CN113299571B - Method for improving Au-Al bonding strength and reliability - Google Patents

Method for improving Au-Al bonding strength and reliability Download PDF

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CN113299571B
CN113299571B CN202110555962.3A CN202110555962A CN113299571B CN 113299571 B CN113299571 B CN 113299571B CN 202110555962 A CN202110555962 A CN 202110555962A CN 113299571 B CN113299571 B CN 113299571B
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bonding
aluminum
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ion sputtering
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CN113299571A (en
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张新宇
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Wuxi Xinghua Henghui Technology Co ltd
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Wuxi Xinghua Henghui Technology Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/80—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected
    • H01L24/85—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected using a wire connector
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • C23C14/14—Metallic material, boron or silicon
    • C23C14/16—Metallic material, boron or silicon on metallic substrates or on substrates of boron or silicon
    • C23C14/165—Metallic material, boron or silicon on metallic substrates or on substrates of boron or silicon by cathodic sputtering
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C23C14/3464—Sputtering using more than one target
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/80—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected
    • H01L2224/85—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected using a wire connector
    • H01L2224/852—Applying energy for connecting
    • H01L2224/85201—Compression bonding
    • H01L2224/85205—Ultrasonic bonding
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

The invention relates to the technical field of semiconductor device packaging, in particular to a method for improving Au-Al bonding strength and reliability. According to the invention, a layer of Zn and a layer of Cu are sequentially deposited on the surface of Al by using an ion sputtering method, so that a Cu-Al-Zn ternary compound thin layer is formed between Au and Al in the bonding process, the direct contact and mutual diffusion between gold and aluminum are prevented, and meanwhile, the Cu-Al-Zn ternary compound thin layer can continuously hinder the mutual diffusion between Au and Al under the action of current, so that the growth of intermetallic compounds at the bonding connection part is inhibited, the strength and reliability of Au-Al bonding are improved, and the problems that the growth of intermetallic compounds cannot be effectively inhibited in the Au-Al bonding method of the traditional semiconductor device, the Au-Al bonding strength and bonding reliability are poor, and the function and service life of the semiconductor device are influenced are effectively solved.

Description

Method for improving Au-Al bonding strength and reliability
Technical Field
The invention relates to the technical field of semiconductor device packaging, in particular to a method for improving Au-Al bonding strength and reliability.
Background
In the packaging process of a semiconductor device, a gold wire is generally used between an aluminum chip and an external lead to connect through an Au-Al bonding, the bonding connection point plays a role in transporting power and signals of an internal circuit and an external circuit of the chip, and the bonding strength and long-term reliability of the Au-Al bonding play a decisive role in the function and the service life of the semiconductor device.
The most widely used Au-Al bonding method at present is ultrasonic bonding, in which a gold wire with a spherical end is welded to an aluminum lead by ultrasonic extrusion and thermal action. Because the electronegativity of Au and Al is greatly different, the diffusion rate, the lattice constant and the thermal expansion coefficient of Au and Al are different, the Au and Al have strong reaction tendency, and a Cokendall cavity and various intermetallic compounds are easily formed at the welding interface between Au and Al in the long-term use process. These intermetallic compounds are brittle materials with poor conductivity, and excessive intermetallic compounds cause a decrease in joint strength and reliability and increase in bonding contact resistance. The formation and growth of the intermetallic compounds are accelerated under the action of current, so that the parameters of the device are drifted and even the device is failed due to open circuit, and the long-term reliability of the product is influenced. Therefore, the inhibition of the formation and growth of the intermetallic compound between Au and Al is an important way for improving the bonding strength and reliability of Au-Al. The existing Au-Al bonding method mainly reduces the formation of intermetallic compounds during bonding as much as possible by optimizing bonding parameters, but the method has high requirements on process stability, and cannot prevent the problem of further growth of intermetallic compounds in the later use process, so that the reliability of a bonding interface is poor, and the function and the service life of a semiconductor device are further influenced.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a method for improving the bonding strength and reliability of Au-Al, which can effectively prevent Au and Al from being in direct contact and mutual diffusion, inhibit the growth of intermetallic compounds at bonding connection parts, and effectively solve the technical problems that the existing Au-Al bonding method cannot effectively inhibit the rapid growth of intermetallic compounds in a bonding interface and the Au-Al bonding strength and reliability in a device are poor.
In order to solve the technical problems, the invention adopts the technical scheme that:
a method for improving Au-Al bonding strength and reliability comprises the following steps:
(1) coating an organic isolating agent on the part of the aluminum device which does not need to be bonded for covering, and cleaning the surface of the part of the aluminum device which needs to be bonded;
(2) placing the aluminum device part to be bonded in a vacuum chamber of an ion sputtering instrument, setting a sputtering target material as zinc, switching on a power supply of ion sputtering equipment and starting a vacuum pump, starting an ion sputtering process after the vacuum degree meets the specified requirement, depositing a layer of zinc on the surface of aluminum, closing an ion sputtering power supply after the deposition is finished, opening a vacuum valve, and restoring the air pressure of the vacuum chamber to atmospheric pressure;
(3) changing a sputtering target material into copper, switching on a power supply of an ion sputtering device, starting a vacuum pump, starting an ion sputtering process after the vacuum degree meets the specified requirement, depositing a layer of copper on the surface of aluminum, generating a Cu-Al-Zn ternary compound thin layer on the surface of an aluminum device after the deposition is finished, closing an ion sputtering power supply, opening a vacuum valve, and restoring the air pressure of a vacuum chamber to the atmospheric pressure;
(4) cleaning the organic separant coated on the surface of the aluminum device, and performing wire drawing and spheroidizing on the gold wire by using an ultrasonic bonding machine to perform Au-Al ultrasonic bonding.
Further, the vacuum degree of the ion sputtering environment is controlled to be 0.01-10 Pa, and the purity of the sputtering target material is 99.99-99.9999%.
Furthermore, after ion sputtering, the thickness of the zinc layer deposited on the surface of the aluminum is 5-1000 nm.
Further, after ion sputtering, the thickness of the copper layer deposited on the surface of the aluminum is 20-1000 nm.
Further, the thickness ratio of the zinc layer to the copper layer is 1: 5-1: 1.2, preferably 1: 5-1: 3.
furthermore, the diameter of the gold wire is 0.005-0.3 mm.
Furthermore, the diameter of the gold wire is preferably 0.01-0.1 mm.
Further, inert gas is used for protection in the ultrasonic bonding process, the ultrasonic frequency is controlled to be 20-40 kHz, the power is 200-600 mW, the bonding pressure is 40-100 cN, the bonding time is controlled to be 2-70 ms, and the temperature is set to be 150-180 ℃.
Furthermore, the viscosity of the organic release agent is 3-500 mPa & s, and the organic release agent can be a removable or water-soluble solder mask.
The method for cleaning the surface of the aluminum device part needing bonding comprises the following steps:
firstly, wiping the surface of the aluminum clean by using filter paper and absolute ethyl alcohol; soaking the surface to be cleaned in absolute ethyl alcohol, and cleaning for 1-3 minutes by using an ultrasonic cleaning machine; and finally, cleaning for 1-3 minutes by using a plasma cleaning machine in an argon protection environment with the air pressure of 0.01 MPa.
Compared with the traditional Au-Al bonding method, the Au-Al bonding method provided by the invention has the following beneficial effects:
according to the invention, a layer of Zn and a layer of Cu are sequentially deposited on the surface of the aluminum device by using an ion sputtering method, and the ternary compound has lower free energy than the binary compound, so that a Cu-Al-Zn ternary compound thin layer is easily generated on a bonding interface between Au and Al in a bonding process, the direct contact and mutual diffusion between Au and Al are prevented, and the formation of other binary compounds is hindered. Meanwhile, the Cu-Al-Zn ternary compound thin layer can continuously hinder mutual diffusion between Au and Al under the action of current, so that the growth of intermetallic compounds at the bonding connection part is inhibited, and the strength and reliability of Au-Al bonding are improved. According to the invention, the growth thickness of the intermetallic compound can be effectively controlled by adjusting the deposition thicknesses of the zinc layer and the copper layer, and further the optimal Au-Al bonding strength can be selected according to actual use requirements.
Detailed Description
The present invention will be described in further detail with reference to the following detailed description, which should be understood that the following examples are only illustrative of the preferred embodiments of the present invention, show and describe the basic principles, main features and advantages of the present invention, and are only illustrative and explanatory of the present invention, but not restrictive thereof.
The method for improving the bonding strength and reliability of Au-Al provided by the invention comprises the following steps:
(1) the surface of the aluminum device part to be bonded is fully cleaned.
Firstly, wiping the surface of aluminum clean by using filter paper and analytically pure absolute ethyl alcohol to remove main dust and pollutants; then immersing the surface to be cleaned in analytically pure absolute ethyl alcohol, and cleaning for 1-3 minutes by using an ultrasonic cleaning machine to further remove impurities and fibers stained on the surface; and finally, cleaning for 1-3 minutes by using a plasma cleaning machine in an Ar gas protection environment with the air pressure of 0.01 MPa. Through sufficient cleaning, the pollutants on the surface of the aluminum can be sufficiently removed, thereby being beneficial to improving the subsequent ion sputtering and bonding effects.
(2) The organic isolating agent is used for covering the part of the aluminum device which does not need to be bonded.
(3) And placing the aluminum device to be bonded in a vacuum chamber of an ion sputtering instrument, wherein the sputtering target is zinc.
(4) The power supply of the ion sputtering equipment is switched on and the vacuum pump is started.
(5) And after the vacuum degree meets the specified requirement, starting an ion sputtering process, and depositing a layer of zinc on the surface of the aluminum.
(6) And after the deposition is finished, closing the ion sputtering power supply, opening the vacuum valve, and restoring the air pressure of the vacuum chamber to the atmospheric pressure.
(7) And (5) replacing the sputtering target material with copper, and repeating the step (4), the step (5) and the step (6).
(8) And cleaning the organic release agent coated on the surface of the aluminum device.
(9) And (3) performing drawing and spheroidizing on the gold wire by adopting an ultrasonic bonding machine, and performing Au-Al ultrasonic bonding.
The invention has no strict limitation on the shape, size and specification of the semiconductor device and the aluminum pin on the semiconductor device.
The method for improving the bonding strength and reliability of Au-Al provided by the present invention will be described in detail with reference to the following specific examples, which should not be construed as limiting the scope of the present invention.
Example 1
The method for improving the bonding strength and reliability of Au — Al in this embodiment specifically includes the following steps:
(1) the surface of the aluminum device part to be bonded is fully cleaned.
(2) And covering the part of the aluminum device which does not need to be bonded by using an organic isolating agent, wherein the organic isolating agent selects a tearable solder resist adhesive Osbang SM-120.
(3) The aluminum device to be bonded is placed in a vacuum chamber of an ion sputtering apparatus, and the sputtering target is set to be zinc with the purity of 99.99%.
(4) The power supply of the ion sputtering equipment is switched on and the vacuum pump is started.
(5) After the vacuum degree reaches 0.1Pa, the ion sputtering process is started, and a layer of zinc with the thickness of 100nm is deposited on the surface of the aluminum.
(6) After deposition, the ion sputtering power supply is closed, the vacuum valve is opened, and the air pressure of the vacuum chamber is restored to the atmospheric pressure.
(7) And (5) replacing the sputtering target with copper with the purity of 99.99%, repeating the steps (4), (5) and (6), and depositing a layer of copper with the thickness of 300nm on the surface of the aluminum.
(8) Tearing off the organic release agent on the surface of the aluminum device, and cleaning the aluminum device for 1-3 minutes by using a plasma cleaning machine in an Ar gas protection environment with the air pressure of 0.01 MPa.
(9) Selecting a gold wire with the diameter of 0.1mm, and performing drawing and spheroidizing on the gold wire by adopting an ultrasonic bonding machine to perform Au-Al ultrasonic bonding. Wherein, 95 percent of nitrogen and 5 percent of hydrogen are used for protection in the ultrasonic bonding process, the ultrasonic frequency is controlled at 20kHz, the power is 600mW, the bonding pressure is 100cN, the bonding time is controlled at 10ms, and the temperature is set at 150 ℃.
Example 2
The method for improving the bonding strength and reliability of Au — Al in this embodiment specifically includes the following steps:
(1) the surface of the aluminum device part to be bonded is fully cleaned.
(2) The aluminum device parts which do not need to be bonded are covered by using an organic release agent, and the WonderMASK WSOL water-washing type solder mask produced by TECHSPRAY is selected as the organic release agent.
(3) The aluminum device to be bonded is placed in a vacuum chamber of an ion sputtering apparatus, and the sputtering target is set to be zinc with the purity of 99.99%.
(4) The power supply of the ion sputtering equipment is switched on and the vacuum pump is started.
(5) After the vacuum degree reaches 0.1Pa, the ion sputtering process is started, and a layer of zinc with the thickness of 300nm is deposited on the surface of the aluminum.
(6) After deposition, the ion sputtering power supply is closed, the vacuum valve is opened, and the air pressure of the vacuum chamber is restored to the atmospheric pressure.
(7) And (5) replacing the sputtering target material with copper with the purity of 99.99%, repeating the steps (4), (5) and (6), and depositing a layer of copper with the thickness of 600nm on the surface of the aluminum.
(8) Cleaning an organic separant on the surface of an aluminum device, immersing the surface to be cleaned in deionized water at 50-85 ℃, and cleaning for 2 minutes by using an ultrasonic cleaner; after no visible organic isolation layer exists on the surface, immersing the surface to be cleaned in analytically pure absolute ethyl alcohol, and cleaning for 2 minutes by using an ultrasonic cleaning machine, wherein the ultrasonic frequency is 20kHz, and the power is 200 w; finally, a plasma cleaning machine is used for cleaning for 2 minutes in the protection of Ar gas with the pressure of 0.01 MPa.
(9) Selecting a gold wire with the diameter of 0.2mm, and performing drawing and spheroidizing on the gold wire by adopting an ultrasonic bonding machine to perform Au-Al ultrasonic bonding. Wherein, 95 percent of nitrogen and 5 percent of hydrogen are used for protection in the ultrasonic bonding process, the ultrasonic frequency is controlled at 40kHz, the power is 600mW, the bonding pressure is 100cN, the bonding time is controlled at 70ms, and the temperature is set at 180 ℃.
Example 3
The method for improving the bonding strength and reliability of Au — Al in this embodiment specifically includes the following steps:
(1) the surface of the aluminum device part to be bonded is fully cleaned.
(2) And covering the part of the aluminum device which does not need to be bonded by using an organic isolating agent, wherein the organic isolating agent selects a tearable solder resist adhesive Osbang SM-120.
(3) The aluminum device to be bonded is placed in a vacuum chamber of an ion sputtering apparatus, and the sputtering target is set to be zinc with the purity of 99.99%.
(4) The power supply of the ion sputtering equipment is switched on and the vacuum pump is started.
(5) After the vacuum degree reaches 0.01Pa, the ion sputtering process is started, and a layer of zinc with the thickness of 30nm is deposited on the surface of the aluminum.
(6) After deposition, the ion sputtering power supply is closed, the vacuum valve is opened, and the air pressure of the vacuum chamber is restored to the atmospheric pressure.
(7) And (5) replacing the sputtering target with copper with the purity of 99.99%, repeating the steps (4), (5) and (6), and depositing a layer of copper with the thickness of 50nm on the surface of the aluminum.
(8) Tearing off the organic release agent on the surface of the aluminum device, and cleaning the aluminum device for 1-3 minutes by using a plasma cleaning machine in an Ar gas protection environment with the air pressure of 0.01 MPa.
(9) Selecting a gold wire with the diameter of 0.025mm, and performing drawing and spheroidizing on the gold wire by adopting an ultrasonic bonding machine to perform Au-Al ultrasonic bonding. Wherein, 95 percent of nitrogen and 5 percent of hydrogen are used for protection in the ultrasonic bonding process, the ultrasonic frequency is controlled at 40kHz, the power is 200mW, the bonding pressure is 20cN, the bonding time is controlled at 2ms, and the temperature is set at 150 ℃.
Example 4
The method for improving the bonding strength and reliability of Au — Al in this embodiment specifically includes the following steps:
(1) the surface of the aluminum device part to be bonded is fully cleaned.
(2) The aluminum device parts which do not need to be bonded are covered by using an organic release agent, and the WonderMASK WSOL water-washing type solder mask produced by TECHSPRAY is selected as the organic release agent.
(3) The aluminum device to be bonded is placed in a vacuum chamber of an ion sputtering apparatus, and the sputtering target is set to be zinc with the purity of 99.99%.
(4) The power supply of the ion sputtering equipment is switched on and the vacuum pump is started.
(5) After the vacuum degree reaches 0.05Pa, the ion sputtering process is started, and a layer of zinc with the thickness of 500nm is deposited on the surface of the aluminum.
(6) After deposition, the ion sputtering power supply is closed, the vacuum valve is opened, and the air pressure of the vacuum chamber is restored to the atmospheric pressure.
(7) And (5) replacing the sputtering target material with copper with the purity of 99.99%, repeating the steps (4), (5) and (6), and depositing a layer of copper with the thickness of 800nm on the surface of the aluminum.
(8) Cleaning an organic separant on the surface of an aluminum device, immersing the surface to be cleaned in deionized water at 50-85 ℃, and cleaning for 2 minutes by using an ultrasonic cleaner; after no visible organic isolation layer exists on the surface, immersing the surface to be cleaned in analytically pure absolute ethyl alcohol, and cleaning for 2 minutes by using an ultrasonic cleaning machine, wherein the ultrasonic frequency is 20kHz, and the power is 200 w; finally, a plasma cleaning machine is used for cleaning for 2 minutes in the protection of Ar gas with the pressure of 0.01 MPa.
(9) Selecting a gold wire with the diameter of 0.2mm, and performing drawing and spheroidizing on the gold wire by adopting an ultrasonic bonding machine to perform Au-Al ultrasonic bonding. Wherein, 95 percent of nitrogen and 5 percent of hydrogen are used for protection in the ultrasonic bonding process, the ultrasonic frequency is controlled at 20kHz, the power is 400mW, the bonding pressure is 100cN, the bonding time is controlled at 50ms, and the temperature is set at 150 ℃.
Example 5
The method for improving the bonding strength and reliability of Au — Al in this embodiment specifically includes the following steps:
(1) the surface of the aluminum device part to be bonded is fully cleaned.
(2) The aluminum device parts which do not need to be bonded are covered by using an organic release agent, and the WonderMASK WSOL water-washing type solder mask produced by TECHSPRAY is selected as the organic release agent.
(3) The aluminum device to be bonded is placed in a vacuum chamber of an ion sputtering apparatus, and the sputtering target is set to be zinc with the purity of 99.99%.
(4) The power supply of the ion sputtering equipment is switched on and the vacuum pump is started.
(5) After the vacuum degree reaches 0.1Pa, the ion sputtering process is started, and a layer of zinc with the thickness of 800nm is deposited on the surface of the aluminum.
(6) After deposition, the ion sputtering power supply is closed, the vacuum valve is opened, and the air pressure of the vacuum chamber is restored to the atmospheric pressure.
(7) And (5) replacing the sputtering target material with copper with the purity of 99.99%, repeating the steps (4), (5) and (6), and depositing a layer of copper with the thickness of 1000nm on the surface of the aluminum.
(8) Cleaning an organic separant on the surface of an aluminum device, immersing the surface to be cleaned in deionized water at 50-85 ℃, and cleaning for 2 minutes by using an ultrasonic cleaner; after no visible organic isolation layer exists on the surface, immersing the surface to be cleaned in analytically pure absolute ethyl alcohol, and cleaning for 2 minutes by using an ultrasonic cleaning machine, wherein the ultrasonic frequency is 20kHz, and the power is 200 w; finally, a plasma cleaning machine is used for cleaning for 2 minutes in the protection of Ar gas with the pressure of 0.01 MPa.
(9) Selecting a gold wire with the diameter of 0.08mm, and performing drawing and spheroidizing on the gold wire by adopting an ultrasonic bonding machine to perform Au-Al ultrasonic bonding. Wherein, 95 percent of nitrogen and 5 percent of hydrogen are used for protection in the ultrasonic bonding process, the ultrasonic frequency is controlled at 40kHz, the power is 300mW, the bonding pressure is 50cN, the bonding time is controlled at 20ms, and the temperature is set at 150 ℃.
The ion sputtering apparatus used in embodiments 1 to 5 of the present invention was an ion sputtering apparatus of type MC1000 produced by hitachi group.
Comparative example
Au-Al bonding is carried out on the semiconductor device by adopting a conventional ultrasonic bonding method, and the steps are as follows:
(1) the surface of the aluminum device part to be bonded is fully cleaned.
(2) Selecting a gold wire with the diameter of 0.1mm, and performing drawing and spheroidizing on the gold wire by adopting an ultrasonic bonding machine to perform Au-Al ultrasonic bonding. Wherein, 95 percent of nitrogen and 5 percent of hydrogen are used for protection in the ultrasonic bonding process, the ultrasonic frequency is controlled at 20kHz, the power is 600mW, the bonding pressure is 100cN, the bonding time is controlled at 10ms, and the temperature is set at 150 ℃.
According to the methods provided by the embodiments 1-5 and the comparative example, Au-Al ultrasonic bonding is respectively carried out on the semiconductor device to prepare a test sample, and the bonding strength is tested according to the national standard GB/T4937.22-2018. In addition, 1.0X 10 of the bonding site of each test sample was passed through4A/cm2After 24 hours, the thickness and peel strength of the intermetallic compound at the bonding interface after the electromigration test were measured. The results of each test are shown in table 1 below.
TABLE 1 Performance parameters and test results for examples 1-5 and comparative examples
Figure GDA0003382673210000081
As can be seen from the performance parameters and test data in table 1, compared with the conventional device bonding method, according to the Au-Al ultrasonic bonding method provided by the present invention, the thickness of the intermetallic compound generated at the bonding interface of the semiconductor device is thinner, the bonding strength is higher, and after electromigration, the growth rate of the intermetallic compound in the bonding interface is significantly reduced, and the intermetallic compound still has higher bonding strength.
Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will understand that various changes, modifications and substitutions can be made without departing from the spirit and scope of the invention as defined by the appended claims. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (8)

1. A method for improving Au-Al bonding strength and reliability is characterized by comprising the following steps:
(1) coating an organic isolating agent on the part of the aluminum device which does not need to be bonded for covering, and cleaning the surface of the part of the aluminum device which needs to be bonded;
(2) placing the aluminum device part to be bonded in a vacuum chamber of an ion sputtering instrument, setting a sputtering target material as zinc, switching on a power supply of ion sputtering equipment and starting a vacuum pump, starting an ion sputtering process after the vacuum degree meets the specified requirement, depositing a layer of zinc on the surface of aluminum, closing an ion sputtering power supply after the deposition is finished, opening a vacuum valve, and restoring the air pressure of the vacuum chamber to atmospheric pressure;
(3) changing a sputtering target material into copper, switching on a power supply of an ion sputtering device, starting a vacuum pump, starting an ion sputtering process after the vacuum degree meets the specified requirement, depositing a layer of copper on the surface of aluminum, generating a Cu-Al-Zn ternary compound thin layer on the surface of an aluminum device after the deposition is finished, closing an ion sputtering power supply, opening a vacuum valve, and restoring the air pressure of a vacuum chamber to the atmospheric pressure;
(4) cleaning the organic separant coated on the surface of the aluminum device, and performing wire drawing and spheroidizing on the gold wire by using an ultrasonic bonding machine to perform Au-Al ultrasonic bonding.
2. The method for improving the bonding strength and reliability of Au-Al as claimed in claim 1, wherein the vacuum degree of the ion sputtering environment is controlled to be 0.01-10 Pa, and the purity of the sputtering target material is 99.99% -99.9999%.
3. The method for improving the bonding strength and reliability of Au-Al as claimed in claim 1, wherein the thickness of the deposited zinc layer on the surface of the aluminum is 5-1000 nm after the ion sputtering.
4. The method for improving the bonding strength and reliability of Au-Al as claimed in claim 1, wherein the thickness of the copper layer deposited on the surface of the aluminum layer after ion sputtering is 20-1000 nm.
5. The method of claim 1, wherein the ratio of the thickness of the zinc layer to the thickness of the copper layer is 1: 5-1: 1.2.
6. the method for improving Au-Al bonding strength and reliability according to claim 1, wherein the diameter of the gold wire is 0.005-0.3 mm.
7. The method for improving the bonding strength and reliability of Au-Al as claimed in claim 1, wherein the protection is performed by using inert gas during the ultrasonic bonding, the ultrasonic frequency is controlled to be 20-40 kHz, the power is 200-600 mW, the bonding pressure is 40-100 cN, the bonding time is controlled to be 2-70 ms, and the temperature is set to be 150-180 ℃.
8. The method for improving the bonding strength and reliability of Au-Al according to claim 1, wherein the viscosity of the organic release agent is 3 to 500 mPa-s.
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