Device structure and determination method of channel carrier mobility of a p-gan / algan / gan hemt device

Abstract

This invention relates to a device structure and method for determining the channel carrier mobility of a P-GaN / AlGaN / GaN HEMT device, belonging to the field of microelectronics research technology. The method includes: fabricating an ohmic metal electrode next to the P-GaN / AlGaN / GaN HEMT device and determining the gate resistance; determining the two-dimensional electron gas concentration of the P-GaN / AlGaN / GaN HEMT device under different gate voltages; and calculating the carrier mobility based on the gate resistance obtained in step S1 and the two-dimensional electron gas concentration obtained in step S2. This invention, by introducing an ohmic metal electrode with a spacing equal to the sum of the gate-source spacing and the gate-drain spacing to the right side of the drain of the P-GaN device, can directly obtain the gold-semiconductor contact resistance and the sum of the gate-source and gate-drain channel resistances, facilitating rapid calculation of the device channel carrier mobility and providing more accurate results.

Description

Technical Field

[0001] This invention relates to a device structure and method for determining the channel carrier mobility of a P-GaN / AlGaN / GaN HEMT device, belonging to the field of microelectronics research technology. Background Technology

[0002] With the development of third-generation semiconductor technology, enhancement-mode AlGaN / GaN high electron mobility transistors (HEMTs) based on GaN materials have attracted widespread attention in the fields of power electronics and radio frequency power devices due to their usually-off characteristics, high power density, and high reliability. Compared with depletion-mode HEMTs, enhancement-mode HEMTs have significant advantages in system safety and simplified drive circuits, and have become an important development direction for GaN power devices. Channel carrier mobility is an important physical parameter characterizing the electrical performance of enhancement-mode AlGaN / GaN HEMT devices, and its magnitude directly affects the device's on-resistance, transconductance characteristics, and high-frequency performance.

[0003] However, in existing technologies, channel carrier mobility is typically extracted using Hall effect measurements or transmission line model (TLM)-based methods. These methods are insufficient to reflect the actual channel carrier mobility in operation or are not directly applicable to enhancement-mode gallium nitride (GaN) devices. Therefore, there is an urgent need to design a device structure for rapidly extracting channel carrier mobility in enhancement-mode AlGaN / GaN HEMTs, and to combine this with a suitable fabrication process to achieve extraction of channel carrier mobility during device operation. Summary of the Invention

[0004] To address the difficulty in accurately extracting channel carrier mobility in current enhancement-mode GaN HEMT devices, this invention provides a device structure and method for determining the channel carrier mobility of a P-GaN / AlGaN / GaN HEMT device. By designing an ohmic metal electrode at a specific distance from the drain of the device, the extraction of channel mobility is simplified and the extraction results are more accurate.

[0005] The present invention adopts the following technical solution: A device structure for a P-GaN / AlGaN / GaN HEMT device with high channel carrier mobility includes, from bottom to top, a P-type doped silicon substrate, an AlN nucleation layer, a GaN buffer layer, an AlN insertion layer, and an AlGaN barrier layer. Source and ohmic metal electrodes are respectively disposed on both sides of the P-GaN / AlGaN / GaN HEMT device above the GaN buffer layer, with a drain electrode disposed between the source and ohmic metal electrodes. A gate electrode is disposed above the AlGaN barrier layer between the source and drain electrodes, and a Schottky metal electrode is disposed above the gate electrode. Gate-source spacing L GS Spacing L with the gateGD The sum equals the distance L1 between the ohmic metal electrode and the drain electrode, i.e., L GS +L GD =L1.

[0006] The preferred method for fabricating P-GaN / AlGaN / GaN HEMT devices is as follows: (1) An AlN nucleation layer, a GaN buffer layer, an AlN insertion layer, an AlGaN barrier layer and a p-GaN cap layer are epitaxially grown sequentially on a p-type doped silicon substrate. (2) Part of the P-GaN cap layer is removed by dry etching, and the remaining P-GaN cap layer forms the gate; (3) Mesa isolation is achieved by dry etching. Metal Ti / Al / Ni / Au is deposited at both ends and in the middle above the GaN buffer layer, and ohmic contacts are formed by annealing to obtain the source, drain and ohmic metal electrodes; the gate-source spacing L is ensured during fabrication. GS Spacing L with the gate GD The sum of these equals the distance L1 between the ohmic metal electrode and the drain electrode; (4) A Schottky metal electrode is formed by vapor deposition of metallic Ni / Au over the p-GaN cap layer.

[0007] Preferably, the thickness of the p-GaN cap layer is 50 ~ 120 nm.

[0008] Preferably, the thickness of Ti in the source, drain and ohmic metal electrodes is 5~100nm, the thickness of Al is 50~200nm, the thickness of Ni is 30~150nm, and the thickness of Au is 30~150nm.

[0009] Preferably, the thickness of Ti in the source, drain and ohmic metal electrodes is 30 nm, the thickness of Al is 150 nm, the thickness of Ni is 50 nm, and the thickness of Au is 50 nm.

[0010] Preferably, the growth method in step (1) is liquid phase epitaxy (LPE), metal-organic chemical vapor deposition (MOCVD), or molecular beam epitaxy (MBE); more preferably, the growth method of AlN nucleation layer, GaN buffer layer and channel layer, AlN insertion layer, AlGaN barrier layer and P-type GaN cap layer in step (1) is metal-organic chemical vapor deposition (MOCVD).

[0011] The dry etching in steps (2) and (3) is inductively coupled plasma etching (ICP) or reactive ion etching (RIE). More preferably, the method for etching the p-GaN cap layer and the mesa etching isolation in steps (2) and (3) is inductively coupled plasma etching (ICP).

[0012] Preferably, the method for depositing metal Ti / Al / Ni / Au in step (3) is electron beam evaporation or magnetron sputtering; the annealing temperature of metal Ti / Al / Ni / Au is 400℃-900℃, and the annealing time is 0.5-3min.

[0013] Further preferred, in step (3), the method for evaporating metal Ti, metal Al, metal Ni, and metal Au is electron beam evaporation, and the annealing condition for ohmic metal is annealing at 850°C for 45s in N2.

[0014] A method for determining the channel carrier mobility of a P-GaN / AlGaN / GaN HEMT device, based on the aforementioned device structure, includes the following steps: S1. Fabricate an ohmic metal electrode next to the P-GaN / AlGaN / GaN HEMT device and determine the gate resistance. ; S2, Determine the two-dimensional electron gas concentration of P-GaN / AlGaN / GaN HEMT devices at different gate voltages. ; S3, based on the gate resistance in step S1 The carrier mobility is calculated from the two-dimensional electron gas concentration in step S2. μ = ,in, The gate length of the device. The amount of electron charge. This represents the gate width of the device.

[0015] Preferably, the gate resistance is determined in step S1. The process is as follows: S11, due to L GS +L GD =L1, then the gate-source resistance R GS and gate-drain resistance R GD The sum of these values ​​is equal to the resistance R1 between the ohmic metal electrode and the drain, i.e., R GS +R GD =R1; A voltage V1 = 0.1V is applied between the drain and the ohmic metal electrode. The current I1 between the two electrodes under this voltage is measured. Then the total resistance R = 2R. C +R1=V1 / I1, where R C R1 is the contact resistance between the drain and the semiconductor or the contact resistance between the ohmic metal electrode and the semiconductor, and R1 is the channel resistance. The gate-source resistance R of P-GaN / AlGaN / GaN HEMT devices GS Gate-drain resistance R GDContact resistance R between source metal and semiconductor C Contact resistance R between drain metal and semiconductor C The sum is R GS +R GD +2R C =R1+2R C =V1 / I1; Since the ohmic metal electrode on the right is fabricated next to the P-GaN HEMT device, the contact resistance between the source / drain of the device and the semiconductor is equal to the contact resistance between the ohmic metal electrode and the semiconductor. Therefore, the gate-source resistance R of the device is equal to the contact resistance between the source / drain of the device and the semiconductor. GS + Gate-drain resistance R GD +Source-to-semiconductor contact resistance R C +Drain-to-semiconductor contact resistance R C = Channel resistance R1 between the drain and the ohmic metal + Contact resistance R between the device drain and the semiconductor C +Contact resistance R between the ohmic metal electrode and the semiconductor C .

[0016] S12, apply voltage V across the gate and source terminals. GS The source-drain voltage is set to V. DS =10V, test the output characteristics of P-GaN / AlGaN / GaN HEMT devices at different gate voltages (I DS -V DS ) curve, take V DS Current I at 0.1V DS -Voltage V DS Data, total source-drain resistance R of the device Z =V DS / I DS The total resistance R under different gate voltages can be obtained. Z ; Depending on the device structure, the total resistance R under different gate voltages Z =2R C +R GS +R G +R GD R here C R is the contact resistance between the source metal and the semiconductor, or the contact resistance between the drain metal and the semiconductor, and its value is equal to the contact resistance between the ohmic metal electrode and the semiconductor. G The gate resistance; according to R in step S11 GS +R GD =R1,R Z =2R C +R GS +R G +R GD =2R C +R1+RG , of which 2R C +R1 has been obtained in step S11, so the gate resistance R under different gate voltages G =R Z –(2R C +R1), the gate resistance R under different gate voltages is obtained by iterative solution. G .

[0017] Preferably, the implementation process in step S2 is as follows: By applying voltages across the gate and source, the enhancement device is tested under different gate voltages. C - V Curve (capacitance-voltage curve), two-dimensional electron gas concentration pass C - V Line integrals yield: ,in To apply gate voltage, The point on the CV curve where the capacitance changes the most rapidly corresponds to value, Obtained by differentiating the capacitance-voltage curve. The gate capacitance is being tested. For the area of ​​the Schottky contact, This represents the electron charge.

[0018] For any details not covered in this invention, please refer to the prior art.

[0019] The beneficial effects of this invention are as follows: 1. This invention introduces an ohmic metal electrode with a spacing equal to the sum of the gate-source spacing and the gate-drain spacing on the right side of the drain of a P-GaN device. This allows for the direct acquisition of the ohmic metal-semiconductor contact resistance and the sum of the gate-source and gate-drain channel resistances, facilitating rapid and accurate calculation of the device channel carrier mobility.

[0020] 2. Due to uneven P-GaN etching in different areas of the wafer, some areas may have thin P-GaN or be slightly over-etched, leading to R... C Test results that are too high or too low can lead to errors in the contact resistance between the source and drain regions of the device, affecting the accuracy of mobility extraction. This invention, by placing an ohmic metal electrode a few micrometers away from the drain side of the device, can almost completely eliminate contact resistance errors caused by uneven etching. The device structure of this invention can directly eliminate errors in metal-semiconductor contact resistance caused by uneven P-GaN etching in different regions of the wafer, improving the accuracy of calculations.

[0021] 3. The device structure in this invention is based on the existing P-GaN / AlGaN / GaN HEMT process manufacturing flow, and the key process steps are designed in a targeted manner. There is no need to introduce additional complex test structures and process steps, which has good feasibility.

[0022] 4. This invention achieves the calculation of channel carrier mobility by designing a new device structure, which can provide new design ideas and theoretical basis for subsequent devices in terms of electrical characteristic control and reliability improvement. Attached Figure Description

[0023] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application.

[0024] Figure 1 The structure obtained in step (1) of this invention; Figure 2 The structure obtained in step (2) of this invention; Figure 3 The structure obtained in step (3) of this invention; Figure 4 This is a schematic diagram of the P-GaN / AlGaN / GaN HEMT device structure of the present invention; In the figure, 1-P-type doped silicon substrate, 2-AlN nucleation layer, 3-GaN buffer layer, 4-AlN insertion layer, 5-AlGaN barrier layer, 6-gate, 7-source, 8-drain, 9-ohmic metal electrode, 10-Schottky metal electrode. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. However, this is not the only description; all aspects not described in detail herein are based on conventional techniques in the art.

[0026] Example 1 A device structure for improving the channel carrier mobility of a P-GaN / AlGaN / GaN HEMT device, such as... Figures 1 to 4 As shown, from bottom to top, the device includes a P-type doped silicon substrate 1, an AlN nucleation layer 2, a GaN buffer layer 3, an AlN insertion layer 4, and an AlGaN barrier layer 5. A source electrode 7 and an ohmic metal electrode 9 are respectively disposed on both sides of the P-GaN / AlGaN / GaN HEMT device above the GaN buffer layer 3. A drain electrode 8 is disposed between the source electrode 7 and the ohmic metal electrode 9. A gate electrode 6 is disposed above the AlGaN barrier layer 5 between the source electrode 7 and the drain electrode 8. A Schottky metal electrode 10 is disposed above the gate electrode 6. Gate-source spacing LGS Spacing L with the gate GD The sum equals the distance L1 between the ohmic metal electrode and the drain electrode, i.e., L GS +L GD =L1.

[0027] Example 2 A device structure for a P-GaN / AlGaN / GaN HEMT device with high channel carrier mobility, as described in Example 2, differs in that the fabrication method of the P-GaN / AlGaN / GaN HEMT device is as follows: (1) An AlN nucleation layer 2, a GaN buffer layer 3, an AlN insertion layer 4, an AlGaN barrier layer 5 and a p-GaN cap layer are epitaxially grown sequentially on a p-type doped silicon substrate 1. (2) Part of the P-GaN cap layer is removed by dry etching, and the remaining P-GaN cap layer forms the gate 6; (3) Mesa isolation is achieved by dry etching. Metal Ti / Al / Ni / Au is deposited at both ends and in the middle above the GaN buffer layer 3, and ohmic contacts are formed by annealing to obtain source 7, drain 8 and ohmic metal electrode 9; the gate-source spacing L is ensured during fabrication. GS Spacing L with the gate GD The sum of these equals the distance L1 between the ohmic metal electrode and the drain electrode; (4) A Schottky metal electrode 10 is formed by vapor deposition of metal Ni / Au over the p-GaN cap layer.

[0028] The thickness of the p-GaN cap layer is 100 nm.

[0029] The thickness of Ti in the source electrode 7, drain electrode 8 and ohmic metal electrode 9 is 30 nm, the thickness of Al is 150 nm, the thickness of Ni is 100 nm and the thickness of Au is 100 nm.

[0030] The growth method in step (1) is metal-organic chemical vapor deposition (MOCVD). The dry etching in steps (2) and (3) is inductively coupled plasma etching (ICP).

[0031] Preferably, the method for depositing metal Ti / Al / Ni / Au in step (3) is electron beam evaporation; the annealing temperature of metal Ti / Al / Ni / Au is 850℃ and the annealing time is 45s.

[0032] Example 3 A method for determining the channel carrier mobility of a P-GaN / AlGaN / GaN HEMT device, based on the device structure of Embodiment 2 above, includes the following steps: S1, Fabricate an ohmic metal electrode 9 next to the P-GaN / AlGaN / GaN HEMT device to determine the gate resistance. ; S2, Determine the two-dimensional electron gas concentration of P-GaN / AlGaN / GaN HEMT devices at different gate voltages. ; S3, based on the gate resistance in step S1 The carrier mobility is calculated from the two-dimensional electron gas concentration in step S2. μ = ,in, The gate length of the device. The amount of electron charge. This represents the gate width of the device.

[0033] Example 4 A method for determining the channel carrier mobility of a P-GaN / AlGaN / GaN HEMT device, as described in Example 3, differs in that the gate resistance is determined in step S1. The process is as follows: S11, due to L GS +L GD =L1, then the gate-source resistance R GS and gate-drain resistance R GD The sum of these values ​​is equal to the resistance R1 between the ohmic metal electrode and the drain, i.e., R GS +R GD =R1; A voltage V1 = 0.1V is applied between the drain and the ohmic metal electrode. The current I1 between the two electrodes under this voltage is measured. Then the total resistance R = 2R. C +R1=V1 / I1, where R C R1 is the contact resistance between the drain and the semiconductor or the contact resistance between the ohmic metal electrode and the semiconductor, and R1 is the channel resistance. The gate-source resistance R of P-GaN / AlGaN / GaN HEMT devices GS Gate-drain resistance R GD Contact resistance R between source metal and semiconductor C Contact resistance R between drain metal and semiconductor C The sum is R GS +R GD +2R C =R1+2R C =V1 / I1; S12, apply voltage V across the gate and source terminals. GS The source-drain voltage is set to V. DS=10V, test the output characteristics of P-GaN / AlGaN / GaN HEMT devices at different gate voltages (I DS -V DS ) curve, take V DS Current I at 0.1V DS -Voltage V DS Data, total source-drain resistance R of the device Z =V DS / I DS The total resistance R under different gate voltages can be obtained. Z ; Depending on the device structure, the total resistance R under different gate voltages Z =2R C +R GS +R G +R GD R here C R is the contact resistance between the source metal and the semiconductor, or the contact resistance between the drain metal and the semiconductor, and its value is equal to the contact resistance between the ohmic metal electrode and the semiconductor. G The gate resistance; according to R in step S11 GS +R GD =R1,R Z =2R C +R GS +R G +R GD =2R C +R1+R G , of which 2R C +R1 has been obtained in step S11, so the gate resistance R under different gate voltages G =R Z –(2R C +R1), the gate resistance R under different gate voltages is obtained by iterative solution. G .

[0034] Example 5 A method for determining the channel carrier mobility of a P-GaN / AlGaN / GaN HEMT device, as described in Example 4, differs in that the implementation process in step S2 is as follows: By applying voltages across the gate and source, the enhancement device is tested under different gate voltages. C - V Curve (capacitance-voltage curve), two-dimensional electron gas concentration pass C - V Line integrals yield: ,in To apply gate voltage, The point on the CV curve where the capacitance changes the most rapidly corresponds to value, It can be obtained by differentiating the capacitance-voltage curve. The gate capacitance is being tested. For the area of ​​the Schottky contact, This represents the electron charge.

[0035] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A device structure for improving the channel carrier mobility of a P-GaN / AlGaN / GaN HEMT device, characterized in that, From bottom to top, the device comprises a P-type doped silicon substrate, an AlN nucleation layer, a GaN buffer layer, an AlN insertion layer, and an AlGaN barrier layer. A source electrode and an ohmic metal electrode are respectively disposed on both sides of the P-GaN / AlGaN / GaN HEMT device above the GaN buffer layer, with a drain electrode disposed between the source and the ohmic metal electrode. A gate electrode is disposed above the AlGaN barrier layer between the source and the drain electrode, and a Schottky metal electrode is disposed above the gate electrode. Gate-source spacing L GS Spacing L with the gate GD The sum equals the distance L1 between the ohmic metal electrode and the drain electrode, i.e., L GS +L GD =L1.

2. The device structure for improving the channel carrier mobility of the P-GaN / AlGaN / GaN HEMT device according to claim 1, characterized in that, The fabrication method of P-GaN / AlGaN / GaN HEMT devices is as follows: (1) An AlN nucleation layer, a GaN buffer layer, an AlN insertion layer, an AlGaN barrier layer and a p-GaN cap layer are epitaxially grown sequentially on a p-type doped silicon substrate. (2) Part of the P-GaN cap layer is removed by dry etching, and the remaining P-GaN cap layer forms the gate; (3) Mesa isolation is achieved by dry etching. Metal Ti / Al / Ni / Au is deposited at both ends and in the middle above the GaN buffer layer, and ohmic contacts are formed by annealing to obtain the source, drain and ohmic metal electrodes; the gate-source spacing L is ensured during fabrication. GS Spacing L with the gate GD The sum of these equals the distance L1 between the ohmic metal electrode and the drain electrode; (4) A Schottky metal electrode is formed by vapor deposition of metallic Ni / Au over the p-GaN cap layer.

3. The device structure for improving the channel carrier mobility of the P-GaN / AlGaN / GaN HEMT device according to claim 2, characterized in that, The thickness of the p-GaN cap layer is 50 ~ 120 nm.

4. The device structure for improving the channel carrier mobility of the P-GaN / AlGaN / GaN HEMT device according to claim 3, characterized in that, The thickness of Ti in the source, drain and ohmic metal electrodes is 5~100nm, the thickness of Al is 50~200nm, the thickness of Ni is 30~150nm, and the thickness of Au is 30~150nm.

5. The device structure for improving the channel carrier mobility of the P-GaN / AlGaN / GaN HEMT device according to claim 4, characterized in that, The thickness of Ti in the source, drain and ohmic metal electrodes is 30 nm, the thickness of Al is 150 nm, the thickness of Ni is 50 nm, and the thickness of Au is 50 nm.

6. The device structure for improving the channel carrier mobility of the P-GaN / AlGaN / GaN HEMT device according to claim 5, characterized in that, The growth method in step (1) is liquid phase epitaxy, metal-organic chemical vapor deposition, or molecular beam epitaxy; The dry etching in steps (2) and (3) is either inductively coupled plasma etching or reactive ion etching.

7. The device structure for improving the channel carrier mobility of the P-GaN / AlGaN / GaN HEMT device according to claim 6, characterized in that, In step (3), the method for depositing metal Ti / Al / Ni / Au is electron beam evaporation or magnetron sputtering; the annealing temperature of metal Ti / Al / Ni / Au is 400℃-900℃, and the annealing time is 0.5-3min.

8. A method for determining the channel carrier mobility of a P-GaN / AlGaN / GaN HEMT device, implemented based on the device structure described in any one of claims 1-7, comprising the following steps: S1. Fabricate an ohmic metal electrode next to the P-GaN / AlGaN / GaN HEMT device and determine the gate resistance. ; S2, Determine the two-dimensional electron gas concentration of P-GaN / AlGaN / GaN HEMT devices at different gate voltages. ; S3, based on the gate resistance in step S1 The carrier mobility is calculated from the two-dimensional electron gas concentration in step S2. μ = ,in, The gate length of the device. The amount of electron charge. This represents the gate width of the device.

9. The method for determining the channel carrier mobility of a P-GaN / AlGaN / GaN HEMT device according to claim 8, characterized in that, In step S1, the gate resistance is determined. The process is as follows: S11, due to L GS +L GD =L1, then the gate-source resistance R GS and gate-drain resistance R GD The sum of these values ​​is equal to the resistance R1 between the ohmic metal electrode and the drain, i.e., R GS +R GD =R1; A voltage V1 = 0.1V is applied between the drain and the ohmic metal electrode. The current I1 between the two electrodes under this voltage is measured. Then the total resistance R = 2R. C +R1=V1 / I1, where R C R1 is the contact resistance between the drain and the semiconductor or the contact resistance between the ohmic metal electrode and the semiconductor, and R1 is the channel resistance. The gate-source resistance R of P-GaN / AlGaN / GaN HEMT devices GS Gate-drain resistance R GD Contact resistance R between source metal and semiconductor C Contact resistance R between drain metal and semiconductor C The sum is R GS +R GD +2R C =R1+2R C =V1 / I1; S12, apply voltage V across the gate and source terminals. GS The source-drain voltage is set to V. DS =10V, test the output characteristic curves of P-GaN / AlGaN / GaN HEMT devices at different gate voltages, and take V DS Current I at 0.1V DS -Voltage V DS Data, total source-drain resistance R of the device Z =V DS / I DS The total resistance R under different gate voltages can be obtained. Z ; Depending on the device structure, the total resistance R under different gate voltages Z =2R C +R GS +R G +R GD R here C R is the contact resistance between the source metal and the semiconductor, or the contact resistance between the drain metal and the semiconductor, and its value is equal to the contact resistance between the ohmic metal electrode and the semiconductor. G The gate resistance; according to R in step S11 GS +R GD =R1,R Z =2R C +R GS +R G +R GD =2R C +R1+R G , of which 2R C +R1 has been obtained in step S11, so the gate resistance R under different gate voltages G =R Z –(2R C +R1), the gate resistance R under different gate voltages is obtained by iterative solution. G .

10. The method for determining the channel carrier mobility of a P-GaN / AlGaN / GaN HEMT device according to claim 3, characterized in that, The implementation process in step S2 is as follows: By applying voltages across the gate and source, the enhancement device is tested under different gate voltages. C - V Curve, two-dimensional electron gas concentration pass C - V Line integrals yield: ,in To apply gate voltage, The point on the CV curve where the capacitance changes the most rapidly corresponds to value, Obtained by differentiating the capacitance-voltage curve. The gate capacitance is being tested. For the area of ​​the Schottky contact, This represents the electron charge.

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