Compensation polarization doped aluminum nitride Schottky diode and manufacturing method thereof

Abstract

The invention relates to a compensation polarization doped aluminum nitride Schottky diode and a manufacturing method thereof. The compensation polarization doped aluminum nitride Schottky diode comprises a substrate, an unintentionally doped AlN layer, a Si doped AlN layer and a Si compensation doped Al component slowly-decreasing layer from bottom to top. The surface of the Si-doped AlN layer is in Schottky contact with the anode of the diode; the Si compensation doped Al component slowly-decreasing layer is from AlN to Al < x > Ga < 1-x > N from bottom to top, the value range of x is 0-0.3, and ohmic contact is formed between the Si compensation doped Al component slowly-decreasing layer and the cathode of the diode. According to the aluminum nitride Schottky diode, through compensation polarization doping, the metal contact performance is improved, the problems that the material surface is rough and the carrier mobility is low due to impurity doping are solved, and the Schottky diode with the high potential barrier and the low ideal factor is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor devices, and particularly relates to a compensated polarization-doped aluminum nitride Schottky diode and a manufacturing method thereof. Background Art

[0002] The bandgap of the semiconductor material aluminum nitride (AlN) is 6.2 eV. At the same time, it has good electron mobility, high electron saturation velocity, high breakdown field strength, high thermal conductivity, etc., and has an extremely high Baliga figure of merit, enabling high-power and high-temperature applications. In recent years, with the breakthrough of AlN material epitaxial technology, large-size AlN single-crystal materials with low defect density have been grown on substrates such as sapphire and SiC, greatly promoting the development of AlN power technology. However, due to problems related to the activation of donor doping (such as Si), devices based on AlN channels face problems such as low carrier concentration, low mobility, and large electrode contact resistance. The reason is that the activation energy level of donor impurities in the AlN crystal is deep and the activation rate is low. In order to maintain a certain carrier concentration, AlN is always heavily doped, resulting in a rough surface morphology and low carrier mobility. This leads to an excessively high ideality factor of the AlN diode, and the on-current is much lower than the ideal value. Therefore, in order to fully utilize the advantages of the ultra-wide bandgap semiconductor material AlN in the field of power electronics, it is necessary to improve the existing AlN doping technology, improve the metal contact performance, and realize a Schottky diode with a high barrier and a low ideality factor. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a compensated polarization-doped aluminum nitride Schottky diode to improve the metal contact performance and realize a Schottky diode with a high barrier and a low ideality factor.

[0004] The present invention provides a compensated polarization-doped aluminum nitride Schottky diode, which includes a substrate, an unintentionally doped AlN layer, a Si-doped AlN layer, and a Si-compensated doped Al composition gradually decreasing layer from bottom to top; a Schottky contact is formed between the surface of the Si-doped AlN layer and the anode of the diode; the Si-compensated doped Al composition gradually decreasing layer changes from AlN to Al x Ga 1-x N from bottom to top, where the value range of x is 0 to 0.3, and an ohmic contact is formed between this layer and the cathode of the diode.

[0005] Preferably, the Si-doped AlN layer is a voltage-resistant layer, and the Si doping concentration is 10 15 cm -3 order of magnitude.

[0006] Preferably, the Si-compensated doped Al composition gradually decreasing layer is an ohmic contact layer, and the Al composition gradually decreases from 1 to x. The decrease in the Al composition is to facilitate the formation of an ohmic contact. However, when the Al composition decreases, a distributed polarization P-type doping will be formed. By increasing the thickness of this layer, the change gradient of the Al composition is slowed down to reduce the hole concentration introduced by the polarization doping. The thickness is 300 nm to 1 μm. At the same time, N-type heavy doping is achieved by using Si doping compensation, and the electron concentration is 10 17 ~10 18 cm -3 。

[0007] Preferably, the anode of the diode is a first metal electrode, and its material includes any one or a combination of several of V, Al, Ni, Au, TiN, W, and Ta.

[0008] Preferably, the cathode of the diode is a second metal electrode, and its material includes any one or a combination of several of Ti, Al, Ni, Au, TiN, W, Ta, Pt, and Pd.

[0009] Preferably, the material of the substrate includes any one of single crystal AlN, SiC, sapphire, or single crystal GaN.

[0010] Preferably, the compensated polarization doped aluminum nitride Schottky diode further includes an insulating dielectric layer, and its material includes any one or a combination of several of SiO2, silicon nitride, Al2O3, and AlN.

[0011] The present invention also provides a method for manufacturing a compensated polarization doped aluminum nitride Schottky diode, including the following steps:

[0012] S1: Material epitaxy: Sequentially epitaxially grow an unintentionally doped AlN layer, a Si-doped AlN layer, and a Si-compensated doped Al composition gradually decreasing layer (decreasing from AlN to Al x Ga 1-x N) on the substrate;

[0013] S2: Step etching: Determine the etching window by lithography, then etch away the Si-compensated doped Al composition gradually decreasing layer, stop at the surface of the Si-doped AlN layer, and optimize the solution to treat the etched surface;

[0014] S3: Surface passivation: Deposit an insulating dielectric layer to passivate the etched surface;

[0015] S4: Dielectric etching: Determine the etching window by lithography, and etch away the insulating dielectric layer at the Schottky contact and ohmic contact positions through RIE;

[0016] S5: Metal Deposition and Annealing: Deposit Schottky contact metal and Ohmic contact metal respectively, then form the first metal electrode and the second metal electrode through etching respectively, and form Schottky contact and Ohmic contact after annealing treatment.

[0017] Preferably, the epitaxial method in step S1 includes any one of metal organic chemical vapor deposition (MOCVD), metal organic vapor phase epitaxy (MOVPE), or molecular beam epitaxy (MBE).

[0018] Preferably, the etching method in step S2 includes but is not limited to inductively coupled plasma - reactive ion etching (ICP - RIE); the etching method in step S4 includes but is not limited to reactive ion etching (RIE).

[0019] Preferably, the deposition method in step S3 includes any one of atomic layer deposition (ALD) or plasma enhanced chemical vapor deposition (PECVD).

[0020] Beneficial effects

[0021] The present invention uses an Si - doped AlN layer, and at the same time places the Schottky contact and the voltage - withstand layer above the unintentionally doped AlN layer. Compared with the structure where the top layer is the voltage - withstand layer in distributed polarization doping, its advantage lies in reducing the material defects caused by hetero - epitaxy with Al - component changes and the leakage current caused thereby, improving the material properties of the voltage - withstand layer. At the same time, since the required Si doping concentration in the voltage - withstand layer is relatively low, the problems of surface roughness and low carrier mobility introduced by doping are within a controllable range. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic structural diagram of a compensated polarization - doped aluminum nitride Schottky diode in the present invention.

[0023] Reference Numerals: 1 - Substrate, 2 - Unintentionally doped AlN layer, 3 - Si - doped AlN layer, 4 - Si - compensated doped Al - component gradual change reduction layer, 5 - Insulating dielectric layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The following further elaborates the present invention in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0025] Embodiment

[0026] This embodiment provides a compensated polarization - doped aluminum nitride Schottky diode, and its structure is asFigure 1 As shown in the figure, from bottom to top, it includes a substrate 1, an unintentionally doped AlN layer 2, a Si-doped AlN layer 3, and a Si-compensated doped Al-composition gradually decreasing layer 4, and also includes an insulating dielectric layer 5; a Schottky contact is formed between the surface of the Si-doped AlN layer 3 and the anode of the diode; the Si-compensated doped Al-composition gradually decreasing layer 4 gradually changes from AlN to Al x Ga 1-x N, where the value range of x is 0 to 0.3, and an ohmic contact is formed between this layer and the cathode of the diode.

[0027] The manufacturing method of the above-mentioned compensated polarization-doped aluminum nitride Schottky diode includes the following steps:

[0028] S1: Material epitaxy: The unintentionally doped AlN layer 2, the Si-doped AlN layer 3, and the Si-compensated doped Al-composition gradually decreasing layer 4 are sequentially epitaxially grown on the substrate 1 by MOCVD or MOVPE or MBE.

[0029] S2: Step etching: The etching window is determined by photolithography, and the Si-compensated doped Al-composition gradually decreasing layer 4 is etched away by ICP-RIE, stopping at the surface of the Si-doped AlN layer 3, and the etched surface is optimized by solution treatment.

[0030] S3: Surface passivation: The insulating dielectric layer 5 is deposited by ALD or PECVD or other methods to passivate the etched surface.

[0031] S4: Dielectric etching: The etching window is determined by photolithography, and the insulating dielectric layer 5 at the Schottky contact and ohmic contact positions is etched away by RIE.

[0032] S5: Metal deposition and annealing: The Schottky contact metal and the ohmic contact metal are respectively deposited, and then the first metal electrode and the second metal electrode, that is, the anode and cathode of the diode, are formed by etching. After annealing treatment, the Schottky contact and the ohmic contact are formed.

Claims

1. A compensated polarization doped aluminum nitride Schottky diode, characterized in that, The compensated polarization-doped aluminum nitride Schottky diode includes, from bottom to top, a substrate, an unintentionally doped AlN layer, an Si-doped AlN layer, and an Si-compensated doped Al composition gradually decreasing layer; a Schottky contact is formed between the surface of the Si-doped AlN layer and the anode of the diode; the Si-compensated doped Al composition gradually decreasing layer ranges from AlN to Al from bottom to top x Ga 1-x N, where the value range of x is 0 to 0.3, and this layer forms an ohmic contact with the cathode of the diode.

2. The compensated polarization doped aluminum nitride Schottky diode according to claim 1, wherein The thickness of the Si-compensated doped Al composition gradually decreasing layer is 300 nm to 1 μm.

3. The compensated polarization-doped aluminum nitride Schottky diode according to claim 1, wherein The anode of the diode is the first metal electrode, and its material includes any one or a combination of several of V, Al, Ni, Au, TiN, W, and Ta.

4. The compensated polarization doped aluminum nitride Schottky diode according to claim 1, characterized in that, The cathode of the diode is the second metal electrode, and its material includes any one or a combination of several of Ti, Al, Ni, Au, TiN, W, Ta, Pt, and Pd.

5. The compensated polarization-doped aluminum nitride Schottky diode according to claim 1, wherein The material of the substrate includes any one of single crystal AlN, SiC, sapphire, or single crystal GaN.

6. The compensated polarization-doped aluminum nitride Schottky diode according to claim 1, wherein The compensated polarization doped aluminum nitride Schottky diode further includes an insulating dielectric layer, and its material includes any one or a combination of several of SiO2, silicon nitride, Al2O3, and AlN.

7. A manufacturing method of a compensated polarization doped aluminum nitride Schottky diode, comprising the following steps: S1: Material epitaxy: sequentially epitaxially grow an unintentionally doped AlN layer, a Si-doped AlN layer, and a Si-compensated doped Al composition gradually decreasing layer on the substrate; S2: Step etching: photolithography to determine the etching window, then etch away the Si-compensated doped Al composition gradually decreasing layer, stop at the surface of the Si-doped AlN layer, and optimize the solution to treat the etched surface; S3: Surface passivation: deposit an insulating dielectric layer to passivate the etched surface; S4: Dielectric etching: photolithography to determine the etching window, and etch away the insulating dielectric layer at the Schottky contact and ohmic contact positions by RIE; S5: Metal deposition and annealing: deposit the Schottky contact metal and the ohmic contact metal respectively, then form the first metal electrode and the second metal electrode by etching respectively, and form the Schottky contact and the ohmic contact after annealing treatment.

8. The manufacturing method according to claim 7, characterized in that, The epitaxy method in the step S1 includes any one of metal organic chemical vapor deposition, metal organic vapor epitaxial growth, or molecular beam epitaxy.

9. The manufacturing method according to claim 7, characterized in that, The etching method in the step S2 includes inductively coupled plasma-reactive ion etching; the etching method in the step S4 includes reactive ion etching.

10. The manufacturing method according to claim 7, wherein The deposition method in the step S3 includes any one of atomic layer deposition or plasma enhanced chemical vapor deposition.

Images