Patent Application
20250163600
The present invention relates to an α-Al2O3 phase anodic aluminum oxide and a preparation method therefor.
Recently, with the high integration of semiconductors, the importance of a probe card for testing the performance of a semiconductor in post-semiconductor processes is being increased. Accordingly, there is a need to improve an integration rate of the probe of the probe card. In response to this demand, recently, research has been conducted to solve a manufacturing yield of a probe card and high integration of a probe pad by forming a ceramic substrate using an anodic aluminum oxide.
However, since the ceramic substrate is formed of an amorphous porous anodic aluminum oxide, the ceramic substrate has low characteristics such as hardness and chemical resistance. In addition, a low permittivity is required to solve an electrical problem occurring between metal wirings on the stacked ceramic substrate. To solve this problem, there has been an attempt to heat-treat the porous anodic aluminum oxide, but due to a difference in stress between upper and lower parts of the porous anodic aluminum oxide, problems such as cracking and bending have occurred.
One technical problem to be solved by the present invention is to provide an α-Al2O3 phase anodic aluminum oxide and a preparation method therefor.
Another technical problem to be solved by the present invention is to provide an anodic aluminum oxide having significantly reduced cracking and bending during heat treatment, and a preparation method therefor.
Still another technical problem to be solved by the present invention is to provide an anodic aluminum oxide with an improved thermal conductivity and a preparation method therefor.
Still another technical problem to be solved by the present invention is to provide an anodic aluminum oxide with improved hardness and a preparation method therefor.
Still another technical problem to be solved by the present invention is to provide an anodic aluminum oxide with improved chemical resistance.
Still another technical problem to be solved by the present invention is to provide an anodic aluminum oxide with a reduced permittivity and a preparation method therefor.
The technical problems to be solved by the present invention are not limited to those described above.
To solve the above technical problems, the present invention provides a preparation method for an anodic aluminum oxide.
According to one embodiment, the preparation method for an anodic aluminum oxide may include: anodizing aluminum in an electrolyte including oxalic acid to prepare anodic aluminum oxide having upper pores; applying a water-repellent coating to the upper pores of the anodic aluminum oxide; etching a lower part of the anodic aluminum oxide having the upper pores to which the water-repellent coating has been applied to form lower pores; immersing the anodic aluminum oxide in a pore-widening solution to widen a diameter of the lower pores such that the diameter of the lower pores is equal to a diameter of the upper pores; and heat-treating the anodic aluminum oxide in which the upper pores and the lower pores have the same diameter.
According to one embodiment, as the anodic aluminum oxide is heat-treated, a phase of the anodic aluminum oxide may be changed from amorphous Al2O3 to α-Al2O3.
According to one embodiment, a crack occurrence rate of the anodic aluminum oxide may be reduced due to the same diameter of the upper pores and the lower pores during the heat treatment of the anodic aluminum oxide.
According to one embodiment, in the widening of the diameter of the lower pores, the diameter of the upper pores may be maintained by the water-repellent coating.
According to one embodiment, a concentration and a temperature of the pore-widening solution may be controlled to reduce a difference in the diameter between the upper pores and the lower pores.
According to one embodiment, the concentration of the pore-widening solution may be controlled to be greater than 5 wt % and less than 15 wt %, thereby reducing the difference in the diameter between the upper pores and the lower pores.
According to one embodiment, the temperature of the pore-widening solution may be controlled to be higher than 25° C. and lower than 40° C., thereby reducing the difference in the diameter between the upper pores and the lower pores.
According to one embodiment, the anodic aluminum oxide may be heat-treated at a temperature exceeding 850° C.
According to one embodiment, the pore-widening solution may include a phosphoric acid solution.
According to one embodiment, as the anodic aluminum oxide is heat-treated, a thermal conductivity and a hardness are improved, and a permittivity is reduced.
To solve the above technical problems, the present invention provides an anodic aluminum oxide.
According to one embodiment, the anodic aluminum oxide may have hollows for allowing upper pores and lower pores to communicate with each other, in which the anodic aluminum oxide may include the upper pores and the lower pores that have the same diameter, and may have an α-Al2O3 phase.
According to one embodiment, the anodic aluminum oxide may have a Vickers hardness of 800 GPa or greater.
According to one embodiment, the anodic aluminum oxide may have a thermal conductivity of 13.7 W/m·K or greater.
According to one embodiment, the anodic aluminum oxide may be applied to any one of a semiconductor probe card, a photonic structure, a sensor, a template, a membrane, a drug delivery substrate, and a composite functional layer.
According to the embodiment of the present invention, the preparation method for an anodic aluminum oxide may include: anodizing aluminum in an electrolyte including oxalic acid to prepare anodic aluminum oxide having upper pores; applying a water-repellent coating to the upper pores of the anodic aluminum oxide; etching a lower part of the anodic aluminum oxide having the upper pores to which the water-repellent coating has been applied to form lower pores; immersing the anodic aluminum oxide in a pore-widening solution to widen a diameter of the lower pores such that the diameter of the lower pores is equal to a diameter of the upper pores; and heat-treating the anodic aluminum oxide in which the upper pores and the lower pores have the same diameter.
Accordingly, an α-Al2O3 phase anodic aluminum oxide having a high thermal conductivity of 13.7 W/m·K or greater and a high hardness of 8.00 GPa or greater may be prepared. Accordingly, the anodic aluminum oxide may be easily applied to a semiconductor probe card, a photonic structure, a sensor, a template, a membrane, a drug delivery substrate, a composite functional layer, and the like, which require high physical stability and chemical stability.
In addition, since the difference in stress between the upper and lower parts of the anodic aluminum oxide is significantly reduced, problems such as cracking and bending that occur during the heat treatment may be significantly reduced.
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, the embodiments introduced herein are provided so that the disclosed contents may be thorough and complete and the spirit of the present invention may be sufficiently conveyed to those skilled in the art.
In the present specification, it will be understood that when an element is referred to as being “on” another element, it can be formed directly on the other element or intervening elements may be present. In the drawings, the thicknesses of layers and regions are exaggerated for clarity.
In addition, it will be also understood that although the terms first, second, third, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Thus, a first element in some embodiments may be termed a second element in other embodiments without departing from the teachings of the present invention. Embodiments explained and illustrated herein include their complementary counterparts. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed elements.
The singular expression also includes the plural meaning as long as it does not differently mean in the context. In addition, the terms “comprise”, “have” etc., of the description are used to indicate that there are features, numbers, steps, elements, or combination thereof, and they should not exclude the possibilities of combination or addition of one or more features, numbers, operations, elements, or a combination thereof. Furthermore, it will be understood that when an element is referred to as being “connected” or “coupled” to another element, it may be directly connected or coupled to the other element or intervening elements may be present.
In addition, when detailed descriptions of related known functions or constitutions are considered to unnecessarily cloud the gist of the present invention in describing the present invention below, the detailed descriptions will not be included.
Referring to
More specifically, after a high-purity aluminum foil is prepared (S110), the organic contaminants may be removed by ultrasonic treatment in anhydrous acetone for 2 minutes (S120), and the aluminum foil may be electropolished for 120 seconds at 0° C. and 20 V in a mixture of perchloric acid and ethanol (1:4 volume %)(S130).
Thereafter, the primary anodization may be performed for 30 minutes in 0.3 M of oxalic acid at a temperature of 5° C. to 20° C. and 50 V (S140). As the primary anodization is performed, the porous anodic aluminum oxide 100 may be formed on the aluminum foil.
The anodic aluminum oxide 100 formed through the primary anodization may be wet-chemical etched with 1.8 wt/of chromic acid and 6 wt % of phosphoric acid at 60° C. for 2 hours (S150). Accordingly, irregular pores formed on a surface of the anodic aluminum oxide 100 prepared through the primary anodization may be removed.
The wet-chemical etched anodic aluminum oxide 100 may be secondarily anodized in 0.3 M of oxalic acid at a temperature of 5° C. to 20° C. and 55 V for 8 hours (S160). As the secondary anodization is performed, the anodic aluminum oxide 100 is grown and regular pores may be formed in the anodic aluminum oxide 100.
The secondarily anodic aluminum oxide 100 may be immersed in a mixture of 0.1 M of copper chloride and 20 vol % of hydrochloric acid (HCl) for 1 hour. Accordingly, the anodic aluminum oxide 100 may be separated from the aluminum foil by selectively removing the aluminum foil (S170). Therefore, the anodic aluminum oxide 100 having the upper pores UP may be prepared. According to one embodiment, the anodic aluminum oxide 100 prepared in step S100 may have a structure in which an upper region thereof has pores, but a lower region thereof has no pores, as shown in
Unlike the above description, when a material other than oxalic acid (e.g., sulfuric acid, phosphoric acid, etc.) is used as the electrolyte for preparing the anodic aluminum oxide 100, uniformity of the pores may be reduced. Accordingly, during the heat treatment of the anodic aluminum oxide in step S500 to be described later, cracks may be formed in the anodic aluminum oxide, or a thermal conductivity and a hardness of the heat-treated anodic aluminum oxide may be reduced.
After the anodic aluminum oxide 100 having the upper pores UP is prepared, a water-repellent coating may be applied to the upper pores UP of the anodic aluminum oxide 100 (S200). According to one embodiment, the upper pores UP may be applied with the water-repellent coating by using a micro stopper. For example, a sfront-off lacquer (Miccrosfron, Tolber, USA) may be used as the micro stopper.
A lower part of the anodized aluminum oxide 100 having the upper pores UP to which the water-repellent coating is applied may be etched to form lower pores BP (S300). According to one embodiment, the lower pores BP may be formed in the lower part of the anodic aluminum oxide 100 by immersing the lower part of the anodic aluminum oxide 100 having the upper pores UP to which the water-repellent coating is applied in a mixture of 0.1 M of copper chloride and 20 vol % of hydrochloric acid (HCI). A diameter d2 of the lower pores BP formed in step S300 may be smaller than a diameter d1 of the upper pores UP.
The anodic aluminum oxide 100 in which the upper pores UP and the lower pores BP are formed may be immersed in a pore-widening solution. Accordingly, the diameter d2 of the lower pores BP may be widened such that the diameter d2 of the lower pores BP is equal to the diameter d1 of the upper pores UP (S400). That is, the diameter d2 of the lower pores BP may be widened through the pore-widening solution. In this case, since the upper pores UP are applied with the water-repellent coating through the micro stopper, the upper pores UP may not react with the pore-widening solution, thereby maintaining the diameter d1. According to one embodiment, a phosphoric acid solution may be used as the pore-widening solution.
According to one embodiment, a concentration and a temperature of the pore-widening solution may be controlled to reduce the difference between the diameter d1 of the upper pores UP and the diameter d2 of the lower pores BP. Specifically, the concentration of the pore-widening solution may be controlled to be greater than 5 wt % and less than 15 wt %, thereby reducing the difference between the diameter d1 of the upper pores UP and the diameter d2 of the lower pores BP. In addition, the temperature of the pore-widening solution may be controlled to be higher than 25° C. and lower than 40° C., thereby reducing the difference between the diameter d1 of the upper pores UP and the diameter d2 of the lower pores BP.
That is, the diameter d1 of the upper pores UP and the diameter d2 of the lower pores BP may be the same under a condition in which the concentration of the pore-widening solution is controlled to be greater than 5 wt % and less than 15 wt % or a condition in which the temperature of the pore-widening solution is controlled to be higher than 25° C. and lower than 40° C. In contrast, when the concentration of the pore-widening solution is controlled to be equal to or less than 5 wt % or equal to or greater than 15 wt %, or the temperature of the pore-widening solution is controlled to be equal to or lower than 25° C. or equal to or less than 4° C., there may be a problem in a large difference between the diameter d1 of the upper pores UP and the diameter d2 of the lower pores BP.
The anodic aluminum oxide 100 in which the diameter d1 of the upper pores UP and the diameter d2 of the lower pores BP are the same may be heat-treated (S500). Unlike the above description, when the anodic aluminum oxide 100 is heat-treated in a state where the diameter d1 of the upper pores UP and the diameter d2 of the lower pores BP are different from each other, problems such as cracking and bending may occur due to a difference in stress between the upper and lower parts of the anodic aluminum oxide 100. On the other hand, when the anodic aluminum oxide 100 is heat-treated in a state where the diameter d1 of the upper pores UP and the diameter d2 of the lower pores BP are the same, a difference in stress between the upper and lower parts is reduced, and thus problems such as cracking and bending occurring during the heat treatment may be significantly reduced.
As the anodic aluminum oxide 100 is heat-treated, the anodic aluminum oxide 100 may be changed from an amorphous Al2O3 phase to an α-Al2O3 phase. The anodic aluminum oxide 100 having the α-Al2O3 phase may have improved thermal conductivity and hardness, and a reduced permittivity as compared to the anodic aluminum oxide 100 having the amorphous Al2O3 phase. For example, the heat-treated anodic aluminum oxide 100 may have a high thermal conductivity of 13.7 W/m·K or greater and a high hardness of 8.00 GPa or greater.
According to one embodiment, the anodic aluminum oxide 100 may be heat-treated at a temperature exceeding 850° C. For example, the anodic aluminum oxide 100 may be heat-treated at a temperature of 1300° C. Accordingly, the anodic aluminum oxide 100 may be changed from the amorphous Al2O3 phase to the α-Al2O3 phase. On the other hand, when the anodic aluminum oxide 100 is heat-treated at a temperature of 850° C., the anodic aluminum oxide 100 is changed to a γ-Al2O3 phase or a δ-Al2O3 phase, not the α-Al2O3 phase, so that the thermal conductivity and the hardness may be relatively reduced and the permittivity may be increased as compared to the α-Al2O3 phase.
As a result, the preparation method for an anodic aluminum oxide according to the embodiment of the present invention may include: the step S100 of anodizing aluminum in an electrolyte including oxalic acid to prepare anodic aluminum oxide having upper pores; the step S200 of applying a water-repellent coating to the upper pores of the anodic aluminum oxide; the step S300 of etching a lower part of the anodic aluminum oxide having the upper pores to which the water-repellent coating has been applied to form lower pores; the step S400 of immersing the anodic aluminum oxide in a pore-widening solution to widen a diameter of the lower pores such that the diameter of the lower pores is equal to a diameter of the upper pores; and the step S500 of heat-treating the anodic aluminum oxide in which the upper pores and the lower pores have the same diameter.
Accordingly, an α-Al2O3 phase anodic aluminum oxide having a high thermal conductivity of 13.7 W/m·K or greater and a high hardness of 8.00 GPa or greater may be prepared. Accordingly, the anodic aluminum oxide may be easily applied to a semiconductor probe card, a photonic structure, a sensor, a template, a membrane, a drug delivery substrate, a composite functional layer, and the like, which require high physical stability and chemical stability.
In addition, since the difference in stress between the upper and lower parts of the anodic aluminum oxide is significantly reduced, problems such as cracking and bending that occur during the heat treatment may be significantly reduced.
Hereinabove, the anodic aluminum oxide and the preparation method therefor according to the embodiment of the present invention has been described. Hereinafter, specific experimental examples and characteristic evaluation results of the anodic aluminum oxide and the preparation method therefor according to the embodiment of the present invention will be described.
After a high-purity aluminum foil was prepared, the organic contaminants were removed by ultrasonic treatment in anhydrous acetone for 2 minutes, and the aluminum foil was electropolished for 120 seconds at 0° C. and 20 V in a mixture of perchloric acid and ethanol (1:4 volume %).
Thereafter, primary anodization was performed for 30 minutes in 0.3 M of oxalic acid at a temperature of 5° C. to 20° C. and 50 V to form a porous anodic aluminum oxide on the aluminum foil.
The anodic aluminum oxide formed through the primary anodization was wet-chemical etched with 1.8 wt % of chromic acid and 6 wt % of phosphoric acid at 60° C. for 2 hours to remove irregular pores formed on a surface of the anodic aluminum oxide.
The wet-chemical etched anodic aluminum oxide was secondarily anodized in 0.3 M of oxalic acid at a temperature of 5° C. to 20° C. and 55 V for 8 hours to grow the anodic aluminum oxide.
The secondarily anodized aluminum oxide was immersed in a mixture of 0.1 M of copper chloride and 20 vol % of hydrochloric acid (HCl) for 1 hour to selectively remove the aluminum foil, thereby preparing the anodic aluminum oxide having upper pores. The upper pores were applied with a water-repellent coating by using a sfront-off lacquer (Miccrosfron, Tolber, USA).
A lower part of the anodic aluminum oxide was immersed in the mixture of 0.1 M of copper chloride and 20 vol % of hydrochloric acid (HCl) to form lower pores. The anodic aluminum oxide having the lower pores was immersed in a pore-widening solution to widen a diameter of the lower pores such that the diameter of the lower pores was equal to a diameter of the upper pores. As the pore-widening solution, a phosphoric acid solution was used. Finally, the anodic aluminum oxide, in which the diameters of the upper and lower pores were the same, was heat-treated to prepare an anodic aluminum oxide according to an experimental example.
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As can be seen from (a), (d), and (g) of
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As can be seen from (c), (f), and (i) of
As can be seen from (j) and (k) of
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That is, it was confirmed that as the anodic aluminum oxide according to the experimental example of the present invention is changed from an amorphous-Al2O3 phase to an α-Al2O3 phase by heat treatment, the Vickers hardness is significantly improved (about 3 times improved).
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In addition, an indentation hardness and a Martens hardness were measured for each of the anodic aluminum oxide (amorphous) before heat treatment and the anodic aluminum oxide (α-Al2O3) that has been heat-treated, and the measurement results are summarized through the following <Table 2>.
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(Space permittivity: 8.854×10−12 F/m, Vertical distance between amorphous-Al2O3 anodic aluminum oxide electrodes: 99 μm, Capacitance of amorphous-Al2O3 anodic aluminum oxide: 8.38×10−11 F, Vertical distance between α-Al2O3 anodic aluminum oxide electrodes: 101 μm, α-Al2O3 Capacitance of anodic aluminum oxide: 4.20×10−11 F)
As a result of measuring the dielectric constant, the anodic aluminum oxide (amorphous) before heat treatment showed a dielectric constant of 9.37, and the anodic aluminum oxide (α-Al2O3) that has been heat-treated showed a dielectric constant of 4.79. That is, it was confirmed that as the anodic aluminum oxide according to the experimental example of the present invention is changed from an amorphous-Al2O3 phase to an α-Al2O3 phase by heat treatment, the permittivity is reduced.
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As can be seen from (a) to (c) of
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Specifically, (a) of
The measurement results of the diameter of the upper and lower pores are summarized through the following <Table 3>.
As can be seen from <Table 3>, it was confirmed that in a case of the anodic aluminum oxide prepared through the pore-widening solution (phosphoric acid solution) having a concentration of 10 wt %, a difference in diameter between the upper pores and the lower pores is significantly reduced.
As a result, it was found that the concentration of the pore-widening solution (phosphoric acid solution) needs to be controlled to be greater than 5 wt % and less than 15 wt % in order to form the upper pores and the lower pores that have the same diameter.
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As can be seen from (b) of
As a result, it was found that the temperature of the pore-widening solution (phosphoric acid solution) needs to be controlled to be higher than 25° C. and lower than 40° C. in order to form the upper pores and the lower pores that have the same diameter.
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Specifically, (a) of
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While the present invention has been described in connection with the embodiments, it is not to be limited thereto but will be defined by the appended claims. In addition, it is to be understood that those skilled in the art can substitute, change, or modify the embodiments in various forms without departing from the scope and spirit of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2022-0112477 | Sep 2022 | KR | national |
This application is a bypass continuation of pending PCT International Application No. PCT/KR2023/013317, which was filed on Sep. 6, 2023, and which claims priority to and the benefit of Korean Patent Application No. 10-2022-0112477, which was filed in the Korean Intellectual Property Office on Sep. 6, 2022, the disclosure of which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/KR2023/013317 | Sep 2023 | WO |
| Child | 19035407 | US |
