A preparation method for vias of a diamond substrate GaN device

Abstract

The present invention discloses a method for preparing vias in a diamond substrate GaN device, comprising: laser etching vias on the back of the diamond substrate to penetrate the source metal of the front GaN device; bonding the front of the diamond substrate GaN device to a temporary carrier using a temporary bonding material; depositing a seed layer metal on the back of the diamond substrate and inside the vias, and electroplating and depositing back gold; removing the front temporary carrier and the temporary bonding material; electroplating metal a second time on the source metal of the front GaN device to achieve interconnection between the source metal and the via metal. The method of the present invention directly uses laser etching to form vias, which has the advantages of simplicity and rapidity. At the same time, the method of temporary bonding combined with secondary electroplating is used to solve the problem of electroplating interconnection of diamond-etched vias, and good electrical grounding is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor processes, and particularly to a method for preparing through holes of a GaN device on a diamond substrate. Background Art

[0002] As a third-generation wide-bandgap compound semiconductor device, the GaN device has characteristics such as a high two-dimensional electron gas concentration, a high breakdown field strength, and a high electron saturation velocity. However, at present, with the increase in the power density of the GaN device, the heat accumulation effect in the active region of the device increases rapidly, resulting in a rapid degradation of its DC and power performance, and the power advantage not being fully exerted. Therefore, the heat dissipation problem has become one of the main technical bottlenecks restricting the further development of GaN devices. Currently, the commonly used substrate materials for GaN devices include silicon, sapphire, and silicon carbide, etc. These materials have low thermal conductivity and are difficult to meet the heat dissipation requirements under high-power conditions. Using diamond with high thermal conductivity as the substrate for high-power GaN devices can reduce the thermal effect of GaN devices and is expected to solve the problem of rapid decline in power density caused by heat dissipation problems. However, a series of problems need to be solved for the actual application of GaN devices on diamond substrates, including the through-hole problem of diamond substrates.

[0003] Due to the hard characteristic of the diamond substrate material, the process of preparing through holes of GaN devices on diamond substrates has always been a difficult problem. The through holes directly affect the grounding quality of the devices, thus restricting the performance of the devices. Currently, there is a problem that it is difficult to interconnect electroplated metals after forming through holes by laser etching the diamond substrate, which affects the electrical performance of GaN devices. Summary of the Invention

[0004] In view of the above problems, the present invention proposes a method for preparing through holes of a GaN device on a diamond substrate.

[0005] To achieve the object of the present invention, there is provided a method for preparing through holes of a GaN device on a diamond substrate, which is used for a GaN device on a diamond substrate formed by sequentially stacking a diamond substrate, a GaN epitaxial layer, and a GaN device source electrode metal in sequence, and the following steps are performed to realize the preparation of through holes of the GaN device on the diamond substrate;

[0006] The preparation method specifically includes the following steps:

[0007] S1: Use a pulsed laser to irradiate the laser from the side of the diamond substrate facing away from the GaN epitaxial layer for etching, and the etching penetrates through the diamond substrate, the GaN epitaxial layer, and the GaN device source electrode metal in sequence, thereby forming through holes;

[0008] S2: Bond a prepared temporary carrier onto the side of the GaN device source electrode metal facing away from the GaN epitaxial layer through a prefabricated temporary bonding material, and the temporary carrier covers the through holes;

[0009] S3: First deposit seed layer metal on the side of the diamond substrate facing away from the GaN epitaxial layer and within the through-holes, and then electroplate and deposit metal.

[0010] S4: Mechanically remove the temporary carrier wafer and clean the remaining temporary bonding material.

[0011] S5: Deposit seed layer metal on the side of the source electrode metal of the GaN device facing away from the GaN epitaxial layer, and then perform secondary electroplating and deposition of metal.

[0012] Furthermore, the prefabricated diamond substrate GaN device is a high electron mobility transistor, a field effect transistor or a Schottky diode, and the thickness of the diamond substrate is 80 - 120 μm.

[0013] Furthermore, in step S1, the pulsed laser used is a laser including femtosecond, picosecond and nanosecond; the incident aperture size of the laser etching is 30 - 80 μm, and the exit aperture size is 20 - 70 μm.

[0014] Furthermore, in step S2, the prefabricated temporary bonding material is a resin material or a wax material, and the prepared temporary carrier wafer is a silicon wafer.

[0015] Furthermore, in step S3, the seed layer metal includes at least two metals among W, Ti, Ni, and Au, the thickness of the seed layer metal is 200 - 500 nm, and the thickness of the electroplated and deposited metal is 2 - 5 μm.

[0016] Furthermore, in step S4, the method of mechanically removing the temporary carrier wafer includes: mechanical separation or thermal decomposition separation.

[0017] Furthermore, in step S5, the seed layer metal includes at least two metals among W, Ti, Ni, and Au, the thickness of the seed layer metal is 200 - 500 nm, and the thickness of the second electroplated and deposited metal is 2 - 5 μm.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects:

[0019] Laser etching of diamond through-holes has the advantages of simplicity and rapidity compared with plasma dry etching. At the same time, the method of temporary bonding combined with secondary electroplating is adopted to solve the problem of electroplating interconnection of etched through-holes in diamond, and good electrical grounding is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic flow chart of a method for preparing through-holes of a diamond substrate GaN device in an embodiment;

[0021] Figure 2 Schematic diagram of a diamond substrate GaN device sample of an embodiment;

[0022] Figure 3 Schematic diagram of a via hole of a diamond substrate GaN device of an embodiment;

[0023] Figure 4 Schematic diagram of a temporary bonding of a diamond substrate GaN device of an embodiment;

[0024] Figure 5 Schematic diagram of electroplating on the back and via holes of a diamond substrate GaN device of an embodiment;

[0025] Figure 6 Schematic diagram after separation of a temporary carrier wafer of an embodiment;

[0026] Figure 7 Schematic diagram of secondary electroplating interconnection of source metal of a diamond substrate GaN device of an embodiment. Detailed implementation manners

[0027] In order to make the objectives, technical solutions and advantages of the present application clearer and more understandable, the present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0028] Referring to

[0029] As shown in Figure 1 below, Figure 1 is a flow schematic diagram of a method for preparing a via hole of a diamond substrate GaN device of an embodiment, which mainly includes the following steps:

[0030] 1) Prepare a sample: Complete the preparation of a diamond substrate GaN device, where the GaN device is a high electron mobility transistor, and the thickness of the diamond substrate is 100 μm. As Figure 2 shown is a schematic diagram of a diamond substrate GaN device sample.

[0031] 2) Etch the via hole: Use picosecond laser to etch from the back of the diamond substrate. The incident aperture size of the laser etching is 50 μm, and the exit aperture size is 40 μm. Etch through the diamond substrate, GaN epitaxial layer, and source metal of the GaN device to form an etched via hole. As Figure 3The figure shows a schematic diagram of the vias of a GaN device on a diamond substrate.

[0032] 3) Temporary bonding: Use a sapphire wafer as a temporary carrier. Use a coater to apply a bonding material on the front side of the temporary carrier. The rotational speed of the coater is 1000 rpm and the time is 30 s. The bonding material is a resin material. Place the GaN device on the diamond substrate and the sapphire wafer face to face into a bonder and bond them under the condition of a temperature of 150 °C. Figure 4 It is a schematic diagram of the temporary bonding of the GaN device on the diamond substrate.

[0033] 4) Electroplating metal: Deposit a seed layer metal on the back side and in the vias of the diamond substrate. The seed layer metal is composed of two metals, Ti and Au. The thickness of the seed layer metal is 200 nm, and the thickness of the electroplated deposited metal is 4 μm. Figure 5 It is a schematic diagram of electroplating on the back side and in the vias of the GaN device on the diamond substrate.

[0034] 5) Debonding: Use a mechanical separation method to separate the sapphire wafer and use a cleaning agent to clean the resin material thoroughly; as Figure 6 The figure shows a schematic diagram after the temporary carrier is separated.

[0035] 6) Secondary electroplating interconnection: Deposit a seed layer metal on the source metal of the GaN device on the diamond substrate. The seed layer metal is composed of two metals, Ti and Au. The thickness of the seed layer metal is 200 nm, and the thickness of the metal deposited by secondary electroplating is 3 μm. Figure 7 It is a schematic diagram of the secondary electroplating interconnection of the source metal of the GaN device on the diamond substrate.

[0036] After the above steps, the preparation of the via interconnection of the GaN device on the diamond substrate is achieved.

[0037] In one embodiment, the GaN device is a field effect transistor.

[0038] In one embodiment, the incident aperture size of the laser etching is 60 μm and the exit aperture size is 50 μm.

[0039] In one embodiment, the temporary carrier is a silicon wafer, the temporary bonding material is a glue-like material, the rotational speed of the coater is 2000 rpm, the time is 40 s, and the bonding temperature is 180 °C.

[0040] In one embodiment, the seed layer metal contains three metals, W, Ti, and Au; the thickness of the seed layer metal is 300 nm; the thickness of the back gold deposited by electroplating is 3 μm.

[0041] In one embodiment, use a pyrolytic separation method to separate the temporary carrier.

[0042] In one embodiment, the seed layer metal includes three metals: W, Ti, and Au; the thickness of the seed layer metal is 300 nm; the thickness of the metal deposited by secondary electroplating is 2 μm.

[0043] In one embodiment, the GaN device is a Schottky diode.

[0044] In one embodiment, the incident aperture size of the laser etching is 80 μm, and the exit aperture size is 70 μm.

[0045] In one embodiment, the temporary carrier is a silicon carbide wafer, the temporary bonding material is a wax-like material, the rotation speed of the coater is 3000 rpm, the time is 50 s, and the bonding temperature is 200 °C.

[0046] In one embodiment, the seed layer metal includes four metals: W, Ti, Ni, and Au; the thickness of the seed layer metal is 500 nm; the thickness of the back gold deposited by electroplating is 5 μm.

[0047] In one embodiment, the seed layer metal includes four metals: W, Ti, Ni, and Au; the thickness of the seed layer metal is 500 nm; the thickness of the metal deposited by secondary electroplating is 4 μm.

[0048] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0049] It should be noted that the terms "first / second / third" involved in the embodiments of the present application are only used to distinguish similar objects and do not represent a specific order for the objects. It can be understood that "first / second / third" can be interchanged with a specific order or sequence when permitted. It should be understood that the objects distinguished by "first / second / third" can be interchanged under appropriate circumstances so that the embodiments of the present application described here can be implemented in an order other than those illustrated or described here.

[0050] The terms "including" and "having" in the embodiments of the present application and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, device, product, or equipment that includes a series of steps or modules is not limited to the listed steps or modules, but may optionally further include steps or modules not listed, or may optionally further include other steps or modules inherent to these processes, methods, products, or equipment.

[0051] The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A method for preparing through holes of a diamond substrate GaN device, characterized in that: For a diamond substrate GaN device composed of a diamond substrate, a GaN epitaxial layer, and a GaN device source metal stacked in sequence, the following steps are performed to realize the preparation of vias in the diamond substrate GaN device; The preparation method specifically includes the following steps: S1: Use a pulsed laser to irradiate the laser from the side of the diamond substrate facing away from the GaN epitaxial layer for etching, and the etching penetrates through the diamond substrate, the GaN epitaxial layer, and the GaN device source metal in sequence, thereby forming a via; S2: Bond the prepared temporary carrier to the side of the GaN device source metal facing away from the GaN epitaxial layer through a prefabricated temporary bonding material, and the temporary carrier covers the via; S3: First deposit a seed layer metal on the side of the diamond substrate facing away from the GaN epitaxial layer and in the via, and then electroplate and deposit metal; S4: Mechanically remove the temporary carrier and clean the remaining temporary bonding material; S5: Deposit a seed layer metal on the side of the GaN device source metal facing away from the GaN epitaxial layer, and then perform secondary electroplating and deposition of metal.

2. The method for preparing a via hole of a diamond substrate GaN device according to claim 1, wherein The prefabricated diamond substrate GaN device is a high electron mobility transistor, a field effect transistor, or a Schottky diode, and the thickness of the diamond substrate is 80 - 120 μm.

3. The method for preparing a via hole of a diamond substrate GaN device according to claim 2, wherein In step S1, the pulsed laser is a laser including femtosecond, picosecond, and nanosecond; the incident aperture size of the laser etching is 30 - 80 μm, and the exit aperture size is 20 - 70 μm.

4. The method for preparing a through hole of a diamond substrate GaN device according to claim 3, wherein In step S2, the prefabricated temporary bonding material is a resin material or a wax material, and the prepared temporary carrier is a silicon wafer.

5. The method for preparing a via hole of a diamond substrate GaN device according to claim 4, wherein, In step S3, the seed layer metal includes at least two of W, Ti, Ni, and Au, the thickness of the seed layer metal is 200 - 500 nm, and the thickness of the electroplated and deposited metal is 2 - 5 μm.

6. The method for preparing a via hole of a diamond substrate GaN device according to claim 5, characterized in that, In step S4, the method of mechanically removing the temporary carrier includes mechanical separation or pyrolytic separation.

7. The method for preparing a through hole of a diamond substrate GaN device according to claim 6, characterized in that, In step S5, the seed layer metal includes at least two of W, Ti, Ni, and Au, the thickness of the seed layer metal is 200 - 500 nm, and the thickness of the secondary electroplated and deposited metal is 2 - 5 μm.

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