Gallium nitride radio frequency device structure with high long-term reliability and preparation method thereof

Abstract

The invention relates to the technical field of semiconductor devices and manufacturing thereof, and discloses a gallium nitride radio frequency device structure with high long-term reliability and a preparation method of the gallium nitride radio frequency device structure. A source electrode and a drain electrode are arranged at two ends of the surface of a barrier layer, a gate electrode is arranged between the source electrode and the drain electrode, grooves are etched in a substrate layer and an III-N composite buffer layer; the metal layer is attached to the bottom of the substrate layer and the inner side wall of the groove, and is also attached to the side wall of the III-N composite buffer layer in the groove and the bottom of the channel layer, the groove is located near the gate electrode and close to one side of the drain electrode, and the channel layer and the barrier layer form a heterojunction. Two-dimensional electron gas 2DEG is formed on one side, close to the channel layer, of a heterojunction interface formed by the channel layer and the barrier layer and serves as a conducting channel of the gallium nitride device, and the metal layer can extract holes accumulated in the III-N composite buffer layer in a grounding mode. Therefore, hole accumulation in the composite buffer layer caused by high drain voltage during off-state operation is suppressed, and long-term stability and reliability of the device are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices and their manufacturing, and in particular to a gallium nitride radio frequency device structure with high long-term reliability and a preparation method thereof. Background Art

[0002] Since the early 1990s, the research focus of compound semiconductor electronic devices has shifted to wide bandgap semiconductor devices. Wide bandgap materials represented by gallium nitride (GaN) are the third generation of semiconductor materials after silicon (Si) and gallium arsenide (GaAs). GaN has a larger bandgap width (3.4eV), stronger critical breakdown field strength and higher electron migration rate, and has superior properties such as high frequency, high efficiency, high power, high voltage resistance, high temperature resistance and strong radiation resistance. It is a key core material and electronic component supporting the independent innovation development and transformation and upgrading of new generation mobile communications, new energy vehicles, high-speed rail trains, new energy Internet and other industries. Therefore, it has received extensive attention from researchers at home and abroad. It has huge advantages and potential in power electronic devices and high-frequency devices, and has become the focus of global semiconductor technology and industry competition.

[0003] When GaN RF devices are working in the off state, the drain bias voltage is high, and the electric lines are more concentrated where the gate electrode is close to the drain electrode, resulting in a higher local electric field peak. This causes the electrons in the two-dimensional electron gas channel to obtain higher energy, intensifying the collision between internal electrons and lattice atoms, thereby generating a large number of electrons and holes. The holes are sputtered to the buffer layer below the channel layer and accumulate, seriously affecting the long-term stability and reliability of the device.

[0004] To this end, we propose a GaN RF device structure with high long-term reliability and a preparation method thereof, which inhibits the accumulation of holes in the buffer layer of the GaN device and improves the stability and reliability of the device. Summary of the invention

[0005] In order to make up for the deficiencies of the prior art, the purpose of the present invention is to provide a gallium nitride radio frequency device structure with high long-term reliability and a preparation method thereof, so as to suppress the accumulation of holes in the buffer layer of the gallium nitride device and improve the stability and reliability of the device.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A gallium nitride radio frequency device structure with high long-term reliability comprises a back metal, a substrate, a III-N composite buffer layer, a channel layer, and a barrier layer arranged in sequence from bottom to top, a source electrode and a drain electrode are arranged at both ends of the barrier layer surface, and a gate electrode is arranged between the source electrode and the drain electrode. The channel layer and the barrier layer are made of III-N materials, and the channel layer and the barrier layer form a heterojunction. A two-dimensional electron gas (2DEG) is formed at the heterojunction interface formed by the channel layer and the barrier layer and on one side close to the channel 3, serving as a conductive channel of the gallium nitride device. Grooves are etched inside the substrate and the III-N composite buffer layer, and the back metal is attached to the bottom of the substrate and the inner sidewall of the groove, and is also attached to the sidewall of the III-N composite buffer layer in the groove and the bottom of the channel layer.

[0008] The groove is located near the gate electrode and close to the drain electrode. The back metal can extract the holes accumulated in the III-N composite buffer layer by grounding, thereby suppressing the accumulation of holes in the composite buffer layer caused by the high drain voltage during off-state operation, and improving the long-term stability and reliability of the device.

[0009] In the present invention, the source electrode and the drain electrode both form an ohmic contact with the two-dimensional electron gas channel in the channel layer; and the gate electrode forms a Schottky contact with the two-dimensional electron gas channel in the channel layer through the barrier layer.

[0010] In one embodiment of the present invention, a cap layer is provided between the gate electrode and the barrier layer, which has a depletion effect on the two-dimensional electron gas in the channel layer, thereby realizing the enhanced operation of the gallium nitride device. The material of the cap layer is GaN or InGaN, and the doping impurity is Mg with a doping concentration of 1x10 18 -1x10 21 cm -3 .

[0011] In one embodiment of the present invention, the III-N composite buffer layer includes three layers, namely, a nucleation layer, a transition layer and a buffer layer from bottom to top; the material of the nucleation layer is AlN or GaN, with a thickness of 50-300nm; the material of the transition layer is AlGaN, with a thickness of 200-1000nm; the material of the buffer layer is GaN or AlGaN, with a thickness of 100nm-10μm; the nucleation layer, transition layer and buffer layer are unintentionally doped.

[0012] In one embodiment of the present invention, the material of the back metal is Ni and one of Ti, Au, Cu or other metals therein.

[0013] The back metal can extract the holes accumulated in the III-N composite buffer layer by grounding, thereby suppressing the accumulation of holes in the composite buffer layer caused by the high drain voltage during off-state operation, and improving the long-term stability and reliability of the device.

[0014] In one embodiment of the present invention, in one embodiment of the present invention, the material of the substrate is high-resistance silicon, or silicon carbide, or sapphire, or diamond, and the thickness is 50-1200 μm.

[0015] In one embodiment of the present invention, the material of the channel layer is GaN or InGaN, and the thickness is 50-500nm;

[0016] In one embodiment of the present invention, the barrier layer is made of AlGaN, with an Al component of 0.1-0.3, a thickness of 5-50 nm, and is not intentionally doped;

[0017] In one embodiment of the present invention, the structures of the source electrode and the drain electrode are Ti / Al and other metals, or TiN / Al and other metals from bottom to top;

[0018] In one embodiment of the present invention, the gate electrode is Ni and other metals, or Ti and other metals, or TiN and other metals from bottom to top;

[0019] The present invention also proposes a method for preparing a gallium nitride radio frequency device with high long-term reliability, which is characterized by comprising the following steps:

[0020] S1: substrate cleaning;

[0021] S2: epitaxially growing a III-N composite buffer layer, a channel layer and a barrier layer on the substrate in sequence;

[0022] S3: preparing a source electrode and a drain electrode at both ends of the front barrier layer;

[0023] S4: preparing a gate electrode between the source electrode and the drain electrode of the front barrier layer;

[0024] S5: etching a part of the substrate by deep silicon etching or laser drilling process;

[0025] S6: etching away a portion of the III-N composite buffer layer at the groove where the substrate is etched away obtained in step S5 to form a back deep groove;

[0026] S7: Depositing back metal on the back substrate and the sidewalls and bottom of the back deep trench to obtain a gallium nitride radio frequency device with high long-term reliability.

[0027] Beneficial Effects

[0028] Compared with the prior art, the present invention provides a gallium nitride radio frequency device structure with high long-term reliability and a preparation method thereof, which has the following beneficial effects:

[0029] 1. When the gallium nitride RF device is working in the off state, the drain bias voltage is relatively high, and the electric lines are relatively concentrated where the gate electrode is close to the drain electrode, thereby generating a relatively high local electric field peak, so that the electrons in the two-dimensional electron gas channel obtain higher energy, intensifying the collision between the internal electrons and the lattice atoms, thereby generating a large number of electrons and holes, among which the holes are sputtered to the buffer layer under the channel layer and accumulate, seriously affecting the long-term stability and reliability of the device. The metal layer introduced in the present invention can extract the holes accumulated in the III-N composite buffer layer by grounding, thereby suppressing the accumulation of holes in the composite buffer layer caused by the high drain voltage during the off state, and improving the long-term stability and reliability of the device.

[0030] 2. The method for preparing a gallium nitride device for inhibiting hole accumulation provided by the present invention is compatible with the original process, the process preparation is relatively simple, and the cost of the materials used is low, which can significantly improve the device performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a front view of a gallium nitride radio frequency device structure with high long-term reliability and a preparation method thereof with a cap layer according to the present invention;

[0032] Figure 2 A top view of a gallium nitride radio frequency device structure with high long-term reliability and a method for preparing the same according to the present invention;

[0033] Figure 3 This is a front view of a gallium nitride radio frequency device structure with high long-term reliability and a preparation method thereof according to the present invention;

[0034] Figure 4 This is a diagram of the preparation steps of a gallium nitride radio frequency device structure with high long-term reliability and a preparation method thereof according to the present invention.

[0035] In the figure: 1. substrate layer; 2. III-N composite buffer layer; 3. channel layer; 4. barrier layer; 5. source electrode; 6. drain electrode; 7. gate electrode; 8. metal layer; 11. cap layer; 21. nucleation layer; 22. transition layer; 23. buffer layer. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0037] Embodiment 1:

[0038] See also Figure 1 , Figure 2 A gallium nitride radio frequency device structure with high long-term reliability includes a back metal, a substrate, a III-N composite buffer layer, a channel layer, and a barrier layer arranged in sequence from bottom to top, a source electrode and a drain electrode are arranged at both ends of the barrier layer surface, a cap layer is arranged between the source electrode and the drain electrode, and a gate electrode is arranged on the top of the cap layer.

[0039] The channel layer and the barrier layer are made of III-N materials, and form a heterojunction with the channel layer and the barrier layer. A two-dimensional electron gas (2DEG) is formed at the heterojunction interface formed by the channel layer and the barrier layer and on one side close to the channel layer, serving as a conductive channel of a GaN-based transistor.

[0040] Grooves are etched inside the substrate and the III-N composite buffer layer, and the back metal is attached to the bottom of the substrate and the inner sidewall of the groove, and also to the sidewall of the III-N composite buffer layer in the groove and the bottom of the channel layer.

[0041] The groove is located near the gate electrode and close to the drain electrode.

[0042] The substrate is made of high-resistance silicon and has a thickness of 80 μm.

[0043] The III-N composite buffer layer includes three layers, namely, a nucleation layer, a transition layer and a buffer layer from bottom to top; the material of the nucleation layer is AlN, with a thickness of 200nm; the material of the transition layer is AlGaN, with a thickness of 800nm; the material of the buffer layer is GaN, with a thickness of 4000nm; the nucleation layer, transition layer and buffer layer are unintentionally doped.

[0044] The material of the channel layer is GaN, and the thickness is 200nm;

[0045] The barrier layer is made of AlGaN, with an Al component of 0.15 and a thickness of 30 nm, and is not intentionally doped;

[0046] The structures of the source electrode and the drain electrode are Ti / Al / Ni / Au from bottom to top, with thicknesses of 20 / 120 / 40 / 50 nm; the gate electrode is Ni / Au from bottom to top, with thicknesses of 50 / 200 nm; both the source electrode and the drain electrode form ohmic contacts with the two-dimensional electron gas channel in the channel layer, and the gate electrode forms a Schottky contact with the two-dimensional electron gas channel in the channel layer.

[0047] The materials of the back metal are Ni and Au from bottom to top using electron beam evaporation technology, with thicknesses of 50nm and 150nm respectively.

[0048] Embodiment 2:

[0049] Based on the structure of Example 1, a cap layer is provided between the gate electrode and the barrier layer, which has a depletion effect on the two-dimensional electron gas in the channel layer, thereby realizing the enhanced operation of the gallium nitride device. The material of the cap layer is GaN, and the doping impurity is Mg, with a doping concentration of 5x10 19 cm -3 .

[0050] Embodiment 3:

[0051] This embodiment provides a method for preparing a gallium nitride radio frequency device with high long-term reliability, comprising the following steps:

[0052] S1: substrate 1 cleaning;

[0053] S2: epitaxially growing a III-N composite buffer layer 2, a channel layer 3 and a barrier layer 4 on a substrate 1 in sequence;

[0054] S3: preparing a source electrode 5 and a drain electrode 6 at both ends of the front barrier layer 4;

[0055] S4: preparing a gate electrode between the source electrode 5 and the drain electrode 6 of the front barrier layer 4;

[0056] S5: etching a partial area of ​​the substrate 1 by using deep silicon etching or laser drilling process;

[0057] S6: etching away a portion of the III-N composite buffer layer at the groove where the substrate is etched away obtained in step S5, to form a back deep groove 9;

[0058] S7: Deposit back metal 8 on the sidewalls and bottom of the back substrate 1 and the back deep trench 9 to obtain a gallium nitride radio frequency device with high long-term reliability.

[0059] In the example, the III-N composite buffer layer in S2 is grown from bottom to top in sequence by metal organic chemical vapor deposition (MOCVD) to form a nucleation layer 21, a transition layer 22 and a buffer layer 23;

[0060] In the example, after the metal deposition in S3, a high temperature annealing is performed in a N2 atmosphere at 830°C for 30 seconds;

[0061] In the example, the back high-resistance silicon substrate in S5 is operated by a deep silicon etching process;

[0062] In the embodiment, the etching in S6 is performed by using a semiconductor material etcher ICP;

[0063] Embodiment 3:

[0064] See also Figure 2 , Figure 3A high long-term reliability GaN radio frequency device structure includes a back metal 8, a substrate 1, a III-N composite buffer layer 2, a channel layer 3, and a barrier layer 4 arranged in sequence from bottom to top, a source electrode 5 and a drain electrode 6 are arranged at both ends of the surface of the barrier layer 4, and a gate electrode 7 is arranged between the source electrode and the drain electrode. A back deep groove 9 is etched inside the substrate 1 and the III-N composite buffer layer 2, and the back metal is attached to the bottom of the substrate and the inner sidewall of the back deep groove 9, and is also attached to the sidewall of the III-N composite buffer layer in the back deep groove 9 and the bottom of the channel layer.

[0065] The back deep trench 9 is located near the gate electrode 7 and close to the drain electrode.

[0066] The channel layer 3 and the barrier layer 4 are made of III-N materials, and form a heterojunction with the channel layer 3 and the barrier layer 4. A two-dimensional electron gas (2DEG) is formed at the heterojunction interface formed by the channel layer 3 and the barrier layer 4 and on one side close to the channel layer, serving as a conductive channel of the GaN RF device.

[0067] The material of the back metal 9 is made by magnetron sputtering and electroplating process, and is Ti and Au from bottom to top, with thicknesses of 100 nm and 3 μm respectively.

[0068] The substrate 1 is made of silicon carbide and has a thickness of 50 μm.

[0069] The III-N composite buffer layer 2 includes three layers, namely, a nucleation layer 21, a transition layer 22 and a buffer layer 23 from bottom to top; the material of the nucleation layer 21 is AlN, with a thickness of 200nm; the material of the transition layer 22 is AlGaN, with a thickness of 800nm; the material of the buffer layer 23 is GaN, with a thickness of 4000nm; the nucleation layer 21, the transition layer 22 and the buffer layer 23 are unintentionally doped.

[0070] The material of the channel layer 3 is GaN, and the thickness is 200nm;

[0071] The barrier layer 4 is made of AlGaN, with an Al component of 0.15 and a thickness of 30 nm, and is not intentionally doped;

[0072] The structures of the source electrode 5 and the drain electrode 5 are Ti / Al / Ni / Au from bottom to top, with thicknesses of 20 / 120 / 40 / 50 nm; the gate electrode 7 is Ni / Au from bottom to top, with thicknesses of 50 / 200 nm; both the source electrode 5 and the drain electrode 6 form ohmic contacts with the two-dimensional electron gas channel in the channel 3 layer, and the gate electrode 7 forms a Schottky contact with the two-dimensional electron gas channel in the channel 3 layer.

[0073] Embodiment 4:

[0074] See also Figure 4, a method for preparing a gallium nitride radio frequency device with high long-term reliability, comprising the following steps:

[0075] S1: substrate 1 cleaning;

[0076] S2: epitaxially growing a III-N composite buffer layer 2, a channel layer 3, a barrier layer 4 and a cap layer 11 in sequence on a substrate 1 by using a metal organic chemical vapor deposition (MOCVD) method;

[0077] S3: A source electrode 5 and a drain electrode 6 are prepared at both ends of the front barrier layer 4 by vacuum evaporation or magnetron sputtering process, and high-temperature annealing is performed, so that the source electrode 5 and the drain electrode 6 simultaneously form an ohmic contact with the two-dimensional electron gas generated near the heterojunction interface formed by the channel layer 3 and the barrier layer 4;

[0078] S4: A gate electrode 7 is prepared between the source electrode 5 and the drain electrode 6 of the front barrier layer by vacuum evaporation or magnetron sputtering to obtain a gallium nitride radio frequency device with high long-term reliability.

[0079] S5: etching a part of the back substrate 1 by using deep silicon etching or laser cutting process;

[0080] S6: etching away a portion of the III-N composite buffer layer by using a semiconductor material etching ICP process at the groove where the substrate is etched away;

[0081] S7: Prepare back metal 8 on the back substrate by vacuum evaporation or magnetron sputtering process

[0082] In the example, the III-N composite buffer layer in S2 is grown from bottom to top in sequence by metal organic chemical vapor deposition (MOCVD) to form a nucleation layer 21, a transition layer 22 and a buffer layer 23;

[0083] In the example, the cap layer in S2 is grown by metal organic chemical vapor deposition (MOCVD) method, and the doping impurity is Mg, and the doping concentration is 5x10 19 cm -3 .

[0084] For example, the high temperature annealing in S3 is a thermal annealing treatment performed at 850° C. for 30 seconds in a N 2 atmosphere.

[0085] In the example, the back side silicon carbide substrate in S5 is operated by a laser cutting process;

[0086] In one embodiment, the etching in S6 is performed using a semiconductor material etcher ICP.

[0087] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0088] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A gallium nitride radio frequency device structure with high long-term reliability, characterized in that: The invention comprises a metal layer (8), a substrate layer (1), a III-N composite buffer layer (2), a channel layer (3), and a barrier layer (4) which are arranged in sequence from bottom to top. A source electrode (5) and a drain electrode (6) are arranged at both ends of the surface of the barrier layer (4). A gate electrode (7) is arranged between the source electrode (5) and the drain electrode (6). Grooves are etched inside the substrate layer (1) and the III-N composite buffer layer (2). The metal layer (8) is attached to the bottom of the substrate layer (1) and the inner side wall of the groove, and is also attached to the III-N composite buffer layer (7) in the groove. 2) and the bottom of the channel layer (3), the groove is located near the gate electrode (7) and close to the drain electrode (6), the channel layer (3) and the barrier layer (4) are III-N materials, the channel layer (3) and the barrier layer (4) form a heterojunction, and a two-dimensional electron gas (2DEG) is formed at the heterojunction interface formed by the channel layer (3) and the barrier layer (4) and close to the side of the channel layer (3). As a conductive channel of the gallium nitride device, the metal layer (8) can extract the holes accumulated in the III-N composite buffer layer (2) by grounding.

2. The gallium nitride radio frequency device structure with high long-term reliability according to claim 1, characterized in that: The source electrode (5) and the drain electrode (6) both form an ohmic contact with the two-dimensional electron gas channel in the channel layer (3), and the gate electrode (7) forms a Schottky contact with the two-dimensional electron gas channel in the channel layer (3).

3. The gallium nitride radio frequency device structure with high long-term reliability according to claim 1, characterized in that: A cap layer (11) is provided between the gate electrode (7) and the barrier layer (4), which has a depletion effect on the two-dimensional electron gas in the channel layer (3) to achieve enhanced operation of the gallium nitride device. The material of the cap layer (11) is GaN or InGaN, and the doping impurity is Mg, and the doping concentration is 1x10 18 -1x10 21 cm -3 .

4. The gallium nitride radio frequency device structure with high long-term reliability according to claim 1, characterized in that: The III-N composite buffer layer (2) comprises three layers, which are, from bottom to top, a nucleation layer (21), a transition layer (22) and a buffer layer (23); The material of the nucleation layer (21) is AlN or GaN, with a thickness of 50-300nm, the material of the transition layer (22) is AlGaN, with a thickness of 200-1000nm, and the material of the buffer layer (23) is GaN or AlGaN, with a thickness of 100nm-10μm. The nucleation layer (21), the transition layer (22) and the buffer layer (23) are unintentionally doped.

5. The gallium nitride radio frequency device structure with high long-term reliability according to claim 1, characterized in that: The material of the metal layer (8) is one of Ni, Ti, Au, Cu or other metals therein.

6. The gallium nitride radio frequency device structure with high long-term reliability according to claim 1, characterized in that: The substrate (1) is made of high-resistance silicon, silicon carbide, sapphire or diamond, and has a thickness of 50-1200 μm; The material of the channel layer (3) is GaN or InGaN, and the thickness is 50-500nm; The barrier layer (4) is made of AlGaN, with an Al component of 0.1-0.3 and a thickness of 5-50 nm, and is not intentionally doped.

7. The gallium nitride radio frequency device structure with high long-term reliability according to claim 1, characterized in that: The structures of the source electrode (5) and the drain electrode (6) are Ti / Al and other metals, or TiN / Al and other metals from bottom to top; The gate electrode (7) is made of Ni and other metals, or Ti and other metals, or TiN and other metals from bottom to top.

8. The method for preparing a gallium nitride radio frequency device structure with high long-term reliability according to claim 1, characterized in that: The following steps are involved: S1: substrate (1) cleaning; S2: epitaxially growing a III-N composite buffer layer (2), a channel layer (3) and a barrier layer (4) in sequence on a substrate (1); S3: preparing a source electrode (5) and a drain electrode (6) at both ends of the front barrier layer (4); S4: preparing a gate electrode (7) between the source electrode (5) and the drain electrode (6) of the front barrier layer; S5: etching a part of the substrate (1) by using deep silicon etching or laser drilling process; S6: etching away a portion of the III-N composite buffer layer at the groove where the substrate is etched away obtained in step S5, to form a back-deep groove (9); S7: Depositing back metal (8) on the back substrate and the sidewalls and bottom of the back deep groove (9) to obtain a gallium nitride radio frequency device with high long-term reliability.

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