JP2008115448A - Electroless plating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroless plating method with which the forming rate of a plating layer can be remarkably improved, and further, the plating layer can be selectively formed only on a plating region in the material to be plated uniformly at high precision. <P>SOLUTION: An organic complexing agent is stuck to the non-plating region in the material to be plated, and the material to be plated is subjected to electroless plating treatment, thus a plating layer is selectively formed on the plating region in the material to be plated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a method for selectively forming a chemical plating film, and more particularly to an electroless plating method suitable for use in printed wiring boards, semiconductor substrates, and the like.

  An electroless plating method is known as a plating method for fine portions of a substrate, such as providing wiring on the surface of a semiconductor wafer. One of the electroless plating methods is an electroless gold plating method.

  This electroless gold plating method has a problem that the deposition rate of plating is very slow and a problem that temperature management of the plating solution is very difficult. Actually, even if the plating layer is thickened on the material to be plated using the electroless gold plating method, the film thickness of the gold plating layer usually obtained is about 0.5 μm. In order to obtain a film thickness greater than this, for example, a method (high-speed plating method) in which the material to be plated is immersed in a plating solution at 80 ° C. or higher for 3 to 4 hours and the temperature of the plating solution is controlled with high accuracy is used. A gold plating layer having a thickness of about 1 μm was deposited on the surface of the material to be plated. And it is very difficult to perform such temperature control of the plating solution over a long period of time with high accuracy and to maintain a constant ion concentration in the plating solution near the surface of the member to be plated. This was a major factor in the abnormal deposition of plating. Therefore, the electroless gold plating method has not been put to practical use for a device provided with fine wiring such as an electronic device component. In addition, the gold wiring provided on the base metal to which wire bonding is connected is indispensable to the base metal, so the adhesion between the base metal and the plating layer is low due to uneven plating. The electroless gold plating method as described above could not be applied to the formation of high-definition wiring and the mounting of integrated circuits. Furthermore, since such high-definition wiring and integrated circuits require plating coverage on a submicron basis, if a plating layer is formed using an electroless gold plating method, a base at the end of the plating layer is formed. There have been problems such as poor adhesion due to metal, short circuit failure due to abnormal deposition of plating between wires, and poor corrosion.

  On the other hand, there is a method of forming a gold plating layer with high accuracy by performing pretreatment before performing electroless gold plating (see, for example, Patent Documents 1 and 2). Examples of the pretreatment for electroless gold plating include substitution gold plating and substitution treatment with palladium or silver.

Japanese Patent Laid-Open No. 10-326345 JP-A-4-32574

  However, if electroless gold plating is performed after the pretreatment as described above, a substitution layer made of a substituted metal is formed between the base metal and the gold plating layer. Compared to the case where the gold plating layer is formed directly on the base metal using this method, the adhesion strength between the base metal and the gold plating layer is reduced, or nuclei that cause precipitation of foreign substances are generated in the replacement layer. There is a problem that a plating layer is partially formed and plating unevenness is likely to occur. Further, in order to perform such pretreatment, there is a problem that the entire substrate must be immersed in a solution containing an expensive noble metal even if the area of the portion to be plated is small.

  In view of the above-described circumstances, the present invention can remarkably improve the formation rate of a plating layer, and can selectively form a plating layer uniformly and accurately only in the plating region of the material to be plated. An object is to provide an electroless plating method.

  The present inventor made an organic electroless plating treatment after adhering an organic complexing agent to a part of the material to be plated without being trapped by the concept that impurities should not be mixed in the plating solution. The knowledge that a plating layer is not formed in the part which made the complexing agent adhere was acquired.

Based on this knowledge, the present invention is a method in which an organic complexing agent is attached to a non-plating region of a material to be plated, and electroplating is performed on the material to be plated, thereby removing the non-plating region of the material to be plated. An electroless plating method is characterized in that a plating layer is selectively formed in a region.
In this aspect, the organic complexing agent can prevent the formation of the plating layer in the non-plating region and can selectively form the plating layer only in the plating region, so that the formation speed of the plating layer can be remarkably improved. In addition, the plating layer can be formed uniformly and accurately only in the plating region of the material to be plated.

Here, the non-plating of the material to be plated is caused by attaching the organic complexing agent to the material to be plated and selectively exposing the plating region to decompose the organic complexing agent adhering to the plating region. The organic complexing agent is preferably attached only to the region.
According to this, by decomposing and removing the organic complexing agent attached to the plating region, the organic complexing agent can be easily attached only to the non-plating region of the material to be plated.

Moreover, after forming the protective film patterned so that the said non-plating area | region may be exposed on the said to-be-plated material, and being immersed in the said organic complexing agent, the said to-be-plated material is removed by removing the said protective film It is preferable to attach the organic complexing agent only to the non-plating region.
According to this, the organic complexing agent can be easily attached only to the non-plating region of the material to be plated.

In addition, a metal layer is formed in the plating region of the material to be plated, and after the organic complexing agent is attached to the material to be plated, the metal layer is heated by induction heating to the plating region. It is preferable that the organic complexing agent is attached only to the non-plating region of the material to be plated by thermally decomposing the attached organic complexing agent.
According to this, the organic complexing agent attached to the plating region can be easily attached only to the non-plating region of the material to be plated by thermally decomposing and removing the organic complexing agent.

Moreover, it is preferable to perform a roughening process at least on the non-plating area | region of the said to-be-plated material, before making the said organic complexing agent adhere to the to-be-plated material.
According to this, since the non-plating region is roughened, the organic complexing agent can be easily attached to the non-plating region.

The organic complexing agent is preferably a surfactant.
According to this, since the surfactant is difficult to be decomposed in the cleaning process, it is possible to reliably prevent the formation of the plating layer in the non-plating region of the material to be plated.

The organic complexing agent is preferably a nonionic surfactant.
According to this, since the nonionic surfactant is less likely to be decomposed in the cleaning process, it is possible to more reliably prevent the formation of a plating layer on the nonplating region of the material to be plated, and to compare the nonionic interface with the plating solution. Even if the activator is dissolved, the plating process is not affected.

Moreover, it is preferable that at least the surface of the non-plating region of the material to be plated is made of silicon oxide.
According to this, since at least the surface of the non-plating area | region of a to-be-plated material is comprised with the silicon oxide, an organic complexing agent can be attached easily.

  The present invention makes use of the property that an organic complexing agent is attached to a non-plating region of a material to be plated, and a plating layer is not formed in the region to which the organic complexing agent is attached. A plating process is performed to selectively form a plating layer in a plating region excluding the non-plating region of the material to be plated. That is, by attaching an organic complexing agent to the non-plating region of the material to be plated, it prevents the formation of a plating layer in the non-plating region during the electroless plating treatment of the material to be plated, and the organic complexing agent adheres. The plating layer is selectively formed only in the plating region that is not formed.

  Here, the organic complexing agent used in the present invention is not particularly limited as long as it is an organic compound that forms a complex compound with another substance in a solution. However, a surfactant is preferable, and a cationic surfactant and a nonionic interface are used. An activator (nonionic surfactant) is more preferred, and a nonionic surfactant is particularly preferred. When a surfactant is used as the organic complexing agent, it is difficult for the surfactant to be decomposed in the cleaning step described later, and therefore it is possible to reliably prevent the formation of a plating layer on the non-plating region of the material to be plated. When a nonionic surfactant is used as the organic complexing agent, the surfactant is more difficult to be decomposed in the cleaning process described later, and thus the formation of a plating layer in the non-plating region of the material to be plated can be more reliably prevented. In addition, even if the nonionic surfactant is dissolved in the plating solution, the plating process is not affected.

  The surfactant is not particularly limited as long as it has a hydrophilic part and a hydrophobic part in the molecule, and is not limited to an ionic surfactant (an anionic surfactant, a cationic surfactant, an amphoteric interface). Active agents) and nonionic surfactants, for example, alkoxylates, alcohol ethoxylates (eg oleyl alcohol ethoxylates), lauryl alcohol, laurylamidopropyl betaine, laurylaminoacetic acid betaine, ethylenediamine propylene oxide-ethylene oxide condensate (Ethylenediamine PO-EO condensate), ether sulfate, octanediol, sorbitan fatty acid ester, hindered ester (aryl polybasic fatty acid, alkyl ester, unsaturated long-chain fatty acid ester of neopentyl polyol, saturation of neopentyl polyol) Medium chain fatty acid ester), phenol ethoxylate, polyalkylene glycol type oil, polyethylene glycol, polyethylene glycol oleate, polyether type quaternary ammonium salt, polyoxyalkylene tallowate, coconut ethanol amide, propylene oxide-ethylene oxide condensate ( PO-EO condensate), quaternary ammonium salt type polymer, dimethicone copolyol, sucrose fatty acid ester, bemulene, poly (oxylene ethylene / oxypropylene) methyl polysiloxane copolymer, polyoxyethylene octyl phenyl ether, poly Oxyethylene hydrogenated castor oil, polyoxyethylene stearyl ether, polyoxyethylene stearamide, polyoxyethylene polyoxypropylene glycol, monosteary Acid ethylene glycol, propylene glycol monostearate, polyoxyethylene sorbite monolaurate, diethanolamide laurate, polyoxyethylene sorbitol tetraoleate (polyoxyethylene sorbitol tetraoleate), lipophilic polyglycerin fatty acid ester mixed emulsifier, mono Examples thereof include polyoxyethylene oleate and sorbitan monooleic acid.

  The cationic surfactant is not particularly limited as long as it is a surfactant that dissociates and becomes a cation when dissolved in water, and examples thereof include tetramethylammonium hydroxide.

  The nonionic surfactant is not particularly limited as long as it is a surfactant having a hydrophilic group that does not ionize when dissolved in water, and those of ester type, ether type, ester / ether type, fatty acid alkanolamide, alkyl Polyglycoxide exists, but for example, dimethicone copolyol, sucrose fatty acid ester, bemulene, poly (oxylene ethylene / oxypropylene) methyl polysiloxane copolymer, polyoxyethylene octyl phenyl ether, polyoxyethylene cured castor Oil, polyoxyethylene stearyl ether, polyoxyethylene stearamide, polyoxyethylene polyoxypropylene glycol, ethylene glycol monostearate, propylene glycol monostearate, polyoxymonolaurate Examples include ethylene sorbit, lauric acid diethanolamide, tetraoleic acid polyoxyethylene sorbitol (polyoxyethylene sorbitol tetraoleate), lipophilic polyglycerol fatty acid ester mixed emulsifier, polyoxyethylene monooleate, and sorbitan monooleic acid. .

  Hereinafter, the best mode for carrying out the present invention when a nonionic surfactant is used as the organic complexing agent will be described. The description of the present embodiment is an exemplification, and the present invention is not limited to the following description.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view of a wiring formed by the electroless plating method according to the first embodiment. As shown in FIG. 1, a plurality of wirings 30 are formed on a wiring surface of a silicon substrate 10 that is a material to be plated. Each wiring 30 is formed by sequentially laminating a base layer 16 made of Ni or NiCr, a sputter metal layer 18 made of gold, and a plating layer 20 made of gold on the silicon substrate 10. The plating layer 20 is formed by the electroless plating method according to this embodiment.

  2 to 4 are views showing the wiring formation process. The electroless plating method of the present embodiment will be described with reference to FIGS.

  First, as shown in FIG. 2A, a NiCr layer 15 having a thickness of about 20 nm and serving as a base layer 16 is formed on the silicon substrate 10 by, for example, sputtering or plating.

  Next, as shown in FIG. 2B, an Au layer 17 having a thickness of about 200 nm to be a sputtered metal layer 18 is formed on the NiCr layer 15 by, for example, a sputtering method.

  Then, as shown in FIG. 2C, the NiCr layer 15 and the Au layer 17 thus formed are patterned into a predetermined shape by a photolithography method, thereby forming the base layer 16 and the sputter metal layer 18. Here, a region where the underlayer 16 and the sputtered metal layer 18 are formed is referred to as a plating region 50, and the other region on the silicon substrate 10 is referred to as a non-plating region 60.

  Next, as shown in FIG. 3A, the silicon substrate 10 is immersed in the processing liquid 110 filled in the processing liquid tank 100 at room temperature for 5 minutes. The processing liquid 110 contains a nonionic surfactant (nonionic surfactant). By immersing the wiring surface of the silicon substrate 10 in the processing liquid 110, nonionic ions are formed on the wiring surface of the silicon substrate 10. A surfactant can be attached. Here, the treatment liquid 110 is not particularly limited as long as it contains a nonionic surfactant and does not affect the process described later. For example, the treatment liquid 110 includes 0.1% nonionic surfactant and 0.8%. % Aqueous solution (such as acetylene alcohol or butyl alcohol). In the present embodiment, an aqueous solution containing 0.1% nonionic surfactant and 0.8% alcohol (acetylene alcohol or butyl alcohol) is used as the treatment liquid 110. In the present embodiment, the entire silicon substrate 10 is immersed in the processing liquid 110, but only the wiring surface of the silicon substrate 10 may be immersed in the processing liquid 110. In this embodiment, the nonionic surfactant is attached to the wiring surface of the silicon substrate 10 by immersing the silicon substrate 10 in the processing liquid 110, but the wiring surface of the silicon substrate 10 is used by brushing or spraying. A nonionic surfactant may be attached to the substrate.

  Then, as shown in FIG. 3B, a mask 150 provided with a through-hole 151 corresponding to the plating region 50 is disposed on the wiring surface of the silicon substrate 10 to which the processing liquid 110 is attached. However, an ultraviolet ray source such as an ultraviolet lamp is disposed above the mask 150 to irradiate the silicon substrate 10 with ultraviolet rays (UV). That is, the silicon substrate 10 is selectively irradiated with ultraviolet rays (UV) so that the ultraviolet rays (UV) irradiated from the ultraviolet ray source are irradiated only to the plating region 50 through the through holes 151. As a result, the nonionic surfactant contained in the treatment liquid 110 attached to the plating region 50 of the silicon substrate 10 is decomposed by the ultraviolet rays (UV). Here, as the mask 150, the wiring mask used when patterning the base layer 16 and the sputtered metal layer 18 by the photolithography method described above may be used as it is. By sharing the mask 150 and the wiring mask, the pattern density of the wiring can be improved, so that the design margin is widened and high-density mounting by high-density wiring is possible.

  Thereafter, when the silicon substrate 10 is ashed with an acid such as sulfuric acid (cleaning step), as shown in FIG. 3C, the processing liquid 110 is removed, but the non-ion adhering to the non-plating region 60 of the silicon substrate 10 is removed. The surfactant remains on the surface of the non-plated region 60 without being removed. That is, the nonionic surfactant remains only on the surface of the non-plating region 60 of the silicon substrate 10. In the present embodiment, ashing is performed using 10 wt% sulfuric acid.

  Next, as shown in FIG. 4A, the silicon substrate 10 is immersed in a plating solution 210 filled in the plating tank 200, and an electroless gold plating process is performed on the wiring surface of the silicon substrate 10. In this embodiment, a non-cyanide electroless gold plating solution is used as the plating solution 210. As a result, as shown in FIG. 4B, the plating layer is not formed in the non-plating region 60 of the silicon substrate 10, but the plating layer 20 having a thickness of about 1 μm is formed in the plating region 60. That is, the plating layer 20 is selectively formed only on the plating region 50 of the silicon substrate 10 to which the nonionic surfactant is not attached. The plated layer 20 has a very sharp end. In addition, when the silicon substrate 10 is immersed in the plating solution 210, a part of the nonionic surfactant attached to the silicon substrate 10 may be dissolved in the plating solution 210. Will not be affected.

  As described above, the plating layer 20 can be selectively formed only in the plating region 50 of the silicon substrate 10 by using the electroless plating method according to the present embodiment. Moreover, in this electroless plating method, a nonionic surfactant adheres to the non-plating region 60 of the silicon substrate 10. That is, the nonionic surfactant adheres to uneven portions or holes (not shown) other than the surface of the sputtered metal layer 18. Therefore, it is possible to prevent the abnormal deposition of plating that occurs in such a portion, and to form the plating layer 20 uniformly and accurately without unevenness. As a result, abnormal leakage due to abnormal deposition of the plating (film residue) or the like can occur. In addition to preventing the manufacturing cost, the manufacturing cost can be reduced by improving the yield. Furthermore, in this electroless plating method, since the plating layer 20 is selectively formed in the plating region 50 and no plating layer is formed in the non-plating region 60, the plating layer is formed over the entire surface of the silicon substrate 10. In comparison, the formation speed of the plating layer 20 can be remarkably improved, and the consumption of the plating components in the plating solution 210 can be suppressed to prevent the plating solution 210 from deteriorating. Moreover, in this embodiment, since a nonionic surfactant is used as the organic complexing agent and no special substance is used, the external environment is not affected and the environment is friendly. Furthermore, in this embodiment, since the nonionic surfactant is used as the organic complexing agent, the concentration of the plating solution 210 can be easily managed.

  Moreover, in the electroless plating method according to the present embodiment, the plating layer 20 is selectively formed only on the sputtered metal layer 18 made of gold, so that the stable plating layer 20 can be formed uniformly. In addition, since this electroless plating method does not include a step of applying a load to the silicon substrate 10, there is an effect that internal stress or the like is not generated in the wiring formed on the wiring surface of the silicon substrate 10.

(Embodiment 2)
In the first embodiment, as described above, the nonionic surfactant contained in the treatment liquid 110 attached to the plating region 50 of the silicon substrate 10 is decomposed by selectively irradiating the silicon substrate 10 with ultraviolet rays (UV). However, before immersing the silicon substrate 10 in the processing solution 110, a protective film patterned so as to expose the non-plating region 60 is formed on the silicon substrate 10, and the silicon substrate 10 is used as the processing solution 110. After the immersion, the non-ionic surfactant may be attached only to the non-plating region 60 by removing the protective film. Even if it does in this way, the effect similar to Embodiment 1 will be acquired.

  FIG. 5 is a schematic view when a protective film is formed on a silicon substrate. As shown in FIG. 5, the protective film 180 is formed so as to cover the silicon substrate 10. The protective film 180 is provided with a through hole 181 corresponding to the non-plating region 60. That is, the protective film 180 is provided with a through hole 181 so that the non-plating region 60 is exposed. Therefore, when the silicon substrate 10 is immersed in the processing liquid 110, the processing liquid 110 adheres to the surface of the protective film 180 and the non-plating region 60. Then, after removing the silicon substrate 10 from the processing liquid 110, the protective film 180 is removed from the silicon substrate 10, so that the processing liquid 110 containing a nonionic surfactant is attached only to the non-plating region 60 of the silicon substrate 10. Can be made.

  Then, by performing the same processing as in the first embodiment, the plating layer 20 can be selectively formed only in the plating region 50 of the silicon substrate 10 to which the nonionic surfactant is not attached. Other steps are the same as those in the first embodiment, and thus the description thereof is omitted.

(Embodiment 3)
In the first embodiment, as described above, the nonionic surfactant contained in the treatment liquid 110 attached to the plating region 50 of the silicon substrate 10 is decomposed by selectively irradiating the silicon substrate 10 with ultraviolet rays (UV). However, the nonionic surfactant contained in the treatment liquid 110 attached to the plating region 50 may be thermally decomposed by selectively heating the plating region 50.

  Specifically, since the base layer 16 and the sputter metal layer 18 are provided in the plating region 50 of the silicon substrate 10 of the present embodiment, the base metal 16 and the sputter metal layer 18 are heated by induction heating to form the sputter metal. The surface of the layer 18, that is, the plating region 50 may be selectively heated to thermally decompose the nonionic surfactant contained in the treatment liquid 110 attached to the plating region 50. Even if it does in this way, the effect similar to Embodiment 1 will be acquired.

  FIG. 6 is a schematic view when electromagnetic induction heating is performed on the silicon substrate according to the present embodiment. As shown in FIG. 6, an electromagnetic induction heater 400 is disposed above the silicon substrate 10 to which the processing liquid 110 is attached over the entire wiring surface. The electromagnetic induction heater 400 includes a coil 410 disposed so as to face the wiring surface of the silicon substrate 10, and an AC power source 420 connected to the coil 410. When an alternating current flows through the coil 410, current flows through the underlayer 16 and the sputter metal layer 18 provided on the silicon substrate 10 by electromagnetic induction, and the underlayer 16 and the sputter metal layer 18 generate heat. As a result, the nonionic surfactant contained in the treatment liquid 110 adhering to the surface of the sputtered metal layer 18, that is, the plating region 50 is thermally decomposed and removed.

  Then, by performing the same processing as in the first embodiment, the plating layer 20 can be selectively formed only in the plating region 50 of the silicon substrate 10 to which the nonionic surfactant is not attached. Other steps are the same as those in the first embodiment, and thus the description thereof is omitted.

(Other embodiments)
In the first embodiment, the nonionic surfactant contained in the treatment liquid 110 attached to the plating region 50 of the silicon substrate 10 is decomposed by selectively irradiating the silicon substrate 10 with ultraviolet rays (UV). The nonionic surfactant contained in the treatment liquid 110 attached to the plating region 50 of the silicon substrate 10 may be decomposed using infrared rays instead of ultraviolet rays. Even if it does in this way, the effect similar to Embodiment 1 will be acquired.

  In the first and second embodiments, the silicon substrate 10 provided with the base layer 16 and the sputtered metal layer 18 is immersed in the processing liquid 110 as it is. However, when the base layer 16 and the sputtered metal layer 18 are patterned, a silicon substrate is used. The ten non-plated regions 60 may be roughened simultaneously, or the non-plated regions 60 of the silicon substrate 10 may be roughened after the underlayer 16 and the sputter metal layer 18 are patterned. By roughening the wiring surface of the silicon substrate 10, the treatment liquid 110 can be easily attached to the non-plating region 60 of the silicon substrate 10.

  Further, in the first and second embodiments, the silicon substrate 10 is used as the material to be plated, and the surface of the non-plating region is formed of silicon oxide, so that the nonionic surfactant can be easily attached. . In the first and second embodiments, since the sputtered metal layer 18 is formed of Au, the nonionic surfactant attached to the surface of the sputtered metal layer 18 can be easily removed by washing with water.

Schematic of the wiring formed by the electroless plating method according to Embodiment 1. FIG. FIG. 3 is a schematic cross-sectional view illustrating a wiring formation process according to the first embodiment. FIG. 3 is a schematic cross-sectional view illustrating a wiring formation process according to the first embodiment. FIG. 3 is a schematic cross-sectional view illustrating a wiring formation process according to the first embodiment. FIG. 5 is a schematic cross-sectional view when a protective film is formed on a silicon substrate according to Embodiment 2. FIG. 4 is a schematic cross-sectional view when electromagnetic induction heating is performed on a silicon substrate according to a third embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Silicon substrate, 16 Underlayer, 18 Sputtered metal layer, 20 Plating layer, 30 Wiring, 50 Plating area, 60 Non-plating area, 100 Treatment liquid tank, 110 Treatment liquid, 150 Mask, 151 Through-hole, 180 Protective film, 181 Through hole, 200 plating tank, 210 plating solution, 400 electromagnetic induction heater, 410 coil, 420 AC power supply

Claims (8)

An organic complexing agent is attached to a non-plating region of the material to be plated, and an electroless plating process is performed on the material to be plated to selectively form a plating layer in a plating region other than the non-plating region of the material to be plated. An electroless plating method characterized by the above. The organic complexing agent is attached to the material to be plated, and the plating region is selectively exposed to decompose only the non-plating region of the material to be plated by decomposing the organic complexing agent attached to the plating region. The electroless plating method according to claim 1, wherein the organic complexing agent is adhered. A protective film patterned so that the non-plating region is exposed on the material to be plated is immersed in the organic complexing agent, and then the non-plating material is removed by removing the protective film. The electroless plating method according to claim 1, wherein the organic complexing agent is attached only to a plating region. A metal layer is formed in the plating region of the material to be plated, and after the organic complexing agent is attached to the material to be plated, the metal layer is heated by induction heating and attached to the plating region. 2. The electroless plating method according to claim 1, wherein the organic complexing agent is adhered only to the non-plating region of the material to be plated by thermally decomposing the organic complexing agent. The surface-roughening process is performed to at least the non-plating area | region of the said to-be-plated material, before making the said organic complexing agent adhere to the said to-be-plated material, The Claim 1 characterized by the above-mentioned. Electroless plating method. The electroless plating method according to any one of claims 1 to 5, wherein the organic complexing agent is a surfactant. The electroless plating method according to any one of claims 1 to 6, wherein the organic complexing agent is a nonionic surfactant. The electroless plating method according to any one of claims 1 to 7, wherein at least a surface of the non-plating region of the material to be plated is made of silicon oxide.

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