A nonplanar GaN HEMT lateral power device

Abstract

The application belongs to the field of power semiconductors, and relates to a GaN HEMT (High Electron Mobility Transistor) lateral power device, and particularly provides a non-planar GaN HEMT lateral power device. The application can effectively overcome the design difficulty of the non-planar GaN HEMT lateral power device through structural innovation. Specifically, a V-shaped groove is formed on a silicon (100) crystal surface, a silicon (001) crystal surface or a silicon (010) crystal surface along a [110] direction through a mature silicon etching technology, an included angle between side walls (111) of the V-shaped groove is 70.52°, then polar epitaxial growth of GaN and an AlGaN barrier layer are performed on the side walls (111), a non-planar device structure is formed, a 2DEG channel is curved from a source electrode to a drain electrode, the 2DEG channel is significantly increased under the condition of the same device area, finally, a Baliga figure of merit of the device is significantly increased, a performance limit is broken through, and further reliability is improved.

Description

Technical Field

[0001] This invention belongs to the field of power semiconductors and relates to gallium nitride (GaN) materials, which can be used to optimize GaN HEMT (High Electron Mobility Transistor) lateral power devices. Specifically, it provides a structure and fabrication method for a non-planar GaN HEMT lateral power device. Background Technology

[0002] GaN is a wide-bandgap semiconductor material with high breakdown strength, high saturated electron mobility, and high thermal conductivity, and is considered one of the most promising semiconductor materials after silicon. HEMT lateral power devices based on GaN exhibit an order-of-magnitude improvement in Baliga figure of merit (defined as the square of the breakdown voltage divided by the product of the on-resistance and the device area) compared to silicon devices, reflecting a significant increase in the limits of device performance. Therefore, GaN has become an ideal choice for high-speed, integrable power switches.

[0003] The superiority of GaN HEMT lateral power devices lies primarily in their high-density, high-mobility two-dimensional electron gas (2DEG). The 2DEG is generated by the GaN / AlGaN heterojunction on the device surface through polarization effects. Ignoring gate edge electric field concentration and other non-ideal factors affecting reliability, the length of the 2DEG channel significantly impacts the device's breakdown voltage and on-resistance. Existing GaN HEMT lateral power devices are all planar structures, such as... Figure 11 As shown, this means that doubling the length of the 2DEG channel theoretically doubles the device's breakdown voltage, on-resistance, and area. Therefore, the overall Baliga figure of merit remains unchanged, and the device's performance limit is not improved. However, if the GaN HEMT lateral power device is modified to a non-planar structure—that is, the 2DEG path is not a direct path from the source to the drain but rather a zigzag path—then, with the same device area, the 2DEG channel length will increase. Even though this still leads to a proportional increase in breakdown voltage and on-resistance, the Baliga figure of merit for the non-planar structure will increase because the device area remains constant.

[0004] However, the structural concept and fabrication method of nonplanar GaN HEMT lateral power devices have not been reported to date. This is because, compared to nonplanar silicon devices, nonplanar GaN HEMT lateral power devices are more difficult to realize. The main difficulties are as follows:

[0005] 1) GaN materials are not easy to etch compared to silicon materials. GaN has stable physical and chemical properties, making it difficult to obtain satisfactory etching rates and good controllability using wet etching. Only dry etching techniques such as RIE, ECR, ICR, and IBE can be used. Currently, these techniques are generally only used to etch the isolation region or active region of GaN HEMT devices.

[0006] 2) The etching process inevitably causes damage to the GaN surface, resulting in various defective microstructures at the GaN / AlGaN heterojunction interface, which exacerbates the reliability problems of this type of device.

[0007] 3) GaN has a hexagonal wurtzite crystal structure, in which only the c-plane perpendicular to the polar axis is a polar plane, which can form a high-density 2DEG in the device. Therefore, even if GaN is etched with good uniformity and repeatability using a certain technique, the surface crystal plane of the obtained non-planar GaN cannot be perpendicular to the polar axis everywhere. That is, the c-plane of GaN cannot be exposed everywhere on the surface, and a continuous high-density 2DEG channel cannot be formed in the device. Summary of the Invention

[0008] The purpose of this invention is to provide a non-planar GaN HEMT lateral power device that effectively overcomes the design and fabrication difficulties of the aforementioned non-planar GaN HEMT lateral power devices through structural innovation, thereby significantly increasing the device's Baliga figure of merit, further breaking through performance limits, and improving reliability.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A nonplanar GaN HEMT lateral power device, characterized in that it comprises:

[0011] A silicon substrate, wherein a V-shaped groove with an included angle of 70.52° is etched along the

[110] crystal direction on a silicon (100) crystal plane, a silicon (001) crystal plane or a silicon (010) crystal plane, and the groove wall of the V-shaped groove is a silicon (111) crystal plane;

[0012] A transition layer is provided along the wall of the V-shaped groove, and a buffer layer, a channel layer, and a barrier layer are sequentially stacked on the transition layer. The transition layer, buffer layer, channel layer, and barrier layer are all V-shaped with an included angle of 70.52°.

[0013] A passivation layer is set on the barrier layer;

[0014] The device includes a metal source, a metal drain, and a gate control terminal, all of which are located on the wall of the V-shaped groove. The metal source and the metal drain are located on the two side walls of the V-shaped groove, and the metal source and the gate control terminal are located on the same side wall of the V-shaped groove.

[0015] Another nonplanar GaN HEMT lateral power device, characterized in that it comprises:

[0016] A silicon substrate, wherein a V-shaped groove with an included angle of 70.52° is etched along the

[110] crystal direction on a silicon (100) crystal plane, a silicon (001) crystal plane or a silicon (010) crystal plane, and the groove wall of the V-shaped groove is a silicon (111) crystal plane;

[0017] A transition layer is disposed along the upper surface of the silicon substrate and the wall of the V-shaped groove. A buffer layer, a channel layer, and a barrier layer are sequentially stacked on the transition layer. The transition layer, buffer layer, channel layer, and barrier layer all have a V-shaped structure with an included angle of 70.52°.

[0018] A passivation layer is set on the barrier layer;

[0019] It also includes a metal source, a metal drain, and a gate control terminal, wherein the gate control terminal is located on the wall of the V-shaped groove, and the metal source and metal drain are located on the upper surface of the substrate and on both sides of the sidewall of the V-shaped groove, respectively.

[0020] Furthermore, in the two types of nonplanar GaN HEMT lateral power devices mentioned above, a high dielectric constant (HK) passivation layer is also disposed between the barrier layer and the passivation layer.

[0021] Furthermore, in the two types of non-planar GaN HEMT lateral power devices mentioned above, the channel layer is made of GaN and the barrier layer is made of AlGaN.

[0022] Furthermore, in the two types of non-planar GaN HEMT lateral power devices mentioned above, the transition layer is made of AlGaN or AlN, the buffer layer is made of AlGaN or GaN, and the passivation layer is made of Si3N4 or SiO2.

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

[0024] This invention provides a non-planar GaN HEMT lateral power device. Through structural innovation, it effectively overcomes the design and processing difficulties of the aforementioned non-planar GaN HEMT lateral power devices. Specifically, through mature silicon etching technology, a V-shaped groove is etched along the

[110] direction on the silicon (100), silicon (001), or silicon (010) crystal planes. The included angle between the sidewalls (111) is 70.52°. Then, a buffer layer, a channel layer, and a barrier layer are grown polarly on the sidewalls (111) to form a non-planar device structure. Its 2DEG channel extends from the source to the drain along a V-shaped bend. Therefore, under the same device area, the 2DEG channel will be significantly increased, increasing the device's Baliga figure of merit, breaking through the performance limit, and improving reliability. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the V-shaped GaN HEMT enhancement-type device structure in Embodiment 1 of the present invention.

[0026] Figure 2 This is a process flow diagram of the fabrication process of the V-shaped GaN HEMT enhancement-type device in Embodiment 1 of the present invention.

[0027] Figure 3 This is a schematic diagram of the V-shaped GaN HEMT enhancement-type device structure with an HK passivation layer in Embodiment 2 of the present invention.

[0028] Figure 4 The diagram shows the constraint effect of the HK passivation layer on the interface charge in GaN HEMT in Embodiment 2 of the present invention. (a) is the off-state IV characteristic curve, and (b) is the on-state IV characteristic curve (gate voltage 5V).

[0029] Figure 5 This is a schematic diagram of the V-shaped GaN HEMT depletion-type device structure in Embodiment 3 of the present invention.

[0030] Figure 6 This is a schematic diagram of the V-shaped GaN HEMT depletion-type device structure with an HK passivation layer in Embodiment 4 of the present invention.

[0031] Figure 7 This is a schematic diagram of the V-shaped GaN HEMT enhancement-type device structure in Embodiment 5 of the present invention.

[0032] Figure 8 This is a schematic diagram of the V-shaped GaN HEMT enhancement-type device structure with an HK passivation layer in Embodiment 6 of the present invention.

[0033] Figure 9 This is a schematic diagram of the V-shaped GaN HEMT depletion-type device structure in Embodiment 7 of the present invention.

[0034] Figure 10 This is a schematic diagram of the V-shaped GaN HEMT depletion-type device structure with an HK passivation layer in Embodiment 8 of the present invention.

[0035] Figure 11 This is a structural diagram of a traditional GaN HEMT enhancement-mode device. Detailed Implementation

[0036] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0037] Example 1

[0038] This embodiment provides a V-shaped GaN HEMT enhancement-mode lateral power device (V-GaN HEMT for short), whose cell structure is as follows: Figure 1 As shown, the preparation process is as follows: Figure 2 As shown; specifically including:

[0039] A silicon substrate 01, wherein a V-shaped groove with an included angle of 70.52° is etched on the silicon (100) crystal surface along the

[110] crystal direction, and the groove wall of the V-shaped groove is a silicon (111) crystal surface;

[0040] A transition layer 02 is disposed along the wall of the V-shaped groove. A buffer layer 03, a channel layer 04 (GaN), and a barrier layer 05 (AlGaN) are sequentially stacked on the transition layer 02. A passivation layer 07 and a (p-GaN) 06 are disposed on the barrier layer 05 (AlGaN). The transition layer 02 (AlN), the buffer layer 03 (GaN), the channel layer 04 (GaN), and the barrier layer 05 (AlGaN) are all V-shaped with an included angle of 70.52°.

[0041] And the metal source, metal drain and gate control terminals located on the wall of the V-shaped groove, with the gate located on p-GaN;

[0042] In the aforementioned devices, the transition layer is generally made of AlGaN or AlN, and AlN is used in this embodiment; the buffer layer is generally made of AlGaN or GaN, and GaN is used in this embodiment; the passivation layer is generally made of Si3N4 or SiO2, and Si3N4 is used in this embodiment; the enhancement-mode device is generally implemented using p-GaN gate, recessed gate, insulating gate, fluorine ion implantation, etc., and p-GaN gate is used in this embodiment. The metal source and metal drain can form a good conductive connection with the two-dimensional electron gas through Schottky contacts or ohmic contacts. In this embodiment, the metal source and metal drain are extended into the channel layer to form ohmic contacts with the two-dimensional electron gas.

[0043] It should be noted that in the above structural description, "silicon (100) crystal plane", "

[110] crystal orientation" and "silicon (111) crystal plane" are proper nouns, and "parentheses ()" and "square brackets []" are also proper nouns. Furthermore, compared to the traditional planar structure, the arrangement of the metal source, metal drain and gate control terminals is no different, so this invention will not elaborate further. In addition, in this invention, the etching of the silicon substrate can be directly achieved using existing mature silicon etching processes, and other passivation materials are present on the outermost layer of the device.

[0044] In terms of working principle,

[0045] Based on the aforementioned V-shaped GaN HEMT enhancement-mode lateral power device structure, this invention can form a continuous 2DEG channel in a V-shape with an included angle of 70.52°. Under the premise that the lateral dimensions of the V-GaN HEMT cell in this invention are the same as those in the conventional structure, calculations show that the 2DEG channel of the V-GaN HEMT is 1.73 times larger than that of the conventional structure. Therefore, theoretically, its breakdown voltage and on-resistance will also increase by 1.73 times. However, since the cell area remains unchanged under the same lateral dimensions, the Baliga figure of merit of the V-GaNHEMT will theoretically increase by 1.73 times, indicating that the device of this invention can achieve a significant performance improvement.

[0046] Furthermore, since the (111) crystal plane of Si best matches the lattice distribution of GaN, polar epitaxial growth of GaN along the (111) crystal plane of Si allows the GaN film to grow along its polar axis (c-axis), thereby generating a high-density 2DEG on the polar plane perpendicular to the polar axis. Simultaneously, due to the anisotropy of Si, the etching rate of silicon on the (111) crystal plane is much lower than that on the (100) crystal plane. Therefore, by selecting appropriate etching temperature and time, stable and consistent V-grooves can be obtained in batches on the silicon substrate. Moreover, epitaxial growth of GaN on the inclined walls of the V-grooves allows for the concentrated annihilation of dislocations in GaN, effectively reducing the dislocation density.

[0047] Example 2

[0048] This embodiment provides a V-shaped GaN HEMT enhancement-mode lateral power device (V-GaN HEMT for short), whose cell structure is as follows: Figure 3 As shown, the only difference between this embodiment and Embodiment 1 is that an HK passivation layer 11 is further disposed between the passivation layer 07 and the barrier layer 05. The HK passivation layer 11 is a material with a relative permittivity greater than 200, such as STO or PZT. By setting the HK passivation layer 11, the influence of interface charge on the device surface can be constrained, thereby improving reliability. In this embodiment, the constraint effect of the HK passivation layer 11 on the influence of interface charge in GaN HEMT is simulated as follows: Figure 4 As shown in the figure, the HK passivation layer significantly constrains the deviation of the breakdown voltage from its standard value under various interface charge densities without affecting the forward conduction characteristics, thus suppressing the adverse effects of interface charge on the device.

[0049] Example 3

[0050] This embodiment provides a V-shaped GaN HEMT depletion-mode lateral power device, whose cell structure is as follows: Figure 5 As shown, it specifically includes:

[0051] A silicon substrate 01, wherein a V-shaped groove with an included angle of 70.52° is etched on the silicon (100) crystal surface along the

[110] crystal direction, and the groove wall of the V-shaped groove is a silicon (111) crystal surface;

[0052] A transition layer 02 is provided along the wall of the V-shaped groove. A buffer layer 03, a channel layer 04 (GaN), a barrier layer 05 (AlGaN), and a passivation layer 07 are sequentially stacked on the transition layer 02. The transition layer 02, the buffer layer 03, the channel layer 04 (GaN), and the barrier layer 05 (AlGaN) are all V-shaped with an included angle of 70.52°.

[0053] And the metal source, metal drain and gate control terminals located on the wall of the V-shaped groove;

[0054] In the above devices, the transition layer is generally made of AlGaN or AlN, and AlN is used in this embodiment; the buffer layer is generally made of AlGaN or GaN, and GaN is used in this embodiment; the passivation layer is generally made of Si3N4 or SiO2, and Si3N4 is used in this embodiment.

[0055] The working principle of the V-shaped GaN HEMT depletion-type device in this embodiment is the same as that in Embodiment 1.

[0056] Example 4

[0057] This embodiment provides a V-shaped GaN HEMT depletion-mode device, whose cell structure is as follows: Figure 6 As shown, the only difference between it and Embodiment 3 is that an HK passivation layer 11 (material is STO or PZT) is also provided between the passivation layer 07 and the barrier layer 05; by providing the HK passivation layer 11, the influence of the interface charge on the device surface can be constrained and the reliability can be improved.

[0058] Example 5

[0059] This embodiment provides a V-shaped GaN HEMT enhancement-mode lateral power device (V-GaN HEMT for short), whose cell structure is as follows: Figure 7 As shown; specifically including:

[0060] A silicon substrate 01, wherein a V-shaped groove with an included angle of 70.52° is etched on the silicon (100) crystal surface along the

[110] crystal direction, and the groove wall of the V-shaped groove is a silicon (111) crystal surface;

[0061] A transition layer 02 is disposed along the upper surface of the silicon substrate and the wall of the V-shaped groove. A buffer layer 03, a channel layer 04 (GaN), and a barrier layer 05 (AlGaN) are sequentially stacked on the transition layer 02. A passivation layer 07 and a (p-GaN) 06 are disposed on the barrier layer 05 (AlGaN). The transition layer 02, buffer layer 03, channel layer 04 (GaN), and barrier layer 05 (AlGaN) all have a V-shaped structure with an included angle of 70.52°.

[0062] The device includes a metal source, a metal drain, and a gate control terminal. The gate control terminal is located on the wall of the V-shaped groove and on (p-GaN)O6. The metal source and the metal drain are located on the upper surface of the substrate and on both sides of the V-shaped groove, respectively.

[0063] In the above-mentioned devices, the transition layer material is generally AlGaN or AlN, and AlN is used in this embodiment; the buffer layer material is generally AlGaN or GaN, and GaN is used in this embodiment; the passivation layer material is generally Si3N4 or SiO2, and Si3N4 is used in this embodiment.

[0064] The working principle of the V-shaped GaN HEMT enhancement-type lateral power device in this embodiment is the same as that in Embodiment 1. However, by adopting a design that places the source and drain on the upper surface of the substrate, this embodiment can further improve the power density of the chip compared to Embodiment 1.

[0065] Example 6

[0066] This embodiment provides a V-shaped GaN HEMT enhancement-mode lateral power device (V-GaN HEMT for short), whose cell structure is as follows: Figure 8 As shown, the only difference between it and Example 5 is that an HK passivation layer 11 (a material with a relative permittivity greater than 200, such as STO or PZT) is also provided between the passivation layer 07 and the barrier layer 05; by providing the HK passivation layer 11, the influence of the interface charge on the device surface can be constrained and the reliability can be improved.

[0067] Example 7

[0068] This embodiment provides a V-shaped GaN HEMT depletion-mode lateral power device, whose cell structure is as follows: Figure 9 As shown, it specifically includes:

[0069] A silicon substrate 01, wherein a V-shaped groove with an included angle of 70.52° is etched on the silicon (100) crystal surface along the

[110] crystal direction, and the groove wall of the V-shaped groove is a silicon (111) crystal surface;

[0070] A transition layer 02 is disposed along the upper surface of the silicon substrate and the wall of the V-shaped groove. A buffer layer 03, a channel layer 04 (GaN), and a barrier layer 05 (AlGaN) are sequentially stacked on the transition layer 02. A passivation layer 07 is disposed on the barrier layer 05 (AlGaN). The transition layer 02, buffer layer 03, channel layer 04 (GaN), barrier layer 05 (AlGaN), and passivation layer 07 all have a V-shaped structure with an included angle of 70.52°.

[0071] It also includes a metal source, a metal drain, and a gate control terminal, wherein the gate control terminal is located on the wall of the V-shaped groove, and the metal source and metal drain are located on the upper surface of the substrate and respectively on both sides of the V-shaped groove.

[0072] In the above devices, the transition layer is generally made of AlGaN or AlN, and AlN is used in this embodiment; the buffer layer is generally made of AlGaN or GaN, and GaN is used in this embodiment; the passivation layer is generally made of Si3N4 or SiO2, and Si3N4 is used in this embodiment.

[0073] The working principle of the V-shaped GaN HEMT depletion-type lateral power device in this embodiment is the same as that in Embodiment 1.

[0074] Example 8

[0075] This embodiment provides a V-shaped GaN HEMT depletion-mode lateral power device, whose cell structure is as follows: Figure 10 As shown, the only difference between it and Embodiment 7 is that an HK passivation layer 11 (a material with a relative permittivity greater than 200, such as STO or PZT) is also provided between the passivation layer 07 and the barrier layer 05; by providing the HK passivation layer 11, the influence of the interface charge on the device surface can be constrained and the reliability can be improved.

[0076] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A nonplanar GaN HEMT lateral power device, characterized in that, include: A silicon substrate, wherein a V-shaped groove with an included angle of 70.52° is etched along the [110] crystal direction on a silicon (100) crystal plane, a silicon (001) crystal plane or a silicon (010) crystal plane, and the groove wall of the V-shaped groove is a silicon (111) crystal plane; A transition layer is provided along the wall of the V-shaped groove, and a buffer layer, a channel layer, and a barrier layer are sequentially stacked on the transition layer. The transition layer, buffer layer, channel layer, and barrier layer are all V-shaped with an included angle of 70.52°. A passivation layer is set on the barrier layer; The device includes a metal source, a metal drain, and a gate control terminal, all of which are located on the wall of the V-shaped groove. The metal source is located on one side wall of the V-shaped groove, and the metal drain is located on the other side wall of the V-shaped groove. The metal source and the gate control terminal are located on the same side wall of the V-shaped groove.

2. The non-planar GaN HEMT lateral power device as described in claim 1, characterized in that, An HK passivation layer is also disposed between the barrier layer and the passivation layer.

3. The non-planar GaN HEMT lateral power device as described in claim 1, characterized in that, The channel layer is made of GaN, and the barrier layer is made of AlGaN.

4. The non-planar GaN HEMT lateral power device as described in claim 1, characterized in that, The transition layer is made of AlGaN or AlN, the buffer layer is made of AlGaN or GaN, and the passivation layer is made of Si3N4 or SiO2.

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