JP2002368082A - Method and device for filling metal into fine space - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable filling of metal into a fine hole made in a silicon substrate or the like and having a high aspect ratio without a space and to prevent generation of warpage or cracking in a specimen. SOLUTION: A silicon substrate 14 having a fine hole formed therein and a metallic sheet 15 are fixed by means of a specimen fixing jig 12 and positioned within a vacuum chamber 11. Thereafter, the vacuum chamber 11 is evacuated until the internal pressure of the chamber 11 reaches a predetermined vacuum level. At this time, the metallic sheet 15 is melted by a heating means 16 and then the chamber 11 is compressed with an inert gas up to an atmospheric pressure or higher. Thereby the melted metal is vacuum sucked into the fine hole. Next, the vacuum chamber is made open, the melted metal remaining on the specimen is removed, and thereafter the chamber is cooled down to the room temperature. Metal can be filled into the fine hole having a high aspect ratio without generating of a cavity or the like. Since the melted metal has a smaller heat capacity than that when compared with a method for immersing the metal into a melted metal bath or the like, no warpage or cracking takes place in the specimen. Excessive metal can be suppressed to a minimum level and its cost can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for filling metal into a fine space such as a fine hole or a fine gap formed in a sample, and more particularly to a method for filling a fine hole with a high aspect ratio in a silicon substrate or the like with a metal. The present invention relates to a method and an apparatus for filling a metal into a fine space suitable for filling.

[0002]

2. Description of the Related Art Conventionally, when metal is filled in a fine space, for example, a fine hole formed in a workpiece (hereinafter, referred to as a sample), a through electrode (via hole electrode) is formed in a silicon substrate in a manufacturing process of, for example, a silicon IC chip. )), A through hole for a through electrode is formed in a silicon substrate, and this silicon substrate is inserted into a molten metal (plating solution) obtained by melting a metal for a conductor, and the molten metal is filled in the through hole. A common plating method is used.

[0003]

However, when the through hole is a fine hole having a high aspect ratio (hole depth / opening diameter), the molten metal cannot enter deep into the fine hole. As shown in FIG. 7, the molten metal 3 grows in a concentrated manner near the entrance of the fine hole 2 in the silicon substrate 1 to form a void inside, or the molten metal 3 in the fine hole 2 as shown in FIG. 4) It is difficult to perform uniform metal filling without voids, for example, it is difficult to form a good through electrode.

By the way, for example, when performing high-density three-dimensional mounting in which silicon IC chips are stacked, it is necessary to form through electrodes for connecting wiring patterns formed on the front and back of one silicon substrate. However, if it is attempted to form this through-electrode by the above-mentioned conventional method, the through-hole formed in the silicon substrate becomes a deep hole having a high aspect ratio. As described above, the fine hole is filled with a metal by plating. It is difficult to form a through electrode.

By the way, in order to solve the above problem,
Under the present applicant, a sample is inserted into a metal bath melted in a vacuum, and then the atmosphere is returned to the atmospheric pressure, so that a pressure difference is generated between the atmosphere and the inside of the micropore (vacuum). Based on the difference, the molten metal was filled into the micropores, and after the filling was completed, the sample was pulled up.

However, in the metal filling method utilizing the pressure difference between the atmosphere and the micropores, a dipping method in which the sample is immersed in a molten metal bath is employed, so that the coefficient of thermal expansion between the metal and the sample is reduced. There is a problem that the sample is warped due to the difference, and in an extreme case, the sample may be broken. Furthermore, in the metal filling method employing the dipping method together with this pressure difference, a molten metal having a capacity sufficient to immerse the sample is required, and the metal is fixed to the sample surface after the above-described sample lifting. A large amount of surplus metal other than the metal filled in the micropores can only be recycled for maintaining the required purity. there were.

The present invention has been made in view of the above circumstances, and enables a metal to be filled in a minute space formed in a sample, such as a silicon substrate, without voids. It does not require a large-capacity molten metal bath and the like, and minimizes excess metal other than the metal filled in the minute space.Low cost even when expensive precious metal elements are used It is an object of the present invention to provide a metal filling method and apparatus capable of performing metal filling by using a method.

[0008]

According to a first aspect of the present invention, there is provided a method of filling a fine space with a metal, the method comprising the steps of: A metal body for filling is arranged so as to cover the fine space, and after heating and melting the metal body for filling, the inside of the vacuum chamber is pressurized to above atmospheric pressure with an inert gas, and the molten metal is filled into the fine space. It is characterized by vacuum suction.

[0009] The method for filling metal into a fine space according to claim 2 is as follows.
A sample in which a fine space to be filled with metal is formed and a metal body for filling are fixed to a jig for fixing a sample, and after these are arranged in a vacuum chamber, the inside of the vacuum chamber is depressurized. After reaching the degree of vacuum, the filling metal body is melted by heating means, and then the inside of the vacuum chamber is pressurized to above atmospheric pressure with an inert gas, whereby the melted metal is vacuum sucked into a fine space, and then vacuum The method is characterized in that the chamber is opened to remove the metal in the molten state remaining on the sample surface, and then cooled to room temperature.

According to a third aspect of the present invention, in the method for filling a metal into a fine space according to the first or second aspect, a metal sheet is used as the metal body for filling.

A fourth aspect of the present invention is an apparatus for filling a fine space with a metal, which implements the method for filling a fine space with a metal according to the first or second aspect. A vacuum chamber having a pressurizing means for pressurizing to a pressure higher than the atmospheric pressure, and a sample fixing jig for fixing a sample in which a fine space to be filled with metal is formed in a state where a metal body for filling is stacked thereon, In the vacuum chamber, a main heating device provided so as to face the filling metal body on the sample fixed to the sample fixing jig and an auxiliary heating device provided on the sample mounting surface of the sample fixing jig And a heating means.

[0012]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described with reference to FIGS. FIG. 1 is a schematic perspective view of a metal filling apparatus 10 according to one embodiment of the present invention, and a vacuum chamber provided with a depressurizing means for depressurizing the inside and a pressurizing means for pressurizing the inside with an inert gas to a pressure higher than the atmospheric pressure. 11, a sample fixing jig 12 for fixing a sample in which fine holes to be filled with metal are formed and a metal body for filling on the sample, and the sample fixing jig in the vacuum chamber 11 Heating means 13 for heating the filling metal body on the sample fixed to 12.

In this embodiment, as shown in FIG. 2, a substantially disk-shaped silicon substrate 14 having a plurality of fine holes 14a is used as a sample. In addition, a disk-shaped metal sheet 15 shown in FIG. 3 is used as a filling metal body for filling the fine holes 14a with metal. However, the metal body to be used is not limited to a circular shape, and a metal sheet of an appropriate shape can be used. Further, the metal body is not limited to a sheet shape and may be a large number of granular or massive shapes. In short, any metal body that can be arranged so as to face the micropores in such a manner as to be vacuum-sucked into the micropores when melted, as described later, may be used. In this embodiment, the heating means 13 for heating the metal sheet 15 includes a main heating device 16 such as an infrared heater provided in the vacuum chamber 11 so as to face the metal sheet 15 and the jig for fixing the sample. And an auxiliary heating device 17 such as an electric heater provided on the twelve sample mounting surfaces 12a.

As described above, FIG. 1 is a schematic view, and the sample fixing jig 12 and the heating device 16 are mounted inside the vacuum chamber 11 by appropriate means. Although not shown, a vacuum pump for reducing the pressure inside the vacuum chamber 11 to a vacuum pressure is connected to the vacuum chamber 11 via a suction pipe. In addition, a cylinder or the like for pressurizing the inside to an atmospheric pressure or more by purging with an inert gas such as nitrogen gas (N ₂ ) is provided in a gas introduction pipe (1 in FIG. 4C).
8).

The procedure for filling the metal into the fine holes 14a formed in the silicon substrate 14 by the metal filling apparatus 10 will be described with reference to FIGS. Will be explained. First, a metal sheet 15 is attached with a solder ball or the like to the upper surface of the silicon substrate 14 in which the fine holes 14a are formed, and the metal sheet 15 is fixed to the sample fixing jig 12 and set inside the vacuum chamber 11 (FIG. A), FIG. 5 (a)). Examples of the metal filling the fine holes 14a include indium, tin, and gold-tin eutectic solder.
A metal having a relatively low vapor pressure is preferable, and a metal sheet made of these materials is used. However, it is not particularly limited to these. Next, the inside of the vacuum chamber 11 is, for example, 10 ^−2.
The pressure is reduced to a vacuum pressure such as 〜１０10 ⁻³ Pa (Pascal). When the pressure is reduced to the vacuum pressure, it is necessary to keep the obstacles on the fine holes 14a so that no air remains in the fine holes 14a. )
Also, as shown in FIG. 5A, by providing a slight gap between the silicon substrate 14 and the silicon substrate 14, it is easy to dispose them on the plurality of micro holes 14a so as not to be an obstacle.

When the inside of the vacuum chamber 11 reaches a predetermined degree of vacuum, the metal sheet 15 is heated and melted by the main heating device 16 and the auxiliary heating device 17 built in the sample fixing jig 12 (FIG. 4B). 5 (b)). In FIG. 5, the molten metal is indicated by 15 '. After the metal sheet 15 is melted, the inside of the vacuum chamber 11 is inert gas, for example, nitrogen gas (N ₂ ).
Above atmospheric pressure, for example, about 1-5 × 10 ⁵ Pa
(1-5 kgf / cm ² ). By generating a pressure difference between the atmosphere (atmospheric pressure or higher) and the inside of the fine holes 14a (vacuum pressure), the fine holes 14a of the silicon substrate 14 are formed.
Molten metal 15 'is sucked in vacuum (FIG. 4 (c), FIG. 5).
(C)). Thereafter, the vacuum chamber 11 is opened, and the metal 15 ′ remaining on the surface of the silicon substrate 14 is removed on the sample fixing jig 12 before the molten metal 15 ′ is hardened (FIG. 4 (d), FIG. 5). (D)). Finally, when left to cool as it is at room temperature, the molten metal in the micropores 14a solidifies (FIG. 4 (e), FIG. 5 (e)). The filling metal solidified by the fine holes 14a is indicated by 15 ". This completes the work of filling the fine holes 14a of the silicon substrate 14 with the metal.

As described above, according to the present invention, it is possible to fill a metal into fine pores having a high aspect ratio, and to fill a metal without generating voids such as voids. Therefore, when forming a through electrode on a silicon substrate or the like,
A through electrode having no void can be manufactured. Since the molten metal is sucked into the fine pores of the vacuum pressure with a pressure difference, it is possible to fill the fine pores that do not penetrate the metal.

The size of the fine holes in the silicon substrate is as follows:
Although not particularly limited, for example, a diameter of 15 μm and a depth of 360
μm (aspect ratio 24) or 40 μm in diameter,
The depth is 100 μm (aspect ratio 2.5) or the like. The micropores are formed, for example, by photoelectropolishing or ICP-
RIE (Inductively Coupled Plasma-Ractive Ion Etc
hing) or the like.

Further, as other sample materials, glass,
Resins that have relatively high heat resistance and do not melt at the metal melting temperature, such as ceramic, Teflon (registered trademark) (fluororesin), and polyimide, can be employed. Incidentally, the melting temperature of tin is about 2
The melting temperature of 30 ° C., the melting temperature of indium is about 157 ° C., and the melting temperature of gold-tin varies depending on the ratio of the metal. However, if the material does not easily melt at the melting temperature of the metal, the present invention It can be used as a sample. Further, in the present invention, since the metal is filled by pressing the metal to a pressure higher than the atmospheric pressure after melting the metal with a vacuum pressure, the presence of a pressure difference is necessary, but the absolute value of the ambient pressure before and after is not limited to the examples. . Further, in the present invention, the fine holes formed in the sample are not limited to the fine holes in silicon that extend straight in one direction when viewed in cross section. For example, the present invention can be applied to a case where a hole is bent in the middle. For example, in a multilayer substrate in which two or more silicon substrates are stacked as a plate-like sample, there is a pattern in which holes are bent (as viewed from a cross section) along the inner surface of the sample in some cases. According to this, it becomes possible to fill the bent hole with metal. Furthermore, even when the cross-sectional profile of the hole is branched in a dendritic manner, metal filling at the dendritic tip is possible. Further, according to the present invention, it is possible to fill the gap with metal. For example, the present invention can be applied to a case where a minute gap formed in a sample is filled with metal in a sample composed of a composite material or a structure formed by combining single members.

[0020]

According to the present invention, a filling metal body is disposed on a surface of a sample such as a silicon substrate or a glass material having a fine space formed therein in a vacuum chamber reduced in pressure so as to cover the fine space. After heating and melting the metal body for filling,
Since the inside of the vacuum chamber is pressurized to a pressure higher than the atmospheric pressure and the molten metal is sucked into the minute space by vacuum, the metal can be filled into minute spaces such as minute holes having various cross sections in various samples. In addition, metal can be filled not only into the fine holes having a high aspect ratio, but also into the fine holes not penetrating as well as the fine holes penetrating therethrough, and the metal without voids such as voids can be formed. Filling can be performed. When filling a penetrating microhole with metal to form a through electrode,
A good through electrode without voids can be formed.

[0021] Also, compared with a method in which a sample is immersed in a molten metal bath, a small amount of molten metal obtained by melting a metal sheet or the like only needs to touch the sample, so that the sample may be warped or cracked due to thermal stress. Is less. Further, since it is not necessary to melt a large amount of metal as in the molten metal bath method, even when a noble metal element such as gold is used, the cost of metal filling can be reduced.

Further, since the molten metal on the surface of the sample can be removed before the metal is solidified, the metal does not adhere to the sample. Also in this regard, it is possible to minimize damage due to thermal stress or stress caused by fixing. Also,
Since the surplus metal does not adhere to the sample, the surplus metal can be minimized, and in this respect also, the cost of metal filling can be reduced.

When a metal sheet is used as the filling metal body, the filling metal body is placed on the plurality of fine holes without any obstacle so that no air remains in the fine holes when the pressure is reduced. It is easy and appropriate to place it in a state.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a metal filling apparatus for carrying out a method for filling a fine space with a metal according to an embodiment of the present invention.

FIG. 2 is a plan view of a silicon substrate in which fine holes to be filled with metal are formed by the apparatus of FIG. 1;

3 is a plan view of a metal sheet used for filling metal into fine holes of the silicon substrate in FIG. 2.

FIG. 4 is a view for explaining a step of performing metal filling into fine holes in a silicon substrate by the metal filling apparatus of FIG. 1;
To (e).

5 (a) to 5 (e) are diagrams for schematically explaining the metal filling action to the fine holes in the step of FIG.
These correspond to the respective steps (a) to (e).

FIG. 6 is a view for explaining a poor filling state when a fine hole is filled with metal by a conventional metal filling method, and is a schematic cross-sectional view of a fine hole portion of a silicon substrate filled with metal.

FIG. 7 is a view for explaining a defective filling state in which pores are generated when a fine hole is filled with metal by a conventional metal filling method, and is a schematic cross-sectional view of a metal-filled fine hole portion of a silicon substrate. It is.

[Explanation of symbols]

 Reference Signs List 10 metal filling device 11 vacuum chamber 12 sample fixing jig 13 heating means 14 silicon substrate (sample) 14a fine hole (micro space) 15 metal sheet (metal body for filling) 16 main heating device 17 auxiliary heating device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Isao Takizawa 1-5-1 Kiba, Koto-ku, Tokyo Fujikura Co., Ltd. F-term (reference) 4M104 CC01 DD06 DD78 HH13 HH14 5F033 JJ00 KK01 QQ37 QQ73 QQ86 XX02 XX04 XX19 XX34

Claims (4)

[Claims] 1. A metal body for filling is arranged on a surface of a sample in which a fine space to be filled with metal is formed in a vacuum chamber under reduced pressure so as to cover the fine space, and the metal body for filling is heated. A method for filling a fine space with a metal, characterized in that after melting, the inside of the vacuum chamber is pressurized to above atmospheric pressure with an inert gas, and the molten metal is sucked into the fine space by vacuum. 2. A sample in which a fine space to be filled with metal is formed and a metal body for filling are fixed to a jig for fixing a sample, and these are arranged in a vacuum chamber. After the inside of the vacuum chamber reaches a predetermined degree of vacuum, the filling metal body is melted by heating means, and then the inside of the vacuum chamber is pressurized to above atmospheric pressure with an inert gas, so that the molten metal is evacuated to a fine space. Inhaled,
Then, the vacuum chamber is opened, the molten metal remaining on the surface of the sample is removed, and then cooling is performed at room temperature. 3. The method for filling a fine space with a metal according to claim 1, wherein a metal sheet is used as the metal body for filling. 4. An apparatus for filling a fine space with a metal, wherein the method for filling a fine space with a metal according to claim 1 or 2 is performed. A vacuum chamber having a pressurizing means for pressurizing, a sample fixing jig for fixing a sample in which a fine space to be filled with metal is formed and a metal body for filling over the sample, and a vacuum chamber inside the vacuum chamber. A heating means comprising a main heating device provided so as to face the filling metal body on the sample fixed to the sample fixing jig and an auxiliary heating device provided on the sample mounting surface of the sample fixing jig A device for filling a metal into a fine space, comprising: