CN113284839B - A diamond crystal heterogeneous bonding method and heterogeneous structure - Google Patents

Abstract

The application relates to the technical field of semiconductors, and discloses a heterogeneous bonding method and a heterogeneous structure of a diamond crystal. According to the heterogeneous bonding method provided by the application, the bonding medium layer is introduced on the surface of the diamond crystal, and then hydrophilic bonding or SAB bonding and other bonding methods can be adopted, so that the defects that the diamond crystal is not easy to polish and bond are overcome, and the bonding method has the advantages of flexible bonding and high bonding strength.

Description

A diamond crystal heterogeneous bonding method and heterogeneous structure

Technical Field

The invention relates to the field of semiconductor technology, and in particular to a diamond crystal heterogeneous bonding method and a heterogeneous structure.

Background technique

Diamond has an ultra-wide bandgap (Eg≈5.5eV), and exhibits very high electron mobility and hole mobility at room temperature, and a breakdown field strength that is superior to 4H-SiC and GaN. Therefore, as a semiconductor, diamond is a material with great potential in the field of electronic devices. It can be applied to high-frequency field-effect transistors and high-power devices, and has the potential to replace traditional high-power vacuum tubes. In addition, the thermal conductivity of diamond at 2200Wm-1K-1 is almost an order of magnitude higher than that of other materials, which further establishes its application in the high-power field. It is also suitable for use as a substrate for high-power devices to achieve efficient heat dissipation. The chemical properties of single crystal diamond are quite stable and its Mohs hardness is 10. Devices made based on diamond can cope with various extreme environments.

In addition, diamond is an excellent optical platform with high transmittance in an ultra-wide range from visible light to infrared bands, especially in the near-infrared band, breaking through the bottleneck of traditional silicon photonics; the relatively high refractive index (2.38) can form an effective refractive index difference with the traditional waveguide cladding to achieve effective light wave transmission; the excellent nonlinear optical effect makes it very promising in the direction of parameter oscillation and Raman laser; the Young's modulus is 1220GPa, which can provide a very high mechanical resonance frequency of the microresonator and achieve efficient coupling of the optical resonance mode and the mechanical resonance mode.

However, in the prior art, the application of diamond crystals in the fields of electronics and photonics is limited due to the large number of defects in diamond epitaxially grown on foreign substrates.

Summary of the invention

The present invention aims to solve the technical problem that the above-mentioned prior art cannot realize the preparation of qualified diamond crystals on a foreign substrate.

In order to solve the above technical problems, the present application discloses, on one hand, a diamond crystal heterogeneous bonding method, characterized in that it comprises the following steps:

Cleaning of diamond crystals;

epitaxially growing a first bonding medium layer on the surface of the cleaned diamond crystal to obtain a diamond crystal structure to be bonded;

Providing a substrate to be bonded;

The diamond crystal to be bonded and the substrate to be bonded are bonded to obtain a heterostructure; the first bonding medium layer is bonded to the substrate to be bonded.

Optionally, after epitaxially growing a first bonding medium layer on the surface of the cleaned diamond crystal to obtain a diamond crystal structure to be bonded, the method further comprises:

Performing a first annealing treatment on the diamond crystal structure to be bonded;

The temperature of the first annealing treatment is 300°C-800°C;

The first annealing process may be performed in an atmosphere of vacuum, argon or nitrogen.

Optionally, the cleaning method is one or more of organic solution cleaning, RCA cleaning and plasma treatment.

Optionally, after epitaxially growing a first bonding medium layer on the surface of the cleaned diamond crystal to obtain a diamond crystal structure to be bonded, the method further comprises:

Performing surface treatment on the diamond crystal structure to be bonded;

The surface treatment method includes chemical mechanical polishing, low energy particle irradiation, ion beam grazing incidence polishing or reactive ion beam etching.

Optionally, the epitaxial growth method includes microwave plasma chemical vapor deposition, thermally assisted chemical vapor deposition, plasma enhanced chemical vapor deposition and sputtering;

The thickness of the first bonding medium layer is 1 nanometer to 5 micrometers;

The material of the first bonding dielectric layer includes silicon dioxide, silicon nitride, aluminum oxide or nano silicon.

Optionally, after the diamond crystal to be bonded and the substrate to be bonded are bonded to obtain a heterostructure, the method further includes:

The heterostructure is subjected to a second annealing treatment.

Optionally, the bonding method includes surface activated (SAB) bonding and hydrophilic bonding;

The temperature range of this bonding is 20°C-800°C;

The bonding atmosphere includes vacuum, normal temperature and pressure, or nitrogen atmosphere.

Optionally, a substrate to be bonded is provided, comprising:

providing a substrate;

forming the second bonding dielectric layer on the surface of the substrate;

The first bonding medium layer is bonded to the second bonding medium layer.

Optionally, the material of the substrate includes silicon, silicon on insulator (SOI), sapphire, silicon carbide, silicon carbide on insulator (SiCOI) and aluminum nitride;

The material of the second bonding dielectric layer includes silicon dioxide, silicon nitride, aluminum oxide or nano silicon.

The present application also discloses a heterostructure in another aspect, characterized in that it includes a substrate, a bonding medium layer and a diamond crystal;

The bonding medium layer is provided on the top of the substrate;

The diamond crystal is disposed on the top of the bonding medium layer;

The bonding medium layer is bonded to the substrate and the diamond crystal respectively.

By adopting the above technical solution, the heterogeneous bonding method of diamond crystals provided in this application has the following beneficial effects:

The method provided in the present application introduces a bonding medium layer on the surface of the diamond crystal, and then a bonding method such as hydrophilic bonding or SAB bonding can be adopted, thereby bypassing the shortcomings of diamond crystals that are difficult to polish and bond. The above bonding method has the advantages of simple bonding and high bonding strength. The heterostructure finally formed also provides a material basis for the subsequent development of diamond crystals in integrated photonics, quantum information science, high-power devices and other applications.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

FIG1 is a flow chart of an optional heterogeneous bonding method of diamond crystals according to the present application;

FIG2 is a schematic diagram of the process of the heterogeneous bonding method of diamond crystals of the present application;

FIG3 is a flow chart of another optional diamond crystal heterogeneous bonding method of the present application.

The following is a supplementary description of the attached drawings:

1-diamond crystal structure to be bonded; 11-diamond crystal; 12-first bonding medium layer; 2-substrate to be bonded; 21-substrate; 22-second bonding medium layer; 3-heterostructure.

Detailed ways

The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those generally understood by ordinary technicians in the field to which the present invention belongs. When there is a contradiction, the definition in this specification shall prevail.

The term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present application. In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "top", "bottom", etc. is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present application. In addition, the terms "first" and "second" are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may include one or more of the features explicitly or implicitly. Moreover, the terms "first", "second", etc. are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described here can be implemented in an order other than those illustrated or described here.

When a numerical range is disclosed herein, the above range is considered to be continuous and includes the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all sub-ranges included therein. For example, a specified range from "1 to 10" should be considered to include any and all sub-ranges between a minimum of 1 and a maximum of 10. Exemplary sub-ranges of ranges 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

In order to better illustrate the heterogeneous bonding method provided by the present application, the problems existing in the prior art will be explained below. Diamond, as a third-generation semiconductor material, has many relatively excellent material properties, such as ultra-wide bandgap, high thermal conductivity and high transmittance in an ultra-wide region from visible light to infrared band, so that it can be used in electronics and photonics; but due to the lattice mismatch and thermal mismatch problems of diamond crystals, the diamond directly epitaxially grown on a foreign substrate has many defects and the crystal quality is imperfect, which seriously limits the application of diamond in the fields of electronics and photonics.

In order to promote the continuous development of diamond in the above applications, it is essential to realize the heterogeneous integration of diamond. Based on this, the present application discloses a heterogeneous bonding method of diamond crystals, characterized in that, referring to Figures 1-2, Figure 1 is a flow chart of an optional heterogeneous bonding method of diamond crystals in the present application; Figure 2 is a process schematic diagram of the heterogeneous bonding method of diamond crystals in the present application. It includes the following steps:

S1O1: Cleaning the diamond crystal 11; thereby improving the cleanliness of the surface of the diamond crystal, thereby increasing the bonding strength between the diamond crystal 11 and subsequent materials.

Optionally, the diamond crystal 11 may be a single crystal or a polycrystalline crystal.

In an optional embodiment, the cleaning method is one or more of organic solution cleaning, RCA cleaning and plasma treatment; optionally, the organic solvent used in the organic solution cleaning includes acetone, isopropyl alcohol, sulfuric acid and hydrogen peroxide mixture (SPM) solution and hydroxypropyl methacrylate (HPM) solution, etc., so as to achieve the effect of cleaning organic pollutants on the surface of the diamond crystal; wherein, the SPM solution can be used to clean organic particles and surface organic functional groups, the HPM solution can be used to clean metal pollution, and the plasma treatment of the diamond crystal 11 can change the suspended functional groups on its surface, especially increase the proportion of C-OH, thereby further improving its bonding strength with the first bonding medium layer 12 generated by subsequent epitaxy.

S1O2: epitaxially grow a first bonding medium layer 12 on the surface of the cleaned diamond crystal 11 to obtain a diamond crystal structure 1 to be bonded.

In an optional embodiment, the epitaxial growth method includes but is not limited to microwave plasma chemical vapor deposition (MPCVD), heat-assisted chemical vapor deposition (HFCVD), plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD) and sputtering; the thickness of the first bonding medium layer 12 is 1 nanometer-5 microns; the material of the first bonding medium layer 12 includes but is not limited to silicon dioxide, silicon nitride, aluminum oxide or nano-silicon.

S1O3: Provide a substrate 2 to be bonded.

S1O4: The diamond crystal 11 to be bonded and the substrate 2 to be bonded are bonded to obtain a heterostructure 3; the first bonding medium layer 12 is bonded to the substrate 2 to be bonded.

In an optional embodiment, the bonding method of the above-mentioned diamond crystal structure 1 to be bonded and the substrate 2 to be bonded includes surface activated (SAB) bonding and hydrophilic bonding; the bonding temperature range is 20°C-800°C; the bonding atmosphere includes vacuum, normal temperature and pressure or nitrogen atmosphere.

It can be seen from the above steps S101-S104 that this method introduces a bonding medium layer on the surface of the diamond crystal, and then adopts a bonding method such as hydrophilic bonding or SAB bonding, thereby bypassing the shortcomings of diamond crystals that are difficult to polish and bond. The above bonding method has the advantages of simple bonding and high bonding strength.

In an optional embodiment, in order to promote the bonding process between the diamond crystal 11 and the first bonding medium layer 12, after the above step S102, it also includes: performing a first annealing treatment on the diamond crystal structure 1 to be bonded; the temperature of the first annealing treatment is 300°C-800°C; the atmosphere of the first annealing treatment includes vacuum, argon or nitrogen.

In an optional embodiment, in order to make the surface roughness of the diamond crystal structure 1 to be bonded meet the bonding condition, which is generally the surface roughness Rq<0.5nm, and thus improve the bonding strength, after the above step S102, it also includes: surface treatment of the diamond crystal structure 1 to be bonded; the surface treatment method includes but is not limited to chemical mechanical polishing (CMP), low-energy particle irradiation, ion beam grazing incidence polishing or reactive ion beam etching (RIE).

In an optional embodiment, in order to improve the bonding strength within the heterostructure, after step S104, the method further includes: performing a second annealing treatment on the heterostructure 3.

In an optional embodiment, refer to FIG3 , which is a flow chart of another optional diamond crystal heterogeneous bonding method of the present application. The above step S103 may include:

S1031: Provide a substrate 21.

S1032 : forming the second bonding medium layer 22 on the surface of the substrate 21 ; the first bonding medium layer 12 is bonded to the second bonding medium layer 22 , which is conducive to forming a stronger bond with the diamond crystal 11 .

In an optional embodiment, the material of the substrate 21 includes but is not limited to silicon, silicon on insulator (SOI), sapphire, silicon carbide, silicon carbide on insulator (SiCOI) and aluminum nitride; the material of the second bonding dielectric layer 22 includes but is not limited to silicon dioxide, silicon nitride, aluminum oxide or nano-silicon.

On the other hand, the present application also discloses a heterostructure 3, characterized in that it includes a substrate 21, a bonding medium layer and a diamond crystal 11; the bonding medium layer is provided on the top of the substrate 21; the diamond crystal 11 is provided on the top of the bonding medium layer; the bonding medium layer is bonded to the substrate 21 and the diamond crystal 11 respectively.

Optionally, the bonding dielectric layer includes a first bonding dielectric layer 12 and a second bonding dielectric layer 22 that are bonded to each other; the first bonding dielectric layer 12 is bonded to the diamond crystal 11 , and the second bonding dielectric layer 22 is bonded to the substrate 21 .

It should be noted that the materials and thicknesses of the substrate 21 , the first bonding dielectric layer 12 , and the second bonding dielectric layer 22 in this embodiment can refer to the above description, which will not be repeated here.

In summary, the present application provides a method for heterogeneous bonding of diamond crystal 11, which is used to achieve high-strength bonding of diamond crystal 11. This method strengthens the interaction between diamond crystal 11 and first bonding medium layer 12 through a series of surface treatment methods for diamond crystal 11, which not only achieves heterogeneous bonding of diamond crystal 11, but also ensures that the bonding strength is high enough. Subsequently, the first bonding medium layer 12 can be epitaxially grown on the surface after plasma activation of the diamond crystal surface, and annealing and reinforcement can be performed to form a more solid connection between the first bonding medium layer 12 and the diamond crystal surface; the first bonding medium layer 12 is introduced on the surface of the diamond crystal, and different first bonding medium layer 12 materials can be used to respectively achieve bonding methods such as hydrophilic bonding and SAB bonding. This bonding method provides a relatively simple and efficient method for bonding diamond crystal 11, bypassing the disadvantages of diamond crystal 11 being difficult to polish and bond. The heterostructure 3 obtained based on the above method provides a material basis for the subsequent development of integrated photonics, quantum information science, and high-power devices for diamond crystal 11.

In order to better reflect the scheme and beneficial effects of the present application, the following is a description of specific embodiments:

The specific steps of the method for heterogeneous bonding of diamond crystal 11 in the present application are as follows: 1) providing a diamond crystal 11, and cleaning the surface of the diamond with acetone solution, anhydrous ethanol solution, SPM solution and HPM solution in sequence; 2) performing oxygen plasma activation treatment on the surface of the diamond crystal after the cleaning; 3) epitaxially growing a 500nm layer of silicon dioxide on the surface of the diamond crystal after the oxygen plasma activation by using the PECVD method to obtain a diamond crystal structure 1 to be bonded, and the silicon dioxide is the first bonding medium layer 12; 4) placing the diamond crystal structure 1 to be bonded in an annealing furnace for a first annealing treatment, and the first annealing treatment is a high temperature annealing ; 5) Surface treatment is performed on the first bonding medium layer 12 on the surface of the annealed diamond crystal to reduce the surface roughness to a bonding level; 6) A silicon wafer with a sufficiently low surface roughness is provided as a substrate 21, and a 500nm layer of silicon dioxide is formed on the surface through a thermal oxidation process to obtain a substrate 2 to be bonded, and the silicon dioxide is the second bonding medium layer 22; 7) The first bonding medium layer 12 on the surface of the diamond crystal is hydrophilically bonded with the second bonding medium layer 22 on the surface of the silicon wafer to obtain a heterostructure 3; 8) The heterostructure 3 is placed in an annealing furnace for a second annealing treatment, and the second annealing is also a high-temperature annealing to improve the bonding strength.

In this embodiment, the first bonding dielectric layer 12 may be silicon dioxide, aluminum oxide or silicon nitride.

In this embodiment, the surface treatment method is chemical mechanical polishing. Optionally, reactive ion etching (RIE) or ion beam grazing incidence polishing may be used to perform surface treatment on the first bonding medium layer 12 to reduce surface roughness.

In this embodiment, the first annealing treatment is performed under the conditions of: annealing at 500° C. for 2 h in a nitrogen atmosphere.

It should be noted that, in the above method, acetone and anhydrous ethanol are used to clean the surface of the diamond crystal mainly to clean the organic pollution on the surface, and solutions such as isopropanol that can dissolve organic matter can also be selected; the use of SPM solution can further clean the insoluble organic particles on the surface of the diamond crystal, remove the organic functional groups on the surface of the diamond crystal and increase the hydroxyl (-OH) hanging bonds, and the use of HPM solution can clean the remaining metal particles; the above-mentioned use of oxygen plasma to activate the surface of the diamond crystal can further and more effectively remove the organic hanging bonds on the surface of the diamond crystal and increase the hydroxyl hanging bonds, greatly improving the hydrophilicity of the surface of the diamond crystal.

The first annealing treatment can promote the dehydration reaction of hydroxyl groups at the contact interface between the silicon dioxide formed by PECVD and the diamond crystal 11 to form Si-O-C bonds, thereby enhancing the strength of the heterojunction and improving the structural stability, which is beneficial to subsequent process treatments.

The above-mentioned bonding method for the bonded crystal structure and the bonded substrate 2 can select corresponding bonding methods according to the materials of the first bonding medium and the second bonding medium, such as hydrophilic bonding and SAB bonding. In this embodiment, the first bonding medium and the second bonding medium are both silicon dioxide, so preferably, hydrophilic bonding is adopted.

The above description is only an optional embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims (7)

1. A diamond crystal heterogeneous bonding method, characterized in that it comprises the following steps: The diamond crystal (11) is cleaned by organic solution cleaning, RCA cleaning and plasma treatment; the organic solvent used in the organic solution cleaning includes acetone, isopropyl alcohol, a sulfuric acid and hydrogen peroxide mixed solution and a hydroxypropyl methacrylate solution; epitaxially growing a first bonding medium layer (12) on the surface of the cleaned diamond crystal (11) to obtain a diamond crystal structure (1) to be bonded; A substrate to be bonded (2) is provided, comprising: A substrate (21) is provided, a second bonding medium layer (22) is formed on a surface of the substrate (21), and the first bonding medium layer (12) is bonded to the second bonding medium layer (22); The diamond crystal to be bonded (11) and the substrate to be bonded (2) are bonded to obtain a heterostructure (3); the first bonding medium layer (12) is bonded to the substrate to be bonded (2); The bonding methods include surface activated (SAB) bonding and hydrophilic bonding; The bonding temperature range is 20°C-800°C; The bonding atmosphere includes vacuum, normal temperature and pressure, or nitrogen atmosphere. 2. The diamond crystal heterogeneous bonding method according to claim 1 is characterized in that after epitaxially growing a first bonding medium layer (12) on the surface of the cleaned diamond crystal (11) to obtain the diamond crystal structure (1) to be bonded, the method further comprises: Performing a first annealing treatment on the diamond crystal structure (1) to be bonded; The temperature of the first annealing treatment is 300°C-800°C; The first annealing treatment is performed in an atmosphere including vacuum, argon or nitrogen. 3. The diamond crystal heterogeneous bonding method according to claim 1 is characterized in that after epitaxially growing a first bonding medium layer (12) on the surface of the cleaned diamond crystal (11) to obtain the diamond crystal structure (1) to be bonded, the method further comprises: Performing surface treatment on the diamond crystal structure (1) to be bonded; The surface treatment method includes chemical mechanical polishing (CMP), low-energy particle irradiation, ion beam grazing incidence polishing or reactive ion beam etching. 4. The diamond crystal heterogeneous bonding method according to claim 1, characterized in that the epitaxial growth method comprises microwave plasma chemical vapor deposition, thermally assisted chemical vapor deposition, plasma enhanced chemical vapor deposition, atomic layer deposition and sputtering; The thickness of the first bonding medium layer (12) is 1 nanometer to 5 micrometers; The material of the first bonding medium layer (12) includes silicon dioxide, silicon nitride, aluminum oxide or nano silicon. 5. The diamond crystal heterogeneous bonding method according to claim 1, characterized in that after the diamond crystal (11) to be bonded and the substrate (2) to be bonded are bonded to obtain a heterogeneous structure (3), the method further comprises: The heterostructure (3) is subjected to a second annealing treatment. 6. The heterogeneous bonding method of diamond crystal according to claim 1, characterized in that the material of the substrate (21) comprises silicon, silicon on insulator (SOI), sapphire, silicon carbide, silicon carbide on insulator (SiCOI) and aluminum nitride; The material of the second bonding medium layer (22) includes silicon dioxide, silicon nitride, aluminum oxide or nano silicon. 7. A heterostructure, characterized in that it is obtained by the heterogeneous bonding method of diamond crystals according to any one of claims 1 to 6, comprising a substrate (21), a bonding medium layer and a diamond crystal (11); The bonding medium layer is provided on the top of the substrate (21); The diamond crystal (11) is arranged on the top of the bonding medium layer; The bonding medium layer is bonded to the substrate (21) and the diamond crystal (11) respectively; The bonding medium layer comprises a first bonding medium layer (12) and a second bonding medium layer (22) which are bonded to each other; the first bonding medium layer (12) is bonded to the diamond crystal (11), and the second bonding medium layer (22) is bonded to the substrate (21); The first bonding medium layer (12) and the second bonding medium layer (22) on the surface of the diamond crystal are subjected to hydrophilic bonding or SAB bonding to obtain a heterogeneous structure (3).