Patent Application
20180100218
This invention relates to a process for forming a cobalt-iron alloy film. In particular, the process is performed under ultrasonic vibrations to form the cobalt-iron alloy film with a special crystal form and low phosphorus content.
Traditionally, cobalt is effective in blocking copper diffusion and capable of being the potential diffusion barrier layer material in electronic packaging industry. However, a cobalt-iron alloy film with high phosphorus content ranges from 6 to 13wt. % was formed on a substrate, such as copper foil, in a conventional electroless plating process. The cobalt-iron alloy film with high phosphorus content ranges from 6 to 13 wt. % does not have an excellent diffusion barrier function.
The most difficult problem in conventional electroless plating process is the P-containing deposited thin films. In general, the crystallites of the deposited thin films are lower in the conventional electroless plating process, accordingly. Higher crystalline is required to develop to promotes the diffusion barrier function of the deposited thin films.
Based on the aforementioned, the important target of current industries is to develop a process which is able to form a cobalt-iron alloy film with low phosphorus content on varied substrates so as to promote the diffusion barrier function of the cobalt-iron alloy film.
In accordance with the present invention, a process for forming a cobalt-iron alloy film on a substrate is disclosed. In particular, the process is performed under ultrasonic vibrations to form the cobalt-iron alloy film with a special crystal form and low phosphorus content. Therefore, the process substantially obviates one or more of the problems resulted from the limitations and disadvantages of the prior art mentioned in the background.
The first objective in the present invention is to disclose a process for forming a cobalt-iron alloy film on a substrate. The process comprises following steps: provide a substrate: apply a surface activation treatment to surfaces of the substrate to produce activated surfaces; provide a formulation which comprises a cobalt compound, a iron compound and a phosphorus compound and perform a coating process operated at 60-90° C. and under ultrasonic vibrations simultaneously to have the formulation form a cobalt-iron alloy film on the activated surfaces. The content of the cobalt-iron alloy film comprises about 75-95 wt. % of cobalt, 4.5-20 wt. % of iron and 0.5-5 wt. % of phosphorus.
In one embodiment, the substrate is made of one selected from the group consisting of Cu, Au, Al, Si, C and Al2O3.
In one embodiment, the surface activation treatment is performed in the presence of a palladium compound to produce the activated surfaces.
In one embodiment, the process further comprises surface roughening of the substrate and surface sensitizing of the substrate in the presence of a tin compound before applying the surface activation treatment.
In one embodiment, the formulation further comprises a buffering agent including boric acid (H3BO3), acetic acid and propionic acid, and a complexing agent including trisodium citrate (Na3C6H5O7), ammonium chloride (NH4Cl), lactic acid, ethylenediamine (C2H4(NH2)2), and potassium sodium tartrate.
In one embodiment, pH value of the formulation is adjusted to a range of 10-13.
In another embodiment, the cobalt compound comprises CoCl2 and CoSO4.
In another embodiment, the iron compound comprises FeCl2, FeCl3, FeSO4 and Fe2(SO4)3.
In another embodiment, the phosphorus compound comprises NaH2PO2.
In a preferred embodiment, the formulation consists of 10-50 g/L of CoCl2, 1-5 g/L of FeSO4, 10-50 g/L of NaH2PO2, 10-50 g/L of H3BO3 and 100-200 g/L of Na3C6H5O7.
In a preferred embodiment, power of the ultrasonic vibrations is between 100 and 400 watts.
In a particular embodiment, the cobalt-iron alloy film has an X-ray powder diffraction pattern comprising peaks at about 43.2±0.2, 45.1±0.2, 50.4±0.2, 65.5±0.2, 74.1±0.2, and 83.2±0.2 2-theta degree.
In a particular embodiment, the aforementioned process is an electroless plating process.
According to the invention process, the cobalt-iron film with phosphorus content less than 6 wt. % is formed on the substrates. As a result, the cobalt-iron film has a higher degree of crystalline which is evidenced by X-ray diffraction analysis.
Another objective of the present invention is to provide a cobalt-iron alloy film which consists of about 75-95wt. % of cobalt, 4.5-20 wt. % of iron and 0.5-5wt. % of phosphorus. In addition, the cobalt-iron alloy film comprises peaks at about 43.2±0.2, 45.1±0.2, 50.4±0.2, 65.5±0.2, 74.1±0.2 and 83.2±0.2 2-theta degree in X-ray powder diffraction analysis.
In a certain embodiment, X-ray powder diffraction pattern of the cobalt-iron alloy film is shown in one selected from
In another embodiment, the cobalt-iron alloy film has a thickness between 200 nm and 2000 nm.
In another embodiment, the cobalt-iron alloy film is part of a flip chip packaging, chip scale packaging or wafer level chip scale packaging.
In another embodiment, the cobalt-iron alloy film is part of a printed circuit board or a light-emitting diode device.
Accordingly, the present invention discloses the process for forming the cobalt-iron alloy film on the substrate. Particularly, the process is performed under ultrasonic vibrations to form the cobalt-iron alloy film on the substrate. Moreover, the cobalt-iron alloy film with low phosphorus content and a special X-ray diffraction pattern is provided in the invention.
The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the disclosure. In the drawings:
What is probed into the invention is a process for forming a cobalt-iron alloy film. Detail descriptions of the structure and elements will be provided in the following in order to make the invention thoroughly understood. Obviously, the application of the invention is not confined to specific details familiar to those who are skilled in the art. On the other hand, the common structures and elements that are known to everyone are not described in details to avoid unnecessary limits of the invention. Some preferred embodiments of the present invention will now be described in greater detail in the following. However, it should be recognized that the present invention can be practiced in a wide range of other embodiments besides those explicitly described, that is, this invention can also be applied extensively to other embodiments, and the scope of the present invention is expressly not limited except as specified in the accompanying claims.
In a first embodiment of the present invention, a process for forming a cobalt-iron alloy film on a substrate is disclosed. The process as shown in
In one example of the first embodiment, the substrate is made of one selected from the group consisting of Cu, Au, Al, Si, C and Al2O3. Preferably, the substrate is Cu.
In one example of the first embodiment, the surface activation treatment is performed in the presence of a palladium compound to produce activated surfaces. Preferably, the palladium compound is palladium dichloride (PdCl2).
In one example of the first embodiment, the process further comprises surface roughening of the substrate and surface sensitizing of the substrate in the presence of a tin compound before applying the surface activation treatment. Preferably, the tin compound is tin dichloride (SnCl2).
In one example of the first embodiment, the formulation further comprises a buffering agent including boric acid (H3BO3), acetic acid and propionic acid, and a complexing agent including trisodium citrate (Na3C6H5O7), ammonium chloride (NH4Cl), lactic acid, ethylenediamine (C2H4(NH2)2), and potassium sodium tartrate. Preferably, the buffering agent is boric acid, and the complexing agent is trisodium citrate (Na3C6H5O7).
In one example of the first embodiment, pH value of the formulation is adjusted to a range of 10-13. Preferably, the pH value of the formulation is adjusted to 11-12.
In another example of the first embodiment, the cobalt compound comprises CoCl2 and CoSO4.
In another example of the first embodiment, the iron compound comprises FeCl2, FeCl3, FeSO4 and Fe2(SO4)3.
In another example of the first embodiment, the phosphorus compound comprises NaH2PO2. Preferably, the phosphorus compound is NaH2PO2.
In a preferred example of the first embodiment, the formulation consists of 10-50 g/L of CoCl2, 1-5 g/L of FeSO4, 10-50 g/L of NaH2PO2, 10-50 g/L of H3BO3 and 100-200 g/L of Na3C6H5O7.
In a preferred example of the first embodiment, power of the ultrasonic vibrations is between 100 and 400 watts. More preferably, the power of the ultrasonic vibrations is between 120 and 200 watts.
In a particular example of the first embodiment, the cobalt-iron alloy film has an X-ray powder diffraction pattern comprising peaks at about 43.2±0.2, 45.1±0.2, 50.4±0.2, 65.5±0.2, 74.1±0.2, and 83.2±0.2 2-theta degree.
In a particular example of the first embodiment, the aforementioned process is an electroless plating process.
In a representative example of the first embodiment, copper (Cu) is used as the substrate. At first, surfaces of the copper is roughened by 20 wt. % of hydrochloride aqueous solution under ultrasonic vibrations and then washed with water. After the surface roughening, surface sensitizing is carried out in the presence of tin dichloride and then surface activation is performed in the presence of palladium dichloride. Therefore, the copper with activated surfaces is formed. A formulation which consists of 31.5 g/L of CoCl2, 3.5 g/L of FeSO4, 20 g/L of NaH2PO2, 30 g/L of H3BO3 and 140 g/L of Na3C6H5O7 is put into a beaker and then adjusted pH value of the formulation to 12 by adding sodium hydroxide. Finally, the copper with activated surfaces is immersed into the formulation and then perform a coating procedure at 65° C. and 200 watts ultrasonic vibrations simultaneously for 120 minutes to have the formulation form a cobalt-iron alloy film on the copper.
The aforementioned cobalt-iron alloy film on the copper is analyzed by SEM, X-ray diffraction analysis and element analysis. The element analysis shows that the cobalt-iron alloy film comprises about 90.8. wt of cobalt, 8.3 wt % of iron and 0.9 wt. % of phosphorus.
According to the invention process, the cobalt-iron film with phosphorus content less than 5 wt. % is formed on the substrate. In the meanwhile, crystalline degree of the cobalt-iron film with phosphorus content less than 5 wt. % increases and is evidenced by X-ray diffraction pattern as shown in both
In a second embodiment, a cobalt-iron alloy film which consists of about 75-95wt. % of cobalt, 4.5-20 wt. % of iron and 0.5-5 wt. % of phosphorus is disclosed. In addition, the claimed cobalt-iron alloy film also comprises peaks at about 43.2±0.2, 45.1±0.2, 50.4±0.2, 65.5+0.2, 74.1±0.2 and 83.2±0.2 2-theta degree in X-ray powder diffraction pattern.
In a certain example of the second embodiment, the X-ray powder diffraction pattern of the cobalt-iron alloy film is shown in
In another example of the second embodiment, the cobalt-iron alloy film has a thickness between 200 nm and 2000 nm.
In another example of the second embodiment, the cobalt-iron alloy film is part of a flip chip packaging, chip scale packaging or wafer level chip scale packaging.
In another example of the second embodiment, the cobalt-iron alloy film is part of a printed circuit board or a light-emitting diode device.
Accordingly, the present invention discloses a process for forming a cobalt--iron alloy film on a substrate. Particularly, the process is performed under ultrasonic vibrations to form the cobalt-iron alloy film on the substrate. In addition, the cobalt--iron alloy film with low phosphorus content and a special X-ray diffraction pattern is also provided in the invention.
Example: The preparation of the cobalt-iron alloy film on copper.
At first, surfaces of the copper was roughened by 20wt. % of hydrochloride aqueous solution under ultrasonic vibrations and then washed with water. After the surface roughening, surface sensitizing was carried out in the presence of tin dichloride (100 g/L). Removed the residual tin dichloride by washing with de-ionized water and then performed surface activation in the presence of palladium dichloride (1 g/L). After removing the residual palladium dichloride, the copper with activated surfaces was obtained. Prepared a formulation which consists of 31.5 g/L of CoCl2, 3.5 g/L of FeSO4, 20 g/L of NaH2PO2, 30 g/L of H3BO3 and 140 g/L of Na3C6H5O7 in a beaker. The formulation was then adjusted to pH value of 12 by adding 5M of sodium hydroxide. The copper with activated surfaces was immersed into the formulation and performed the coating procedure at 65° C. and under ultrasonic vibrations simultaneously for different times to have the formulation form the cobalt-iron alloy film on the copper. The cobalt-iron alloy film on the copper was analyzed by element analysis and the weight percentage of iron (Fe) in the cobalt-iron alloy film was shown in Table 1. The weight percentage of phosphorus (P) in the cobalt-iron alloy film was shown in Table 2.
The cobalt-iron alloy films were characterized by X-ray diffraction for checking their crystal forms and degree of crystalline.
The cobalt-iron alloy films formed according to the invention process have peaks at about 43.2, 45.1, 50.4, 65.5, 74.1 and 83.2 2-theta degree (2 0) and the peak intensity was shown in Table 3 and Table 4.
In contrast, cobalt-iron alloy films prepared without using ultrasonic vibration (0 watt) have different X-ray diffraction pattern. Moreover, the peak intensity as shown in Table 5 and Table 6 was obviously less than the peak intensity of the cobalt-iron films prepared by the present invention process. Accordingly, the invention process is able to produce the cobalt-iron alloy films with the unique crystals form and higher degree of crystalline.
As shown in
Although specific embodiments have been illustrated and described, it will be obvious to those skilled in the art that various modifications may be made without departing from what is intended to be limited solely by the appended claims.
