JP4717290B2 - Manufacturing method of through electrode - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a through electrode used for electrical wiring when, for example, silicon IC chips are stacked and mounted at high density, and a manufacturing method thereof.
[0002]
[Prior art]
A through electrode may be used for high-density mounting of silicon IC chips and various devices such as electronic devices and optical devices. For example, as shown in FIG. 5C, the through electrode has an insulating layer 63 formed on a hole wall of a pore formed in a semiconductor substrate 61 such as a silicon substrate and penetrating the semiconductor substrate. The hole is filled with a conductive material 64 such as metal.
In the manufacturing method for manufacturing the through electrode, first, as shown in FIG. 5A, a pore forming step for forming a pore 62 penetrating the semiconductor substrate 61 is performed on the semiconductor substrate 61. As a method for forming the pore 62, a DRIE (Deep-Reactive Ion Etching) method represented by ICP-RIE (Inductively Coupled Plasma-Reactive Ion Etching), an anisotropic etching method using a KOH solution, etc., a micro drill And the like, and the machining method by photoexcited electrolytic polishing.
Next, in the oxidation step, as shown in FIG. 5B, the silicon substrate is heat-treated in an oxidizing atmosphere and thermally oxidized to form an insulating layer 63 made of a silicon oxide film on the surface of the silicon substrate 61.
Next, in the metal filling step, as shown in FIG. 5C, the pores are filled with a conductive material 64 such as metal by sputtering, plating, screen printing, or the like. In this way, a through electrode can be obtained.
[0003]
[Problems to be solved by the invention]
However, in the conventional through electrode manufacturing method described above, the thermal oxidation in the oxidation step has to be performed at a high temperature of about 1000 ° C. For this reason, not only the amount of energy required to maintain a high temperature state is increased, but also the equipment required for the processing conditions is expensive. Furthermore, the time required for the oxidation treatment was long, and the productivity of through electrode manufacturing was low. As a result, the cost of the through electrode has been increased.
The present invention has been made in view of the above circumstances, and provides a through electrode manufacturing method and a through electrode that can be subjected to an oxidation treatment at a low temperature in a short time when forming an insulating layer on the pore wall surface. The purpose is to provide.
[0004]
[Means for Solving the Problems]
The inventors of the present invention have found that an insulating film can be formed without oxidizing a semiconductor substrate after it has been made porous without performing a thermal oxidation treatment exposed to a high temperature for a long time.
That is, the through electrode manufacturing method of the present invention includes at least a porous layer forming step of forming a porous layer by making a pore wall surface of pores formed in a direction perpendicular to a main surface of a semiconductor substrate. A through electrode manufacturing method comprising: an oxidation step of oxidizing the porous layer to form an insulating layer; and a metal filling step of filling the pores with a conductive material, further comprising the porous layer forming step Before forming a conductive film on a surface of the semiconductor substrate opposite to the pore forming surface, and in the porous layer forming step, the semiconductor film is used as an electrode for the semiconductor. By energizing the substrate, the pore wall surface of the pores is made porous , and before the metal filling step, the conductive film is peeled off and the semiconductor substrate is polished, Penetration work that penetrates the pore between both sides It is characterized by having a.
[0005]
The method for producing a through electrode of the present invention includes a porous layer forming step and an oxidizing step, and after forming a porous layer on the pore wall surface of the pores formed in the pore forming step, the porous layer is formed. By oxidizing the layer, the porous layer can be oxidized at a low temperature and in a short time without performing thermal oxidation treatment that is exposed to a high temperature of about 1000 ° C. for a long time, and an insulating film can be formed. For this reason, the amount of energy required for oxidation is reduced, and equipment that can withstand high temperatures is not required, so that manufacturing equipment is inexpensive. Further, since the processing time is shortened, productivity is improved. As a result of these, the cost of the through electrode can be reduced.
[0006]
Also, in the manufacturing method of the through electrode of the present invention, in the oxidation step, preferably to oxidize the porous layer with an acid solution. In the oxidation step, when the porous layer is oxidized with an acid solution, the porous layer can be oxidized at room temperature, so that the amount of energy for oxidation can be further reduced.
[0007]
In the case where the porous layer is oxidized with an acid solution, the acid solution is preferably at least one selected from oxalic acid, phosphoric acid, nitric acid, sulfuric acid, and aqua regia. When the acid solution is at least one selected from oxalic acid, phosphoric acid, nitric acid, sulfuric acid, and aqua regia, the porous layer can be oxidized quickly, so that the productivity of the oxidation process is improved. As a result, productivity of through electrode manufacturing is improved. Moreover, since oxalic acid, phosphoric acid, nitric acid, sulfuric acid, and aqua regia are readily available and cheap in price, as a result, the cost of the through electrode can be further reduced.
[0008]
The pores are preferably perforated by at least one of a deep-reactive ion etching method, an anisotropic etching method using a solution, a laser processing method, and a micro drilling method. If the pore forming step is performed by at least one of the deep-reactive ion etching method, the anisotropic etching method using a solution, the laser processing method, and the microdrill processing method, fine processing is easy. Can be efficiently formed in the semiconductor substrate.
[0009]
In addition, when an n-type silicon substrate is used as the semiconductor substrate and the pore forming step is performed by a photoexcited electropolishing method, the pore forming step, the porous layer forming step, and the oxidation step include an apparatus configuration and Since the reaction processes are similar, the pore formation step, the porous layer formation step, and the oxidation step can be performed continuously using the same processing apparatus. When the pore forming step, the porous layer forming step, and the oxidation step are continuously performed using the same processing apparatus, a continuous process can be established and the time between each step can be shortened. The manufacturing time of the electrode can be shortened, and as a result, productivity can be improved.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
The manufacturing method of the penetration electrode of 1st embodiment which concerns on this invention is demonstrated referring FIG. 1 and FIG. The through electrode manufacturing method of the present embodiment is characterized in that a p-type silicon substrate is used as a semiconductor substrate and pores are formed by DRIE.
FIG. 1 shows the method of manufacturing the through electrode according to this embodiment in the order of steps, and is a cross-sectional view when the semiconductor substrate is cut in the extending direction of the pores. FIG. 2 is used in this embodiment. It is a figure which shows the outline of a processing apparatus typically.
[0012]
In the manufacturing method of the present embodiment, first, in the pore forming step, as shown in FIG. 1A, a p-type silicon substrate (hereinafter referred to as the semiconductor substrate 11 in the present embodiment) which is a semiconductor substrate 11 having a thickness of 300 μm. Is referred to as a p-type silicon substrate 11), and pores 12 having a diameter of 100 μm and a depth of 250 μm are formed by the DRIE method.
Next, as shown in FIG. 1B, an aluminum film (hereinafter referred to as the conductive film 13 in the present embodiment) is formed on the opposite surface where the pores 12 are formed. Called). Here, the main surface is a surface having the widest area, and is a surface that becomes a front or back surface when a semiconductor substrate is usually used.
Next, as shown in FIG. 1C, a mask 14 made of a metal thin film is applied to the surface of the p-type silicon substrate 11 other than the surfaces of the pores 12.
[0013]
Next, in the porous layer forming step, as shown in FIG. 1 (d), the porous wall 15 is formed by making the pore wall surfaces of the pores 12 of the p-type silicon substrate 11 porous. When making the pore wall surface of the pores 12 porous, as shown in FIG. 2, a reaction vessel 22 filled with an electrolytic solution 21, a platinum plate 23 provided inside the reaction vessel 22, A processing device 25 having a constant current power supply 24 is used. The p-type silicon substrate 11 is attached to the processing device 25 at a position facing the platinum plate 23, and the platinum plate 23 and the p-type silicon substrate 11 are connected via a constant current power supply 24. The electrolyte solution 21 is a mixture of 50% by weight hydrogen fluoride aqueous solution and ethanol in a ratio of 2: 1.
Then, the p-type silicon substrate 11 is used as an anode and the platinum plate 23 is used as a cathode, and current is supplied for 5 minutes at a constant current density of 50 mA / cm2. The p-type silicon substrate 11 is made porous by energization. However, since the p-type silicon substrate 11 is provided with a mask 14, a porous layer 15 having a thickness of about 8 μm is formed only on the pore 12 hole wall. Can be formed. Since the porous layer 15 has a very large surface area per unit volume, it has a high electrical resistivity and is highly reactive.
[0014]
Next, in the oxidation step, the porous layer 15 is oxidized to form the insulating layer 16. In this oxidation step, the electrolytic solution 21 in the reaction vessel 22 is replaced with a 5 wt% oxalic acid aqueous solution in the processing apparatus 25 used in the above-described porous step, the p-type silicon substrate 12 is used as the anode, and the platinum plate 23. As a cathode, the porous layer 15 is oxidized by flowing a constant current at a current density of 50 mA / cm 2 at room temperature.
[0015]
Next, in the penetration step, as shown in FIG. 1E, the aluminum film 13 and the mask 14 laminated on the p-type silicon substrate 11 are peeled off and further polished, whereby the pores 12 are formed on the p-type silicon substrate surface. Penetration between backsides.
Next, in the metal filling step, as shown in FIG. 1 (f), the through-hole electrode 18 can be obtained by filling the pores 12 with indium as the conductive material 17 by a molten metal suction method.
[0016]
After the p-type silicon substrate 11 is masked, the porous layer 15 is formed only on the walls of the pores 12 in the porous forming step, but the mask 14 is not applied to the p-type silicon substrate 11. In the porous forming step, a porous layer may be formed on the surface of the p-type silicon substrate 11 other than the pore 12 hole wall due to the structure of the p-type silicon substrate 11. In addition, even if a porous layer is formed on the surface of the p-type silicon substrate 11 other than the pore 12 hole wall, the effect of the present invention is not significantly impaired.
In the porous formation process described above, an electrolytic solution obtained by mixing a 50% by weight hydrogen fluoride aqueous solution and ethanol in a ratio of 2: 1 was used. The current density was 50 mA / cm 2 and the reaction time was 5 minutes. These conditions can be appropriately changed according to the size and number of pores to be formed, the target thickness of the porous layer, and the like. However, if the current density exceeds 200 mA / cm 2, it may not be possible to make it porous, and therefore it is preferably 200 mA / cm 2 or less.
[0017]
In the oxidation step described above, a 5% by weight oxalic acid aqueous solution was used, but an acid aqueous solution such as phosphoric acid, nitric acid, sulfuric acid, aqua regia, etc. can also be used. Further, although the current density is 50 mA / cm 2, it can be changed as appropriate.
[0018]
In the first embodiment described above, since the pore forming step can be performed by the DRIE method and fine processing can be performed, the pores 12 can be efficiently formed in the p-type silicon substrate 11. Further, in the porous layer forming step, the porous layer 15 made porous is formed on the surface of the pore wall 12 to enhance the reactivity of the surface of the pore wall, and then in the oxidation step, oxalic acid is used at room temperature. Since the insulating layer 16 is formed by oxidizing the porous layer 15, it is not necessary to use a high temperature as in the case of thermal oxidation, the amount of energy required for the oxidation can be reduced, and the apparatus for oxidation is also inexpensive. In addition, the time required for oxidation is shortened and productivity is improved. As a result, the cost of the through electrode 18 can be reduced.
[0019]
In the first embodiment described above, the pore forming step is performed by the DRIE method. However, the present invention is not limited to this, and depending on the thickness of the silicon substrate to be used and the size of the pore to be formed, An anisotropic etching method using a potassium oxide aqueous solution or the like, a laser processing method, a machining method such as a micro drilling method, or the like can also be performed.
Further, in the first embodiment described above, the metal filling step is performed by a molten metal filling method, but the present invention is not limited to this, and a sputtering method, a plating method, It can be performed by a screen printing method or the like.
[0020]
In the first embodiment described above, the p-type silicon substrate 11 is used, but an n-type silicon substrate may be used. The surface orientation of the n-type silicon substrate is not particularly limited, but when the pore forming step is performed by a photoexcited electrolytic polishing method, the surface orientation is preferably (100). In addition, since the formation of the porous layer involves holes (holes) in the silicon substrate, when an n-type silicon substrate is used, in order to generate holes that are minority carriers, It is necessary to irradiate light.
[0021]
(Second embodiment)
Next, a through electrode manufacturing method according to a second embodiment of the present invention will be described with reference to FIGS. The through electrode manufacturing method of the present embodiment uses an n-type silicon substrate as a semiconductor substrate, forms pores by a photoexcited electrolytic polishing method, and performs the same processing for the pore formation step, the porous layer formation step, and the oxidation step. It is characterized by being continuously performed using an apparatus.
FIG. 3 shows the method of manufacturing the through electrode according to this embodiment in the order of steps, and is a cross-sectional view when the semiconductor substrate is cut in the direction in which the pores extend. FIG. 4 is used in this embodiment. It is a figure which shows the outline of a processing apparatus typically.
[0022]
In the manufacturing method of the present embodiment, first, in the pore forming step, as shown in FIG. 3A, an n-type silicon substrate which is the semiconductor substrate 41 (hereinafter, in the present embodiment, the semiconductor substrate 41 is made of n-type silicon). The pores 42 are formed in the substrate 41). At this time, the n-type silicon substrate 41 has an aluminum film 43 (hereinafter referred to as the aluminum film 43 in the present embodiment), which is a conductive film 43 patterned on the back surface. The surface orientation is (100) and the thickness is 300 μm.
In this n-type silicon substrate 41, a V-shaped groove is previously formed at a position where a pore is to be formed. The reason for patterning the aluminum film 43 is to irradiate the substrate with light from the back surface of the n-type silicon substrate, as will be described later, in order to generate holes in the n-type silicon substrate. This is for irradiating light.
In the pore forming step, as shown in FIG. 4, a reaction vessel 52 filled with a 2.5 wt% aqueous solution of hydrogen fluoride 51, a platinum plate 53 provided inside the reaction vessel 52, A processing apparatus 56 having a current power source 54 and a light source 55 that emits light from the back surface of the n-type silicon substrate 41 is used. The n-type silicon substrate 41 is attached to the processing device 56, and the light source 55 emits light from the back surface side of the n-type silicon substrate 41 to the portion corresponding to the V-shaped groove, while the n-type silicon substrate 41 is the anode, platinum A constant current is passed using the plate 53 as a cathode. In this way, the V-shaped groove tips are selectively etched to form pores 42 having a diameter of about 100 μm.
[0023]
Next, in the porous layer forming step, as shown in FIG. 3B, the pore walls of the pores 42 of the n-type silicon substrate 41 in which the pores 42 are formed are made porous to form a porous layer 44. . In this porous layer forming step, the processing apparatus 56 described above is used without removing the n-type silicon substrate 41 after the pore forming step. That is, with the n-type silicon substrate 41 attached to the processing device 56, the electrolytic solution 51 in the reaction vessel 52 used in the pore forming step was mixed with a 50% by weight hydrogen fluoride solution and ethanol in a ratio of 2: 1. Next, the n-type silicon substrate 41 is used as an anode and the platinum plate 53 is used as a cathode, and a current density of 50 mA / cm 2 is applied for 5 minutes to form a porous layer on the pore wall surface of the pores 42 having a thickness of about 8 μm. 44 is formed.
[0024]
Next, in the oxidation step, the porous layer 44 is oxidized. Also in this oxidation process, after the porous layer forming process, the processing apparatus 56 described above is used without removing the n-type silicon substrate. That is, with the n-type silicon substrate attached to the processing apparatus 56, a solution obtained by mixing 50% by weight hydrogen fluoride solution and ethanol in the reaction vessel 52 used in the porous layer forming step in a ratio of 2: 1 is 5 Then, the porous layer 44 is oxidized by passing a constant current at a current density of 50 mA / cm 2 at room temperature using the n-type silicon substrate 41 as an anode and the platinum plate 53 as a cathode.
In this way, the pore forming step, the porous layer forming step, and the oxidation step are continuously performed by the same processing apparatus.
[0025]
Next, in the penetration step, as shown in FIG. 3C, the aluminum film 43 on the back surface of the n-type silicon substrate 41 is peeled off and further polished to penetrate the front and back of the n-type silicon substrate 41.
Next, in the metal filling step, as shown in FIG. 3 (d), the formed pores 46 are filled with indium, which is a conductive material 47, by a molten metal suction method, whereby the through electrode 48 can be obtained.
[0026]
In the second embodiment described above, since the pore formation step of the n-type silicon substrate is performed by the photoexcited electrolytic polishing method, the apparatus configuration and process in the pore formation step, the porous layer formation step, and the oxidation step are Similar. Therefore, the pore forming step, the porous layer forming step, and the oxidation step can be continuously performed by the same processing apparatus, and the time between the steps can be shortened. As a result, the manufacturing time of the through electrode can be shortened, and as a result, productivity can be improved.
[0027]
【The invention's effect】
According to the method for manufacturing a through electrode of the present invention, an insulating film can be formed by oxidizing a porous layer at a low temperature in a short time. Therefore, the amount of energy for oxidation is reduced. Also, since no equipment that can withstand high temperatures is required, the manufacturing equipment is inexpensive. Furthermore, since the processing time is shortened, productivity is improved. As a result of these, the cost of the through electrode can be reduced.
Further, in the oxidation step, when the porous layer is oxidized with an acid solution, the porous layer can be oxidized at room temperature, so that the amount of energy for oxidation can be further reduced.
Further, when the porous layer is oxidized with an acid solution, the productivity of the oxidation process is improved when the acid solution is at least one selected from oxalic acid, phosphoric acid, nitric acid, sulfuric acid, and aqua regia. In addition, the cost of the through electrode can be further reduced.
In addition, if the front pore is drilled by at least one of the deep-reactive ion etching method, anisotropic etching method using solution, laser processing method, and micro drilling method, the target pore is efficiently formed in the semiconductor substrate. Can be formed.
Further, an n-type silicon substrate is used as the semiconductor substrate, the pore forming step is performed by a photoexcited electrolytic polishing method, and the pore forming step, the porous layer forming step, and the oxidizing step are continuously performed using the same processing apparatus. And the manufacturing time of a penetration electrode can be shortened, and productivity can be improved further as a result.
Further, since the through electrode of the present invention is obtained by the above-described method for manufacturing a through electrode, it can be efficiently produced and the cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a through electrode manufacturing method according to a first embodiment of the present invention in the order of steps.
FIG. 2 is a schematic view showing a processing apparatus used in the method for manufacturing a through electrode according to the first embodiment.
FIG. 3 is a cross-sectional view showing a through electrode manufacturing method according to a second embodiment of the present invention in the order of steps.
FIG. 4 is a schematic view showing a processing apparatus used in the method for manufacturing a through electrode according to the second embodiment.
FIG. 5 is a cross-sectional view showing a conventional through electrode manufacturing method in the order of steps.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11,41 ... Semiconductor substrate (p-type silicon substrate, n-type silicon substrate), 12, 42 ... pore, 13, 43 ... conductive film (aluminum film), 15, 44 ... porous layer, 16, 45 ... insulation Layer, 17, 47 ... conductive material, 25, 56 ... processing equipment

Claims (5)

At least a porous layer that forms a porous layer (15, 44) by making the pore wall surfaces of the pores (12, 42) formed in a direction perpendicular to the main surface of the semiconductor substrate (11, 41) porous. A through electrode having a forming step, an oxidation step of oxidizing the porous layer to form an insulating layer (16, 45), and a metal filling step of filling the pores with a conductive substance (17, 47) A manufacturing method comprising:
Furthermore, before the porous layer forming step, it has a step of forming a conductive film on the surface opposite to the pore forming surface of the semiconductor substrate,
In the porous layer forming step, by energizing the semiconductor substrate using the conductive film as an electrode, the pore wall surface of the pore is made porous ,
Furthermore, before the metal filling step, the through electrode has a penetrating step of penetrating the pores between both surfaces of the semiconductor substrate by peeling the conductive film and polishing the semiconductor substrate Manufacturing method. Wherein in the oxidation step, the manufacturing method of the through electrode according to claim 1, characterized by oxidizing the porous layer with an acid solution. The method for producing a through electrode according to claim 2 , wherein the acid solution is at least one selected from oxalic acid, phosphoric acid, nitric acid, sulfuric acid, and aqua regia. The pores, Deep-Reactive Ion Etching method, an anisotropic etching method using the solution, a laser processing method, one of the claims 1-3, characterized in that it is perforated with at least one of the micro-drilling method A method for producing a through electrode according to claim 1. An n-type silicon substrate is used as the semiconductor substrate, the pore formation step is performed by a photoexcited electropolishing method, and the pore formation step, the porous layer formation step, and the oxidation step are performed in the same processing apparatus (25, 56). method for producing a through electrode according to any one of claims 1 to 3, wherein the continuously be carried out using).

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