JP2008081389A - Catalyst-aided chemical processing method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst-aided chemical processing method, by which hard-to-process materials, especially SiC, GaN, or the like, whose importance as electronic device materials increases these days, can be processed with high processing efficiency and high precision even for a space wavelength range of not less than several tens of μm. <P>SOLUTION: The catalyst-aided chemical processing method comprises: putting a workpiece 28 such as GaN or SiC in a processing liquid 22 in which halogen-containing molecules such as hydrofluoric acid or the like are dissolved; and moving the workpiece 28 and a catalyst 26 composed of molybdenum or a molybdenum compound relative to each other while bringing the catalyst 26 into contact with or close proximity to the surface to be processed of the workpiece 28, thereby processing the surface to be processed of the workpiece 28. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a catalyst-assisted chemical processing method and apparatus, and more particularly, to a catalyst-assisted chemical processing method and apparatus for processing a workpiece using a catalytic action capable of chemical reaction.

  In general, mechanical processing has been used in various scenes since ancient times. For example, in mechanical polishing, a tool is pressed against a surface to be processed, thereby introducing a material defect by a mechanical action and stripping off the surface atoms for processing. Such a mechanical polishing method damages the crystal lattice and makes it very difficult to obtain a highly accurate surface. Therefore, in order to create a thing with high accuracy, it is necessary to use chemical processing that can be processed without generating lattice defects.

  The suspension in which the ultrafine powder is dispersed is caused to flow along the work surface of the work piece, and the ultra fine powder is brought into contact with the work surface with almost no load. We already know the processing by so-called EEM (Elastic Emission Machining), which processes by removing the atoms on the surface to be processed in an order close to atomic units by the interaction (a kind of chemical bond) at the interface between the powder and the surface to be processed (Patent Documents 1 to 4).

  In addition, neutral radicals based on the reaction gas generated by the machining electrode to which a high voltage is applied are supplied to the work surface of the workpiece, and generated by a radical reaction between the neutral radicals and atoms or molecules on the work surface. The volatile material is removed by vaporization, and the processing electrode is processed while being changed relative to the surface to be processed, which is determined according to the type of reaction gas and the material of the workpiece. Plasma CVM (Chemical Vaporization Machining) is also proposed to perform machining by numerically controlling the machining time according to the coordinate difference based on the correlation data between the machining time and machining amount and the coordinate data of the previous machining surface and the target machining surface. (Patent Document 5).

  Furthermore, there is also a high-efficiency processing method by high-density radical reaction using a rotating electrode that rotates and rotates the rotating electrode to form a gas flow across the processing gap by entraining gas on the surface of the rotating electrode. It has been proposed (Patent Document 6).

  The aforementioned EEM and plasma CVM are very excellent as chemical processing. The EEM can obtain a smooth surface on an atomic scale, and the plasma CVM can perform highly efficient processing comparable to mechanical processing with high accuracy.

EEM can obtain a very smooth surface with respect to a high-frequency spatial wavelength in view of its processing principle. EEM is characterized in that fine particles such as SiO ₂ are supplied to the surface with ultrapure water, and the processing proceeds by the atoms on the surface of the fine particles and the atoms on the surface of the workpiece being chemically bonded. At this time, the surface of the fine particles is a very flat surface, which is considered to be a reference surface and transferred to the surface. Therefore, it is possible to create a flat surface with an atomic size order without disturbing the atomic arrangement. However, EEM is difficult to flatten the spatial wavelength region of several tens of μm or more because of its processing principle.

  Plasma CVM is an extremely efficient processing method because it uses active radicals. The processing of plasma CVM uses a chemical reaction between neutral radicals in the plasma and the surface of the workpiece, and generates a high-density plasma in a high-pressure atmosphere of 1 atm. Is made to act on atoms on the surface of the workpiece, and is converted into a volatile substance. Therefore, it has a machining efficiency comparable to conventional machining without disturbing the atomic arrangement of the work surface. However, since the processing method does not have a reference surface, it is easily affected by the index surface.

On the other hand, chemical mechanical polishing (CMP) uses SiO ₂ or Cr ₂ O ₃ as abrasive grains to reduce the mechanical action and attempt to form an undisturbed surface by the chemical action. For example, as shown in Patent Document 7, a method is disclosed in which a diamond thin film is immersed in an oxidizing polishing liquid in which abrasive grains having an oxidation catalytic action are dispersed, and the diamond thin film is polished while rubbing the thin film surface with abrasive grains. ing. Here, it is disclosed that chromium oxide or iron oxide is used as abrasive grains, and a polishing liquid in which the abrasive grains are dispersed in a hydrogen peroxide solution, a nitrate aqueous solution or a mixture thereof is disclosed.

  Further, the workpiece is disposed in a treatment liquid composed of hydrohalic acid, and a catalyst composed of platinum, gold, or a ceramic solid catalyst is disposed in contact with or in close proximity to the workpiece surface of the workpiece, There has been proposed a processing method for processing a workpiece by eluting a halogen compound generated by a chemical reaction between a halogen radical generated by molecular dissociation of hydrogen halide on the surface and a surface atom of the workpiece (patent) Reference 8).

Japanese Patent Publication No. 2-25745 Japanese Patent Publication No. 7-16870 Japanese Patent Publication No. 6-44989 JP 2000-167770 A Japanese Patent No. 2962583 Japanese Patent No. 3069271 Japanese Patent No. 3734722 JP 2006-114632 A

  In view of the above-mentioned situation, the present invention has a high processing efficiency and high accuracy over a spatial wavelength region of several tens of μm or more in difficult-to-work materials, particularly SiC and GaN, which have recently been increasing in importance as materials for electronic devices. The purpose is to propose a new processing method that can be processed. If the processing method is a mechanical processing method, lattice defects are introduced on the surface and high-precision processing becomes difficult, so that it must be a chemical processing method in consideration of crystallography. In the present invention, the principle of transferring the reference surface by a chemical reaction is used, but it is important that the reference surface does not change. This is because if the reference surface changes, the processing surface changes as processing proceeds. Therefore, the present invention proposes a catalyst-assisted chemical processing method and apparatus utilizing a catalytic action that allows a chemical reaction without changing the reference plane.

  In order to solve the above-mentioned problems, the present invention arranges a workpiece in a treatment solution in which molecules containing halogen are dissolved, and contacts or close proximity of a catalyst made of molybdenum or a molybdenum compound with the workpiece surface of the workpiece. The catalyst-assisted chemical processing method is characterized in that the processing surface of the workpiece is processed by moving the catalyst and the workpiece relative to each other.

  Here, it is preferable that the treatment liquid is hydrofluoric acid (HF aqueous solution). Moreover, it is preferable that the workpiece is one selected from Si, SiC, GaN, sapphire, ruby and diamond.

  The surface plate and the work piece are brought into contact with the work surface of the work piece held by a holder in the presence of the processing liquid on the surface of the flat surface plate having the catalyst on the surface. The surface to be processed of the workpiece can be processed flat by being moved relatively.

  Further, the present invention provides the workpiece in a processing solution in which molecules containing halogen are dissolved, and a catalyst made of platinum, gold, a ceramic-based solid catalyst, molybdenum, or a molybdenum compound is provided on the processing surface of the workpiece. A catalyst-assisted chemical processing method for processing a workpiece by placing it in contact or in close proximity, and applying a voltage between the workpiece surface of the workpiece and the catalyst during the processing, A light irradiation step of irradiating light on the workpiece surface during or before the machining, a workpiece temperature control step for controlling the temperature of the workpiece during the machining, and a temperature control of the processing liquid A processing solution temperature control step, and a catalyst temperature control step for controlling the temperature of the catalyst. A method is provided (claims) ).

By applying a voltage between the work surface of the work piece and the catalyst during processing, the dissociation reaction of the halogen-containing molecules is assisted, and the amount of halogen atoms generated on the catalyst surface is increased, thereby processing speed. Can be increased.
By irradiating the work surface of the workpiece with light during or before processing and exciting the work surface of the workpiece with light, the work surface can be activated to increase the processing speed.

  As is known from the Arrhenius equation, the higher the reaction temperature, the higher the chemical reaction. For this reason, the processing speed can be changed by controlling at least one of the temperature of the workpiece, the temperature of the processing liquid, and the temperature of the catalyst during the processing of the workpiece and controlling the reaction temperature.

  The catalyst-assisted chemical processing apparatus of the present invention includes a surface plate having a catalyst made of molybdenum or a molybdenum compound on the surface, a holder for holding the workpiece and bringing the processing surface of the workpiece into contact with the surface plate, A treatment liquid supply unit for supplying a treatment liquid in which molecules containing halogen are dissolved between the surface plate and a workpiece held in contact with the surface plate, and held by the surface plate and the holder. And a drive unit that relatively moves the workpiece brought into contact with the surface plate (Claim 6).

  Still another catalyst-assisted chemical processing apparatus according to the present invention includes a surface plate having a catalyst made of platinum, gold, a ceramic solid catalyst, molybdenum, or a molybdenum compound on the surface, and a workpiece that holds the workpiece. A processing solution in which molecules containing halogen are dissolved is supplied between a holder for bringing a surface to be processed into contact with the surface plate, and a workpiece held by the surface plate and the holder to be in contact with the surface plate. A voltage is applied between a processing liquid supply unit, a driving unit that relatively moves a workpiece held by the surface plate and the holder and brought into contact with the surface plate, and a work surface of the workpiece and the catalyst. A power source to be applied, a light source for irradiating light on the work surface of the work piece, a work piece temperature control mechanism for controlling the temperature of the work piece during the work, and a treatment liquid temperature control for controlling the temperature of the treatment liquid Mechanism and catalyst temperature control for controlling the temperature of the catalyst Having one or more of the mechanism (claim 7).

  The catalyst-assisted chemical processing method of the present invention uses a catalyst made of molybdenum (Mo) or a molybdenum compound as a processing reference surface, and generates halogen radicals by dissociating halogen-containing molecules in the treatment liquid on the surface of the catalyst. The processing proceeds by the halogen radicals and the OH radicals generated by decomposing water molecules by the halogen radicals acting on the surface to be processed. In the present invention, molybdenum or a molybdenum compound that performs a catalytic function is brought into contact with or in close proximity to a work surface in a processing solution without using abrasive grains or an abrasive, and the molybdenum or molybdenum compound and the work surface are moved relative to each other. As a result, a new work surface always appears and processing proceeds. Here, the radicals generated on the catalyst surface are inactivated rapidly when they are separated from the catalyst surface, so that the radicals are present only on the catalyst surface, which is the reference surface, or in the immediate vicinity of the surface. Can be processed in a controlled manner.

  Since the catalyst-assisted chemical processing method of the present invention is a chemical processing having a processing reference surface, it is possible to highly planarize a spatial wavelength region of several tens of μm or more, which was difficult with EEM and plasma CVM. it can. In addition to Si processing, SiC and GaN, which have been difficult to process, and sapphire, ruby and diamond can be processed with high precision and may be used in semiconductor manufacturing processes. .

  The catalyst-assisted chemical processing method of the present invention uses a platinum, gold or ceramic solid catalyst, molybdenum, or a molybdenum compound catalyst on the processing reference surface, and a treatment liquid in which molecules containing halogen are dissolved on the catalyst surface is a molecule. The workpiece is processed by dissociating to generate halogen radicals and eluting halogen compounds generated by chemical reaction between the surface atoms of the workpiece and the halogen radicals that are in contact with or in close proximity to the catalyst. Here, when a treatment liquid made of hydrohalic acid that is not or hardly soluble in a workpiece in a normal state is used, halogen radicals generated on the catalyst surface are separated from the catalyst surface. Chemical process where the halogen radicals exist only on the catalyst surface, which is the reference surface, or only in the immediate vicinity of the surface, so that the processing proceeds only directly below the reference surface consisting of the catalyst. Can be law.

  Next, the present invention will be described in more detail based on embodiments. The processing principle of the present invention is that a workpiece is disposed in a treatment solution in which molecules containing halogen are dissolved, and the catalyst made of molybdenum or a molybdenum compound is brought into contact with or in close proximity to the workpiece surface of the workpiece. The workpiece surface is processed by moving the workpiece relative to the workpiece.

  The conceptual diagram of the processing method of this invention which uses hydrofluoric acid (HF aqueous solution) as a process liquid is shown in FIG. As shown in FIG. 1A, when a catalyst 1 made of molybdenum (Mo) is placed in a treatment solution in which hydrogen fluoride (HF) is dissolved, HF 6 is dissociated on the surface of the catalyst 1 to form H atoms 7 and halogen. A radical (F radical) 8 is generated. Although this F radical 8 has a short lifetime but is very reactive, as shown in FIG. 1 (b), the catalyst 1 made of molybdenum (Mo) and the work surface of the work piece 2 are in contact with each other. When contacting or extremely approaching in hydrofluoric acid (HF aqueous solution), the surface atoms of the surface to be processed at the contact portion are dissolved in the treatment liquid by a chemical reaction. Then, as shown in FIG. 1C, when the catalyst 1 is separated from the workpiece surface of the workpiece 2, the radical reaction generated on the catalyst surface does not act on the workpiece surface, so that the dissolution reaction stops. Therefore, the work surface of the work piece 2 is processed only while the catalyst 1 is in contact or in close proximity.

  Here, when the workpiece 2 is SiC, as shown in the following (Chemical Formula 1), the SiC surface is fluorinated by F radicals (F.), and the portion is preferentially processed. Guessed.

(Chemical formula 1)
SiC + 8F ・ → SiF ₄ ↑ + CF ₄ ↑

  Such a catalyst-assisted chemical processing method according to the present invention has the following three characteristics. (1) Reactive species (halogen radicals) are created only on the reference surface (catalyst). (2) When separated from the reference plane, reactive species (halogen radicals) are inactivated. (3) The physical properties of the reference surface do not change for a long time.

  The advantages of the present invention obtained by having such characteristics will be described below. Since “reactive species are created only on the reference surface”, it can be processed without being affected by the surface index of the surface unlike chemical etching. Since “reactive species are inactivated when leaving the reference plane”, it becomes a chemical processing method for transferring the reference plane, and flattening at the atomic scale as seen by EEM can be expected. Since “the physical properties of the reference surface do not change for a long time”, even if the reference surface is transferred and processing proceeds, the surface of the reference surface does not change. In other words, from the above, it is considered that this catalyst-assisted chemical processing method may be an efficient ultraprecision processing method.

  Here, although the hydrofluoric acid is mentioned as said process liquid, not only hydrofluoric acid but another hydrogen halide solution can also be used by the combination of a to-be-processed object, processing conditions, etc.

(Example 1)
In order to confirm the processing principle of the catalyst-assisted chemical processing method of the present invention, a processing apparatus was produced. A conceptual diagram of the processing apparatus for the basic experiment is shown in FIG. This processing apparatus is fixed to the bottom surface of the chemical solution tank 12, the chemical solution tank 12 that is opened upward to fix the processing sample 10 on the bottom surface and fills the inside with the chemical solution, the drive mechanism 14 that reciprocates the chemical solution tank 12 in one direction. The coin-shaped catalyst 16 that contacts the surface (processed surface) of the processed sample 10 with a predetermined pressing force is provided. The coin-shaped catalyst 16 comes into contact with the surface of the processed sample 10 at its lower end, and the processed sample 10 reciprocates in parallel with the surface of the coin-shaped catalyst 16, thereby linearizing the surface of the processed sample 10. It is designed to be processed (grooved) in the depth direction along.

  Then, molybdenum (Mo) having a purity of 99.95% is used as a material for the coin-shaped catalyst 16 and hydrofluoric acid (50% HF) is used as a chemical solution, respectively, and is made of GaN soaked in hydrofluoric acid. The processed sample 10 was reciprocated at 10 mm / sec while the coin-shaped catalyst 16 was in contact with the surface of the processed sample 10 to groove the surface of the processed sample (GaN) 10 for 3 hours.

  The processing results at this time are shown in FIGS. Here, FIG. 3 shows a perspective view of the processed sample surface after processing, and FIG. 4 shows a cross-sectional profile of the processed sample after processing. As shown in FIGS. 3 and 4, on the surface of the processed sample made of GaN, grooves (concave portions) extending in two lines that are processed into a linear shape in contact with a coin-shaped catalyst made of molybdenum are formed, Thereby, it turns out that GaN can be processed with the coin-shaped catalyst which consists of molybdenum.

As Comparative Example 1, platinum (Pt) having a purity of 99.98% was used as the coin-shaped catalyst 16, and the other conditions were the same as in Example 1, and the surface of the processed sample 10 made of GaN was applied for 3 hours. processed.
The processing results at this time are shown in FIGS. Here, FIG. 5 shows a perspective view of the processed sample surface after processing, and FIG. 6 shows a cross-sectional profile of the processed sample after processing. As shown in FIGS. 5 and 6, the surface of the processed sample made of GaN after processing is a flat surface without forming a groove (concave portion). It turns out that GaN cannot be processed.

  GaN, which is generally difficult to chemically etch, can be easily processed by simply rubbing it with a catalyst made of molybdenum in hydrofluoric acid (50% HF). In addition, it is considered that the reference surface was transferred because only the coin catalyst which is the reference surface was processed. That is, the usefulness of the newly proposed catalyst-assisted chemical processing method could be demonstrated. Further, hydrofluoric acid (50% HF) is inexpensive and relatively easy to handle, so that the present invention can be said to be beneficial from a practical viewpoint.

For example, since F radicals are very active, it is difficult to generate a sufficient amount of F radicals only by dissociative adsorption by the catalytic action of molybdenum, for example. Therefore, when hydrofluoric acid (HF aqueous solution) is used as the treatment liquid, a voltage is applied between the molybdenum catalyst and the workpiece to assist the dissociation reaction of HF, and halogen on the catalyst surface. By increasing the amount of atoms generated, the processing speed can be increased. Thus, when an HF aqueous solution is used as the treatment liquid, the voltage applied between the molybdenum catalyst and the workpiece is about 3 V, which is the standard electrode voltage value of the HF decomposition reaction shown in the following reaction formula. preferable.
F ₂ + 2H ⁺ + 2e ⁻ = 2HF + 3.053 eV

  In FIG. 7, hydrofluoric acid (HF aqueous solution) is used as a treatment liquid, and a voltage is applied between the catalyst 1 made of molybdenum (Mo) and the workpiece 2 to process the surface of the workpiece 2. The conceptual diagram of the processing method made to do is shown. As shown in FIG. 7, a power source 40 capable of reversing the anode and the cathode is provided, and a lead wire 44a extending from one pole of the power source 40 and having a switch 42 interposed between the catalyst 1 and the other pole of the power source 40. The extending conducting wires 44b are connected to the workpiece 2, respectively. Others are the same as those shown in FIG.

  Even in this case, as shown in FIG. 7A, when the catalyst 1 and the workpiece 2 are arranged in the treatment liquid in which hydrogen fluoride (HF) is dissolved, HF6 is dissociated on the surface of the catalyst 1. Thus, H atoms 7 and halogen radicals (F radicals) 8 are generated. In this state, as shown in FIG. 7 (b), when the switch 42 is turned ON and a voltage is applied between the catalyst 1 and the workpiece 2 so that the catalyst 1 becomes an anode, for example, the surface of the catalyst 1 ( The surface facing the workpiece 2) becomes the active region 1a, the dissociation reaction of HF6 on the surface of the catalyst 1 is promoted, and a large amount of F radicals 8 are generated. In this state, as shown in FIG. 7 (c), when the catalyst 1 is brought into contact with or very close to the work surface of the work piece 2, the surface atoms of the work surface at the contact portion are dissolved in the processing liquid by a chemical reaction. Is done. At this time, processing of the workpiece 2 is promoted by the active region 1a of the catalyst 1 in which a large amount of F radicals 8 are present.

  And as shown in FIG.7 (d), when the catalyst 1 is separated from the to-be-processed surface of the to-be-processed object 2, since the radical produced | generated on the catalyst surface will not act on the to-be-processed surface, a dissolution reaction will stop, Further, by turning off the switch 42, the surface of the catalyst 1 is no longer an active region. Therefore, the work surface of the work piece 2 is processed only while the catalyst 1 is in contact or in close proximity.

(Examples 2 to 7)
In order to confirm the processing principle shown in FIG. 7, a processing apparatus was produced. FIG. 8 shows a conceptual diagram of the basic experimental processing apparatus. The processing device is different from the processing device shown in FIG. 2 in that a voltage can be applied between the processed sample 10 and the coin-shaped catalyst 16 via the power source 18. Other configurations are the same as those of the processing apparatus shown in FIG.

  Then, molybdenum (Mo) having a purity of 99.95% is used as a material for the coin-shaped catalyst 16 and hydrofluoric acid (50% HF) is used as a chemical solution, respectively, and SiC is immersed in hydrofluoric acid. While the coin-shaped catalyst 16 was brought into contact with the surface of the processed sample 10 with an additional load of 74 g, the processed sample 10 was reciprocated at 3 mm / sec to groove the surface of the processed sample (SiC) 10 for 1 hour. During this processing, a voltage of 1 V was applied between the processed sample 10 and the coin-shaped catalyst 16 with the coin-shaped catalyst 16 as an anode (Example 2).

  The processing results at this time are shown in FIGS. Here, FIG. 9 shows a perspective view of the processed sample surface after processing, and FIG. 10 shows a cross-sectional profile of the processed sample after processing. As a result, a groove having a depth of about 200 nm could be processed on the processed sample surface. For reference, the surface of the processed sample before processing is shown in FIG. 11, and the processed sample (SiC) 10 is processed without applying a voltage between the processed sample 10 and the coin-shaped catalyst 16 in FIGS. 12 and 13. Results are shown when done. 12A is a perspective view of the surface of the processed sample, FIG. 12B is a partially enlarged view of FIG. 12A, and FIG. 13 is a cross-sectional profile of the processed sample after processing. Show. In this case, a groove having a depth of about 175 nm could be processed on the processed sample surface.

  Thus, processing is performed without applying a voltage by processing SiC while applying a voltage of 1 V with the coin-shaped catalyst 16 as an anode between the processed sample (SiC) 10 and the coin-shaped catalyst 16. It can be seen that the processing speed of SiC can be increased.

  As Example 3, a 2 V voltage with the coin-shaped catalyst 16 as an anode was applied between the processed sample 10 and the coin-shaped catalyst 16, and the other conditions were the same as in Example 2, and the processed sample made of SiC. Ten surfaces were processed for 1 hour. The processing results at this time are shown in FIGS. Here, FIG. 14 shows a perspective view of the processed sample surface after processing, and FIG. 15 shows a cross-sectional profile of the processed sample after processing. As a result, a groove having a depth of about 200 to 250 nm could be processed on the processed sample surface.

  As Example 4, a 3 V voltage using the coin-shaped catalyst 16 as an anode was applied between the processed sample 10 and the coin-shaped catalyst 16, and the other conditions were the same as in Example 2, and the processed sample made of SiC was used. Ten surfaces were processed for 1 hour. The processing results at this time are shown in FIGS. Here, FIG. 16 shows a perspective view of the processed sample surface after processing, and FIG. 17 shows a cross-sectional profile of the processed sample after processing. As a result, a groove having a depth of about 200 to 250 nm could be formed on the processed sample surface.

  From Examples 3 and 4, when an aqueous HF solution is used as the treatment liquid, the voltage applied between the molybdenum catalyst and the workpiece is preferably about 3 V, which is the standard electrode voltage value of the HF decomposition reaction. I understand.

  As Example 5, a voltage of 1V (-1V) using the coin-shaped catalyst 16 as a cathode was applied between the processed sample 10 and the coin-shaped catalyst 16, and the other conditions were the same as in Example 2 except that SiC. The surface of the processed sample 10 made of was processed for 1 hour. The processing results at this time are shown in FIGS. Here, FIG. 18 shows a perspective view of the processed sample surface after processing, and FIG. 19 shows a cross-sectional profile of the processed sample after processing. As a result, a groove having a depth of about 100 nm could be formed on the surface of the processed sample.

  As Example 6, a voltage of 2 V (−2 V) using the coin-shaped catalyst 16 as a cathode was applied between the processed sample 10 and the coin-shaped catalyst 16, and the other conditions were the same as in Example 2 except that SiC. The surface of the processed sample 10 made of was processed for 1 hour. The processing results at this time are shown in FIGS. Here, FIG. 20 shows a perspective view of the processed sample surface after processing, and FIG. 21 shows a cross-sectional profile of the processed sample after processing. As a result, a groove having a depth of about 80 nm could be formed on the surface of the processed sample.

  As Example 7, a voltage of 3 V (−3 V) using the coin-shaped catalyst 16 as a cathode was applied between the processed sample 10 and the coin-shaped catalyst 16, and the other conditions were the same as in Example 2 except that SiC. The surface of the processed sample 10 made of was processed for 1 hour. The processing results at this time are shown in FIGS. Here, FIG. 22 shows a perspective view of the processed sample surface after processing, and FIG. 23 shows a cross-sectional profile of the processed sample after processing. As a result, a groove having a depth of about 100 nm could be formed on the surface of the processed sample.

  When comparing Examples 2 to 4 and Examples 5 to 7, when hydrofluoric acid is used as the treatment liquid and molybdenum is used as the catalyst, and SiC is processed, the space between the catalyst and the workpiece is determined. By applying the catalyst to the anode as compared with the case where no voltage is applied, the processing speed of SiC can be increased, but if a voltage using the catalyst as the cathode is applied between the catalyst and the workpiece, On the contrary, it can be seen that when the SiC processing speed is reduced and the applied voltage is increased, the surface flatness deteriorates.

  In the above example, hydrofluoric acid is used as the treatment liquid and molybdenum is used as the catalyst, and the surface of the workpiece is processed while applying a voltage between the catalyst and the workpiece. . Thus, when processing the surface of a workpiece while applying a voltage between the catalyst and the workpiece, platinum, gold, a ceramic solid catalyst or a molybdenum alloy is used as a catalyst in addition to molybdenum. May be used. Also in this manner, as shown in FIG. 7B, the surface of the catalyst made of platinum, gold, or the like (the surface facing the workpiece) is used as an active region, and the halogen radical dissociation reaction on the catalyst surface is performed. It can be promoted and a large amount of halogen radicals can be generated to improve the processing speed.

  For example, wide band gap materials such as SiC and GaN are chemically very stable, so that even when halogen atoms generated by dissociative adsorption by molybdenum catalysis react, a sufficient reaction rate can be obtained. difficult. Therefore, the processing speed can be increased by irradiating the workpiece surface (work surface) with light during the reaction to activate the work surface. The wavelength of the light irradiated at this time is equal to or less than the wavelength corresponding to the band gap of the workpiece, for example, the band gap of 4H-SiC is 3.26 eV. Therefore, when processing SiC, the band gap of GaN is 383 nm or less. Is 3.42 eV, and when processing GaN, it is preferably 365 nm or less.

In FIG. 24, hydrofluoric acid (HF aqueous solution) is used as the treatment liquid, and molybdenum (Mo) is used as the catalyst 1, and the surface (working surface) of the work piece 2 is irradiated with light to process the work piece. The conceptual diagram of the processing method which processed the surface of 2 is shown. As shown in FIG. 24, a light source 50 is provided above the catalyst 1, and an excitation light transmission window 52 is provided between the catalyst 1 and the light source 50, and light passes through the catalyst 1 vertically. A number of light passage holes 1b are provided. Others are the same as those shown in FIG. Thus, by inserting the excitation light transmission window 52 that transmits light from the light source 1 between the catalyst 1 and the light source 50, the light source 1 is corroded by the treatment liquid in which hydrogen fluoride (HF) or the like is dissolved. Can be prevented. The material used for the excitation light transmitting window 52 is preferably a fluoride glass such as CaF ₂ .

  Even in this case, as shown in FIG. 24A, when the catalyst 1 and the workpiece 2 are arranged in the treatment liquid in which hydrogen fluoride (HF) is dissolved, HF is dissociated on the surface of the catalyst 1. Thus, H atoms 7 and halogen radicals (F radicals) 8 are generated. Then, the surface (working surface) of the workpiece 2 is irradiated with light having a wavelength equal to or less than the wavelength corresponding to the band gap of the workpiece 2 from the light source 50, for example, and the surface (working surface) of the workpiece 2 is irradiated. The excited portion 2a is activated. In this state, as shown in FIG. 24 (b), when the catalyst 1 is brought into contact with or very close to the work surface of the work piece 2, the surface atoms of the work surface at the contact portion are dissolved in the processing liquid by a chemical reaction. Is done. At this time, the surface to be processed is an excited portion 2a excited by light and is activated, so that the processing speed is increased. Then, as shown in FIG. 24 (c), when the catalyst 1 is separated from the workpiece surface of the workpiece 2, the radical reaction generated on the catalyst surface does not act on the workpiece surface, so that the dissolution reaction stops, Further, when the light irradiation is stopped, the surface of the workpiece 2 is not an active part. Therefore, the work surface of the work piece 2 is processed only while the catalyst 1 is in contact or in close proximity.

  In the above example, hydrofluoric acid is used as the treatment liquid and molybdenum is used as the catalyst, and the surface of the workpiece is processed while irradiating light on the surface of the workpiece (processing surface). I have to. Thus, when processing the surface of the workpiece while irradiating light on the surface of the workpiece (processing surface), in addition to molybdenum, platinum, gold, a ceramic solid catalyst or A molybdenum alloy may be used. Also by this, as shown in FIG. 24 (a), the processing surface can be activated by being an excited portion excited by light, and the processing speed can be improved.

  As is known from the Arrhenius equation, the reaction rate of a chemical reaction increases as the reaction temperature increases. This processing method is based on chemical reactions. Therefore, the processing speed can be controlled by controlling at least one of the temperature of the workpiece, the temperature of the treatment liquid, and the temperature of the catalyst to control the temperature at which the chemical reaction occurs.

  FIG. 25 shows a simplified perspective view of a catalyst-assisted chemical processing apparatus applied to the polishing apparatus according to the embodiment of the present invention. The polishing apparatus (catalyst-assisted chemical processing apparatus) 20 includes a container 24 filled with a treatment liquid 22, a catalyst surface plate 26 made of molybdenum or a molybdenum alloy and rotatably disposed in the container 24. A holder 30 is provided for holding the workpiece 28 in a detachable manner with the workpiece surface facing downward. The holder 30 is made of, for example, SiC excellent in processability, chemical resistance and temperature resistance, but may be made of hard vinyl chloride or PEEK material, and is parallel to the rotational axis of the catalyst surface plate 26. And it is connected with the front-end | tip of the rotating shaft 32 which can be moved up and down provided in the eccentric position. Since the holder 30 is pivotally supported (ball bearing supported) with respect to the rotating shaft 32, the workpiece holding surface of the holder 30 can follow the surface of the catalyst surface plate 26, and the workpiece 28 is The catalyst surface plate 26 can be brought into surface contact.

  Accordingly, the catalyst platen 26 and the workpiece 28 are rotated while the vessel 24 is filled with the processing liquid and the workpiece 28 held by the holder 30 is pressed against the catalyst platen 26 with a predetermined pressure. The surface (lower surface) of the object 28 is processed to be flat. In addition, the surface of the catalyst surface plate 26 is appropriately provided with a knitted, concentric, or spiral groove structure so that fresh processing liquid is supplied to the processing region as the catalyst surface plate 26 rotates. Is possible.

  In addition, the catalyst platen 26 and the workpiece 28 are not limited to the immersion type in which the catalyst platen 26 and the workpiece 28 are arranged in the container 24 filled with the treatment liquid, and the catalyst is supplied from a nozzle (not shown) arranged above the catalyst platen 26. A processing liquid may be supplied between the surface plate 26 and the workpiece 28. When the treatment liquid is recycled, it is preferably purified and reused in order to remove sludge. Moreover, the form which turned upside down with FIG. 25 may be sufficient. In that case, the work surface is arranged with the work surface facing upward, and the catalyst surface plate placed above the work surface may be brought close to the work piece with light contact or with a small interval. Good.

  Then, molybdenum (Mo) or a molybdenum compound is used as a material for the catalyst surface plate 26, and a solution in which molecules containing hydrofluoric acid or halogen are used as the treatment liquid 22, respectively, and a workpiece made of a SiC wafer or the like. 28 surfaces are processed.

(Example 8)
In the polishing apparatus shown in FIG. 25, molybdenum (Mo) having a purity of 99.95% is used as the material of the catalyst surface plate 26, and hydrofluoric acid (50% HF) is used as the treatment liquid 22, respectively. The surface of a processed sample composed of a SiC wafer immersed in the substrate is processed flat for 18 hours by applying a load of 5 kg to a 2-inch wafer while rotating both the catalyst surface plate 26 and the processed sample at 20 rpm. did. When the weight of the processed sample (SiC wafer) was measured before and after processing, the weight of the processed sample, which was 2.4368 g before processing, changed to 2.4357 g after processing, and the processing amount was 0.0011 g. It corresponds to 1.8 μm in terms of thickness.

  As Comparative Example 2, platinum (Pt) having a purity of 99.98% was used as the material of the catalyst surface plate 26, and the other conditions were the same as in Example 2, and the surface of the processed sample made of the SiC wafer was kept for 18 hours. It was processed to be flat. When the weight of the processed sample (SiC wafer) was measured before and after processing, the weight of the processed sample, which was 2.4310 g before processing, was changed to 2.4308 g after processing, and the processing amount was 0.0002 g. It corresponds to 0.3 μm in terms of thickness.

  Thus, it can be seen that, when processing (polishing) SiC, using molybdenum as the catalyst surface plate 26 provides a processing speed of about 6 times that when using platinum. This is thought to be because the reaction in which HF dissociates and H atoms and F radicals are generated is more likely to occur on the surface of the catalyst plate 26 made of molybdenum than platinum.

  FIG. 26 is a simplified perspective view of a catalyst-assisted chemical processing apparatus according to another embodiment of the present invention applied to a polishing apparatus. The polishing apparatus (catalyst assisted chemical processing apparatus) 20a shown in FIG. 26 differs from the polishing apparatus (catalyst assisted chemical processing apparatus) 20 shown in FIG. 25 in that it includes a power source 34 that can invert the anode and the cathode, A conductor 38a extending from one pole of the power supply 34 and having a switch 36 interposed therebetween is connected to the catalyst surface plate 26, and a conductor 38b extending from the other pole of the power supply 34 is connected to the workpiece 28. is there. In this example, platinum, gold, or a ceramic solid catalyst can be used as the catalyst surface plate 26 in addition to molybdenum or a molybdenum alloy.

As schematically shown in FIG. 24, a large number of light passage holes are provided inside the catalyst surface plate 26, and a light source is disposed below the catalyst surface plate 26, so that the surface of the workpiece 28 (the object to be processed). The surface) may be irradiated with light having a wavelength corresponding to the band gap of the workpiece 28 or less. At this time, an excitation light transmission window that transmits light from the light source is inserted between the light source and the treatment liquid in which hydrogen fluoride (HF) is dissolved, so that the light source is dissolved in hydrogen fluoride (HF) or the like. Corrosion by liquid can be prevented. The material used for the excitation light transmitting window is preferably a fluoride glass such as CaF ₂ .

  In this example, the catalyst platen 26 and the workpiece 28 are rotated while the workpiece 24 is filled with the processing liquid and the workpiece 28 held by the holder 30 is pressed against the catalyst platen 26 with a predetermined pressure. Thus, the surface (lower surface) of the workpiece 28 is processed to be flat. At this time, a predetermined voltage using, for example, the catalyst platen 26 as an anode is applied between the catalyst platen 26 and the workpiece 28 as necessary. Moreover, when a light source is provided, the light of a predetermined frequency is irradiated to the surface (processed surface) of the workpiece 28 as needed.

  FIG. 27 shows a simplified perspective view of a catalyst-assisted chemical processing apparatus according to another embodiment of the present invention applied to a polishing apparatus. The polishing apparatus (catalyst-assisted chemical processing apparatus) 20b shown in FIG. 27 is different from the polishing apparatus (catalyst-assisted chemical processing apparatus) 20 shown in FIG. 25 as follows. That is, a heater 70 as a temperature control mechanism for controlling the temperature of the workpiece 28 held by the holder 30 is embedded in the holder 30 so as to extend to the rotary shaft 32. Above the container 24, a processing liquid supply nozzle 74 is disposed as a temperature control mechanism for supplying the processing liquid controlled to a predetermined temperature by the heat exchanger 72 into the container 24. Furthermore, a fluid flow path 76 as a temperature control mechanism for controlling the temperature of the catalyst surface plate 26 is provided inside the catalyst surface plate 26.

  In this example, the heater 70 as a temperature control mechanism for controlling the temperature of the workpiece 28, the treatment liquid supply nozzle 74 as a temperature control mechanism for controlling the temperature of the treatment liquid, and the temperature of the catalyst surface plate 26 are controlled. Although an example in which the fluid flow path 76 is provided as a temperature control mechanism is shown, any one may be provided. In this example, as in the example shown in FIG. 26, platinum, gold, or a ceramic solid catalyst can be used as the catalyst platen 26 in addition to molybdenum or a molybdenum alloy.

  As is known from the Arrhenius equation, the higher the reaction temperature, the higher the chemical reaction. According to this example, the processing speed can be changed by controlling the reaction temperature by controlling at least one of the temperatures of the workpiece 28, the treatment liquid, and the catalyst surface plate 26.

  The present invention is not limited to the uniaxial processing and planar processing exemplified in the above embodiment, and various types of processing such as processing to a desired shape by bringing a spherical or cylindrical catalyst into contact with a three-dimensional sample. It can be applied to the removal process. Further, the above-described voltage application, light irradiation, and temperature control may be performed alone or in an appropriate combination to promote processing.

The processing conceptual diagram of the catalyst-assisted chemical processing method of the present invention is shown, wherein (a) is a reaction species in which the halogen-containing molecules are dissociated on the molybdenum catalyst surface disposed in the treatment liquid in which the halogen-containing molecules are dissolved. (B) is a concept in which the molybdenum catalyst shown in (a) is brought into contact with or in close proximity to the work surface of the work piece, and the reaction species produced on the catalyst surface and the work piece. The concept that the workpiece surface atoms are dissolved in the processing liquid by the chemical reaction of the surface atoms and the processing proceeds, (c) is because the molybdenum catalyst shown in (b) is separated from the processing surface of the workpiece. Each shows how the reaction stops. It is a perspective view which shows the concept of the processing apparatus for basic experiments which implements the method shown in FIG. 2 is a perspective view showing a processed sample surface after processing in Example 1. FIG. 2 is a cross-sectional profile of a processed sample after processing in Example 1. 6 is a perspective view showing a processed sample surface after processing in Comparative Example 1. FIG. 3 is a cross-sectional profile of a processed sample after processing in Comparative Example 1. The processing conceptual diagram of the other catalyst assistance type chemical processing method of this invention is shown, (a) is a figure equivalent to Fig.1 (a), (b) is when a voltage is applied between a catalyst and a to-be-processed object. (C) is a diagram corresponding to FIG. 1 (b), and (d) is a diagram corresponding to FIG. 1 (c). It is a perspective view which shows the concept of the processing apparatus for basic experiments which implements the method shown in FIG. 6 is a perspective view showing a processed sample surface after processing in Example 2. FIG. 3 is a cross-sectional profile of a processed sample after processing in Example 2. It is a perspective view which shows the process sample surface before a process. (A) is a perspective view which shows the processed sample surface when processing a processed sample (GaN) without applying a voltage between a processed sample and a coin-shaped catalyst, (b) is the part of (a) It is an enlarged view. It is a cross-sectional profile of a processed sample when the processed sample (SiC) is processed without applying a voltage between the processed sample and the coin-shaped catalyst. 6 is a perspective view showing a processed sample surface after processing in Example 3. FIG. 6 is a cross-sectional profile of a processed sample after processing in Example 3. It is a perspective view which shows the process sample surface after the process in Example 4. FIG. 6 is a cross-sectional profile of a processed sample after processing in Example 4. FIG. 10 is a perspective view showing a processed sample surface after processing in Example 5. 7 is a cross-sectional profile of a processed sample after processing in Example 5. It is a perspective view which shows the process sample surface after the process in Example 6. FIG. 10 is a cross-sectional profile of a processed sample after processing in Example 6. It is a perspective view which shows the process sample surface after the process in Example 7. FIG. 10 is a cross-sectional profile of a processed sample after processing in Example 7. The processing conceptual diagram of the further another catalyst assisted chemical processing method of this invention is shown, (a) is the concept which irradiates light to the to-be-processed surface of a workpiece, (b) is processing of a catalyst and a to-be-processed object. The concept that the workpiece surface atoms are dissolved in the processing liquid by the chemical reaction between the reactive species generated on the catalyst surface and the workpiece surface atoms by bringing the surface into contact or in close proximity, and the processing proceeds (c ) Shows how the processing reaction stops due to the separation of the catalyst and the processed surface of the workpiece. It is a perspective view which shows the outline | summary of the catalyst assistance type chemical processing apparatus applied to the polishing apparatus of embodiment of this invention. It is a perspective view which shows the outline | summary of the catalyst assistance type chemical processing apparatus applied to the polishing apparatus of other embodiment of this invention. It is a perspective view which shows the outline | summary of the catalyst assistance type chemical processing apparatus applied to the polishing apparatus of further another embodiment of this invention.

Explanation of symbols

1 Catalyst 2 Workpiece 6 Hydrogen fluoride (HF)
7 H atom 8 F radical 10 Processing sample 12 Chemical solution tank 14 Drive mechanism 16 Coin-shaped catalyst 18, 34, 40 Power source 20, 20a, 20b Polishing device (catalyst-assisted chemical processing device)
22 Processing liquid 24 Container 26 Catalyst surface plate 28 Workpiece 30 Holder 32 Rotating shaft 50 Light source 70 Heater (temperature control mechanism)
74 Treatment liquid supply nozzle (temperature control mechanism)
76 Fluid flow path (temperature control mechanism)

Claims (7)

  The workpiece is placed in a treatment solution in which molecules containing halogen are dissolved, and the catalyst and the workpiece are moved relative to each other while the catalyst made of molybdenum or a molybdenum compound is in contact with or in close proximity to the workpiece surface. A catalyst-assisted chemical processing method characterized by processing a processed surface of a workpiece.   The catalyst-assisted chemical processing method according to claim 1, wherein the treatment liquid is hydrofluoric acid.   The catalyst-assisted chemical processing method according to claim 1 or 2, wherein the workpiece is one selected from Si, SiC, GaN, sapphire, ruby and diamond.   The surface plate and the work piece are brought into contact with the work surface of the work piece held by a holder in the presence of the processing liquid on the surface of the flat surface plate having the catalyst on the surface. The catalyst-assisted chemical processing method according to any one of claims 1 to 3, wherein the processing surface of the workpiece is processed flat by being moved relatively. The workpiece is placed in a treatment solution in which molecules containing halogen are dissolved, and a catalyst made of platinum, gold, a ceramic-based solid catalyst, molybdenum, or a molybdenum compound is brought into contact with or in close proximity to the machining surface of the workpiece. A catalyst-assisted chemical processing method for processing a workpiece,
A voltage applying step of applying a voltage between the workpiece surface of the workpiece and the catalyst during the machining, a light irradiation step of irradiating the workpiece surface of the workpiece during or before the machining, the machining One of a workpiece temperature control step for controlling the temperature of the workpiece in the inside, a treatment liquid temperature control step for controlling the temperature of the treatment liquid, and a catalyst temperature control step for controlling the temperature of the catalyst or A catalyst-assisted chemical processing method characterized by processing a workpiece by applying two or more types in combination. A surface plate having a catalyst made of molybdenum or a molybdenum compound on the surface;
A holder for holding a workpiece and contacting the surface of the workpiece with the surface plate;
A treatment liquid supply unit for supplying a treatment liquid in which molecules containing halogen are dissolved between the surface plate and a workpiece held by the holder and brought into contact with the surface plate;
A catalyst-assisted chemical processing apparatus, comprising: a drive unit configured to relatively move the surface plate and a workpiece held by the holder and brought into contact with the surface plate. A surface plate having a catalyst made of platinum, gold, a ceramic solid catalyst, molybdenum, or a molybdenum compound on the surface;
A holder for holding a workpiece and contacting the surface of the workpiece with the surface plate;
A treatment liquid supply unit for supplying a treatment liquid in which molecules containing halogen are dissolved between the surface plate and a workpiece held by the holder and brought into contact with the surface plate;
A drive unit for relatively moving the surface plate and the work piece held by the holder and brought into contact with the surface plate;
A power source for applying a voltage between the workpiece surface of the workpiece and the catalyst, a light source for irradiating light on the workpiece surface of the workpiece, and a workpiece temperature for controlling the temperature of the workpiece during the machining A catalyst-assisted chemical processing comprising a control mechanism, a treatment liquid temperature control mechanism for controlling the temperature of the treatment liquid, and a catalyst temperature control mechanism for controlling the temperature of the catalyst. apparatus.

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