阅读说明：本技术 一种高温高可靠厚膜Al焊盘的制备方法 (Preparation method of high-temperature high-reliability thick-film Al bonding pad ) 是由 刘欣 钱满满 刘军 王鹏 胡宗亮 孙玉达 崔久鹏 丁长春 赵秋山 于 2020-08-04 设计创作，主要内容包括：本发明公开一种高温高可靠厚膜Al焊盘的制备方法,属于航天微电子封装技术领域,通过在厚膜金导带上原位生成Al焊盘,实现了Al-Al的键合方式,将其应用在200～250℃的高温电路产品上也具有长期的可靠性；通过选择性的在金导带上印刷烧结一层5～8um厚的Ni过渡层,以及溅射形成的钛钨复合层相互配合起到阻挡层的作用,实现隔绝金和铝之间的互扩散；然后在TiW层的表面用磁控溅射的方式沉积一层3～5um的Al金属层,为厚膜电路的内引线互连提供Al-Al的键合体系,可以消除Au-Al键合产生的金属间化合物和柯肯达尔效应带来的不利影响,在200～250℃的高温环境下长期工作,依然可以提供有效地引线键合强度和导通电阻,实现了高温高可靠的产品应用。(The invention discloses a preparation method of a high-temperature high-reliability thick-film Al bonding pad, which belongs to the technical field of space micro-electronic packaging, wherein an Al bonding pad is generated in situ on a thick-film gold conduction band, so that an Al-Al bonding mode is realized, and the high-temperature thick-film Al bonding pad has long-term reliability when applied to a high-temperature circuit product at the temperature of 200-250 ℃; selectively printing and sintering a 5-8 um thick Ni transition layer on a gold conduction band, and mutually matching a titanium-tungsten composite layer formed by sputtering to play a role of a barrier layer, so as to realize the isolation of mutual diffusion between gold and aluminum; and then depositing a 3-5 um Al metal layer on the surface of the TiW layer in a magnetron sputtering mode to provide an Al-Al bonding system for interconnection of inner leads of the thick film circuit, so that the adverse effects caused by intermetallic compounds generated by Au-Al bonding and the Kendall effect can be eliminated, the effective lead bonding strength and the on-resistance can still be provided after long-term operation in a high-temperature environment of 200-250 ℃, and high-temperature and high-reliability product application is realized.)

1. A preparation method of a high-temperature high-reliability thick-film Al pad is characterized by comprising the following steps:

al with purity of more than 96 percent is adopted₂O₃Ceramic substrates as a base for printed circuits, in which Al₂O₃The surface roughness of the ceramic substrate is not more than 0.6 um;

adopting H with the mass fraction ratio of 5:1:1₂O、HCl、H₂O₂Prepared mixed solution is to Al₂O₃Pickling the surface of the ceramic substrate, heating the ceramic substrate to boiling state in the pickling process, and adding Al₂O₃Boiling and pickling the ceramic substrate for one hour, performing ultrasonic cleaning by using deionized water so as to rinse and remove acid on the surface, and finally cleaning by using absolute ethyl alcohol and drying for later use;

after cleaning of Al₂O₃Printing an Au conductor circuit on the surface of the ceramic substrate in a silk screen printing missing mode, drying the printed circuit pattern by using a 150 ℃ mesh belt furnace, and sintering, curing and molding the printed circuit pattern at a high temperature of 850 ℃;

printing a Ni metal barrier layer on a corresponding gold conductor by adopting a silk screen model at a gold conduction band needing to be bonded with Si-Al, and drying and sintering in a nitrogen atmosphere furnace;

printing the sintered Al₂O₃Coating a film protective film on the gold conductor of the ceramic substrate, sputtering a layer of Al on the surface of the Ni barrier layer by using a magnetron sputtering method as long as the Ni pad to be sputtered leaks, and sputtering the Al₂O₃And alloying the ceramic substrate at 300-400 ℃ in a nitrogen atmosphere.

2. The preparation method according to claim 1, wherein a Ni metal barrier layer is screen-printed on the corresponding gold conductor at the position of the gold conduction band to be bonded with Si-Al by using a screen model, and is sintered and dried in a nitrogen furnace, specifically:

printing a layer of Ni metal substrate layer on a corresponding gold conductor by adopting a silk screen model at a gold conduction band needing to be bonded with Si-Al, and sintering and drying in a nitrogen furnace;

and sputtering a TiW barrier layer on the surface of the Ni metal substrate layer by adopting a magnetron sputtering mode, and carrying out alloying treatment at the temperature of 550-750 ℃ in a nitrogen atmosphere so as to enhance the ohmic contact performance and the composite strength of the TiW barrier layer.

3. The preparation method of claim 2, wherein the thickness of the Ni metal substrate layer is 1-3 μm, and the thickness of the TiW barrier layer is 3-5 μm.

4. The method according to claim 2, wherein the oxygen content in the nitrogen furnace is controlled to be less than 100ppm during the sintering, curing and forming process at a high temperature of 850 ℃.

Technical Field

The invention relates to the technical field of aerospace microelectronic packaging, in particular to a preparation method of a high-temperature high-reliability thick-film Al bonding pad.

Background

At present, in the assembly process of an integrated circuit, wire bonding is still the main mode of interconnection between a chip bonding pad and a substrate, and an interconnection welding point bears the transportation of power and signals of a chip internal circuit and an external circuit, and the quality and reliability of the interconnection welding point play a decisive role in the function and the service life of a device. The thick film hybrid integrated circuit generally uses Si-Al wire and Au wire to realize internal interconnection, and during the steps of bonding, high-temperature storage and device aging, the high temperature, electric field and water vapor action at the bonding part can cause intermetallic compounds to be formed at the aluminum-gold bonding part.

In the process of wedge-shaped welding of Si-Al wires, an aluminum-gold bonding system between an aluminum wire and a gold conduction band inevitably occurs, and the long-term reliability problem is mainly reflected in the failure of gold-aluminum bonding in the working or storage process of an integrated circuit. Because the aluminum wire and the gold welding disk are dissimilar metals, the lattice constant and the thermal expansion coefficient are different, the diffusion rate of gold and aluminum is obviously different, and after long-term use, a Kirkendall cavity and AuAl and Au are easily formed at the gold and aluminum welding interface within a certain temperature and a certain time range₅Al₂、Au₄Al、AuAl₂、Au₂Al and other intermetallic compounds with extremely poor mechanical strength, and along with the increase of temperature and time, the formation of cavities and intermetallic compounds is accelerated, and along with the generation of the intermetallic compounds, the bonding contact resistance is increased, the electrical property of a contact area is reduced, so that the parameter drift of a device is caused, even the device fails due to open circuit, and the long-term reliability of the product is influenced.

Disclosure of Invention

The invention provides a preparation method of a high-temperature high-reliability thick-film Al bonding pad, which forms a bonding system of single metal by a method of directly preparing the Al bonding pad in situ, avoids the formation of compounds between gold and aluminum, reduces the risk of forming a Kirkat hole, and thoroughly solves the problem of long-term reliability of an aluminum wire bonding gold bonding pad.

The specific technical scheme provided by the invention is as follows:

the preparation method of the high-temperature high-reliability thick-film Al bonding pad provided by the invention comprises the following steps:

al with purity of more than 96 percent is adopted₂O₃Ceramic substrates as a base for printed circuits, in which Al₂O₃The surface roughness of the ceramic substrate is not more than 0.6 um;

adopting H with the mass fraction ratio of 5:1:1₂O、HCl、H₂O₂Prepared mixed solution is to Al₂O₃Pickling the surface of the ceramic substrate, heating the ceramic substrate to boiling state in the pickling process, and adding Al₂O₃Boiling and pickling the ceramic substrate for one hour, performing ultrasonic cleaning by using deionized water so as to rinse and remove acid on the surface, and finally cleaning by using absolute ethyl alcohol and drying for later use;

after cleaning of Al₂O₃Printing an Au conductor circuit on the surface of the ceramic substrate in a silk screen printing missing mode, drying the printed circuit pattern by using a 150 ℃ mesh belt furnace, and sintering, curing and molding the printed circuit pattern at a high temperature of 850 ℃;

printing a Ni metal barrier layer on a corresponding gold conductor by adopting a silk screen model at a gold conduction band needing to be bonded with Si-Al, and sintering and drying in a nitrogen atmosphere furnace;

printing the sintered Al₂O₃Coating a film protective film on the gold conductor of the ceramic substrate, sputtering a layer of Al on the surface of the Ni barrier layer by using a magnetron sputtering method as long as the Ni pad to be sputtered leaks, and sputtering the Al₂O₃And alloying the ceramic substrate at 300-400 ℃ in a nitrogen atmosphere.

Optionally, a Ni metal barrier layer is printed on the corresponding gold conductor by using a silk screen model at the position of the gold conduction band to be bonded with Si — Al, and is sintered and dried in a nitrogen furnace, specifically:

printing a layer of Ni metal substrate layer on a corresponding gold conductor by adopting a silk screen model at a gold conduction band needing to be bonded with Si-Al, and sintering and drying in a nitrogen furnace;

and sputtering a TiW barrier layer on the surface of the Ni metal substrate layer by adopting a magnetron sputtering mode, and carrying out alloying treatment at the temperature of 550-750 ℃ in a nitrogen atmosphere so as to enhance the ohmic contact performance and the composite strength of the TiW barrier layer.

Optionally, the thickness of the Ni metal substrate layer is 1-3 μm, and the thickness of the TiW barrier layer is 3-5 μm.

Optionally, the oxygen content in the nitrogen furnace is controlled to be less than 100ppm in the sintering, curing and forming process at a high temperature of 850 ℃.

The invention has the following beneficial effects:

according to the preparation method of the high-temperature high-reliability thick-film Al pad provided by the embodiment of the invention, the Al pad is generated in situ on the thick-film gold conduction band, so that an Al-Al bonding mode is realized, and the high-temperature high-reliability thick-film Al pad has long-term reliability when being applied to a high-temperature circuit product at 200-250 ℃; selectively printing and sintering a Ni transition layer with the thickness of 5-8 um on a gold conduction band, and mutually matching titanium-tungsten composite layers formed by sputtering to play a role of a barrier layer, so that mutual diffusion between gold and aluminum is isolated; depositing a 3-5 um Al metal layer on the surface of the TiW layer in a magnetron sputtering mode, providing an Al-Al bonding system for interconnection of inner leads of the thick film circuit, eliminating the adverse effects caused by intermetallic compounds generated by Au-Al bonding and the Kenkard effect, still providing effective lead bonding strength and on-resistance after long-term operation in a high-temperature environment of 200-250 ℃, and realizing high-temperature and high-reliability product application; by adopting the method for directly preparing the Al bonding pad in situ, a bonding system of single metal is formed, the formation of compounds between gold and aluminum is avoided, the risk of forming a Kirkshire cavity is reduced, and the problem of long-term reliability of the aluminum wire bonding gold bonding pad is thoroughly solved.

Detailed Description

The method for manufacturing the high-temperature high-reliability thick-film Al pad according to the embodiment of the present invention will be described in detail below.

The preparation method of the high-temperature high-reliability thick-film Al pad provided by the embodiment of the invention comprises the following steps:

(1) al with purity of more than 96 percent is adopted₂O₃Ceramic substrates as a base for printed circuits, in which Al₂O₃The surface roughness of the ceramic substrate is not more than 0.6 um.

(2) Adopting H with the mass fraction ratio of 5:1:1₂O、HCl、H₂O₂Prepared mixed solution is to Al₂O₃Pickling the surface of the ceramic substrate, heating the ceramic substrate to boiling state in the pickling process, and adding Al₂O₃The ceramic substrate is boiled and pickled for one hour, ultrasonic cleaning is carried out by adopting deionized water so as to rinse and remove acid on the surface, and finally, absolute ethyl alcohol is adopted to carry out cleaning and then drying for later use.

The embodiment of the invention selects the Al with the purity of more than 96 percent₂O₃The ceramic substrate is used as a substrate of a printed circuit, the surface roughness is less than or equal to 0.6um, and further, the gold conductor can be firmly adhered to Al₂O₃Surface of ceramic substrate, Al₂O₃Before the ceramic substrate is used, the ceramic substrate needs to be pickled to change the surface roughness of the ceramic substrate and improve the adhesion effect of the gold conductor. In the specific cleaning process, H with the mass fraction ratio of 5:1:1 is adopted₂O、HCl、H₂O₂Prepared mixed solution is to Al₂O₃Pickling the surface of the ceramic substrate, heating the ceramic substrate to a boiling state in the pickling process, and boiling the ceramic substrate in the mixed solution for 1 hour; then ultrasonically cleaning with deionized water, rinsing acid on the surface, cleaning with absolute ethyl alcohol, and drying for later use.

(3) After cleaning of Al₂O₃Printing Au conductor lines on the surface of the ceramic substrate in a silk screen printing missing mode, drying the printed circuit patterns by using a 150 ℃ mesh belt furnace, and sintering and curing the printed circuit patterns at a high temperature of 850 ℃ to form the ceramic substrateAnd (5) performing type treatment.

(4) And (3) printing a Ni metal barrier layer on a corresponding gold conductor by adopting a silk screen model at a gold conduction band needing to be bonded with Si-Al, and sintering and drying in an air furnace.

Printing a Ni metal layer at a gold conduction band needing to be bonded with Si-Al, selecting Ni slurry, printing on a corresponding gold conductor through a manufactured silk screen model, drying in an air furnace, selecting a nitrogen furnace during sintering to prevent oxidation of Ni, controlling the oxygen content in the nitrogen furnace to be less than 100ppm, sintering at a sintering temperature of 850 ℃ to form the Ni metal layer, wherein the Ni layer can effectively prevent mutual diffusion between Au and Al, and storing in a nitrogen cabinet after sintering.

Further, a Ni metal substrate layer is printed on a corresponding gold conductor by adopting a silk screen model at a gold conduction band needing to be bonded with Si-Al, and is sintered and dried in a nitrogen furnace; and sputtering a TiW barrier layer on the surface of the Ni metal substrate layer by adopting a magnetron sputtering mode, and carrying out alloying treatment at the temperature of 550-750 ℃ in a nitrogen atmosphere so as to enhance the ohmic contact performance and the composite strength of the TiW barrier layer.

The titanium-tungsten barrier layer and the nickel metal layer form a titanium-tungsten alloy composite layer after being subjected to alloying treatment, and an aluminum bonding pad is welded on the lower surface of the titanium-tungsten alloy composite layer, so that mutual diffusion between gold and aluminum atoms can be prevented, formation of compounds between gold and aluminum is avoided, the risk of forming a Kirkdall cavity is reduced, and the problem of long-term reliability of the aluminum wire bonding gold bonding pad is thoroughly solved.

Preferably, the thickness of the Ni metal substrate layer is 1-3 μm, and the thickness of the TiW barrier layer is 3-5 μm. The Ni metal substrate layer and the TiW barrier layer under the thickness are mutually matched, the barrier effect is better after the composition, and the mutual diffusion between Au and Al can be more effectively prevented.

(5) Printing the sintered Al₂O₃Coating a film protective film on the gold conductor of the ceramic substrate, sputtering a layer of Al on the surface of the Ni barrier layer by using a magnetron sputtering method as long as the Ni pad to be sputtered leaks, and sputtering the Al₂O₃Alloying the ceramic substrate in a nitrogen atmosphere at 300-400 DEG CAnd (6) processing.

And (3) covering a film protective film on the gold conductor part on the ceramic substrate after printing and sintering, sputtering a layer of Al on the surface of the Ni bonding pad by using a magnetron sputtering method as long as the Ni bonding pad to be sputtered leaks, and carrying out alloying treatment on the ceramic substrate at a low temperature (300-400 ℃) in a nitrogen atmosphere after sputtering is finished, so that ohmic contact among multiple layers of metals is realized, and the bonding strength between metal layers is improved. In an example, AMAT endura 5500 is selected as the magnetron sputtering equipment, the process parameters are set to be 1.0 × E-8Torr of background vacuum, the target base distance is 4730step, the heating power is 80%, the substrate temperature is 200 ℃, and the magnet rotating speed is 80 r/min.

According to the preparation method of the high-temperature high-reliability thick-film Al pad provided by the embodiment of the invention, the Al pad is generated in situ on the thick-film gold conduction band, so that an Al-Al bonding mode is realized, and the high-temperature high-reliability thick-film Al pad has long-term reliability when being applied to a high-temperature circuit product at the temperature of 200-250 ℃; selectively printing and sintering a Ni transition layer with the thickness of 5-8 um on a gold conduction band, and mutually matching titanium-tungsten composite layers formed by sputtering to play a role of a barrier layer, so that mutual diffusion between gold and aluminum is isolated; depositing a 3-5 um Al metal layer on the surface of the TiW layer in a magnetron sputtering mode, providing an Al-Al bonding system for interconnection of inner leads of the thick film circuit, eliminating the adverse effects caused by intermetallic compounds generated by Au-Al bonding and the Kenkard effect, still providing effective lead bonding strength and on-resistance after long-term operation in a high-temperature environment of 200-250 ℃, and realizing high-temperature and high-reliability product application; by adopting the method for directly preparing the Al bonding pad in situ, a bonding system of single metal is formed, the formation of compounds between gold and aluminum is avoided, the risk of forming a Kirkshire cavity is reduced, and the problem of long-term reliability of the aluminum wire bonding gold bonding pad is thoroughly solved.

It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments of the present invention without departing from the spirit or scope of the embodiments of the invention. Thus, if such modifications and variations of the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to encompass such modifications and variations.