Novel metal-oxide-semiconductor field effect transistor (MOSFET) device with diamond structure and manufacturing method thereof

Abstract

The invention discloses a novel MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) device with a diamond structure and a manufacturing method thereof. The device comprises a diamond substrate and a diamond P-type doping layer on the surface of the diamond substrate, and the surface of the diamond P-type doping layer is subjected to hydrogen plasma treatment to form a hydrogen terminal layer; the source electrode and the drain electrode are arranged on the upper surface of the hydrogen terminal layer at intervals; the dielectric layer comprises a first sub-part located on the surface of the side, away from the diamond substrate, of the hydrogen terminal layer, and in the direction perpendicular to the plane where the diamond substrate is located, the orthographic projection of the first sub-part is located in a channel region between the source electrode and the drain electrode; the first sub-part comprises a plurality of bulge structures which are periodically arranged, and the plurality of bulge structures continuously extend along the channel direction to form a wavy interface; the grid electrode is located on the surface of the first sub-part away from the hydrogen terminal layer. The maximum transconductance of the diamond device can be improved under the condition that the output current is kept basically unchanged, and the breakdown field strength of the device is also improved due to the fact that the electric field distribution in the channel region is more uniform.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology, specifically relating to a novel diamond-structured MOSFET device and its fabrication method. Background Technology

[0002] Diamond is considered the ultimate semiconductor material, possessing excellent properties such as a wide bandgap, high breakdown electric field, high frequency response, and high temperature resistance. Single-crystal diamond reacts with hydrogen gas to form hydrogen terminals on its surface; this structure can achieve a polarization greater than 4500 cm⁻¹ at room temperature. 2 The electron mobility is / Vs, and it is as high as 1.5×10 7 Saturated electron velocities of cm / s are obtained, and up to 10 cm / s can be achieved. 12 -10 14 cm -2 The high two-dimensional hole gas density and bandgap of approximately 5.5 eV give diamond excellent breakdown resistance, with a maximum breakdown electric field strength reaching 10 MV / cm, approximately 3.3 times that of GaN and 33 times that of Si. In addition to its high breakdown electric field, diamond also boasts high thermal conductivity, reaching 2200 W / m·K, providing excellent heat dissipation. This demonstrates diamond's potential as an ideal material for fabricating high-temperature, high-pressure devices.

[0003] Although significant progress has been made in the research of diamond-based devices, the superiority of these devices has not been fully realized due to the insufficient quality of the obtained diamond materials. Because of the difficulty in preparing single-crystal diamond, diamond films are currently mainly obtained through homoepitaxial growth on single-crystal diamond substrates.

[0004] Table 1 Comparison of Semiconductor Material Properties

[0005] As can be seen from the semiconductor material characteristics described in Table 1, diamond is more suitable for high-frequency power devices. Diamond's Johnson quality factor (a measure of a semiconductor material's suitability for microwave power devices) is as high as approximately 3700, which is 4.7 times that of GaN. This indicates that diamond power devices offer higher power output and lower power loss than GaN power devices. Currently, the gate dielectric layer structure used in diamond MOSFET devices causes the electric field at the electrode edge to concentrate, which can lead to gate breakdown under high voltage conditions. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, this invention provides a novel diamond-structured MOSFET device and its fabrication method. The technical problem to be solved by this invention is achieved through the following technical solution: In a first aspect, the present invention provides a novel diamond-structured MOSFET device, comprising: Diamond substrate; A diamond P-type doped layer is located on one side surface of the diamond substrate, and the surface of the diamond P-type doped layer is treated with hydrogen plasma to form a hydrogen terminal layer. The source and drain electrodes are spaced apart on the surface of the hydrogen terminal layer away from the diamond substrate. The dielectric layer includes a first sub-section located on the surface of the hydrogen terminal layer away from the diamond substrate. In a direction perpendicular to the plane of the diamond substrate, the orthographic projection of the first sub-section is located in the channel region between the source and the drain. The first sub-section includes a plurality of periodically arranged protrusions that extend continuously along the channel direction to form a wavy interface. The gate is located on the surface of the first sub-section away from the hydrogen terminal layer.

[0007] In one embodiment of the present invention, the dielectric layer further includes a second sub-section and a third sub-section; wherein, The second sub-part covers the surface of the source electrode near the drain electrode and at least a portion of the upper surface of the source electrode, and the third sub-part covers the surface of the drain electrode near the source electrode and at least a portion of the upper surface of the drain electrode.

[0008] In one embodiment of the present invention, the material of the dielectric layer includes TiO2.

[0009] In one embodiment of the present invention, the thickness of the dielectric layer is 10 nm to 1 μm.

[0010] In one embodiment of the present invention, the source electrode and the drain electrode respectively form an ohmic contact with the hydrogen terminal layer.

[0011] In one embodiment of the invention, the cross-sectional shape of each protrusion structure is configured to disperse the gate electric field.

[0012] In one embodiment of the present invention, the cross-sectional shape of each protrusion structure is arc-shaped. In one embodiment of the present invention, the thickness of the diamond substrate is at least 1 μm, and the thickness of the diamond P-type doped layer is 100 nm to 500 nm.

[0013] In a second aspect, the present invention also provides a method for fabricating a novel diamond-structured MOSFET device, used to fabricate the novel diamond-structured MOSFET device described in the first aspect. The method includes: A diamond substrate is provided, and a diamond P-type doped layer is grown on the upper surface of the diamond substrate using a microwave plasma chemical vapor deposition (MPCVD) process. The surface of the diamond P-type doped layer is subjected to hydrogen plasma treatment to form a hydrogen terminal layer; A source electrode and a drain electrode are formed at intervals on the upper surface of the hydrogen terminal layer, and the source electrode and the drain electrode respectively form an ohmic contact with the hydrogen terminal layer. A Ti thin film is deposited on the surface of the hydrogen terminal layer, at least a portion of the surface of the drain electrode, and at least a portion of the surface of the source electrode, and then subjected to thermal oxidation to form a dielectric layer; wherein the Ti thin film located in the channel region is wavy and forms the first sub-section of the dielectric layer after thermal oxidation. A gate is formed on the upper surface of the first sub-section of the dielectric layer.

[0014] In one embodiment of the present invention, the step of performing hydrogen plasma treatment on the surface of the diamond P-type doped layer to form a hydrogen terminal layer includes: Hydrogen gas was introduced into the MPCVD reaction chamber at a flow rate of 700 sccm, the chamber pressure was maintained at 90 mBar, and a microwave power of 2000 W was applied. The lower surface of the diamond substrate with the P-type doped layer was exposed to hydrogen plasma for 30 min at a temperature of 700℃ to form a hydrogen terminal layer.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention provides a novel diamond structure MOSFET device and its fabrication method. In the MOSFET device, the dielectric layer includes a first sub-part located on the upper surface of the hydrogen terminal layer, and the first sub-part includes a plurality of periodically arranged protrusion structures. The plurality of protrusion structures extend continuously along the channel direction to form a wave-shaped interface. This structure can effectively improve the electric field strength inside the device, disperse the electric field distribution of the gate, and thus improve the breakdown voltage of the device.

[0016] (2) The MOSFET device formed by the fabrication method provided by the present invention can increase the maximum transconductance of the diamond device while keeping the output current basically unchanged. Moreover, because the electric field distribution in the channel region is more uniform, the breakdown field strength of the device is also improved. At the same time, combined with the original high breakdown voltage, high current density and excellent pinch-off characteristics of the diamond device, it is more suitable for high voltage high power electronic devices and radio frequency microwave power devices.

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a cross-sectional view of a novel diamond-structured MOSFET device provided in an embodiment of the present invention; Figure 2This is a flowchart of a method for fabricating a novel diamond-structured MOSFET device provided in an embodiment of the present invention. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0020] Figure 1 This is a cross-sectional view of a novel diamond-structured MOSFET device provided in an embodiment of the present invention. Figure 1 As shown, an embodiment of the present invention provides a novel diamond-structured MOSFET device, comprising: Diamond substrate 1; A diamond P-type doped layer 2 is located on one side of the surface of the diamond substrate 1. The surface of the diamond P-type doped layer 2 is treated with hydrogen plasma to form a hydrogen terminal layer. Source 3 and drain 4 are disposed at intervals on the surface of the hydrogen terminal layer away from the diamond substrate 1. The dielectric layer 5 includes a first sub-section 501 located on the surface of the hydrogen terminal layer away from the diamond substrate 1. In a direction perpendicular to the plane of the diamond substrate 1, the orthographic projection of the first sub-section 501 is located in the channel region between the source electrode 3 and the drain electrode 4. The first sub-section 501 includes a plurality of periodically arranged protrusion structures that extend continuously along the channel direction to form a wavy interface. Gate 6 is located on the surface of the first sub-section 501 on the side away from the hydrogen terminal layer.

[0021] In this embodiment, the MOSFET device includes a diamond substrate 1 and a diamond P-type doped layer 2 above it. The thickness of the diamond substrate 1 is at least 1 μm, and the thickness of the diamond P-type doped layer 2 is 100 nm to 500 nm. The surface of the diamond P-type doped layer 2 is treated with hydrogen plasma to form a hydrogen termination layer. In the hydrogen termination layer, due to the bending of the surface band, a high concentration of two-dimensional hole gas (2DHG) is spontaneously formed, thereby forming the channel region of the MOSFET device, which is beneficial for providing a high-mobility conductive channel. A source electrode 3 and a drain electrode 4 are spaced apart on the surface of the hydrogen termination layer, both of which form ohmic contacts with the hydrogen termination layer. The first sub-part 501 of the dielectric layer 5 covers the channel region between the source and drain electrodes 4. Figure 1 As can be seen, the first sub-part 501 has periodically arranged protrusions that extend continuously along the channel direction from the source 3 to the drain 4, forming a wavy cross-section. From the cross-section, the cross-sectional shape of each protrusion is configured to disperse the electric field of the gate 6. For example, the cross-sectional shape of each protrusion is arc-shaped.

[0022] Furthermore, the MOSFET device also includes a gate 6 located on the surface of the first sub-section 501 away from the substrate 1. The gate 6, together with the underlying dielectric layer 5 and the hydrogen termination layer, constitutes a MIS (metal-insulator-semiconductor) structure. The first sub-section 501 of the dielectric layer 5 can isolate the hydrogen termination layer from direct contact with the gate 6, reduce gate leakage current, and deplete two-dimensional cavitation gas. It should be understood that since electric field lines tend to be distributed along the normal direction of the dielectric surface, when the first sub-section 501 of the dielectric layer 5 has a wavy structure, the vertical electric field lines applied to the gate 6 will be deflected in the raised area. At the arc-shaped raised area, the electric field lines will diverge. The redistribution of electric field lines can effectively reduce the peak value of the local electric field intensity, so that the high electric field region originally concentrated at the edge of the gate 6 is extended to the surface of the entire raised structure. In other words, the periodically undulating wavy interface can disperse the electric field concentration below the gate 6, making the electric field distribution more uniform. Moreover, the arc-shaped cross-section avoids the electric field accumulation at the sharp corners, thereby increasing the effective gate area of ​​6 and improving the gate control capability without changing the device size. This is beneficial for the device to obtain the excellent characteristics of high breakdown voltage and low on-resistance at the same time.

[0023] Optionally, the dielectric layer 5 further extends to cover part of the sidewalls and upper surfaces of the source electrode 3 and the drain electrode 4. Specifically, the dielectric layer 5 further includes a second sub-part 502 and a third sub-part 503; wherein the second sub-part 502 covers the surface of the source electrode 3 near the drain electrode 4 and at least part of the upper surface of the source electrode 3, and the third sub-part 503 covers the surface of the drain electrode 4 near the source electrode 3 and at least part of the upper surface of the drain electrode 4. In this embodiment, by using the dielectric layer 5 to cover the electrode edges, the electric field concentration caused by the three-dimensional field plate effect can be effectively suppressed, the peak electric field intensity at the electrode terminal can be reduced, and the uniformity of the electric field distribution can be optimized; in addition, the dielectric layer 5 can also form a complete dielectric-metal interface with the electrode, reducing the interface state density.

[0024] In this embodiment, the material of the dielectric layer 5 includes TiO2, and the thickness is 10nm~1μm.

[0025] Figure 2 This is a flowchart illustrating a method for fabricating a novel diamond-structured MOSFET device according to an embodiment of the present invention. Figure 1-2 As shown, this embodiment of the invention also provides a method for fabricating a novel diamond-structured MOSFET device. The above methods include: S1. Provide a diamond substrate 1, and grow a diamond P-type doped layer 2 on the upper surface of the diamond substrate 1 using microwave plasma chemical vapor deposition (MPCVD) process.

[0026] In step S1, the diamond substrate 1, which has undergone HPHT (high temperature and high pressure) screening, is placed in the MPCVD reaction chamber for homoepitaxial growth, and a diamond P-type doped layer 2 is grown on the surface of the diamond substrate 1. During the growth process, a mixed gas of H2, CH4, and BH3 is used, with the proportion of CH4 being 3%~7%. Specifically, H2, CH4, and BH3 are introduced into the MPCVD chamber at flow rates of 700 sccm, 15 sccm, and 5 sccm, respectively, while maintaining a chamber pressure of 90 mBar. A microwave power of 2000 W is applied, and growth is carried out at 700°C for 10 minutes to form a diamond P-type doped layer 2 with a thickness of approximately 1 μm.

[0027] S2. The surface of the diamond P-type doped layer 2 is subjected to hydrogen plasma treatment to form a hydrogen terminal layer.

[0028] Specifically, hydrogen gas with a flow rate of 700 sccm is introduced into the MPCVD reaction chamber, the chamber pressure is maintained at 90 mBar, and a microwave power of 2000 W is applied. The lower surface of the diamond substrate 1 with the P-type doped layer 2 is exposed to hydrogen plasma for 30 min at a temperature of 700℃ to form a hydrogen terminal layer.

[0029] S3. A source electrode 3 and a drain electrode 4 are formed at intervals on the upper surface of the hydrogen terminal layer, and the source electrode 3 and the drain electrode 4 respectively form ohmic contacts with the hydrogen terminal layer.

[0030] In step S3, a 100 nm thick source / drain metal layer is deposited on the upper surface of the hydrogen termination layer using electron beam evaporation, forming an ohmic contact with the hydrogen termination layer. The source / drain metal layer can be Au. Next, a channel pattern is created on the upper surface of the sample using photolithography. Then, the sample is immersed in a KI / I2 solution for 35 seconds. The portion of the source / drain metal layer without photoresist protection is etched away, and the remaining source / drain metal layer serves as the source 3 and drain 4. Finally, the sample is annealed in air at 100°C for 1 hour.

[0031] S4. A Ti film is deposited on the upper surface of the hydrogen terminal layer, at least a portion of the surface of the drain electrode 4, and at least a portion of the surface of the source electrode 3, and a dielectric layer 5 is formed after thermal oxidation treatment; wherein the Ti film located in the channel region is wavy and forms the first sub-section 501 of the dielectric layer 5 after thermal oxidation treatment.

[0032] In this step, a Ti film with a thickness of 10 nm is deposited on the surface of the hydrogen terminal layer, at least a portion of the surface of the drain electrode 4, and at least a portion of the surface of the source electrode 3 by electron beam evaporation. The Ti film in the channel region on the surface of the hydrogen terminal layer is wavy. It is further oxidized in air at 120°C for 10 h to form a TiO2 dielectric layer 5.

[0033] S5. A gate 6 is formed on the upper surface of the first sub-section 501 of the dielectric layer 5.

[0034] A 100 nm thick metal, such as Al, is deposited on the sample using the E-beam process. Then, the gate pattern is formed on the upper surface of the sample using photolithography, and the gate 6 is formed after etching. As can be seen from the above embodiments, the beneficial effects of the present invention are as follows: (1) The present invention provides a novel diamond structure MOSFET device and its fabrication method. In the MOSFET device, the dielectric layer includes a first sub-part located on the upper surface of the hydrogen terminal layer, and the first sub-part includes a plurality of periodically arranged protrusion structures. The plurality of protrusion structures extend continuously along the channel direction to form a wave-shaped interface. This structure can effectively improve the electric field strength inside the device, disperse the electric field distribution of the gate, and thus improve the breakdown voltage of the device.

[0035] (2) The MOSFET device formed by the fabrication method provided by the present invention can increase the maximum transconductance of the diamond device while keeping the output current basically unchanged. Moreover, because the electric field distribution in the channel region is more uniform, the breakdown field strength of the device is also improved. At the same time, combined with the original high breakdown voltage, high current density and excellent pinch-off characteristics of the diamond device, it is more suitable for high voltage high power electronic devices and radio frequency microwave power devices.

[0036] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0037] The use of terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples" indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0038] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A novel diamond-structured MOSFET device, characterized in that, include: Diamond substrate; A diamond P-type doped layer is located on one side surface of the diamond substrate, and the surface of the diamond P-type doped layer is treated with hydrogen plasma to form a hydrogen terminal layer. The source and drain electrodes are spaced apart on the surface of the hydrogen terminal layer away from the diamond substrate. The dielectric layer includes a first sub-section located on the surface of the hydrogen terminal layer away from the diamond substrate. In a direction perpendicular to the plane of the diamond substrate, the orthographic projection of the first sub-section is located in the channel region between the source and the drain. The first sub-section includes a plurality of periodically arranged protrusions that extend continuously along the channel direction to form a wavy interface. The gate is located on the surface of the first sub-section away from the hydrogen terminal layer.

2. The novel diamond-structured MOSFET device according to claim 1, characterized in that, The dielectric layer further includes a second sub-section and a third sub-section; wherein... The second sub-part covers the surface of the source electrode near the drain electrode and at least a portion of the upper surface of the source electrode, and the third sub-part covers the surface of the drain electrode near the source electrode and at least a portion of the upper surface of the drain electrode.

3. The novel diamond-structured MOSFET device according to claim 2, characterized in that, The material of the dielectric layer includes TiO2.

4. The novel diamond-structured MOSFET device according to claim 3, characterized in that, The thickness of the dielectric layer is 10 nm to 1 μm.

5. The novel diamond-structured MOSFET device according to claim 2, characterized in that, The source and the drain respectively form ohmic contacts with the hydrogen terminal layer.

6. The novel diamond-structured MOSFET device according to claim 1, characterized in that, The cross-sectional shape of each protrusion is configured to disperse the gate electric field.

7. The novel diamond-structured MOSFET device according to claim 6, characterized in that, The cross-sectional shape of each protrusion is arc-shaped.

8. The novel diamond-structured MOSFET device according to claim 1, characterized in that, The thickness of the diamond substrate is at least 1 μm, and the thickness of the diamond P-type doped layer is 100 nm to 500 nm.

9. A method for fabricating a novel diamond-structured MOSFET device, characterized in that, Used to fabricate MOSFET devices with the novel diamond structure as described in any one of claims 1 to 8; The method includes: A diamond substrate is provided, and a diamond P-type doped layer is grown on the upper surface of the diamond substrate using a microwave plasma chemical vapor deposition (MPCVD) process. The surface of the diamond P-type doped layer is subjected to hydrogen plasma treatment to form a hydrogen terminal layer; A source electrode and a drain electrode are formed at intervals on the upper surface of the hydrogen terminal layer, and the source electrode and the drain electrode respectively form an ohmic contact with the hydrogen terminal layer. A Ti thin film is deposited on the surface of the hydrogen terminal layer, at least a portion of the surface of the drain electrode, and at least a portion of the surface of the source electrode, and then subjected to thermal oxidation to form a dielectric layer; wherein the Ti thin film located in the channel region is wavy and forms the first sub-section of the dielectric layer after thermal oxidation. A gate is formed on the upper surface of the first sub-section of the dielectric layer.

10. The method for fabricating a novel diamond-structured MOSFET device according to claim 9, characterized in that, The step of performing hydrogen plasma treatment on the surface of the diamond P-type doped layer to form a hydrogen terminal layer includes: Hydrogen gas was introduced into the MPCVD reaction chamber at a flow rate of 700 sccm, the chamber pressure was maintained at 90 mBar, and a microwave power of 2000 W was applied. The lower surface of the diamond substrate with the P-type doped layer was exposed to hydrogen plasma for 30 min at a temperature of 700℃ to form a hydrogen terminal layer.

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