Reverse conducting gallium oxide field effect transistor with patterned groove and floating field plate

Abstract

The invention belongs to the technical field of power semiconductors, and relates to a reverse conducting gallium oxide field effect transistor with a graphical groove and a floating field plate. During forward conduction, an enhanced device with high threshold voltage is realized through the groove gate; during forward blocking, the patterned groove optimizes electric field distribution, the floating field plate and the gate field plate are combined to relieve the electric field concentration effect, and the breakdown voltage of the device is improved; during forward conduction and blocking, the junction-free diode is switched off, and the conduction and blocking characteristics of the transistor are not influenced; during reverse freewheeling, the reverse conducting transistor with low reverse turn-on voltage is realized by integrating the junctionless diode. The reverse conducting device has the beneficial effects that the reverse conducting device has the advantages of low reverse turn-on voltage, high breakdown voltage and high threshold voltage, the integrated diode is compatible with the transistor process, and the module size and the parasitic effect can be reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of power semiconductors and relates to a reverse-conducting gallium oxide field-effect transistor with a patterned groove and a floating field plate. Background Art

[0002] Ultra-wide bandgap gallium oxide is an emerging strategic semiconductor material, which has the advantages of high critical breakdown field strength (8 MV / cm) and low cost, and the N-type doping can be flexibly adjusted. The breakdown voltage can be greatly improved under the same drift region length. Therefore, the power figure of merit of gallium oxide devices can reach four times that of gallium nitride devices and ten times that of silicon carbide devices. Theoretically, it has significant advantages in high voltage, high power, low loss, miniaturization and high reliability, which is conducive to achieving high efficiency and high power density of the power conversion system. However, on the one hand, the breakdown voltage of gallium oxide power devices is much lower than the theoretical value, and the electric field concentration effect causes the device to break down prematurely; on the other hand, the lack of P-type gallium oxide makes most gallium oxide power field-effect transistors depletion-type and have a large negative threshold voltage, resulting in difficult drive design. In the power conversion topology, to avoid the mis-turn-on of depletion-type transistors, a negative voltage is applied to the gate to ensure the reliable turn-off of the device, but this will cause the reverse turn-on voltage to increase with the increase of the absolute value of the negative gate voltage when the device conducts freewheeling by itself, resulting in significant on-state losses. The conventional method of externally anti-parallel freewheeling diodes will increase the chip volume and introduce additional parasitic inductance and parasitic resistance, resulting in a reduction in the efficiency and an increase in the losses of the power conversion system. Summary of the Invention

[0003] In view of the above problems, the present invention proposes a reverse-conducting gallium oxide field-effect transistor with a patterned groove and a floating field plate.

[0004] The technical solution of the present invention is as follows:

[0005] A reverse-conducting gallium oxide field-effect transistor with a patterned groove and a floating field plate includes, along the vertical direction of the device, a gallium oxide substrate 1, an unintentionally doped gallium oxide buffer layer 2, and a gallium oxide epitaxial layer 3 from bottom to top in sequence; along the lateral direction of the device, a drain metal 4 is provided at one end of the upper surface of the gallium oxide epitaxial layer 3;

[0006] Characterized in that, one end of the device having the drain metal 4 is defined as the first end of the device, and the end of the device far from the drain metal 4 is defined as the second end of the device; the second end of the device is sequentially defined as three regions along the longitudinal direction of the device, namely the first region of the second end of the device, the second region of the second end of the device, and the third region of the second end of the device; along the transverse direction of the device, a source metal 7 and a gate trench are respectively provided at both ends of the first region of the second end of the device, wherein the source metal 7 is located on the upper surface of the gallium oxide epitaxial layer 3, the gate trench is formed by etching the gallium oxide epitaxial layer 3, there is a spacing between the source metal 7 and the gate trench, and the source metal 7 is located at the end far from the drain metal 4; a patterned trench structure is formed by patterned etching in the second region of the second end of the device, wherein the process of the patterned etching is to etch away the gallium oxide epitaxial layer 3 and the unintentionally doped gallium oxide buffer layer 2 in the patterned region until reaching the upper surface of the gallium oxide substrate 1; in the third region of the second end of the device, the end of the gallium oxide epitaxial layer 3 far from the drain metal 4 is etched to form an anode trench; a dielectric layer 5 is provided on the upper surface of the gallium oxide epitaxial layer 3, the bottom and side surfaces of the gate trench, the bottom and side surfaces of the patterned trench structure, and the bottom and side surfaces of the anode trench. Different from completely covering the bottom and side surfaces of the gate trench and the bottom and side surfaces of the patterned trench structure, the side of the anode trench far from the drain metal 4 is not covered by the dielectric layer 5; the anode trench is filled to form an anode metal 8, the bottom of the anode metal 8 is stepped, and the side of the anode metal 8 far from the drain metal 4 is in contact with the upper surface of the gallium oxide epitaxial layer 3, and the side of the anode metal 8 close to the drain metal 4 extends along the upper surface of the dielectric layer 5 towards the drain metal 4; a gate metal 6 is filled in the gate trench, and the two ends of the upper surface of the gate metal 6 extend towards the drain metal 4 and the source metal 7 respectively and are not in contact with the drain metal 4 and the source metal 7; a passivation layer 9 is filled in the patterned trench structure and on the upper layer of the device, so that the passivation layer 9 completely covers the drain metal 4, the gate metal 6, the source metal 7, and the anode metal 8;

[0007] According to the same division method as the second end of the device, the upper surface of the passivation layer 9 is correspondingly divided into three regions in the longitudinal direction, namely the first region of the passivation layer 9, the second region of the passivation layer 9, and the third region of the passivation layer 9; along the transverse direction of the device, a plurality of gate floating field plates 10 with the same size are provided in the first region of the passivation layer 9, and the gate floating field plates 10 are equally spaced from the side close to the drain metal 4 to above the gate metal 6. In the vertical direction, the gate metal 6 and the last gate floating field plate 10 have an overlapping region; an anode floating field plate 11 is provided in the third region of the passivation layer 9, and in the vertical direction, the anode floating field plate 11 and the anode metal 8 have an overlapping region, while in the transverse direction, the anode floating field plate 11 and the gate floating field plates 10 have a spacing;

[0008] The source metal 7 and the anode metal 8 are electrically connected.

[0009] The lateral direction of the device described in the above solution corresponds to Figure 1 the x-axis direction of the coordinate system in Figure 1 , the vertical direction corresponds to the z-axis direction, and the longitudinal direction corresponds to the y-axis direction.

[0010] Further, along the lateral direction of the device, the patterned groove structure is divided into two parts. The side closer to the drain metal (4) is defined as the first part of the patterned groove structure, and the remaining part is defined as the second part of the patterned groove structure; in a top view, the first part of the patterned groove structure is trapezoidal, and the second part of the patterned groove structure is rectangular.

[0011] Further, along the lateral direction of the device, the patterned groove structure is divided into two parts. The side closer to the drain metal 4 is defined as the first part of the patterned groove structure, and the remaining part is defined as the second part of the patterned groove structure; in a top view, the first part of the patterned groove structure is a quarter circle, and the second part of the patterned groove structure is rectangular.

[0012] Further, along the lateral direction of the device, the patterned groove structure is divided into two parts. The side closer to the drain metal 4 is defined as the first part of the patterned groove structure, and the remaining part is defined as the second part of the patterned groove structure; in a top view, the first part of the patterned groove structure is semi-elliptical, and the second part of the patterned groove structure is rectangular.

[0013] Further, both the gate floating field plate 10 and the anode floating field plate 11 extend along the longitudinal direction to the edge of the device.

[0014] The beneficial effects of the present invention are as follows. The device of the present invention realizes a reverse-conducting device with a low reverse turn-on voltage through the integration of a junctionless diode, and realizes an enhancement-mode device with a high threshold voltage through a grooved gate. The patterned groove, combined with the floating field plate and the gate field plate, alleviates the electric field concentration, optimizes the electric field distribution, improves the breakdown voltage of the device, and realizes the advantages of both a low reverse turn-on voltage, a high breakdown voltage, and a high threshold voltage. The integration of the diode and the transistor processes is compatible, which is beneficial to reducing the module volume and the parasitic effects of the power system. Description of the Drawings

[0015] Figure 1 is a schematic structural diagram of Embodiment 1 of the present invention;

[0016] Figure 2 is a schematic structural diagram of Embodiment 1 of the present invention with auxiliary lines;

[0017] Figure 3 is a cross-sectional view along line AA' in Embodiment 1;

[0018] Figure 4 is a cross-sectional view along line BB' in Embodiment 1;

[0019] Figure 5 is a cross-sectional view along line CC' in Embodiment 1;

[0020] Figure 6 is the cross-sectional view along the line DD’ in Embodiment 1;

[0021] Figure 7 is the structural schematic diagram of Embodiment 2 of the present invention;

[0022] Figure 8 is the structural schematic diagram of Embodiment 3 of the present invention;

[0023] Figure 9 is the structural schematic diagram of Embodiment 4 of the present invention. Detailed implementation manners

[0024] The technical solutions of the present invention will be described in detail below in conjunction with the accompanying drawings and embodiments:

[0025] Embodiment 1:

[0026] As Figure 1 shown, this example includes, along the vertical direction of the device, a gallium oxide substrate 1, an unintentionally doped gallium oxide buffer layer 2, and a gallium oxide epitaxial layer 3 in sequence from bottom to top; along the horizontal direction of the device, a drain metal 4 is provided at one end of the upper surface of the gallium oxide epitaxial layer 3;

[0027] It is characterized in that one end of the device with the drain metal 4 is defined as the first end of the device, and the end of the device far from the drain metal 4 is defined as the second end of the device; the second end of the device is sequentially defined as three regions along the longitudinal direction of the device, namely the first region of the second end of the device, the second region of the second end of the device, and the third region of the second end of the device; along the transverse direction of the device, a source metal 7 and a gate groove are respectively provided at both ends of the first region of the second end of the device, wherein the source metal 7 is located on the upper surface of the gallium oxide epitaxial layer 3, the gate groove is formed by etching the gallium oxide epitaxial layer 3, there is a spacing between the source metal 7 and the gate groove, and the source metal 7 is located at the end far from the drain metal 4; a patterned groove structure is formed by patterned etching in the second region of the second end of the device, wherein the process of the patterned etching is to etch away the gallium oxide epitaxial layer 3 and the unintentionally doped gallium oxide buffer layer 2 in the patterned region until reaching the upper surface of the gallium oxide substrate 1; in the third region of the second end of the device, the end of the gallium oxide epitaxial layer 3 far from the drain metal 4 is etched to form an anode groove; a dielectric layer 5 is provided on the upper surface of the gallium oxide epitaxial layer 3, the bottom and side surfaces of the gate groove, the bottom and side surfaces of the patterned groove structure, and the bottom and side surfaces of the anode groove. Different from completely covering the bottom and side surfaces of the gate groove and the bottom and side surfaces of the patterned groove structure, the side of the anode groove far from the drain metal 4 is not covered by the dielectric layer 5; the anode groove is filled to form an anode metal 8, the bottom of the anode metal 8 is stepped, and the side of the anode metal 8 far from the drain metal 4 is in contact with the upper surface of the gallium oxide epitaxial layer 3, and the side of the anode metal 8 close to the drain metal 4 extends along the upper surface of the dielectric layer 5 towards the drain metal 4; a gate metal 6 is filled in the gate groove, and the two ends of the upper surface of the gate metal 6 extend towards the drain metal 4 and the source metal 7 respectively and are not in contact with the drain metal 4 and the source metal 7; a passivation layer 9 is filled in the patterned groove structure and the upper layer of the device, so that the passivation layer 9 completely covers the drain metal 4, the gate metal 6, the source metal 7, and the anode metal 8;

[0028] Along the transverse direction of the device, the patterned groove structure is divided into two parts. The side close to the drain metal 4 is defined as the first part of the patterned groove structure, and the remaining part is defined as the second part of the patterned groove structure; in the top view, the first part of the patterned groove structure is trapezoidal, and the second part of the patterned groove structure is rectangular;

[0029] In the longitudinal direction, the upper surface of the passivation layer 9 is correspondingly divided into three regions in the same division manner as the second end of the device, namely the first region of the passivation layer 9, the second region of the passivation layer 9, and the third region of the passivation layer 9; along the transverse direction of the device, in the first region of the passivation layer 9, there are a plurality of gate floating field plates 10 of the same size, and the gate floating field plates 10 are equally spaced from the side close to the drain metal 4 to above the gate metal 6. In the vertical direction, the gate metal 6 and the last gate floating field plate 10 have an overlapping region; in the third region of the passivation layer 9, there is an anode floating field plate 11, and in the vertical direction, the anode floating field plate 11 and the anode metal 8 have an overlapping region, while in the transverse direction, the anode floating field plate 11 and the gate floating field plates 10 have a spacing; the source metal 7 and the anode metal 8 are electrically connected.

[0030] The working principle of this example is as follows:

[0031] For the inverse-conducting gallium oxide field-effect transistor with patterned grooves and floating field plates proposed by the present invention, in the zero-bias state, the voltages applied to the gate metal 6 and the anode metal 8 are both zero. The gate groove and anode groove structures deplete the conductive channel using the work function difference between the metal and gallium oxide, and both the transistor and the integrated junctionless diode are in the off state, realizing a normally-off enhancement-type device; when conducting forward, as the voltage applied to the gate metal 6 increases, the depletion region under the gate groove gradually shrinks, thereby forming a conductive channel, and the field-effect transistor conducts, realizing a high threshold voltage; in the forward blocking state, the gate floating field plates 10 and the anode floating field plate 11 relieve the electric field concentration effect, and combine with the patterned grooves and gate field plates to optimize the electric field distribution, thereby improving the device breakdown voltage; in the forward conduction and blocking states, the drain metal 4 is at a high potential, the source metal 7 and the anode metal 8 are short-circuited to zero potential, and the conductive channel under the anode groove is still depleted, and the junctionless diode is off, without affecting the conduction and blocking performance of the transistor; when conducting in the reverse direction, the drain metal 4 is connected to a low potential, the source metal 7 and the anode metal 8 are short-circuited to a high potential, and the depletion effect of the anode groove is weaker than that of the gate groove, making the junctionless diode conduct before the transistor, realizing a low turn-on voltage and a low conduction voltage drop, thereby reducing the reverse freewheeling loss. By regulating the depths of the gate groove and the anode groove, the metal work function, the dielectric constant and thickness of the dielectric layer 5, etc., the depletion effect on the conductive channel can be flexibly regulated to achieve a good compromise among the breakdown voltage, the threshold voltage, and the reverse turn-on voltage. Therefore, the device of the present invention realizes an inverse-conducting device with a low reverse turn-on voltage by integrating a junctionless diode, realizes an enhancement-type device with a high threshold voltage through a grooved gate, and the patterned grooves combined with floating field plates and gate field plates relieve the electric field concentration, optimize the electric field distribution, enhance the device breakdown voltage resistance, and realize the advantages of both a low reverse turn-on voltage, a high breakdown voltage, and a high threshold voltage. The integrated diode and transistor processes are compatible, which is beneficial to reducing the module volume and the parasitic effects of the power system.

[0032] Example 2: As Figure 7As shown, the difference between this embodiment and Embodiment 1 is that both the gate floating field plate 10 and the anode floating field plate 11 extend to the device edge, expanding the regulation range of the floating field plate for the electric field distribution, which helps to improve the device breakdown voltage.

[0033] Embodiment 3: As Figure 8 shown, the difference between this embodiment and Embodiment 1 is that along the lateral direction of the device, the patterned slot structure is divided into two parts. The side close to the drain metal 4 is defined as the first part of the patterned slot structure, and the remaining part is defined as the second part of the patterned slot structure. In the top view, the first part of the patterned slot structure is quarter-circular, and the second part of the patterned slot structure is rectangular. The patterned slot further alleviates the electric field concentration effect near the gate metal 6, thereby reducing the leakage current and increasing the breakdown voltage.

[0034] Embodiment 4: As Figure 9 shown, the difference between this embodiment and Embodiment 1 is that along the lateral direction of the device, the patterned slot structure is divided into two parts. The side close to the drain metal 4 is defined as the first part of the patterned slot structure, and the remaining part is defined as the second part of the patterned slot structure. In the top view, the first part of the patterned slot structure is semi-elliptical, and the second part of the patterned slot structure is rectangular. The arc-shaped design of the patterned slot further modulates the electric field distribution at the end of the patterned slot, improving the breakdown voltage of the device.

Claims

1. A reverse-conducting gallium oxide field effect transistor with a patterned groove and a floating field plate, comprising, from bottom to top, a gallium oxide substrate (1), an unintentionally doped gallium oxide buffer layer (2) and a gallium oxide epitaxial layer (3) in a vertical direction of the device; and a drain metal (4) is provided at one end of the upper surface of the gallium oxide epitaxial layer (3) in a lateral direction of the device; It is characterized in that The end of the device having the drain metal (4) is defined as the first end of the device, and the end of the device away from the drain metal (4) is defined as the second end of the device; the second end of the device is defined as three regions in sequence along the longitudinal direction of the device, namely, the first region of the second end of the device, the second region of the second end of the device, and the third region of the second end of the device; along the lateral direction of the device, the two ends of the first region of the second end of the device are provided with a source metal (7) and a gate groove, respectively, wherein the source metal (7) is located on the upper surface of the gallium oxide epitaxial layer (3), and the gate groove is formed by etching the gallium oxide epitaxial layer ( 3), a gap exists between the source metal (7) and the gate groove, and the source metal (7) is located at one end away from the drain metal (4); a patterned groove structure is formed by patterned etching in a second region at the second end of the device, wherein the patterned etching process is to etch away the gallium oxide epitaxial layer (3) and the unintentionally doped gallium oxide buffer layer (2) in the patterned region and then directly reach the upper surface of the gallium oxide substrate (1); in a third region at the second end of the device, an end of the gallium oxide epitaxial layer (3) away from the drain metal (4) is etched to form an anode groove; in the oxide The upper surface of the gallium epitaxial layer (3), the bottom and side of the gate groove, the bottom and side of the patterned groove structure, and the bottom and side of the anode groove are provided with a dielectric layer (5); unlike the bottom and side of the gate groove and the bottom and side of the patterned groove structure that are completely covered, the side of the anode groove that is far from the drain metal (4) is not covered by the dielectric layer (5); the anode groove is filled to form an anode metal (8); the bottom of the anode metal (8) is in a stepped shape, and the side of the anode metal (8) that is far from the drain metal (4) is in contact with the upper surface of the gallium oxide epitaxial layer (3); The side of the anode metal (8) close to the drain metal (4) extends along the upper surface of the dielectric layer (5) in the direction of the drain metal (4); the gate metal (6) is filled in the gate groove, and the two ends of the upper surface of the gate metal (6) extend in the direction of the drain metal (4) and the source metal (7) respectively and do not contact the drain metal (4) and the source metal (7); the passivation layer (9) is filled in the patterned groove structure and the upper layer of the device, so that the passivation layer (9) completely covers the drain metal (4), the gate metal (6), the source metal (7) and the anode metal (8); In the same division method as the second end of the device, the upper surface of the passivation layer (9) is correspondingly divided into three regions in the longitudinal direction, namely, a first region of the passivation layer (9), a second region of the passivation layer (9), and a third region of the passivation layer (9); Along the lateral direction of the device, a first region of the passivation layer (9) is provided with a plurality of gate floating field plates (10) of the same size, the gate floating field plates (10) being evenly spaced from the side close to the drain metal (4) to above the gate metal (6), and in the vertical direction, the gate metal (6) and the last gate floating field plate (10) have an overlapping region; a third region of the passivation layer (9) is provided with an anode floating field plate (11), and in the vertical direction, the anode floating field plate (11) and the anode metal (8) have an overlapping region, and in the lateral direction, the anode floating field plate (11) and the gate floating field plate (10) are spaced apart; The source metal (7) and the anode metal (8) are electrically connected.

2. The reverse-conducting gallium oxide field effect transistor with patterned grooves and floating field plates according to claim 1, characterized in that: The patterned groove structure is divided into two parts along the lateral direction of the device, the side close to the drain metal (4) is defined as the first part of the patterned groove structure, and the remaining part is defined as the second part of the patterned groove structure; in the top view of the device, the first part of the patterned groove structure is trapezoidal, and the second part of the patterned groove structure is rectangular.

3. The reverse-conducting gallium oxide field effect transistor with patterned grooves and floating field plates according to claim 1, characterized in that: The patterned groove structure is divided into two parts along the lateral direction of the device, the side close to the drain metal (4) is defined as the first part of the patterned groove structure, and the remaining part is defined as the second part of the patterned groove structure; in the top view of the device, the first part of the patterned groove structure is a quarter circle, and the second part of the patterned groove structure is a rectangle.

4. The reverse-conducting gallium oxide field effect transistor with patterned grooves and floating field plates according to claim 1, characterized in that: The patterned groove structure is divided into two parts along the lateral direction of the device, the side close to the drain metal (4) is defined as the first part of the patterned groove structure, and the remaining part is defined as the second part of the patterned groove structure; in the top view of the device, the first part of the patterned groove structure is semi-elliptical, and the second part of the patterned groove structure is rectangular.

5. The reverse-conducting gallium oxide field effect transistor with patterned grooves and floating field plates according to claim 1, characterized in that: The gate floating field plate (10) and the anode floating field plate (11) both extend to the edge of the device in the longitudinal direction.

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