阅读说明：本技术 一种在GaN基器件的表面上形成电极结构的方法 (Method for forming electrode structure on surface of GaN-based device ) 是由 冯会会 徐俞 王建峰 徐科 于 2020-05-15 设计创作，主要内容包括：本发明公开了一种在GaN基器件的表面上形成电极结构的方法,所述方法包括：在GaN基器件的表面上生长石墨烯层；在石墨烯层上形成单质金属层,从而使石墨烯层中形成大量结构缺陷,将该结构缺陷作为有效漏电通道,从而使GaN基器件与石墨烯层之间具有良好的欧姆接触；其中,单质金属层作为保护层来使用。与现有技术相比,本发明所公开的在GaN基器件的表面上形成电极结构的过程中并没有对于复合金属层的退火过程,以此避免了现有技术中复合金属层退火过程的高温对于GaN基器件的表面本身的伤害。本发明还公开了通过上述的方法来形成的GaN基器件的电极结构。(The invention discloses a method for forming an electrode structure on the surface of a GaN-based device, which comprises the following steps: growing a graphene layer on the surface of the GaN-based device; forming a simple substance metal layer on the graphene layer, so that a large number of structural defects are formed in the graphene layer, and the structural defects are used as effective leakage channels, so that the GaN-based device and the graphene layer have good ohmic contact; wherein the elementary metal layer is used as a protective layer. Compared with the prior art, the annealing process of the composite metal layer is not carried out in the process of forming the electrode structure on the surface of the GaN-based device, so that the damage of the high temperature of the annealing process of the composite metal layer to the surface of the GaN-based device in the prior art is avoided. The invention also discloses an electrode structure of the GaN-based device formed by the method.)

1. A method of forming an electrode structure on a surface of a GaN-based device, the method comprising only:

growing a graphene layer (2) on the surface of the GaN-based device (1);

and forming an elemental metal layer (3) on the graphene layer (2).

2. Method for forming an electrode structure on a surface of a GaN-based device according to claim 1, characterized in that the elemental metal layer (3) is a patterned elemental metal layer (3).

3. The method of claim 2, wherein the patterning of the elemental metal layer (3) comprises:

coating a photoresist (4) on the graphene layer (2);

patterning the photoresist (4) to form a photoresist pattern layer (4 a);

depositing an elemental metal layer (3) on the photoresist pattern layer (4 a);

and stripping the photoresist pattern layer (4a) and the simple substance metal layer (3) above the photoresist pattern layer to form the patterned simple substance metal layer (3).

4. The method of forming an electrode structure on a surface of a GaN-based device according to any of claims 1 to 3, wherein when growing the graphene layer (2) on the surface of the GaN-based device (1), a structural defect is formed in the graphene layer (2), and the structural defect is used as a leakage path, so that an ohmic contact is formed between the GaN-based device (1) and the graphene layer (2).

5. Method of forming an electrode structure on a surface of a GaN-based device according to claim 4, characterized in that the growth method of the graphene layer (2) is a PECVD process.

6. The method of forming an electrode structure on a surface of a GaN-based device according to claim 5, characterized in that the growth temperature of the graphene layer (2) is 400-600 ℃.

7. Method for forming electrode structures on the surface of GaN-based devices according to claim 6, characterized in that the growth method of the elemental metal layer (3) is an electron beam evaporation process.

8. Method for forming electrode structures on the surface of GaN-based devices according to claim 1, characterized in that the elementary metal layer (3) is one of Au, Ni, Cu, Ag.

9. The method of claim 8, wherein the thickness of the elemental metal layer (3) is 50nm to 150 nm.

10. An electrode structure of a GaN-based device, characterized in that the electrode structure is formed by the method of forming an electrode structure on a surface of a GaN-based device according to any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of semiconductors, in particular to a method for forming an electrode structure on the surface of a GaN-based device.

Background

In the prior art, a conventional method of forming an electrode structure on a surface of a GaN (gallium nitride) -based device is as follows:

sequentially forming Ti, Al, Ni and Au layers on the surface of the GaN-based device so as to form a composite metal layer;

the Ti/Al/Ni/Au complex metal layer will be annealed such that the Ti/Al/Ni/Au complex metal layer is configured as an electrode structure for the GaN-based device. The Ti layer is barrier layer metal, TiN is formed by the Ti layer and the GaN, an N vacancy is formed, ohmic contact is formed beneficially, the Al layer is used for preventing Ga atoms from diffusing outwards, and the Ni layer and the Au layer belong to protective layers.

However, the yield of GaN-based devices formed with the electrode structure by the above method is not high. This is because the high temperature (generally around 800 ℃) generated during the annealing of the clad metal layer affects the GaN-based device. For example: under the condition that the yellow-light gallium nitride-based LED multi-quantum well structure has a high In component, the high temperature generated In the annealing process can enable In atoms to be easily subjected to phase separation, so that the performance of a yellow-light gallium nitride-based LED device is influenced.

Disclosure of Invention

In view of the deficiencies of the prior art, the present invention provides a method of forming an electrode structure on a surface of a GaN-based device that addresses the deficiencies of the prior art.

Aiming at the defects in the prior art, the invention adopts the following technical scheme:

in one aspect of the present invention, there is provided a method of forming an electrode structure on a surface of a GaN-based device, the method including only:

growing a graphene layer on the surface of the GaN-based device;

and forming an elemental metal layer on the graphene layer.

Preferably, the simple substance metal layer is a patterned simple substance metal layer.

Preferably, the patterning process of the elemental metal layer specifically includes:

coating photoresist on the graphene layer;

patterning the photoresist to form a photoresist pattern layer;

depositing a simple substance metal layer on the photoresist pattern layer;

and stripping the photoresist pattern layer and the simple substance metal layer above the photoresist pattern layer to form a patterned simple substance metal layer.

Preferably, when the graphene layer is grown on the surface of the GaN-based device, a structural defect is formed in the graphene layer, and the structural defect is used as a leakage channel, so that ohmic contact is formed between the GaN-based device and the graphene layer.

Preferably, the graphene layer growth method is a PECVD process.

Preferably, the growth temperature of the graphene layer is 400-600 ℃.

Preferably, the growth method of the elemental metal layer is an electron beam evaporation process.

Preferably, the simple substance metal layer is one of Au, Ni, Cu, and Ag.

Preferably, the thickness of the simple substance metal layer is 50 nm-150 nm.

In another aspect of the present invention, an electrode structure of a GaN-based device is provided, the electrode structure being formed by the above-described method of forming an electrode structure on a surface of a GaN-based device.

Aiming at the problem that high temperature generated in the annealing process of a composite metal layer in the prior art damages a GaN-based device, the graphene layer grows on the surface of the GaN-based device, a large number of structural defects are formed in the graphene layer in the growth process of the graphene layer, the structural defects are used as effective leakage channels, good ohmic contact is formed between the GaN-based device and the graphene layer, and a simple substance metal layer is formed on the graphene layer and used as a protective layer to keep the integrity of an electrode structure. The method for forming the electrode structure on the surface of the GaN-based device does not have the annealing process of the composite metal layer in the implementation process, so that the damage of the high temperature of the annealing process of the composite metal layer to the GaN-based device in the prior art is avoided.

Further, the process of the present invention is only a step of forming a graphene layer on the surface of the GaN-based device and forming a metal protection layer on the graphene layer. Compared with the existing scheme of forming the Ti/Al/Ni/Au composite metal layer on the surface of the GaN-based device, the technical scheme of the invention reduces more process flows, such as the forming process of a plurality of metal layers and the annealing process of the composite metal layer, thereby reducing the time length of the GaN-based device exposed in a high-temperature environment and further reducing the possibility of low performance of the GaN-based device caused by high temperature.

Furthermore, the invention simplifies the procedure of forming the electrode structure on the surface of the GaN-based device, and can shorten the finished product manufacturing time of the GaN-based device to a certain extent, thereby bringing the effect of improving the productivity of the GaN-based device.

Drawings

FIGS. 1a and 1b are flow diagrams of forming an electrode structure on a surface of a GaN-based device using a method according to an embodiment of the invention;

FIGS. 2a to 2d are flow charts of the formation of electrode structures on the surface of a GaN-based device using a method according to an embodiment of the invention optimized;

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention are described in detail below with reference to the accompanying drawings. Examples of these preferred embodiments are illustrated in the accompanying drawings. The embodiments of the invention shown in the drawings and described in accordance with the drawings are exemplary only, and the invention is not limited to these embodiments.

It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and/or processing steps closely related to the scheme according to the present invention are shown in the drawings, and other details not so relevant to the present invention are omitted.

Spatially relative terms, such as "below … …," "below … …," "below," "above … …," and "above," may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures for ease of description. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary term "below … …" can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

The present embodiment provides a method of forming an electrode structure a on a surface of a GaN-based device, the method comprising only the steps of:

step S1, as shown in fig. 1a, grows the graphene layer 2 on the surface of the GaN-based device 1. Specifically, a graphene layer 2 is grown on the surface of the GaN-based device 1 by utilizing a PECVD process, wherein the growth temperature of the graphene layer 2 is 400-500 ℃, the pressure intensity is within the range of 10-200 Pa, and the deposition rate is 5-20 layers/hour. Here, the GaN-based device 1 is a semiconductor device mainly made of GaN. For example: a light emitting diode, a crystal diode, a bipolar transistor, a field effect transistor or a semiconductor optical device made of GaN material, i.e. the graphene layer 2 in this step may be grown on the surface of the above exemplified GaN based device.

Step S2, as shown in fig. 1b, forming an elemental metal layer 3 on the graphene layer 2 to serve as a protection layer for protecting the graphene layer 2, so as to form the electrode structure a. Specifically, an elemental metal layer 3 is formed on the graphene layer 2 by an electron beam evaporation process. Wherein the vacuum degree is 6.7 × 10^-3Pa, preheating current of 0.8-0.75A, and finally increasing to 1.6-2.5A. The simple substance metal layer 3 is one of metals with high conductivity, such as Au, Ni, Cu, Ag, and the like. Wherein the thickness of the simple substance metal layer 3 is 50 nm-150 nm.

The invention is based on the microcosmic electrical transport of graphene grown on GaN by an applicantAs a result of the research on the mechanism, the applicant found that the PECVD process is adopted to prepare high-energy CH of graphene on GaN_xPlasma can deposit effectively on non-catalytic GaN surfaces and there are a large number of structural defects. The structural defect is a microscopic electrical transport channel, namely an effective leakage channel, so that good ohmic contact is formed between GaN and graphene. Therefore, unlike the prior art, in this embodiment, only after the graphene layer is formed on the surface of the GaN-based device, the single metal layer is formed on the graphene layer as a protection layer, and the electrode structure a with good ohmic contact performance can be obtained.

As can be seen from the above, the method for forming the electrode structure a on the surface of the GaN-based device disclosed in this embodiment does not have an annealing process of the composite metal layer during the implementation process, so as to avoid the damage of the high temperature of the annealing process of the composite metal layer to the GaN-based device in the prior art. Further, the procedure of the embodiment of the present invention is only a step of forming a graphene layer on the surface of the GaN-based device and forming a metal protection layer on the graphene layer. Compared with the existing scheme of forming a Ti/Al/Ni/Au metal layer or a Ti/Al/Ti/Au metal layer on the surface of the GaN-based device, the technical scheme of the invention greatly reduces the process flow, further reduces the time of exposing the GaN-based device in a high-temperature environment, and therefore reduces the possibility of low performance of the GaN-based device caused by high temperature.

Further, in order to improve the degree of adaptability between the motor structure of the GaN-based device 1 and other electronic devices, in this embodiment, as shown in fig. 2a to 2d, the method for forming the patterned electrode structure a specifically includes:

step S21, as shown in fig. 2a, coats a photoresist 4 on the graphene layer 2. Specifically, the type of the photoresist 4 may be one of a photopolymerization type, a photodecomposition type, a photocrosslinking type, and a silicon-on-resist.

In step S22, as shown in fig. 2b, a pattern to be formed is formed in the photoresist 4 by an exposure and development process. Specifically, a pattern mask (not shown) is provided on the photoresist 4 formed in step S21 and light is irradiated; after the mask plate is removed, a part of the photoresist 4 is removed by using a dissolving agent, a photoresist pattern layer 4a is formed, and a part of the graphene layer 2 is exposed.

Step S23, as shown in fig. 2c, depositing the elemental metal layer 3 on the photoresist pattern layer 4 a. Specifically, the elemental metal layer 3 is deposited using an electron beam evaporation process. Wherein the vacuum degree is 6.7 × 10^-3Pa, preheating current of 0.8-0.75A, and finally increasing to 1.6-2.5A. The simple substance metal layer 3 is one of metals with high conductivity, such as Au, Ni, Cu, Ag, and the like. Wherein the thickness of the simple substance metal layer 3 is 50 nm-150 nm.

Step S24, as shown in fig. 2d, stripping the photoresist pattern layer 4a and the simple substance metal layer 3 above the photoresist pattern layer, where it should be noted that, during the process of stripping the photoresist pattern layer 4a, the graphene layer 2 below the photoresist pattern layer 4a is stripped together, so as to form the patterned electrode structure a.

A cleaning step may also be included after the electrode structure a is formed. The method comprises the following steps:

and cleaning the electrode structure A by using an acetone solution. Specifically, a 25 ℃ acetone solution was applied to the electrode structure a and sonicated for 5 minutes.

And washing the acetone solution on the surface of the electrode structure A by using deionized water, and drying the surface of the electrode structure A by using nitrogen.

It should be noted that the elemental metal layer 3 may take any pattern according to the electronic device to be adapted, and is not particularly limited herein.

After the optimization steps, the GaN-based device can be adapted to other electronic equipment, so that the application range of the GaN-based device is enlarged.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.