METHOD FOR FORMING OHMIC CONTACTS OF GaN-BASED ELECTRONIC ELEMENT AND OHMIC CONTACTS OF GaN-BASED ELECTRONIC ELEMENT MANUFACTURED THEREBY

Abstract

To provide a method for forming an ohmic contact, which allows a resistance value required for a high frequency electronic element to be obtained even when the ohmic contact is formed at a low heat treatment temperature, and an ohmic contact manufactured by the method.SOLUTION: The present invention relates to a method for forming an ohmic contact of a GaN-based electronic element, and the method includes the steps of (A) irradiating a GaN-based electronic element with an ion beam to form an ion region in a part of the interior of the GaN-based electronic element, (B) forming an electrode layer on a part of the surface of the GaN-based electronic element corresponding to the ion region, and (C) heat-treating the GaN-based electronic element on which the electrode layer has been formed. The present invention also relates to an ohmic contact of a GaN-based electronic element manufactured by the method for forming an ohmic contact of a GaN-based electronic element.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for forming an ohmic contact of a GaN-based electronic device and an ohmic contact of a GaN-based electronic device manufactured thereby. [Background technology]

[0002] Gallium nitride (GaN)-based electronic devices are used in high-frequency electronic devices because they can form a two-dimensional electron gas (2DEG) with high electron concentration and fast electron mobility.

[0003] In order for such GaN-based electronic devices to have excellent high frequency characteristics, it is important to reduce the on-resistance of the device. GaN-based electronic devices can have low channel resistance by using 2DEG, but it is difficult to obtain low resistance ohmic contacts in the source and drain regions due to the wide band gap of GaN.

[0004] To solve these problems, titanium (Ti) was deposited and annealed at a high temperature of over 800℃. In this annealing process, the deposited titanium reacts with nitrogen from gallium nitride to form titanium nitride (TiN), which allows ohmic contact. However, the existing ohmic contact formation process requires a annealing process at a very high temperature, which damages the device surface and requires the deposition of an additional surface passivation layer before the process.

[0005] In addition, the gate is formed after the source / drain is formed through a high-temperature heat treatment process for forming the source / drain regions, which places restrictions on changes to the device manufacturing process that must be made to improve device performance.More than anything, there is a limit to how much the high-temperature heat treatment process alone can reduce the ohmic contact resistance, so efforts are being made to simplify the process and improve stability and performance. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention is made to solve the above problems, and aims to provide a method for forming an ohmic contact, which overcomes the limitation of ohmic contact resistance that is difficult to reduce by heat treatment alone, and can obtain a resistance value required for high frequency electronic devices even when an ohmic contact is formed at a low heat treatment temperature, and an ohmic contact manufactured thereby. [Means for solving the problem]

[0007] One embodiment of the present invention relates to a method for manufacturing an on-chip GaN-based electronic device, the method including: (A) irradiating a GaN-based electronic device with an ion beam to form an ion region in a part of the inside of the GaN-based electronic device; (B) forming an electrode layer on a part of the surface of the GaN-based electronic device corresponding to the ion region; and (C) heat-treating the GaN-based electronic device on which the electrode layer is formed. A method for forming a .theta.-based contact is provided.

[0008] Another embodiment of the present invention provides an ohmic contact of a GaN-based electronic device manufactured by the above-mentioned method for forming an ohmic contact of a GaN-based electronic device. Effect of the Invention

[0009] The method for forming an ohmic contact of a GaN-based electronic device according to the present invention can reduce the resistance of the ohmic contact by injecting a metal or metalloid into an area where the ohmic contact is to be formed and forming a nitride between the injected metal or metalloid and nitrogen derived from the GaN-based material inside the device during heat treatment. In particular, the nitride can be easily formed and the ohmic contact can be formed at a low temperature unlike the conventional method. Therefore, the resistance required for a high frequency electronic device can be obtained despite the low temperature heat treatment.

[0010] As a result, it is possible to manufacture an ohmic contact of a GaN-based electronic device that is optimized to prevent a drop in breakdown voltage while lowering the ohmic contact resistance. In addition, it is possible to reduce surface damage that has a significant effect on GaN-based electronic devices, simplify the process, and potentially develop various electronic device structures. [Brief description of the drawings]

[0011] [Figure 1] 1A to 1C are diagrams illustrating a method for forming an ohmic contact of a GaN-based electronic device according to an embodiment of the present invention. [Diagram 2] 1 is a diagram showing a distribution of Ti ions implanted into an electronic device of Example 1 according to Experimental Example 1 of the present invention. [Diagram 3] 1 is a diagram showing the amount of Ti ions implanted depending on the Ti ion implantation depth in an electronic device of Example 1 according to Experimental Example 1 of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention can be modified in various ways and can have various embodiments, and a specific embodiment will be described in detail with reference to the drawings. However, this is not intended to limit the present invention to the specific embodiment, and it should be understood that the present invention includes all modifications, equivalents, and alternatives within the spirit and technical scope of the present invention.

[0013] The terms used in this specification are merely used to describe specific embodiments and are not intended to limit the present invention. The singular expression includes the plural expression unless otherwise clearly indicated in the context.

[0014] In this specification, the expression "on" may mean that the members are directly joined and attached to each other, or may mean that the members are located adjacent to each other.

[0015] Therefore, the configurations illustrated in the embodiments described in this specification are merely preferred embodiments of the present invention and do not represent the entire technical idea of ​​the present invention, and therefore there may be various equivalents and modifications that can replace them at the time of this application.

[0016] The present invention will be described in detail below.

[0017] The present invention provides a method for forming ohmic contacts in GaN-based electronic devices.

[0018] The method for forming an ohmic contact of a GaN-based electronic device includes: (A) providing an ion beam to the GaN-based electronic device; (B) forming an ion region in a part of the interior of the GaN-based electronic device by irradiating a beam; (B) forming an electrode layer on a part of the surface of the GaN-based electronic device corresponding to the ion region; and (C) heat-treating the GaN-based electronic device on which the electrode layer has been formed.

[0019] The electronic element collectively refers to electronic components that utilize the conduction of electrons in a solid, and may refer to, for example, a diode, a transistor, a power semiconductor element, a high-frequency element, a sensor, a light-emitting element (LED), a solar cell, etc., but is not limited thereto.

[0020] The GaN-based electronic device means an electronic device including a GaN-based material, and may be, for example, an electronic device including a wafer including a GaN-based material. Specifically, the GaN-based material may include, but is not limited to, GaN, AlGaN, etc.

[0021] GaN (gallium nitride) is a wide band gap (WBG) material that is stronger at high pressure and high heat than existing silicon (Si). GaN-based electronic devices, especially AlGaN / GaN-based heterojunction structures, utilize a two-dimensional electron gas (2DEG) layer with high electron concentration and mobility, and are suitable for high-frequency and / or charged-power electronic devices due to their excellent current characteristics and high signal conversion speed.

[0022] The GaN-based electronic device may include an AlGaN / GaN-based heterojunction electronic device, that is, the GaN-based electronic device may include a wafer having an AlGaN / GaN-based heterojunction.

[0023] The GaN-based electronic device may further include a substrate, that is, the GaN-based electronic device may include a structure in which substrate / GaN / AlGaN are laminated in this order.

[0024] The substrate may include, for example, sapphire (Al2O3), silicon (Si), or silicon carbide (SiC).

[0025] The GaN-based electronic device may be manufactured using a known thin film deposition growth technique, such as, but not limited to, molecular beam epitaxy (MBE), metal organic chemical vapor deposition (MOCVD), or hydride vapor phase epitaxy (HVPE). In particular, due to the crystal structure and growth direction characteristics of hexagonal gallium nitride (GaN), it is advantageous to use metal organic chemical vapor deposition (MOCVD) in depositing GaN-based materials in that a thin film of better quality can be obtained and deposition can be performed on multiple substrates at the same time, but is not limited to this.

[0026] The metalorganic chemical vapor deposition (MOCVD) method is a method of growing compound crystals by supplying a metalorganic compound (metalorganic source gas) into a reactor and thermally decomposing it on a heated substrate. The MOCVD method has the advantage that the thickness of the heterojunction can be adjusted to the nano level by controlling the flow rate of the highly purified metalorganic compound and the temperature and pressure of the reactor.

[0027] The ion beam in the step (A) includes an ion beam derived from a metal or a metalloid. That's fine.

[0028] The ion beam is a type of charged particle beam made of ions, and is also called a particle beam or an electron beam. The ion beam irradiation technology uses the phenomenon in which the kinetic energy of high-energy ion beam particles (ions) is transferred to the surface of an electronic device and converted into kinetic energy. The ions incident on the surface of the electronic device irradiated with the ion beam cause chain collisions of atoms of the electronic device. In this case, if the ion beam energy is higher than the binding energy of the surface atoms, the ions break the atomic bonds on the surface and release the atoms to the outside, which is called sputtering. On the other hand, if the ion beam energy is lower than the binding energy of the surface atoms, the ions collide with the surface atoms in a chain reaction, which is called ion implantation.

[0029] Immediately after ion implantation, defects occur in the crystal structure due to collisions, and the implanted ions must be at substitution positions in the crystal structure to act as dopants, but the original crystal structure cannot be maintained due to the defects, and they cannot be electrically activated. Therefore, the crystal structure with the defects must be recrystallized through an annealing process to restore it to a normal state, and the implanted ions must be moved to substitution positions in the crystal structure to act as dopants and be electrically activated. Heat treatment methods include furnace annealing, rapid thermal annealing, laser annealing, and e-beam annealing.

[0030] The metal may include at least one selected from the group consisting of titanium (Ti), aluminum (Al), and tantalum (Ta).

[0031] The metalloid may include silicon (Si).

[0032] The metal or semimetal can form low resistance through bonding with nitrogen atoms (N) contained inside the GaN-based electronic device, and among them, the use of an ion beam derived from titanium (Ti) is preferable in terms of low resistance.

[0033] The ion beam in step (A) may be irradiated with an energy of 15 to 20 keV. If the ion implantation energy is less than 15 keV, there is a problem that ions are implanted above the AlGaN / GaN interface, making it difficult to have low resistance, and if it exceeds 20 keV, there is a problem that ions are implanted deeper than the AlGaN / GaN interface, making it difficult to have low resistance.

[0034] When the GaN-based electronic device includes an AlGaN / GaN-based heterojunction electronic device, the thickness of the AlGaN layer may be 100 Å to 400 Å. When the thickness of the AlGaN layer does not satisfy the above range, the characteristics of the 2DEG may be deteriorated.

[0035] Since the 2DEG is located within 100 Å from the AlGaN / GaN interface in the direction of gravity, the depth at which the ion region is formed can be adjusted taking into consideration the position of the 2DEG. The depth at which the ion region is formed in step (A) may be a point that is 100 Å to 500 Å from the surface of the GaN-based electronic device corresponding to the ion region in the direction of gravity (perpendicular to the surface). When the depth at which the ion region is formed satisfies the above range, a nitride layer of ions and nitrogen originating in the GaN-based electronic device is formed at the AlGaN / GaN interface, thereby allowing low contact resistance to be achieved.

[0036] In the step (A), the average ion implantation amount of the ion beam implanted into the GaN-based electronic device is 1×10 14 From 1×10 16 ions / cm 2 When the average ion implantation amount of the ion beam satisfies the above range, ions of the ion beam are bonded with nitrogen atoms (N) inside the GaN-based electronic device to form nitrides, thereby allowing the device to have low ohmic contact resistance.

[0037] Step (A) may include a step of patterning a portion of the GaN-based electronic device to be irradiated with the ion beam before irradiating the ion beam.

[0038] The patterning step may include masking a surface portion of the GaN-based electronic device except for a surface portion into which ions are to be implanted using an ion beam, i.e., ions derived from the ion beam may be selectively implanted into the GaN-based electronic device through unmasked portions of the surface of the GaN-based electronic device.

[0039] The patterning step may be performed by a photolithography method, but is not limited thereto.

[0040] When the patterning step is photolithography, a known photolithography method may be used, and generally, the steps may be performed in the order of wafer cleaning / photoresist coating / masking / exposure / development / photoresist removal, but is not limited thereto. In the present invention, some of the steps listed above may be omitted or additional steps may be added depending on process conditions.

[0041] That is, as described above, the patterned region formed before step (A) may not be removed immediately after step (A), but may be removed after forming the electrode layer in step (B) and before the heat treatment step in step (C).

[0042] For example, if the patterning step is photolithography, removing the patterned areas may refer to removing a coated photoresist.

[0043] That is, the electrode layer may be formed only on a portion of the surface of the GaN-based electronic element that corresponds to the ion region.

[0044] The electrode layer may refer to a concept including a source and / or a drain.

[0045] The electrode layer may include an electrode material having a work function smaller than that of a GaN-based material.

[0046] The electrode layer may be fabricated using known thin film deposition techniques, including, but not limited to, electron beam evaporation, thermal evaporation, sputtering, or electroless plating.

[0047] The electrode material may include at least one selected from the group consisting of titanium (Ti), aluminum (Al), nickel (Ni), gold (Au), silicon (Si), tantalum (Ta), and alloys thereof.

[0048] The electrode layer may be a single layer, or may be a multi-layer formed by depositing multiple electrode materials.

[0049] Finally, the GaN-based electronic device having the electrode layer formed thereon may be subjected to a heat treatment, which may be carried out by a known method for heat treating electronic devices.

[0050] In this case, the heat treatment in step (C) may include forming a nitride in the ion region due to nitrogen atoms (N) contained in the GaN-based electronic device. For example, when the ion region contains titanium (Ti) ions, the nitride may include titanium nitride (TiN).

[0051] The nitride affects the mobility of electrons flowing in and out of the ohmic contact, thereby reducing the ohmic contact resistance.

[0052] The nitride formed by the heat treatment in step (C) may be contacted with the electrode layer.

[0053] The method for forming ohmic contacts of a GaN-based electronic device of the present invention uses an ion beam to form an ion region even inside the GaN-based electronic device, as compared to the conventional technique of vapor-depositing titanium onto the device surface, and the thickness and / or depth of the ion region can be easily adjusted. This makes it easy to form nitrides in which ions of the ion beam are bonded to nitrogen atoms (N), thereby reducing the ohmic contact resistance of the GaN-based electronic device.

[0054] The heat treatment in step (C) may be performed at a temperature of less than 800° C. That is, unlike conventional techniques that require high-temperature heat treatment at 800° C. or more, the method for forming an ohmic contact in a GaN-based electronic device of the present invention can realize an ohmic contact that simultaneously satisfies the characteristics of contact resistance and breakdown voltage even at a low heat treatment temperature. The heat treatment in step (C) may be performed at a temperature of 600° C. or more and less than 800° C.

[0055] The method may further include removing the patterned region before the heat treatment in step (C).

[0056] For example, in the present invention, after forming the ion region in step (A), (B) forming an electrode layer on a surface portion of the GaN-based electronic device corresponding to the ion region, a lift-off process may be performed. In the present invention, the lift-off process may refer to a method of patterning the electrode layer using a material such as photoresist, or may refer to removing the photoresist when the patterning step is photolithography as described above.

[0057] Another embodiment of the present invention provides an ohmic contact of a GaN-based electronic device manufactured by the above-mentioned method for forming an ohmic contact of a GaN-based electronic device.

[0058] The ohmic contact of the GaN-based electronic device has low contact resistance even though it is manufactured at a low heat treatment temperature, and at the same time, the breakdown voltage is improved, making it possible to realize a superior high frequency electronic device.

[0059] Therefore, such high-frequency electronic devices can be applied to a variety of high-frequency application fields, such as 5G, autonomous vehicles, and military laser modules.

[0060] The present invention will now be described in more detail with reference to preferred embodiments.

[0061] However, these examples are merely intended to more specifically illustrate the present invention and are not intended to limit the scope of the present invention.

[0062] <Example 1> As shown in (1) of Figure 1, a heterojunction structure of AlGaN / GaN stacked on a substrate (not shown in the drawing) was used as a wafer, (2) the source / drain areas were patterned using a photolithography process, (3) a 20keV titanium (Ti) ion beam was irradiated, (4) a Ti / Al / Ni / Au electrode layer was deposited on the patterned area using e-beam evaporation, and the photoresist was removed using a lift-off process, and (5) an ohmic contact was formed by heat treatment at a temperature of less than 800℃.

[0063] <Experimental Example 1> In Example 1, the distribution of implanted titanium (Ti) ions when a 20 keV titanium (Ti) ion beam is irradiated is shown in FIG. 2, and the amount of titanium (Ti) ions implanted depending on the titanium (Ti) ion implantation depth is shown in FIG.

Claims

1. (A) irradiating a GaN-based electronic element with an ion beam to form an ion region in a portion of the interior of the GaN-based electronic element; (B) forming an electrode layer on a portion of a surface of the GaN-based electronic device corresponding to the ion region; and (C) heat-treating the GaN-based electronic device on which the electrode layer is formed; A method for forming an ohmic contact of a GaN-based electronic device, comprising the steps of:

2. 2. The method for forming an ohmic contact of a GaN-based electronic device according to claim 1, wherein the GaN-based electronic device includes an AlGaN / GaN-based heterojunction electronic device.

3. 2. The method of claim 1, wherein the ion beam in step (A) includes an ion beam derived from a metal or a metalloid.

4. The metal includes at least one selected from the group consisting of titanium (Ti), aluminum (Al), and tantalum (Ta); 4. The method for forming an ohmic contact of a GaN-based electronic device according to claim 3, wherein the metalloid contains silicon (Si).

5. 2. The method of claim 1, wherein the ion beam in step (A) is irradiated with an energy of 15 to 20 keV.

6. 2. The method of claim 1, wherein in step (A), a portion of the GaN-based electronic device to be irradiated with the ion beam is patterned before irradiating the ion beam.

7. 7. The method of claim 6, wherein the patterning step is performed by a photolithography method.

8. 2. The method of claim 1, wherein the electrode layer comprises an electrode material having a work function smaller than that of a GaN-based material.

9. 9. The method for forming an ohmic contact of a GaN-based electronic device according to claim 8, wherein the electrode material includes at least one selected from the group consisting of titanium (Ti), aluminum (Al), nickel (Ni), gold (Au), silicon (Si), tantalum (Ta), and alloys thereof.

10. 2. The method of claim 1, wherein the heat treatment step of step (C) includes forming a nitride in the ion region due to nitrogen atoms (N) contained inside the GaN-based electronic device.

11. 11. The method of claim 10, further comprising contacting the electrode layer with the nitride formed by the heat treatment in step (C).

12. 2. The method of claim 1, wherein the heat treatment in step (C) is performed at a temperature of less than 800[deg.] C.

13. 7. The method of claim 6, further comprising the step of removing the patterned region before the heat treatment in step (C).

14. An ohmic contact of a GaN-based electronic device manufactured by the method for forming an ohmic contact of a GaN-based electronic device according to any one of claims 1 to 13.

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