is a GaN buffer layer; the multi-channel heterojunction is a multi-channel AlGaN / GaN heterojunction, a multi-channel AlN / GaN heterojunction or a multi-channel InGaN / GaN heterojunction.

[0036] It can be understood that regarding the material selection of the substrate layer, the buffer layer and the multi-channel heterojunction, other common materials in the semiconductor field can be used, which are not limited herein. The thickness of a single heterojunction in the multi-channel heterojunction is a conventional thickness, for example, it can be 55 nm.

[0037] Step 2: Prepare ohmic metal electrodes on both sides of the multi-channel heterojunction to form a source electrode and a drain electrode.

[0038] In this embodiment, Step 2 includes: etching the multi-channel heterojunction on both sides of the device to form an ohmic region on the buffer layer, and preparing an ohmic metal electrode in contact with the multi-channel heterojunction in the ohmic region to form a source electrode and a drain electrode.

[0039] Specifically, the multi-channel heterojunction can be etched to form a source-drain ohmic region etching that enters the device interior, and the etching depth is greater than the total thickness of all heterojunctions, so that the ohmic metal electrodes fabricated subsequently can contact all two-dimensional electron gas channels. The source-drain ohmic metal electrodes can be prepared by evaporation or sputtering processes, and the material of the metal electrodes can be a Ti / Al / Ni / Au stacked metal.

[0040] It can be understood that when simultaneously fabricating multiple multi-channel Fin HEMT devices with three-dimensional T-shaped gates, after the source electrodes and drain electrodes are fabricated, device isolation needs to be performed through ion implantation or etching processes.

[0041] Step 3: Etch the multi-channel heterojunction to form a Fin structure.

[0042] In this embodiment, the Fin region is defined by electron beam lithography, and the Fin structure is etched through an etching process.

[0043] Step 4: Prepare a first layer of gate metal on the top and two side surfaces of the Fin structure to form a three-dimensional I-shaped gate that wraps the top and two side surfaces of the multi-channel heterojunction.

[0044] Optionally, the material of the first layer of gate metal can be a Ni / Au / Ti stacked metal. The three-dimensional I-shaped gate is in direct contact with the top and two side surfaces of the Fin structure, without a passivation layer material, and the contact between the two is good, enabling the device to have effective gate control.

[0045] Step 5: Prepare a passivation layer on the device surface, and etch the passivation layer on the upper surfaces of the source electrode and the drain electrode and the three-dimensional I-shaped gate region.

[0046] Optionally, a passivation layer can be deposited on the device surface by using the PECVD (Plasma Enhanced Chemical Vapor Deposition) process. The material of the passivation layer is SiN, and the thickness can be 60 nm.

[0047] It can be understood that during the etching process of the passivation layer of the three-dimensional type-I gate region, the passivation layer on the surface of the three-dimensional type-I gate at the top of the Fin structure can be etched completely to form a good contact window. For the passivation layer on the surface of the three-dimensional type-I gate on the sidewall part of the Fin structure, due to non-ideal factors such as etching load effect, the etching may not be complete, and there will be residual unetched passivation layer in the part of the three-dimensional type-I gate close to the buffer layer.

[0048] Step 6: Prepare the second layer of gate metal on the surface of the three-dimensional type-I gate to form a gate cap, and the gate cap and the three-dimensional type-I gate form a three-dimensional T-shaped gate.

[0049] Optionally, the second layer of gate metal is a Ni / Au / Ti stacked metal, and the width of the second layer of gate metal exceeds the width of the first layer of gate metal.

[0050] In this embodiment, an evaporation process can be used to evaporate a larger metal layer on the surface of the three-dimensional type-I gate to ensure good contact between this metal layer and the metal of the three-dimensional type-I gate at the top and the upper part of the sidewall of the Fin structure, thereby forming a three-dimensional T-shaped gate.

[0051] In an optional embodiment, after forming the Fin structure, it further includes: preparing a gate dielectric layer on the device surface, and then performing subsequent preparation of the three-dimensional type-I gate and the gate cap on the Fin structure with the gate dielectric layer. It should be noted that when etching the passivation layer on the upper surface of the source and drain, the gate dielectric layer on its upper surface is etched and removed at the same time.

[0052] Optionally, the material of the gate dielectric layer can be Al2O3 or SiN, the thickness can be 5 nm, and the ALD (Atomic Layer Deposition) process can be used to prepare the gate dielectric layer.

[0053] Further, please refer to Figures 3 - 11 , Figures 3 - 11 The figure is a process flow chart of the preparation method of the multi-channel Fin HEMT device with a three-dimensional T-shaped gate provided by the embodiment of the present invention. Combining Figures 3 - 11 The preparation method of the multi-channel Fin HEMT device with a three-dimensional T-shaped gate of the present invention will be described in detail through specific embodiments.

[0054] In this embodiment, the substrate layer is a Si substrate, the buffer layer is a GaN buffer layer, and the multi-channel heterojunction is a 5-channel AlN / GaN heterojunction. Among them, the thickness of the AlN layer is 5 nm, and the thickness of the GaN layer is 50 nm. The preparation process of the multi-channel Fin HEMT device with a three-dimensional T-shaped gate specifically includes the following steps:

[0055] Step a: Prepare a Si substrate, a GaN buffer layer, and a 5-channel AlN / GaN heterojunction stacked from bottom to top. Then, etch the 5-channel AlN / GaN heterojunction into the device interior, and the etching depth is greater than the total thickness of all heterojunctions to form a source-drain ohmic contact region, so as to prepare an ohmic metal electrode in contact with all two-dimensional electron gas channels subsequently, as Figure 3 shown;

[0056] Step b: Use the evaporation process to prepare a Ti / Al / Ni / Au stacked metal in the source-drain ohmic contact region to form a source electrode and a drain electrode, as Figure 4 shown;

[0057] Step c: Use the etching process to isolate the active regions between devices, as Figure 5 shown;

[0058] Step d: Use electron beam lithography to define the Fin region of the device, and combine the etching process to etch the multi-channel heterojunction to form a Fin structure, as Figure 6 shown;

[0059] Step e: Use the ALD process to deposit a 5-nm SiN layer on the device surface to form a gate dielectric layer, as Figure 7 shown;

[0060] Step f: Use the evaporation process to deposit a Ni / Au / Ti stacked metal on the top and two side surfaces of the Fin structure with a gate dielectric layer to form a three-dimensional I-shaped gate that wraps the top and two side surfaces of the 5-channel AlN / GaN heterojunction, as Figure 8 shown;

[0061] Step g: Use the PECVD process to deposit a 60-nm SiN layer on the device surface to form a passivation layer, as Figure 9 shown;

[0062] Step h: Etch the passivation layer on the upper surfaces of the source electrode and the drain electrode, the gate dielectric layer, and the passivation layer in the three-dimensional I-shaped gate region.

[0063] It can be understood that the passivation layer on the surface of the three-dimensional I-shaped gate on the top of the Fin structure can be etched completely to form a good contact window. For the passivation layer on the surface of the three-dimensional I-shaped gate on the side wall part of the Fin structure, due to non-ideal factors such as etching load effect, the etching may not be complete, and there will be a residual unetched passivation layer near the buffer layer, asFigure 10 as shown

[0064] Step i: Use an evaporation process to prepare a Ni / Au / Ti stacked metal on the surface of the three-dimensional I-shaped gate and the surface of the passivation layer with incomplete etching to form a gate cap. The gate cap and the three-dimensional I-shaped gate form a three-dimensional T-shaped gate, as Figure 11 shown

[0065] The preparation method of the multi-channel Fin HEMT device with a three-dimensional T-shaped gate according to the present invention develops an overall process plan for the T-shaped gate suitable for the high-depth sidewall structure of the multi-channel radio frequency device. Innovatively, the I-shaped gate is first fabricated to form good sidewall contact, and then the three-step process of the conventional T-shaped gate, namely passivation layer deposition, gate groove etching, and gate metal preparation, is completed on the I-shaped gate, reducing the process difficulty of the three-dimensional T-shaped gate. The method of the present invention solves the problem of poor contact between the gate metal and the Fin sidewall due to incomplete etching during the preparation of the T-shaped gate of the multi-channel Fin HEMT device, realizes effective gate control of the entire device by the gate, and thus truly realizes a multi-channel radio frequency device with a three-dimensional T-shaped gate structure. Compared with the existing method of reducing the heterojunction thickness, the T-shaped gate can be realized on the multi-channel device without sacrificing the carrier density and material growth quality, and can be compatible with multi-channel materials of different thicknesses and different numbers of heterojunctions. The finally realized device has a higher current output level, smaller leakage, and better breakdown characteristics.

[0066] In a second aspect, an embodiment of the present invention provides a multi-channel Fin HEMT device with a three-dimensional T-shaped gate. Please refer to Figure 12 , Figure 12 which is a schematic diagram of the multi-channel Fin HEMT device with a three-dimensional T-shaped gate provided by an embodiment of the present invention. As Figure 12 shown, the device of this embodiment includes: a substrate layer, a buffer layer, a multi-channel heterojunction, a passivation layer, a source electrode, a drain electrode, and a three-dimensional T-shaped gate. Among them, the source-drain metal penetrates deep into the device and contacts all the heterojunction channels. The multi-channel Fin HEMT device with a three-dimensional T-shaped gate of this embodiment is prepared by the preparation method of the multi-channel Fin HEMT device with a three-dimensional T-shaped gate provided in the first aspect.

[0067] For the specific content and corresponding beneficial effects of the multi-channel Fin HEMT device with a three-dimensional T-shaped gate, please refer to the relevant content of the preparation method of the multi-channel Fin HEMT device with a three-dimensional T-shaped gate provided in the first aspect, and details are not described herein.

[0068] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant are intended to cover non-exclusive inclusion, so that an article or device comprising a series of elements not only includes those elements, but also includes other elements not explicitly listed. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the article or device comprising said element. Words such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The orientation or positional relationship indicated by "upper", "lower", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation on the present invention.

[0069] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification.

[0070] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A preparation method of a multi-channel Fin HEMT device with a three-dimensional T-shaped gate, characterized in that Including: Step 1: Prepare a substrate layer, a buffer layer, and a multi-channel heterojunction stacked from bottom to top; Step 2: Prepare ohmic metal electrodes on both sides of the multi-channel heterojunction to form a source electrode and a drain electrode; Step 3: Etch the multi-channel heterojunction to form a Fin structure; Step 4: Prepare a first-layer gate metal on the top and two side surfaces of the Fin structure to form a three-dimensional type-I gate that wraps the top and two side surfaces of the multi-channel heterojunction; Step 5: Prepare a passivation layer on the device surface, and etch the passivation layer on the upper surfaces of the source electrode and the drain electrode and the three-dimensional type-I gate region; Step 6: Prepare a second-layer gate metal on the surface of the three-dimensional type-I gate to form a gate cap, and the gate cap and the three-dimensional type-I gate form a three-dimensional type-T gate.

2. The manufacturing method of the multi-channel Fin HEMT device with a three-dimensional T-shaped gate according to claim 1, characterized in that, The substrate layer is a Si substrate, a sapphire substrate, or a SiC substrate; the buffer layer is a GaN buffer layer; the multi-channel heterojunction is a multi-channel AlGaN / GaN heterojunction, a multi-channel AlN / GaN heterojunction, or a multi-channel InGaN / GaN heterojunction.

3. The manufacturing method of a multi-channel Fin HEMT device with a three-dimensional T-shaped gate according to claim 1, characterized in that, The step 2 includes: etching the multi-channel heterojunction on both sides of the device to form an ohmic region on the buffer layer, and preparing an ohmic metal electrode in contact with the multi-channel heterojunction in the ohmic region to form a source electrode and a drain electrode.

4. The manufacturing method of the multi-channel Fin HEMT device with a three-dimensional T-shaped gate according to claim 1, characterized in that, The step 3 includes: defining the Fin region by electron beam lithography and etching to form a Fin structure through an etching process.

5. The preparation method of the multi-channel Fin HEMT device with a three-dimensional T-shaped gate according to claim 1, characterized in that, After forming the Fin structure, it further includes: preparing a gate dielectric layer on the device surface.

6. The manufacturing method of the multi-channel Fin HEMT device with a three-dimensional T-shaped gate according to claim 5, characterized in that, The material of the gate dielectric layer is Al2O3 or SiN.

7. The preparation method of the multi-channel Fin HEMT device with a three-dimensional T-shaped gate according to claim 1, characterized in that, The material of the passivation layer is SiN.

8. The manufacturing method of the multi-channel Fin HEMT device with a three-dimensional T-shaped gate according to claim 1, characterized in that, Both the first-layer gate metal and the second-layer gate metal are Ni / Au / Ti laminated metals.

9. The preparation method of the multi-channel Fin HEMT device with a three-dimensional T-shaped gate according to claim 1, characterized in that, The width of the second-layer gate metal exceeds the width of the first-layer gate metal.

10. A multi-channel Fin HEMT device with a three-dimensional T-shaped gate, characterized in that, Prepared by using the preparation method according to any one of claims 1-9.

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