WO2023128687A1

WO2023128687A1 - Nickel alloy composition for copper-bonding layer for copper-bonded nitride substrate

Info

Publication number: WO2023128687A1
Application number: PCT/KR2022/021694
Authority: WO
Inventors: 배진원; 김건호
Original assignee: 주식회사 큐프럼 머티리얼즈
Priority date: 2021-12-30
Filing date: 2022-12-30
Publication date: 2023-07-06

Abstract

The present application relates to a nitride substrate such as AlN and Si₃N₄ having a copper layer bonded thereto and, more specifically, to a composition for a copper-bonding layer, a laminate substrate, and a manufacturing method of the substrate, the composition enhancing the bond strength and thermoelectric properties between the nitride substrate and the copper layer. By using the nickel alloy composition for a copper-bonding layer for a copper-bonded nitride substrate of the present application, a copper-bonded nitride substrate having enhanced bonding force may be manufactured by forming an alloy metal layer between a nitride and a copper layer.

Description

Copper bonding layer nickel alloy composition for copper bonding nitride substrate

The present application relates to a nitride substrate such as AlN, Si ₃ N ₄ to which a copper layer is bonded, and more particularly, to a composition of a copper bonding layer formed to increase bonding strength and thermoelectric properties between a nitride substrate and a copper layer, and a laminated substrate , It relates to a manufacturing method of the substrate.

Circuit substrates used in power modules, etc., are made of alumina, zirconium toughened alumina, silicon nitride (Si ₃ N ₄ ), and aluminum nitride (AlN) for reasons such as thermal conductivity, cost, and safety. Ceramic substrates such as these are mainly used. These ceramic substrates are used as circuit boards by bonding metal circuit boards or heat sinks such as copper or aluminum. These are used as substrates for mounting electronic components with high heat dissipation due to their excellent insulating properties and heat dissipation properties with respect to resin substrates or metal substrates using a resin layer as an insulating material. In addition, for power modules such as elevators, vehicles, and hybrid cars, a ceramic circuit board in which a metal circuit board is bonded to the surface of a ceramic substrate with an active metal solder material and a semiconductor element is mounted at a predetermined position on the metal circuit board is used. .

In recent years, a ceramic substrate of an aluminum nitride sintered body or a silicon nitride sintered body having high thermal conductivity has been used in response to an increase in the amount of heat generated from the semiconductor device due to high integration, high frequency, and high output of the semiconductor device. Since the aluminum nitride substrate has high thermal conductivity but low mechanical strength or toughness, it has a disadvantage in that cracks are easily generated when cracks occur due to tightening in an assembly process or when a thermal cycle is added. In particular, when applied to power modules applied under severe load and thermal conditions, such as automobiles, electric railways, machine tools, and robots, these disadvantages become remarkable. On the other hand, silicon nitride substrates have lower thermal conductivity than AlN but have high durability, so high durability is required for electric vehicles and the like, and are suitable as ceramic circuit boards for mounting electronic components with high heat dissipation. A ceramic circuit board using such a nitride ceramic substrate is produced by an active metal bonding (AMB) method. Such an active metal method is a method of bonding a metal plate on a ceramic substrate through a solder material layer containing an active metal such as a group 4A element or a group 5A element. Generally, a silver-copper-titanium solder material is applied to the silicon nitride substrate The main surface is screen-printed, a metal circuit board and a metal heat sink are placed on the printed surface, and the ceramic substrate and the metal plate are bonded by heat treatment at an appropriate temperature.

In order to use the sintered nitride ceramics as a substrate for semiconductors, a surface conductor layer must be formed and wired. Methods for forming this surface conductor layer include an active metal method in which a copper plate or the like is integrally joined as a conductor layer using an active metal to a sintered substrate, or a conductor on a ceramic substrate using a printing paste containing copper and glass frit. There is a paste sintering method in which a pattern is formed and fired at a high temperature to form a substrate and a conductor layer. The paste sintering method, in which metal powder particles are fired at high temperatures, is being studied in order to expand its use, but it has disadvantages in bonding strength and electrical resistance (conductivity) and needs improvement.

As mentioned above, in the past, in order to lower the thermal stress between Si ₃ N ₄ and copper, a plate or paste with an AgCuTiSn composition was used with a thickness of 10um as AMB (active metal bonding). In this case, Ag-containing The material cost of the AMB plate is high, and the process cost is cheap in the case of AMB paste, but the organic solvent evaporates at a high temperature and voids between the copper and the active layer frequently occur, which reduces durability and yield. there is In addition, titanium used among active metals forms TiO2, which is titanium oxide, in AlN, which is effective for interfacial bonding, but it is difficult to form TiO ₂ in Si ₃ N ₄ and has a disadvantage in that bonding properties are poor.

Instead of the bonding method using expensive active metals such as silver, the diffusion bonding method, which primarily forms IMC (intermetallic compound) at the interface between copper and ceramic substrate at high temperature and performs a heat treatment process, has excellent interfacial bonding properties. There are advantages. However, diffusion bonding is possible for a copper-bonded AlN substrate bonded by CuO generated at the Cu/AlN interface, but in the case of a Si ₃ N ₄ substrate in which CuO is not formed, it is difficult to manufacture a copper-bonded ceramic substrate having excellent bonding strength.

Accordingly, the inventors of the present invention formed a thin sputter layer with improved bonding strength and thermoelectric properties at the interface so that bonding strength between the Si ₃ N ₄ substrate and the copper layer on the substrate is improved, thereby forming a copper-bonded silicon nitride substrate having excellent thermal durability. was manufactured. In the present invention, a nickel alloy composition for a copper bonding layer for a Si ₃ N ₄ substrate, a laminated substrate, and a method for manufacturing the substrate were developed.

[Prior art literature]

[Patent Literature]

(Patent Document 0001) Korea Patent Registration No. 10-2339805

In the present application, in a nitride substrate such as Si ₃ N ₄ to which a copper layer is bonded, a composition of a copper bonding layer (copper lower film) formed to increase the bonding strength and thermoelectric properties between the nitride substrate and the copper layer, a laminated substrate, and the substrate It is an object to provide a manufacturing method of.

However, the problem to be solved by the present application is not limited to the above-mentioned problem, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

A first aspect of the present application provides a copper bonding layer nickel alloy composition for a copper bonding nitride substrate.

A second aspect of the present application provides a method for manufacturing a copper bonded nitride substrate.

A third aspect of the present application provides a copper bonded nitride laminated board.

Using the copper bonding layer nickel alloy composition for a copper bonding nitride substrate of the present disclosure, a copper bonding nitride substrate having improved bonding strength may be manufactured by forming an alloy metal layer between the nitride and the copper layer.

1 is a diagram showing the structure of a test specimen of the present invention.

2 is a flowchart illustrating a heat dissipation substrate manufacturing process applied to a power semiconductor and a driving semiconductor for a vehicle.

FIG. 3 is a diagram showing a high-temperature and low-temperature rising rate and temperature holding time for a thermal shock test prior to evaluating the bondability of a copper-bonded ceramic substrate manufactured according to the present invention.

4 is a view showing photographs of a copper-bonded silicon nitride substrate on which micropatterns are formed using the nickel-chrome bonding layer of the present application before and after a thermal shock test.

5 is a view showing photographs of test samples of cylinder and square pillar patterns manufactured by the manufacturing method of the present invention for interfacial bonding force test of copper bonded nitride substrates.

FIG. 6 is a view showing the results of confirming the bonding force with the Si ₃ N ₄ substrate, the thermal conductivity, and the etching characteristics in the copper etchant according to the composition of the NiCr binary copper underlayer (copper bonding layer).

7 is a view showing the result of confirming the bonding force for each condition of FIG. 6 using a die shear device.

8 is a diagram showing the results of measuring the thermal conductivity of each sample to determine the thermal conductivity of copper formed on a ceramic substrate.

Hereinafter, embodiments of the present application will be described in detail so that those skilled in the art can easily practice with reference to the accompanying drawings. However, the present disclosure may be implemented in many different forms and is not limited to the embodiments described herein. And in order to clearly describe the present application in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout the present specification, when a member is said to be located “on” another member, this includes not only a case where a member is in contact with another member, but also a case where another member exists between the two members.

Throughout the specification, when a part "includes" a certain component, it means that it may further include other components without excluding other components unless otherwise stated. As used throughout this specification, the terms "about", "substantially", and the like, are used at or approximating that number when manufacturing and material tolerances inherent in the stated meaning are given, and do not convey the understanding of this application. Accurate or absolute figures are used to help prevent exploitation by unscrupulous infringers of the disclosed disclosure. The term "step of (doing)" or "step of" as used throughout the present specification does not mean "step for".

Throughout this specification, the term “combination(s) of these” included in the expression of the Markush form means a mixture or combination of one or more selected from the group consisting of the components described in the expression of the Markush form, It means including one or more selected from the group consisting of the above components.

Throughout this specification, reference to “A and/or B” means “A or B, or A and B”.

Hereinafter, embodiments and embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, the disclosure may not be limited to these embodiments and examples and drawings.

A first aspect of the present application provides a copper underlayer nickel alloy composition for a copper junction nitride substrate.

According to one embodiment of the present application, the copper underlayer nickel alloy composition for a copper-bonded nitride substrate of the present application may form a thin film deposited by sputtering capable of improving bonding strength and thermoelectric characteristics at an interface.

The term "copper junction layer" used throughout the present specification is a thin film deposited by a sputtering method, and refers to a film (copper lower film) positioned below the copper layer in the laminated substrate structure of the present application. Nickel alloy, which is the copper bonding layer, may be raised by various methods such as electrolysis, electroless plating, chemical vapor deposition, and evaporation in addition to sputtering.

The term "sputtering" used throughout the present specification means that particles with high energy collide with the surface of a target material (metal) to transfer energy to target atoms on the surface, and the target atoms are emitted. tell how to deposit

According to one embodiment of the present application, the sputtering (sputtering) deposited thin film (copper bonding layer) of the present application can be improved bonding strength between the upper copper and the lower substrate by containing Ni as a main component and a small amount of Cr. In this case, the composition of the Ni-Cr alloy may be 95 wt % to 70 wt % of Ni and 5 wt % to 30 wt % of Cr.

According to one embodiment of the present application, it can be confirmed that when the Ni-Cr binary of the present application is used, the bonding strength is increased by 300% or more compared to when pure copper is used alone. In the case of pure copper, CuO (0.3 μm crystal sizes), which is a small porous copper oxide, is formed on the surface to be bonded to the substrate, resulting in low adhesive strength. Since it forms a strong bond, it is possible to obtain a uniform high-strength bonding surface without dispersion of strength.

A second aspect of the present application provides a method for manufacturing a copper bonded nitride substrate. Content overlapping with the first aspect is also applied to the manufacturing method of the second aspect.

According to one embodiment of the present application, the present application includes forming a curve on the surface of a nitride substrate; Depositing a copper bonding layer (Tie-coat layer) on the nitride substrate by a sputtering method; depositing copper (Cu) on the copper junction layer to form a copper seed layer; forming a patterned mask on the copper seed layer; Performing electrolytic plating using a high speed copper plating bath; and removing a tie-coat layer and a copper seed layer through an etching process (see FIG. 2 ).

In one embodiment of the present application, the nitride substrate may include AlN or Si ₃ N ₄ but is not limited thereto.

In one embodiment of the present application, when the curved surface of the Si ₃ N ₄ ceramic substrate is formed, the contact area between the substrate and the adhesive layer increases, thereby improving the adhesion of the substrate.

In one embodiment of the present application, the depositing of the copper bonding layer may be performed using the composition of the first aspect, but is not limited thereto.

In one embodiment of the present application, the depositing of the copper junction layer may be depositing a copper junction layer to a thickness of 1 nm to 60 nm, preferably 5 nm to 50 nm.

In one embodiment of the present application, the step of forming the copper seed layer may be depositing a copper seed layer thickness of 200 nm to 600 nm, preferably 300 nm to 500 nm.

A third aspect of the present application provides a copper bonded nitride laminated board. Contents overlapping with those of the first and second sides are also applied to the substrate of the third side.

In one embodiment of the present application, the laminated substrate of the present application is a nitride substrate; a copper bonding layer laminated on a nitride substrate by a sputtering method using the composition of the first side; and a copper layer formed on the copper bonding layer, but is not limited thereto.

Hereinafter, the present invention will be described in more detail through examples of the present application, but the following examples are only illustrative to aid understanding of the present application, and the content of the present application is not limited to the following examples.

[실험예][Experimental Example]

[니켈합금 접합층의 접합력 비교 실험][Comparative test of bonding force of nickel alloy bonding layer]

After forming a bonding layer using plasma facilities and a copper (400um) circle pattern with a diameter of 5mm on a Si ₃ N ₄ substrate (2.5cm x 2.5cm substrate), after conducting a thermal shock test (300 times at -50 degrees to 180 degrees), Nordson's die The bonding strength of the copper bonding layer (tie-coat layer, bonding layer) alloy was confirmed using the bonding force test equipment using the shear test equipment (see FIG. 7).

In the case of bonding strength, Example 3 showed a higher bonding strength than Example 2. That is, as the content of chromium in the nickel-chromium alloy increased, the bonding strength was improved. On the other hand, when the chromium content was excessively high, such as 40 wt%, as in Comparative Example 2, the bonding strength was rather deteriorated. , it was found that the thermal stress due to the difference in the thermal expansion coefficient of copper was generated at the interface and the bonding strength at the interface was deteriorated. As in Comparative Example 3, when only copper was loaded without an interlayer bonding material, the interfacial bonding force was measured to be very weak compared to the sample with a nickel-chromium alloy bonding material. When the number of thermal shocks increased more than 50 times, some test patterns were lost.

In addition, copper-bonded silicon nitride substrates on which micropatterns were formed using the nickel-chromium bonding layer of the present application were compared before and after the thermal shock test (see FIG. 4). On a Si ₃ N ₄ substrate with a thickness of 0.3 mm, a nickel-chromium bonding layer was formed by several tens of nm and a copper layer by 400 um.

[열전도도 확인 실험][Thermal conductivity confirmation experiment]

To examine the thermal conductivity of copper formed on a ceramic substrate, the thermal conductivity of each sample was measured at 25 °C and 180 °C using Laser Flash Apparatus equipment from NETZCH.

As shown in the following thermal conductivity graph (see FIG. 8), the thermal conductivity tended to decrease when the chromium content increased. In particular, in the case of Comparative Example 2 having a relatively high chromium content compared to nickel, the value was 130 W/m.k or less at room temperature.

[단일 금속 및 합금의 에칭 특성 확인 실험][Experiment to confirm etching characteristics of single metals and alloys]

Since a copper wiring pattern can be formed only when the copper bonding layer can be etched simultaneously with copper, etching property is one of the important process factors in a copper etchant. In order to examine the etching characteristics of the alloy used as the copper bonding layer, an etching test was performed on the Si ₃ N ₄ substrate/copper bonding layer/copper specimen using a ferric chloride (FeCl ₃ ) etchant. The etching test was performed by depositing about 10 to 50 nm of copper bonding composition on a ceramic substrate through a sputtering process, forming a 1000 nm copper layer thereon, forming a pattern, and then using a spray etching method.

As a result of the experiment, it was confirmed that the etching rate of the NiCr alloy slowed down as the Cr content increased. While there is a disadvantage that residues remain when the Cr content exceeds 50%, a pattern can be formed without etching residues because the binary alloy with less than 50% Cr exhibits a fast etching rate.

Based on all the above experimental results, interfacial bonding strength, thermal conductivity, and etching characteristics according to the composition of the nickel alloy layer used as the copper bonding layer were summarized as follows (see FIG. 6).

When the interfacial bonding force was greater than 30 kgf, it was marked as O (suitable), and when it was less than 30 kgf, it was marked as X (unsuitable).

Thermal conductivity was marked as O when it was 130 W/m*K or more at room temperature (acceptable), and X when it was less than 130 W/m*K (unsuitable).

In addition, when the etching property (etching rate) was 20 A/sec or more, it was marked as O (suitable), and when it was less than 20 A/sec, it was marked as X (unsuitable).

As a result, in NiCr, when Ni exceeds 95 wt % in the composition of the Ni-Cr alloy (Cr is less than 5 wt %), bonding strength and thermal conductivity are significantly reduced, while Ni is less than 70 wt % (Cr is less than 5 wt %). When it exceeds 30 wt %), it was confirmed that bonding strength, thermal conductivity, and etching properties are all deteriorated (see FIG. 6).

The above description of the present application is for illustrative purposes, and those skilled in the art will understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present application. Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

Claims

A copper underlayer nickel alloy composition for a copper bonded nitride substrate comprising NiCr.
According to claim 1,

The composition of the Ni-Cr alloy of NiCr is 95 wt % to 70 wt % of Ni and 5 wt % to 30 wt % of Cr,

A copper underlayer nickel alloy composition for copper bonded nitride substrates.
Forming curves on the surface of the nitride substrate;

Depositing a copper bonding layer (Tie-coat layer) on the nitride substrate by a sputtering method;

depositing copper (Cu) on the copper junction layer to form a copper seed layer;

forming a patterned mask on the copper seed layer;

Performing electrolytic plating using a high speed copper plating bath; and

A method of manufacturing a copper bonded nitride substrate comprising the step of removing a copper bond layer and a copper seed layer through an etching process.
According to claim 3,

Wherein the nitride substrate is AlN or Si 3 N 4

A method for manufacturing copper-bonded nitride substrates.
According to claim 3,

The step of depositing the copper bonding layer (tie-coat layer) is a method of manufacturing a copper bonded nitride substrate made by a sputtering method using the composition of claim 1 or claim 2.
According to claim 3,

The step of depositing the copper bonding layer (Tie-coat layer) is to deposit a copper bonding layer (Tie-coat layer) thickness to 5nm to 50nm, copper bonded nitride substrate manufacturing method.
According to claim 3,

In the step of forming the copper seed layer, the copper seed layer is deposited to have a thickness of 300 nm to 500 nm.
nitride substrate; A copper bonding layer laminated on the nitride substrate by a sputtering method using the composition of claim 1 or 2; and a copper layer formed on the copper junction layer.
According to claim 8,

Wherein the nitride substrate is AlN or Si 3 N 4

Copper bonded nitride laminated board.