JP2004103867A - Method and apparatus of filling fine hole with metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove residues and foreign matters by washing fine holes formed in a substrate using a plasma before filling the fine holes with molten metal. <P>SOLUTION: The fine holes 3 are formed in a silicon substrate 1. Resist residues, foreign matters, and the like which are caused by the formation of the fine holes are washed away by using a plasma. Then, the silicon substrate 1 is dipped in the molten metal 15 at a pressure lower than the atmospheric pressure. The pressure at which the silicon substrate 1 was dipped in the molten metal 15 is raised to a pressure higher than that, and the fine holes 3 are filled with the molten metal by a difference in pressure. Thereafter, the silicon substrate 1 is pulled out from the molten metal 15. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for filling metal into fine holes formed in a substrate suitable for use in wiring of electronic devices, optical devices, and the like, structures of MEMS (Micro Electro Mechanical Systems) devices, and the like. .
[0002]
[Prior art]
In general, metal filled in micropores may be used for wiring of various devices such as an electronic device and an optical device, and a structure constituting a MEMS device.
[0003]
FIG. 6 shows a sectional process drawing of a through electrode for use in wiring of an electronic device or the like as an example. The through-electrode has a substrate 71 made of a semiconductor material such as silicon or an insulator material such as glass, in which fine holes 73 penetrating through the main surfaces are formed. Material 75 is filled.
[0004]
FIG. 7 shows an example of a method of manufacturing this through electrode. First, as shown in FIG. 7A, a fine hole forming step of forming fine holes 73 penetrating the substrate 71 is performed on the substrate 71. As a method of forming the fine holes 73, a Deep-Reactive Ion Etching (DRIE) method typified by an ICP-RIE (Inductively Coupled Plasma-Reactive Ion Etching) method, a wet etching method using an etching solution, and mechanical machining by a microdrill. Law and the like. Further, when a semiconductor substrate such as silicon is used as the substrate 71, an insulating layer is formed on the hole wall as necessary.
[0005]
Next, as shown in FIGS. 7B to 7D, a metal is filled in the fine holes 73 by a metal filling step (molten metal filling method).
[0006]
First, as shown in FIG. 7B, the substrate 71 in which the fine holes 73 are formed is immersed in a molten metal 75 in a chamber 77 maintained at a first pressure lower than the atmospheric pressure.
[0007]
Next, as shown in FIG. 7C, the pressure in the chamber 77 is increased to a second pressure higher than the first pressure, and the pressure difference generated at this time causes the molten metal 75 to be pressured into the fine holes 73. Fill.
[0008]
Next, as shown in FIG. 7D, after taking out the substrate 71 from the molten metal 75, the metal is filled into the fine holes 73 by cooling.
[0009]
Further, for example, there is one such as Patent Document 1.
[0010]
[Patent Document 1]
JP 2002-158191 A
[Problems to be solved by the invention]
As described above, the molten metal filling method is a very effective means as a method for filling fine pores with metal. However, in the above-described conventional method, no consideration has been given to the residue of the resist used in the fine hole forming step, the subsequent processing process, and contamination on the substrate during transport. Therefore, if these resist residues and contamination are present on the substrate on which the micropores are formed, in the subsequent metal filling process, micropores that are not completely filled with metal or micropores that are only partially filled will occur. However, it has been difficult to perform uniform filling in the substrate.
[0012]
The present invention has been made in view of the above circumstances, and even if contamination such as a residue of a resist or oil or fat exists on a substrate on which fine holes are formed, metal is uniformly filled in the fine holes. It is an object to provide a filling method and a filling device for the same.
[0013]
[Means for Solving the Problems]
The present invention has been made in view of the problems as described above, and the invention according to claim 1 is a method for filling metal into fine holes formed in a substrate, wherein at least the fine holes in the substrate are formed. Cleaning the surface with plasma, immersing the substrate in molten metal at a first pressure lower than atmospheric pressure, and increasing the first pressure to a second pressure higher than the first pressure. A method of filling metal into the fine holes, comprising a step of differentially filling the molten metal with the molten metal into the fine holes and a step of pulling up the substrate from the molten metal.
[0014]
The invention according to claim 2 is a plasma that is separately installed in a separate room or a separate chamber inside a chamber divided into two or more rooms, or inside a chamber itself formed into two or more rooms. This is a method for filling a metal into the micropores, wherein the substrate is cleaned and filled with a metal by using an electrode that generates heat and a device that can heat and melt the metal.
[0015]
The invention according to claim 3 is an apparatus for filling metal into fine holes formed in a substrate, comprising: a chamber provided with a depressurizing means for depressurizing the inside; and a pressurizing means for pressurizing the inside; This is a device for filling a fine hole with a metal, comprising a device for generating plasma and a device for heating and melting a metal.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0017]
A method for filling the fine holes formed in the substrate of this example with metal will be described with reference to FIGS.
FIGS. 1A to 2B are cross-sectional views of a method of filling a fine hole with a metal according to the present embodiment in the order of steps, in which the substrate is cut in a direction in which the fine hole extends. () Is a view of the fine hole as viewed from the upper surface of the substrate.
[0018]
In the filling method of the present embodiment, a silicon substrate 1 having a thickness T of 300 μm is used as a substrate on which the fine holes are formed.
[0019]
As shown in FIG. 1A, a fine hole 3 having a diameter D of about 50 μm is formed by a Deep-Reactive Ion Etching (DRIE) method so as to penetrate both main surfaces of the silicon substrate 1. Here, the DRIE method means that the silicon substrate 1 is subjected to deep etching by performing etching with high-density plasma and forming a passivation film on the measurement wall alternately by using sulfur hexafluoride (SF6) as an etching gas (Bosch process). It is to be etched.
[0020]
An insulating layer 5 made of silicon oxide (SiO 2) is formed on the surface of the silicon substrate 1 and on the hole walls of the fine holes 3.
[0021]
The substrate on which the fine holes 3 are formed is not limited to a silicon substrate, but may be another semiconductor substrate such as gallium arsenide (GaAs) or an insulating substrate such as glass.
[0022]
Further, the fine hole 3 may be a non-through hole, the diameter of which is appropriately set according to the thickness of the substrate and the desired use, and the cross-sectional shape perpendicular to the depth direction is also circular, elliptical, triangular, quadrangular. , A rectangle, or any other shape. In addition, the method for forming the micropores is not limited to the DRIE method, and a wet etching method using an aqueous solution of potassium hydroxide (KOH), machining using a microdrill or the like, a photoexcited electrolytic polishing method, or the like can be used.
[0023]
Next, as shown in FIG. 1B, the surface of the silicon substrate 1 in which the fine holes 3 are formed is washed with oxygen (O2) plasma generated from the electrode 7 for one minute. At this time, since the plasma removes the residue and foreign matters of the resist layer 5 on the substrate surface, the metal filling can be uniformly performed in the fine holes 3 in the subsequent metal filling.
[0024]
The plasma used for cleaning is not limited to oxygen plasma, but may be hydrogen (H2) plasma or argon (Ar) plasma, or a combination thereof. Also, the cleaning time is appropriately set according to the power of the plasma generator and the degree of contamination. Further, in this example, the cleaning by oxygen plasma and the subsequent filling of the molten metal are performed by separate apparatuses. However, if the metal filling apparatus of the present invention described later is used, the cleaning of the substrate and the metal filling are performed in a series of processes. Is possible.
[0025]
Next, as shown in FIG. 1C, the silicon substrate 1 in which the fine holes 3 are formed is fixed to a jig 9 and placed in a chamber 11. Although not shown here, the chamber 11 is connected to an exhaust system such as a rotary pump and a gas supply system such as a nitrogen (N2) gas, so that the inside of the chamber 11 can be appropriately evacuated and pressurized. Further, a crucible 13 for heating and melting the metal is installed in the chamber 11, and a melted gold tin (Au (80% by weight) -Sn (20% by weight)) 15 is installed therein.
[0026]
In this example, gold tin (Au (80% by weight) -Sn (20% by weight)) was described as the molten metal. However, the present invention is not limited to this, and gold tin alloys having different compositions and tin ( Sn), metals such as indium (In), tin-lead (Sn-Pb), tin (Sn), lead (Pb), gold (Au), indium (In), and aluminum (Al) A solder such as a base can be used.
[0027]
Next, as shown in FIG. 1D, after the pressure in the chamber 11 is reduced to about 10 Pa (first pressure), the silicon substrate 1 in which the fine holes 3 are formed is immersed in the molten metal 15 in the direction of the arrow AR1. I do. Note that the first pressure may be any pressure as long as it is lower than the atmospheric pressure.
[0028]
Next, as shown in FIG. 2A, the inside of the chamber 11 is pressurized to atmospheric pressure (second pressure) with nitrogen gas. At this time, a pressure difference is generated between the minute holes 3 in the molten metal 15 and the inside of the chamber 11, and the molten metal 15 is pressure-filled in the minute holes 3.
[0029]
The second pressure may be any pressure as long as it is higher than the first pressure. For example, the second pressure may be increased to a pressure higher than the atmospheric pressure.
[0030]
Next, as shown in FIG. 2B, the silicon substrate 1 in which the fine holes 3 have been formed is pulled up from the molten metal 15 in the direction of the arrow AR2 and cooled, thereby filling the fine holes 3 with the metal 17. Is completed.
[0031]
FIG. 2 (c) is a plan view of the silicon substrate 1 having the fine holes 3 filled with the metal 17 formed in the above process, as viewed from above. The metal 17 filled in the fine holes 3 thus produced can be used as a through electrode for electrically connecting the front and back of the substrate, or can be used as a part of a structure in a MEMS device.
[0032]
Next, an apparatus for filling a fine hole formed in a substrate according to the present invention with a metal will be described with reference to FIGS.
[0033]
Each drawing is a schematic view of the metal filling device according to the present invention, and is a cross-sectional view when the device is viewed from the front. By using the metal filling apparatus of the present invention, the metal can be efficiently filled into the fine holes formed in the substrate described above.
[0034]
FIG. 3 is a schematic view showing an example of the metal filling device of the present invention. The apparatus includes a chamber provided with a decompression unit for depressurizing the inside, a pressurizing unit for pressurizing the inside, a device for generating plasma in the chamber, and a device for heating and melting metal. It is characterized by.
[0035]
The interior of the chamber 23 of the metal filling device 21 is divided into a reaction chamber A and a reaction chamber B by a partition plate 25, and each of the chambers is evacuated to a vacuum evacuation system 27 such as a rotary pump or the like, and nitrogen (N2) or oxygen (O2 ) Is connected to a gas supply system 29, so that the pressure can be appropriately reduced and increased.
[0036]
In this example, the independent exhaust system 27 is provided for each of the reaction chamber A and the reaction chamber B. However, it is also possible to use a common exhaust system and change the flow path by using piping and valves. .
[0037]
An openable / closable valve 31 is provided at a part of the partition plate 25. An electrode 33 for generating plasma is provided in the reaction chamber A, and is connected to a plasma generator (not shown) including a high-frequency power supply. In the reaction chamber B, a crucible 35 capable of heating and melting metal and a metal 37 capable of being heated and melted are provided. A transfer jig 41 for transferring the substrate 39 is provided at a position where the substrate 39 can be freely moved between the reaction chambers AB in the direction of the arrow AR3 through the opening / closing valve 31. Hereinafter, metal filling into the fine holes using the present apparatus will be described.
[0038]
First, in the reaction chamber A, the surface of the substrate 39 having the fine holes fixed by the transfer jig 41 is cleaned by oxygen plasma. At this time, by closing the open / close valve 31, the reaction chamber A and the reaction chamber B can be completely separated, so that oxidation of the molten metal 37 by oxygen and entry of foreign matter into the molten metal 37 can be prevented.
[0039]
After the plasma cleaning, both the reaction chamber A and the reaction chamber B are evacuated, and the open / close valve 31 is opened. Next, the substrate 39 is transferred into the reaction chamber B through an open valve, and is immersed in the molten metal 37 under a first pressure lower than the atmospheric pressure. Next, the pressures in the reaction chambers A and B are raised to a second pressure higher than the first pressure, and the fine holes are filled with the molten metal 37 at a differential pressure. Next, the substrate 39 is pulled up from the molten metal 37 and cooled to complete filling of the fine holes with the metal.
[0040]
In the present example, the inside of the chamber 23 is divided by the partition plate 25, but the invention is not limited to this. After the chambers 43 and 45 are used as shown in FIG. , The opening / closing valve 49 and the transfer path 51 in the direction of the arrow AR <b> 4, and the chamber 45 can be filled with molten metal.
[0041]
Further, as shown in FIG. 5, the reaction chambers 53 and 55 or the chambers 53 and 55 are installed in a horizontal direction, the substrate 57 is plasma-cleaned in the reaction chamber 53, and then melted in the reaction chamber 55 or the chamber 55. An apparatus configuration for metal filling is also possible. At this time, a series of metal filling processes (for example, the substrate 57 is moved in the direction of arrows AR5, AR6, AR7, and AR8) by connecting the two reaction chambers or the two chambers by a transfer system 61 including a transfer arm and a transfer belt. ) Can be automatically performed, and the productivity can be dramatically increased.
[0042]
The present invention is not limited to the above-described embodiments, but can be embodied in other modes by making appropriate changes.
[0043]
【The invention's effect】
According to the method for filling metal into the fine holes formed in the substrate of the present invention, a step of cleaning at least the surface of the substrate on which the fine holes are formed with plasma, and the step of cleaning the substrate under a first pressure lower than atmospheric pressure A step of dipping the molten metal in the molten metal, a step of raising the first pressure to a second pressure higher than the second pressure, and differentially filling the molten metal into the fine holes, and a step of lifting the substrate from the molten metal. Therefore, the residue and foreign matters of the resist on the substrate surface are cleaned by the plasma, and the metal can be uniformly filled in the fine holes.
[0044]
Further, the apparatus for filling metal into the fine holes formed in the substrate of the present invention, a chamber provided with a depressurizing means for decompressing the inside and a pressurizing means for pressurizing the inside, an apparatus for generating plasma in the chamber, Since the apparatus is provided with a device capable of heating and melting the metal, the cleaning with the plasma and the metal filling can be performed in a series of processes using one device, so that the metal can be efficiently filled into the fine holes.
[0045]
Further, the inside of the chamber of the metal filling apparatus into the fine holes formed in the substrate of the present invention is divided into at least two or more rooms, or the chamber itself is composed of at least two or more, an electrode for generating plasma, Since the equipment that can heat and melt the metal is installed separately in separate rooms or separate chambers, it is possible to prevent oxidation of the molten metal by oxygen and entry of foreign matter into the molten metal In addition, since an automatic transfer system can be installed, productivity can be dramatically improved.
[0046]
Furthermore, since the chamber divided into two or more rooms or the chamber itself composed of two or more can be configured in parallel or in series, a metal filling device can be selected according to a space to be installed.
[Brief description of the drawings]
FIG. 1 is a sectional process view of a method for filling a fine hole with a metal.
FIG. 2 is a sectional process view continued from FIG. 1;
FIG. 3 is an explanatory diagram illustrating an apparatus for filling a metal into a fine hole formed in a substrate.
FIG. 4 is an explanatory view illustrating an apparatus for filling a fine hole formed in a substrate with a metal.
FIG. 5 is an explanatory diagram illustrating an apparatus for filling a fine hole formed in a substrate with a metal.
FIG. 6 is an explanatory diagram illustrating a conventional technique.
FIG. 7 is an explanatory diagram illustrating a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Silicon substrate 3 Micro hole 5 Insulating layer 7 Electrode 9 Jig 11 Chamber 13 Crucible 15 Melted gold tin

Claims (3)

A method for filling metal into micropores formed in a substrate,
A step of cleaning at least the surface of the substrate on which the fine holes are formed by plasma,
Immersing the substrate in a molten metal under a first pressure lower than atmospheric pressure;
Raising the first pressure to a higher second pressure and differentially filling the molten metal with the molten metal;
Lifting the substrate from the molten metal,
A method for filling metal into micropores, comprising: Inside the chamber divided into two or more chambers, or inside the chamber itself composed of two or more chambers, separate electrodes are installed in separate rooms or separate chambers. 2. The method according to claim 1, wherein the substrate is cleaned and filled with metal by means of a device capable of melting by heating. A device for filling metal into the fine holes formed in the substrate, a decompression means for decompressing the inside, a chamber provided with a pressurizing means for pressurizing the inside, an apparatus for generating plasma in this chamber,
A device for filling metal into fine holes, comprising: a device capable of heating and melting metal.

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