Multi-layer gallium nitride Schottky diode with groove anode and manufacturing method of multi-layer gallium nitride Schottky diode

Abstract

The invention discloses a multi-layer gallium nitride Schottky diode with a groove anode and a manufacturing method of the multi-layer gallium nitride Schottky diode, and mainly relates to the technical field of semiconductors, and the Schottky diode comprises a semiconductor layer, a groove anode layer, a cathode and an anode bonding pad. And the turn-on voltage and the on resistance of the Schottky diode are further reduced. The starting voltage can be reduced to 0.4-0.5 V, and is reduced by 0.3-0.4 V compared with 0.8 V in the prior art; and the forward current can reach the magnitude of 10 <-1 >-10 <-2 > during conduction, which is significantly improved compared with the magnitude of 10 <-3 >-10 <-4 > in the prior art.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a multi-layer gallium nitride Schottky diode with a grooved anode and a manufacturing method thereof. Background Art

[0002] Since the heterojunction formed by AlGaN and GaN can spontaneously generate a high-concentration two-dimensional electron gas with high mobility, a Schottky diode based on the AlGaN / GaN heterojunction is very suitable for working in high-temperature, high-pressure, and high-frequency environments. However, traditional AlGaN / GaN Schottky diodes have the disadvantages of high turn-on voltage, large on-resistance, and small forward current. The method of etching a grooved anode is one of the methods currently found to be able to effectively reduce the turn-on voltage. Another method to improve existing devices is to use a hybrid anode, that is, the anode is composed of a combination of an interconnected Schottky contact and an ohmic contact.

[0003] The present invention aims to combine the method of etching a grooved anode and using a composite anode to improve the forward conduction current as much as possible while reducing the turn-on voltage. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is that traditional AlGaN / GaN Schottky diodes have a high turn-on voltage, a large on-resistance, and a small forward current.

[0005] The above technical problem is solved by the following technical solution: The present invention provides a multi-layer gallium nitride Schottky with a grooved anode, which includes a semiconductor layer, a grooved anode layer, a cathode, and an anode pad.

[0006] In a preferred embodiment of the multi-layer gallium nitride Schottky diode with a grooved anode of the present invention: there are at least two semiconductor layers, each semiconductor layer includes a GaN layer at the bottom and an AlGaN layer at the top, and the two semiconductor layers are arranged in sequence from bottom to top;

[0007] The grooved anode layer, corresponding to the semiconductor layer one by one, includes a first anode and a second anode, the first anode is in ohmic contact with the corresponding GaN layer, and the second anode is in Schottky contact with the corresponding AlGaN layer;

[0008] The cathode is arranged at one end of the top semiconductor layer far from the grooved anode layer, penetrates through all the semiconductor layers, and the cathode is in ohmic contact with the semiconductor layer; and,

[0009] The anode pad is arranged on the top of all the grooved anode layers, and the anode pad is in Schottky contact with the semiconductor layer.

[0010] In a preferred embodiment of the multi-layer gallium nitride Schottky diode with a grooved anode according to the present invention: the thickness of the GaN layer is 0.3 - 20 μm;

[0011] The thickness of the AlGaN layer is 10 - 30 nm, and the molar fraction of Al is 20% - 30%.

[0012] In a preferred embodiment of the multi-layer gallium nitride Schottky diode with a grooved anode according to the present invention: the contact surface between the GaN layer and the AlGaN layer of each semiconductor layer forms a first contact surface, and the contact surface between the AlGaN layer and the GaN layer of adjacent semiconductor layers forms a second contact surface.

[0013] In a preferred embodiment of the multi-layer gallium nitride Schottky diode with a grooved anode according to the present invention: the first anode extends downward from the surface of the AlGaN layer of the semiconductor layer where it is located through to the corresponding GaN layer, and is 1 - 10 nm below the corresponding first contact surface.

[0014] In a preferred embodiment of the multi-layer gallium nitride Schottky diode with a grooved anode according to the present invention: the second anode extends downward from the surface of the AlGaN layer of the semiconductor layer where it is located through to the corresponding AlGaN layer, and is 1 - 2 nm above the corresponding first contact surface.

[0015] In a preferred embodiment of the multi-layer gallium nitride Schottky diode with a grooved anode according to the present invention: the distance between adjacent first anodes and second anodes is 1 - 100 nm.

[0016] In a preferred embodiment of the multi-layer gallium nitride Schottky diode with a grooved anode according to the present invention: the thickness of the grooved anode layer decreases successively along the arrangement in the width direction of the cathode.

[0017] In a preferred embodiment of the multi-layer gallium nitride Schottky diode with a grooved anode according to the present invention: the distance from the boundary of the grooved anode layer close to the cathode to the cathode is 1 - 20 μm.

[0018] In a preferred embodiment of the multi-layer gallium nitride Schottky diode with a grooved anode according to the present invention: the material of the anode pad is one or a combination of nickel and gold, and the thickness is 1 - 50 nm.

[0019] The present invention also provides a manufacturing method of a multi-layer gallium nitride Schottky diode with a grooved anode, which includes depositing a semiconductor layer, etching and filling a grooved anode layer, etching and filling a cathode, and depositing an anode pad.

[0020] In a preferred embodiment of the manufacturing method of the multi-layer gallium nitride Schottky diode with a grooved anode according to the present invention: The deposited semiconductor layer includes depositing a GaN layer and depositing an AlGaN layer on the GaN layer to form the first semiconductor layer; depositing a GaN layer on the AlGaN layer of the previous semiconductor layer and then depositing an AlGaN layer to form the second semiconductor layer;

[0021] Etching and filling the grooved anode layer includes etching a groove on one side of the AlGaN layer of the outermost semiconductor layer and filling it with metal to form the grooved anode layer;

[0022] Etching and filling the cathode includes etching a groove on the side of the AlGaN layer of the outermost semiconductor layer away from the grooved anode layer and filling it with metal to form the cathode;

[0023] Depositing the anode pad includes depositing the anode pad on the grooved anode layer of the AlGaN layer of the outermost semiconductor layer.

[0024] The beneficial effects of the present invention are as follows: The present invention combines the advantages of multi-layer conductive channels and a composite anode structure, further reducing the turn-on voltage and conduction resistance of the Schottky diode. The turn-on voltage can be reduced to 0.4 - 0.5V, a reduction of 0.3 - 0.4V compared with the 0.8V of the prior art level; the forward current during conduction can reach 10 -1 -10 -2 order of magnitude, showing a significant improvement compared with the 10 -3 -10 -4 order of magnitude of the prior art level. Brief Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below only relate to some embodiments of the present invention and do not limit the present invention. Among them:

[0026] Figure 1 Shows a schematic diagram of the semiconductor layer of a multi-layer gallium nitride Schottky diode with a grooved anode;

[0027] Figure 2 Shows the overall structure diagram of a multi-layer gallium nitride Schottky diode device with a grooved anode;

[0028] Figure 3 Shows the equivalent circuit diagram of a multi-layer gallium nitride Schottky diode with a grooved anode. Detailed Embodiments

[0029] In order to enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below in conjunction with the detailed embodiments and the drawings.

[0030] The terms used in the present invention are those general terms that are currently widely used in the art in consideration of the functions of the present invention. However, these terms may vary according to the intentions of those of ordinary skill in the art, precedents, or new technologies in the art. In addition, specific terms may be selected by the applicant, and in such cases, their detailed meanings will be described in the detailed description of the present invention. Therefore, the terms used in the specification should not be construed as simple names, but rather based on the meanings of the terms and the overall description of the present invention.

[0031] Referring to Figure 1 , this embodiment provides a multi-layer gallium nitride Schottky diode with a grooved anode, including a semiconductor layer 1, a grooved anode layer 2, a cathode 3, and an anode pad 4. The multi-layer gallium nitride Schottky diode with a grooved anode, through the design of the multi-layer semiconductor layer 1 and the grooved anode layer 2, combined with the cathode 3 and anode pad 4 structures, effectively reduces the turn-on voltage and improves the forward conduction current, and is applicable to high-temperature, high-pressure, and high-frequency environments.

[0032] The semiconductor layer 1 includes a GaN layer 11 at the bottom and an AlGaN layer 12 at the top. The semiconductor layer 1 of the present invention has at least two layers, and the GaN layer 11 of the upper semiconductor layer 1 is combined with the AlGaN layer 12 of the adjacent lower semiconductor layer 1.

[0033] The multi-layer semiconductor layers 1 are alternately stacked to form a heterojunction structure, which can spontaneously generate a two-dimensional electron gas with high mobility.

[0034] The grooved anode layer 2 and the semiconductor layer 1 correspond one by one in number. Among them, the first anode 21 of the grooved anode layer 2 contacts the GaN layer 11 of the semiconductor layer 1, and the second anode 22 of the grooved anode layer 2 contacts the AlGaN layer 12 of the semiconductor layer 1 to form a composite anode structure, effectively reducing the turn-on voltage.

[0035] The cathode 3 is provided at one end of the semiconductor layer 1 away from the grooved anode layer 2 and penetrates through all the semiconductor layers 1, and forms an ohmic contact with the semiconductor layer 1 to ensure the smooth conduction of current.

[0036] The first anode 21 and the second anode 22 of the grooved anode layer 2 are thinner at the position closer to the cathode 3 in the width direction of the cathode 3.

[0037] The anode pad 4 is provided on the top of all the grooved anode layers 2, covers the two side edges of the grooved anode layer 2, and forms a Schottky contact with the semiconductor layer 1 to further optimize the current conduction performance.

[0038] In some embodiments, the semiconductor layer 1 includes a GaN layer 11 and an AlGaN layer 12. The GaN layer 11 is the base layer of the semiconductor layer, with a thickness of 0.3 - 20 μm, having good electrical conductivity and thermal stability. The AlGaN layer 12 is located above the GaN layer 11, with a thickness of 10 - 30 nm, where the molar fraction of Al is 20% - 30%. It forms a heterojunction with the GaN layer 11, generating a high-concentration two-dimensional electron gas.

[0039] The contact surface between the GaN layer 11 and the AlGaN layer 12 in each semiconductor layer 1 forms a first contact surface 13 to ensure the effective transmission of the electron gas. The contact surface between the AlGaN layer 12 and the GaN layer 11 in adjacent semiconductor layers 1 forms a second contact surface 14 to further optimize the mobility of the electron gas.

[0040] The semiconductor layer 1 where the grooved anode layer 2 is located is the uppermost semiconductor layer 1 in contact with the top of the grooved anode layer 2, and the semiconductor layer 1 corresponding to the grooved anode layer 2 is the semiconductor layer 1 reached by the bottom of the grooved anode layer 2.

[0041] In some embodiments, the grooved anode layer 2 includes a first anode 21 and a second anode 22. The first anode 21 extends downward from the surface of the AlGaN layer 12 in the semiconductor layer 1 where it is located and penetrates through to the GaN layer 11 of the corresponding semiconductor layer 1, and is 1 - 10 nm below the first contact surface 13 of the corresponding semiconductor layer 1 to ensure good contact with the GaN layer 11. The second anode 22 extends downward from the surface of the AlGaN layer 12 in the semiconductor layer 1 where it is located and penetrates through to the AlGaN layer 12 of the corresponding one, and is 1 - 2 nm above the corresponding first contact surface 13 to ensure good contact with the AlGaN layer 12. Thus, in the grooved anode layer 2, the thickness of the first anode 21 is thicker than that of the second anode 22, and within the grooved anode layer 2, the thickness is also thinner closer to the cathode 3.

[0042] In some embodiments, the material of the anode pad 4 is one or a combination of nickel and gold, with a thickness of 1 - 50 nm. The anode pad 4 forms a Schottky contact with the semiconductor layer 1 to further optimize the current conduction performance.

[0043] In an embodiment provided by the present application, the manufacturing method of a multi-layer gallium nitride Schottky diode with a grooved anode includes: depositing the semiconductor layer 1, etching and filling the grooved anode layer 2, etching and filling the cathode 3, and depositing the anode pad 4.

[0044] Depositing the semiconductor layer 1 includes depositing the first semiconductor layer 1 and depositing subsequent semiconductor layers 1.

[0045] Depositing the first semiconductor layer 1 includes, first depositing a 300-nm GaN layer 11 on the substrate, and then depositing a 20-nm AlGaN layer 12 on the GaN layer 11 to form the first semiconductor layer 1.

[0046] Depositing the subsequent semiconductor layers 1 includes depositing a 300-nm GaN layer 11 on the AlGaN layer 12 of the previous semiconductor layer, and then depositing a 20-nm AlGaN layer 12 to form the second semiconductor layer 1; this step is repeated twice.

[0047] Etching and filling the groove anode layer 2 includes etching and filling the first group of groove anode layers 2 and etching and filling the subsequent groups of groove anode layers 2.

[0048] Etching and filling the first group of groove anode layers 2 includes etching a first groove with a depth of 662 nm on the edge side of the AlGaN layer 12 of the outermost semiconductor layer 1, and filling the first groove with metal to form an ohmic contact as the first anode 21; etching a second groove with a depth of 659 nm at a position 15 nm in the width direction of the cathode 3 from the first groove, and filling the second groove with metal to form a Schottky contact as the second anode 22.

[0049] Etching and filling the subsequent groups of groove anode layers 2 includes etching a third groove with a depth of 342 nm at a position 15 nm in the width direction of the cathode 3 from the second anode 22 filled in the second groove, and filling the third groove with metal to form an ohmic contact as the first anode 21 of the second group of groove anode layers 2; etching a fourth groove with a depth of 339 nm at a position 15 nm in the width direction of the cathode 3 from the third groove, and filling the fourth groove with metal to form a Schottky contact as the second anode 22 of the second group of groove anode layers 2; etching a fifth groove with a depth of 22 nm at a position 15 nm in the width direction of the cathode 3 from the second anode 22 filled in the fourth groove, and filling the fifth groove with metal to form an ohmic contact as the first anode 21 of the third group of groove anode layers 2; etching a sixth groove with a depth of 19 nm at a position 15 nm in the width direction of the cathode 3 from the fifth groove, and filling the sixth groove with metal to form a Schottky contact as the second anode 22 of the third group of groove anode layers 2.

[0050] Etching and filling the cathode 3 includes etching a groove on the side of the AlGaN layer 12 of the outermost semiconductor layer 1 away from the groove anode layer 2 and filling it with metal to form the cathode 3.

[0051] Etching a seventh groove with a depth of 960 nm at a position 4.5 μm in the width direction of the cathode 3 from the sixth groove, and filling the seventh groove with metal to form an ohmic contact as the cathode 3.

[0052] The deposition of the anode pad 4 includes depositing the anode pad 4 on the grooved anode layer 2 of the AlGaN layer 12 of the outermost semiconductor layer 1. One side boundary of the anode pad 4 is aligned with the boundary of the first groove away from the second groove, and the other side boundary of the anode pad 4 is aligned with the boundary of the sixth groove away from the fifth groove.

[0053] It should be noted that in the etching and filling of the grooved anode layer 2, the production order of the anode can be swapped, and it can start from any groove after the overall design is determined; the production order of the etching and filling of the grooved anode layer 2 and the etching and filling of the cathode 3 can also be swapped.

[0054] Among them, the deposition temperature of the GaN layer 11 of the semiconductor layer 1 is 100 - 2000 °C, and the deposition temperature of the AlGaN layer 12 is 200 - 2000 °C.

[0055] As an alternative embodiment, Figure 3 This is the equivalent circuit diagram of the multi-layer gallium nitride Schottky diode with a grooved anode of the present invention. Among them, S1, S2, and S3 are the equivalent Schottky diodes of the AlGaN layer 12 of the first semiconductor layer 1, the AlGaN layer 12 of the second semiconductor layer 1, and the AlGaN layer 12 of the third, i.e., the outermost semiconductor layer 1; their conduction voltages are V TS1 、V TS2 、V TS3 . D1, D2, and D3 are imaginary ideal diodes, represented by a dashed box indicating that they do not actually exist, and the conduction voltage of D1 is the same as that of S1, the conduction voltage of D2 is the same as that of S2, and the conduction voltage of D3 is the same as that of S3; the GaN layers 11 of the first semiconductor layer 1, the GaN layers 11 of the second semiconductor layer 1, and the GaN layers 11 of the third, i.e., the outermost semiconductor layer 1, act as resistors, equivalent to resistors R1, R2, and R3.

[0056] The working principle is as follows:

[0057] Two-dimensional electron gas is formed at the contact surface of the GaN layer 11 and the AlGaN layer 12, that is, the first contact surface 13 of each group of semiconductor layers 1. The first anode 21 in the semiconductor layer 1 is controlled by the second anode 22. Specifically, when the Schottky diodes S1, S2, and S3 equivalent to the second anode 22 are not conducting, the two-dimensional electron gas is truncated, and at this time, electrons cannot reach the corresponding first anode 21, equivalent to R1, R2, and R3 being ineffective; when S1, S2, and S3 are conducting, the two-dimensional electron gas is conducting, and electrons can reach the corresponding first anode 21 through the two-dimensional electron gas, equivalent to R1, R2, and R3 being conducting.

[0058] Therefore Figure 3In the figure, an imaginary ideal diode D1, D2, and D3 are respectively added to the branches R1, R2, and R3, and their conduction voltages are respectively controlled to be equal to the conduction voltages of S1, S2, and S3, which is used to describe that the conduction of the branches R1, R2, and R3 is actually controlled by S1, S2, and S3.

[0059] When the cathode is grounded and a positive voltage is applied to the anode, assuming V TS1 <V TS2 <V TS3 , when V < V TS1 , the two-dimensional electron gas on the first contact surface 13 of the three groups of semiconductor layers 1 is truncated, and all six branches are not conducting, and the circuit is in the cut-off state at this time.

[0060] When V TS1 <V < V TS2 , the two-dimensional electron gas on the first contact surface 13 of the first group of semiconductor layers 1 is conducting, and branches 1 and 2 are conducting. At this time, the Schottky diode S1 can be regarded as a non-linear resistor. Since the parallel resistance is smaller than the resistance on any one branch, the resistance of the conduction path is smaller than R1 and S1 at this time. If R1 is controlled to be much smaller than the forward conduction resistance of S1, the total resistance will be much smaller than the conduction resistance of S1, and the forward current will be significantly increased.

[0061] When V TS2 <V < V TS3 , the two-dimensional electron gas on the first contact surface 13 of the first group of semiconductor layers 1 and the first contact surface 13 of the second group of semiconductor layers 1 is conducting, and branches 1, 2, 3, and 4 are conducting. Similarly, at this time, the Schottky diodes S1 and S2 can be regarded as a non-linear resistor, and the total resistance is the parallel connection of S1, S2, R1, and R2, and the total resistance further decreases, and the forward current is further optimized.

[0062] When V TS3 <V, the two-dimensional electron gas on the first contact surface 13 of the three groups of semiconductor layers 1 is all conducting. At this time, all 6 branches are conducting, the total resistance reaches the minimum, and the forward current is the largest. Further, V TS1 = V TS2 = V TS3 = V TS can be achieved through the process. At this time, when V > V TS , the maximum forward conduction current can be obtained.

[0063] When the cathode is grounded and a reverse voltage is applied to the anode, the two-dimensional electron gas is truncated by the Schottky diodes S1, S2, and S3, and electrons cannot flow from the first anode 21 of the three groups of groove anode layers 2 to the cathode 3. Therefore, in the equivalent circuit, branches 2, 4, and 6 are cut off, and the circuit is equivalent to the parallel connection of three Schottky diodes.

[0064] Compared with the prior art, the present invention combines the advantages of a multi-layer conductive channel and a composite anode structure, further reducing the turn-on voltage and conduction resistance of the Schottky diode. The turn-on voltage can be reduced to 0.4 - 0.5V, a decrease of 0.3 - 0.4V compared with the prior art level of 0.8V; the forward current during conduction can reach 10 -1 -10 -2 magnitude, showing a significant improvement compared with the prior art level of 10 -3 -10 -4 magnitude.

[0065] Finally, it should be noted that the methods and devices described in detail above are only examples, and those skilled in the art can modify these examples in different ways as long as they do not depart from the scope of the present invention.

Claims

1. A multi-layer gallium nitride Schottky diode with a grooved anode, characterized in that: including, at least two semiconductor layers (1), each semiconductor layer (1) including a bottom GaN layer (11) and a top AlGaN layer (12), and the two semiconductor layers (1) are arranged in sequence from bottom to top; a grooved anode layer (2), corresponding to the semiconductor layer (1) one by one, including a first anode (21) and a second anode (22), the first anode (21) being in ohmic contact with the corresponding GaN layer (11), and the second anode (22) being in Schottky contact with the corresponding AlGaN layer (12); a cathode (3), disposed at one end of the top semiconductor layer (1) away from the grooved anode layer (2), penetrating through all the semiconductor layers (1), and the cathode (3) being in ohmic contact with the semiconductor layer (1); and, an anode pad (4), disposed on top of all the grooved anode layers (2), and the anode pad (4) being in Schottky contact with the semiconductor layer (1).

2. The multi-layer gallium nitride Schottky diode with a grooved anode according to claim 1, wherein: the thickness of the GaN layer (11) is 0.3 - 20 um; the thickness of the AlGaN layer (12) is 10 - 30 nm, and the molar fraction of Al is 20% - 30%.

3. The multi-layer gallium nitride Schottky diode with a grooved anode according to claim 2, wherein: a first contact surface (13) is formed at the contact surface between the GaN layer (11) and the AlGaN layer (12) of each semiconductor layer (1), and a second contact surface (14) is formed at the contact surface between the AlGaN layer (12) and the GaN layer (11) of adjacent semiconductor layers (1).

4. The multi-layer gallium nitride Schottky diode with a grooved anode according to claim 3, wherein: the first anode (21) extends downward from the surface of the AlGaN layer (12) of the semiconductor layer (1) where it is located and penetrates through to the corresponding GaN layer (11), and is 1 - 10 nm below the corresponding first contact surface (13).

5. The multi-layer gallium nitride Schottky diode with a grooved anode according to claim 4, wherein: the second anode (22) extends downward from the surface of the AlGaN layer (12) of the semiconductor layer (1) where it is located and penetrates through to the corresponding AlGaN layer (12), and is 1 - 2 nm above the corresponding first contact surface (13).

6. The multi-layer gallium nitride Schottky diode with a grooved anode according to claim 5, wherein: the distance between adjacent first anodes (21) and second anodes (22) is 1 - 100 nm.

7. The multi-layer gallium nitride Schottky diode with a grooved anode according to claim 6, wherein: the thickness of the grooved anode layer (2) decreases successively along the arrangement in the width direction of the cathode (3).

8. The multi-layer gallium nitride Schottky diode with a grooved anode according to claim 7, wherein: The distance from the boundary of the grooved anode layer (2) close to the cathode (3) to the cathode (3) is 1 - 20 μm.

9. The multi-layer gallium nitride Schottky diode with a grooved anode according to claim 8, wherein: The material of the anode pad (4) is one or a combination of nickel and gold, and the thickness is 1 - 50 nm.

10. A manufacturing method of a multi-layer gallium nitride Schottky diode with a grooved anode, characterized in that: Applicable to the Schottky diode according to any one of claims 1 to 9; and the method steps are as follows: Deposit a GaN layer (11), and deposit an AlGaN layer (12) on the GaN layer (11) to form a first semiconductor layer (1); Deposit a GaN layer (11) on the AlGaN layer (12) of the previous semiconductor layer (1), and then deposit an AlGaN layer (12) to form a second semiconductor layer (1); Etch a groove on one side of the AlGaN layer (12) of the outermost semiconductor layer (1) and fill it with metal to form a grooved anode layer (2); Etch a groove on the side of the AlGaN layer (12) of the outermost semiconductor layer (1) away from the grooved anode layer (2) and fill it with metal to form a cathode (3); Deposit an anode pad (4) on the grooved anode layer (2) of the AlGaN layer (12) of the outermost semiconductor layer (1).

Images