1. Field of the Invention
The present invention relates to a method for forming a conductor in a minute space.
2. Description of the Related Art
In electronic devices such as semiconductor devices, micromachines and so on, for example, there may be the case where a fine conductor-filled structure, an insulating structure or a functional structure each having a high aspect ratio must be formed therein. In such a case, there are known technologies for realizing a conductor-filled structure, an insulating structure, a functional structure, etc. by filling a previously chosen filler into a minute hole. However, it is extremely difficult to thoroughly fill a high-aspect-ratio minute hole with a filler down to the bottom thereof without forming a void or causing deformation after hardening.
As a related art capable of overcoming such a technical difficulty, there are known a filling method and device disclosed in Japanese Patent Nos. 4278007 and 4505540.
The technology disclosed in Japanese Patent No. 4278007 is a method for filling a molten metal in a fine hole present in a wafer and hardening it, the method having a step of cooling the molten metal and hardening it while applying a forced external force exceeding atmospheric pressure to the molten metal within the fine hole. The forced external force is given by at least one of a pressing pressure, an injection pressure and a rolling compaction and applied to the molten metal from the side on which the fine hole is open, wherein the other end of the fine hole is closed.
Japanese Patent No. 4505540 discloses a device for implementing the method disclosed in Japanese Patent No. 4278007.
The above-described technologies disclosed in Japanese Patent Nos. 4278007 and 4505540 provide the following excellent effects: the fine hole can be filled with a filler without forming an air gap or void, the metal cooled and hardened within the fine hole can be prevented from having a recessed surface, the process can be simplified and the yield can be improved, and so on.
It is an object of the present invention to provide a method for easily forming a conductor that is compact and has a low electrical resistance and high mechanical strength.
In order to attain the above object, the present invention provides a method for forming a conductor in a minute space of an object, comprising the steps of: filling a first metallic material into the minute space, the first metallic material being composed of particles and dispersed in a liquid dispersion medium; evaporating the liquid dispersion medium inside the minute space; and feeding a second metallic material into the minute space. The first and second metallic materials, in combination, include a combination of a high-melting metallic material and a low-melting metallic material.
As described above, since the material (functional material) prepared by dispersing the powdery first metallic material in the liquid dispersion medium is filled into the minute space, although the first metallic material is in the form of powder that is unsuitable for filling in nature, it can be certainly filled into the minute space by exploiting the fluidity of the functional material.
Then, the liquid dispersion medium inside the minute space is evaporated. This results in leaving the powdery first metallic material, i.e., first metallic particles inside the minute space, creating a gap between the first metallic particles.
Then, the second metallic material is fed into the minute space. The first and second metallic materials, in combination, include a combination of a high-melting metallic material and a low-melting metallic material. Therefore, the low-melting metallic material contained in either of the first and second metallic materials can be melted by heating before or after the feeding of the second metallic material. The melted low-melting metallic material is allowed to enter the gap between the first metallic particles, so that a diffusion bond can be formed between the low-melting metallic material and the high-melting metallic particles.
In the production process, therefore, the melting occurs at a low melting point of the low-melting metallic material, but melting after the solidification does not occur below a high melting point of the high-melting metallic particles. This reduces thermal energy consumption during the production process and enables the formation of a thermally stable conductor while reducing thermal damage to semiconductor circuit elements, etc., which may be provided in the object. The high-melting metallic particles form a diffusion bond at the boundary with the low-melting metallic material such that they do not melt and remain largely intact.
The first and second metallic materials, in combination, essentially include a combination of a high-melting metallic material and a low-melting metallic material. The possible combinations are as follows.
(a) First metallic material:
High-melting metallic material
Second metallic material:
Low-melting metallic material
(b) First metallic material:
High-melting metallic material
Second metallic material:
Low-melting metallic material & High-melting metallic material
(c) First metallic material:
High-melting metallic material & Low-melting metallic material
Second metallic material:
Low-melting metallic material
(d) First metallic material:
High-melting metallic material & Low-melting metallic material
Second metallic material:
High-melting metallic material
(e) First metallic material:
High-melting metallic material & Low-melting metallic material
Second metallic material:
Low-melting metallic material & High-melting metallic material
(f) First metallic material:
Low-melting metallic material
Second metallic material:
High-melting metallic material
(g) First metallic material:
Low-melting metallic material
Second metallic material:
High-melting metallic material & Low-melting metallic material
Specific production processes may be as follows.
In this case, according to the combination (a), for example, the first metallic material contains a high-melting metallic material, while the second metallic material contains a low-melting metallic material. The second metallic material is fed into the minute space in a molten state.
After the melted low-melting metallic material is fed into the minute space, preferably, it is cooled under pressure for hardening. This allows the melted low-melting metallic material to enter the gap between the high-melting metallic particles, so that a diffusion bond can be formed between the low-melting metallic material and the high-melting metallic particles. The high-melting metallic particles form a diffusion bond at the boundary with the low-melting metallic material such that they do not melt and remain largely intact. In the production process, therefore, the second metallic material can be melted at a low melting point of the low-melting metallic material, but melting after the solidification does not occur below a high melting point of the high-melting metallic particles constituting the first metallic material. This reduces thermal energy consumption during the production process and enables the formation of a thermally stable conductor while reducing thermal damage to semiconductor circuit elements, etc., which may be provided in the object.
Moreover, since the low-melting and high-melting metallic materials filled in the minute space are subjected to pressure during the cooling process, the low-melting and high-melting metallic materials can deform or move to follow the contraction due to cooling. This suppresses the formation of gaps or voids.
Alternatively, according to the combination (c), the first metallic material may contain a high-melting metallic material and a low-melting metallic material, while the second metallic material may contain a low-melting metallic material.
Also in this case, the same effects as described above can be expected.
The second metallic material may be fed as a metallic powder. In this case, after the evaporation of the liquid dispersion medium inside the minute space, the second metallic material is fed into the minute space and then heated. This melts low-melting metallic particles contained in either of the first and second metallic materials, and the melted low-melting metallic material is allowed to enter the gap between high-melting metallic particles contained in either of the first and second metallic materials, so that a diffusion bond can be formed between the low-melting metallic material and the high-melting metallic particles. In the production process, therefore, the melting occurs at a low melting point of the low-melting metallic material, but melting after the solidification does not occur below a high melting point of the high-melting metallic particles. This reduces thermal energy consumption during the production process and enables the formation of a thermally stable conductor while reducing thermal damage to semiconductor circuit elements, etc., which may be provided in the object.
Moreover, since the low-melting and high-melting metallic materials filled in the minute space are subjected to pressure during the cooling process, the low-melting and high-melting metallic materials can deform or move to follow the contraction due to cooling. This suppresses the formation of gaps or voids.
The second metallic material may also be fed as a metallic film. (4) Definitions
The term “dispersion” as used herein refers to a suspension or paste in which fine solid particles are dispersed in a liquid dispersion medium, including both systems: a monodisperse system in which all the particles have a uniform particle size; a polydisperse system in which the particle size is not uniform. Moreover, it includes not only a coarse dispersion but also a colloidal dispersion. The liquid dispersion medium is an aqueous dispersion medium or a volatile organic dispersion medium.
Throughout the description, the first metallic material and the second metallic material are not limited to a single metallic element but may contain two or more metallic elements.
Specifically, the high-melting metallic material may be a metallic or alloy material containing at least one element selected from the group consisting of Ag, Cu, Au, Pt, Ti, Zn, Al, Fe, Si and Ni. The high-melting metallic material is preferably composed of nm-sized nanoparticles (1 μm or less) or particles having a nanocomposite structure.
The low-melting metallic material may contain at least one metal selected from the group consisting of Sn, Bi, Ga and In or an alloy thereof.
The low-melting metallic material is also preferably composed of nanoparticles or particles having a nanocomposite structure.
The low-melting metallic particles and the high-melting metallic particles may have different particle sizes or a uniform particle size. They may also have any shape such as a spherical shape, a scale shape, a flat shape, etc.
As has been described above, the present invention provides a method for forming a functional part free from a void, gap or hollow in a minute space of an object.
The present invention will be more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus not to be considered as limiting the present invention.
The method shown in
In the present embodiment, the minute space 3 formed in the object 1 is a through-hole or a non-through-hole having a diameter D1 at the opening end and a depth H1. For example, the diameter D1 is 25 μm or less, while an aspect ratio of the depth H1 to the diameter D1 is 1 or more, preferably 5 or more. When the object 1 is a wafer, for example, a large number of the above-described minute spaces 3 are distributed over the surface of the wafer.
Into the minute space 3 of the above-described object 1, a functional material 5 is filled (poured). The functional material 5 is prepared by dispersing a powdery first metallic material in a liquid dispersion medium 51 (
Preferably, the functional material 5 is filled into the minute space 3 under a reduced-pressure atmosphere within a vacuum chamber. There may be adopted a differential pressure filling process, wherein the internal pressure of the vacuum chamber is increased after the pressure reduction. With this differential pressure filling process, the functional material 5 can be reliably filled into the minute space 3.
Then, the liquid dispersion medium 51 inside the minute space 3 is evaporated (
Then, the melted low-melting metallic material 53L is fed into the minute space 3 as the second metallic material (
In the method shown in
Moreover, the gap G1 is created between the high-melting metallic particles 52H by evaporating the liquid dispersion medium 51 inside the minute space 3, and the melted low-melting metallic material 53L is allowed to enter the gap G1 between the high-melting metallic particles 52H, so that a diffusion bond can be formed between the low-melting metallic material 53L and the high-melting metallic particles 52H. The high-melting metallic particles 52H form a diffusion bond at the boundary with the low-melting metallic material 53L such that they do not melt and remain largely intact.
In the production process, therefore, the second metallic material can be melted at a low melting point of the low-melting metallic material 53L, but melting after the solidification does not occur below a high melting point of the high-melting metallic particles 52H constituting the first metallic material. This reduces thermal energy consumption during the production process and enables the formation of a thermally stable conductor 50 while reducing thermal damage to semiconductor circuit elements, etc., which may be provided in the object 1.
Furthermore, since the low-melting metallic material 53L and the high-melting metallic particles 52H filled in the minute space 3 are hardened under pressure Fl during the cooling process, the low-melting metallic and high-melting metallic materials can deform or move to follow the contraction due to cooling. This suppresses the formation of gaps or voids and enables the formation of a low-resistance, highly-reliable, high-quality conductor 50.
Then, after the liquid dispersion medium 51 inside the minute space 3 is evaporated (
Although not described in detail, when feeding the second metallic material as a molten metal, the combination of the first and second metallic materials may be (b), (e) or (g) instead.
In
In the production process, therefore, the second metallic material can be melted at a low melting point of the low-melting metallic material 53L, forming a diffusion bond with the first metallic material, but melting after the solidification does not occur below a high melting point of the high-melting metallic particles 52H constituting the first metallic material.
This reduces thermal energy consumption during the production process and enables the formation of a thermally stable conductor 50 while reducing thermal damage to semiconductor circuit elements, etc., which may be provided in the object 1.
In the process of heating, pressurizing and hardening the low-melting metallic material 53L fed into the minute space 3, moreover, the low-melting metallic material 53L and the high-melting metallic particles 52H filled in the minute space 3 are subjected to pressure F1 during the cooling process, so that the low-melting metallic material 53L and the high-melting metallic material 52 can deform or move to follow the contraction due to cooling. This suppresses the formation of gaps or voids and enables the formation of a low-resistance, highly-reliable, high-quality conductor 50.
In the embodiment shown in
According to this process, the same effects as in the method illustrated in
In the embodiment shown in
According to the above process, the low-melting metallic particles 52L contained in the first metallic material can be melted, so that a diffusion bond can be formed between the low-melting metallic particles 52L and the high-melting metallic particles 52H contained in the first metallic material and the high-melting metallic particles 53H constituting the second metallic material. Therefore, the same effects as in the method illustrated in
In the embodiment shown in
According to the above process, the low-melting metallic particles 52L and 53L contained in the first and second metallic materials can be melted, so that a diffusion bond can be formed between the low-melting metallic particles 52L and 53L and the high-melting metallic particles 52H contained in the first metallic material and the high-melting metallic particles 53H contained in the second metallic material. Therefore, the same effects as in the method illustrated in
In the method shown in
In order to form a conductor inside the minute space 3, at first, the functional material 5 prepared by dispersing the high-melting metallic particles 52H in the liquid dispersion medium 51 is filled into the minute space 3, and then, the liquid dispersion medium 51 inside the minute space 3 is evaporated (
Then, after the evaporation of the liquid dispersion medium 51 inside the minute space 3, the low-melting metallic film 53L in the form of a thin film is placed over the region containing the opening of the minute space 3 (
By heating the low-melting metallic film 53L placed over the region containing the opening of the minute space 3 after the evaporation of the liquid dispersion medium 51 inside the minute space 3, as described above, the low-melting metallic film 53L can be melted, so that a diffusion bond can be formed between the melted low-melting metallic material 53L and the high-melting metallic particles 52H.
In the method shown in
In order to form a conductor inside the minute space 3, at first, the functional material 5 prepared by dispersing the high-melting metallic particles 52H in the liquid dispersion medium 51 is filled into the minute space 3, and then, the liquid dispersion medium 51 inside the minute space 3 is evaporated (
Then, after the evaporation of the liquid dispersion medium 51 inside the minute space 3, the low-melting metallic film 53L and the high-melting metallic film 53H stacked in the named order over the region containing the opening of the minute space 3 (
By heating the low-melting metallic film 53L and the high-melting metallic film 53H stacked over the region containing the opening of the minute space 3 after the evaporation of the liquid dispersion medium 51 inside the minute space 3, as described above, the low-melting metallic film 53L can be melted, so that a diffusion bond can be formed between the melted low-melting metallic material 53L and the high-melting metallic particles 52H and the high-melting metallic film 53H.
In the method shown in
In order to form a conductor inside the minute space 3, at first, the functional material prepared by dispersing the mixed powder 52HL in the liquid dispersion medium is filled into the minute space, and then, the liquid dispersion medium inside the minute space is evaporated (
Then, after the evaporation of the liquid dispersion medium inside the minute space, the high-melting metallic film 53H is placed over the region containing the opening of the minute space (
By heating the high-melting metallic film 53H placed over the region containing the opening of the minute space 3 after the evaporation of the liquid dispersion medium 51 inside the minute space 3, as described above, the low-melting metallic particles 52L of the first metallic material can be melted, so that a diffusion bond can be formed between the melted low-melting metallic material 52L and the high-melting metallic particles 52H and the high-melting metallic film 53H.
In the method shown in
In order to form a conductor inside the minute space, at first, the functional material prepared by dispersing the mixed powder 52HL in the liquid dispersion medium is filled into the minute space, and then, the liquid dispersion medium inside the minute space is evaporated (
Then, after the evaporation of the liquid dispersion medium inside the minute space, the low-melting metallic film 53L and the high-melting metallic film 53H are stacked over the region containing the opening of the minute space (
By heating the low-melting metallic film 53L and the high-melting metallic film 53H stacked over the region containing the opening of the minute space 3 after the evaporation of the liquid dispersion medium 51 inside the minute space 3, as described above, the low-melting metallic particles 52L of the first metallic material and the low-melting metallic film 53L of the second metallic material can be melted, so that a diffusion bond can be formed between the melted low-melting metallic materials 52L and 53L and the high-melting metallic particles 52H and the high-melting metallic film 53H.
Also in the embodiments shown in
First of all, since the functional material 5 is a fluid filler, although the first metallic material is in the form of powder that is unsuitable for filling in nature, it can be certainly filled into the minute space 3 by exploiting the fluidity of the functional material 5, e.g., by means of printing.
Moreover, the formation of the diffusion bond between the melted low-melting metallic material and the high-melting metallic material reduces thermal energy consumption during the production process and enables the formation of a thermally stable conductor 50 while reducing thermal damage to semiconductor circuit elements, etc., which may be provided in the object.
Furthermore, since the low-melting metallic material and the high-melting metallic particles filled in the minute space 3 are hardened under pressure during the cooling process, the low-melting and high-melting metallic materials can deform or move to follow the contraction due to cooling. This suppresses the formation of gaps or voids and enables the formation of a low-resistance, highly-reliable, high-quality conductor 50.
The first and second metallic materials are preferably composed of metallic particles covered with a resin film. This is because the resin-coated metallic particles can prevent oxidation and aggregation.
In Japanese Unexamined Patent Application Publication No. 2006-22384, the resin-coated metallic particles in which the surface of each metallic particle is coated with a resin layer are produced as follows. As the metallic particles, the ones having polymerizable reactive groups on each surface obtained by reacting metallic particles surface-treated with a triazine-thiol compound and an organic compound having polymerizable reactive groups and capable of reacting with a triazine-thiol compound are used, and resin coating is performed by the polymerization between the metallic particles having polymerizable reactive groups on each surface and a polymerizable monomer.
The metallic particles 500 thus covered with the resin film 502 are dispersed in an aqueous dispersion medium or a volatile organic dispersion medium so as to form a functional material.
However, the resin-coated metallic particles in which the surface of each metal particle is coated with a resin layer and the production method thereof is not limited to the one disclosed in Japanese Unexamined Patent
Application Publication No. 2006-22384. Various types of metallic particles including well known ones or ones that may be proposed in the future may also be employed. For example, it is expected that a certain type of hydride is also applicable.
While the present invention has been particularly shown and described with respect to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit, scope and teaching of the invention.
Number | Date | Country | Kind |
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2014-025116 | Feb 2014 | JP | national |