JP2008071857A - Catalytic chemical processing method and apparatus using magnetic fine particles - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalytic chemical processing method and apparatus using magnetic fine particles capable of processing a difficult-to-process workpiece, especially SiC, GaN, etc. with high processing efficiency and with high precision based on a processing principle utilizing a catalytic action enabling the chemical reaction introducing no lattice defect into the surface of the workpiece, and capable of obtaining a crystallographically excellent processed surface. <P>SOLUTION: The workpiece 7 is provided in a solution of an oxidizer 2 and is constrained to a surface plate 4 or a processing head by a magnetic field, and the spatially controlled magnetic fine particles 9 of a transition metal are brought into contact with the processed surface of the workpiece under a very low load and the processed surface and the magnetic fine particles are relatively displaced to remove or elute the compound formed by the chemical reaction between the active species having an oxidizing power formed on the surface of the magnetic fine particles and the surface atoms of the workpiece caused by the catalytic action of the magnetic fine particles, thereby the workpiece is processed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a catalytic chemical processing method and apparatus using magnetic fine particles, and more particularly, uses magnetic fine particles for processing a workpiece using active species generated by decomposing molecules in a processing solution with a catalyst. The present invention relates to a catalytic chemical processing method and apparatus.

  Conventionally, a method of processing with high accuracy without introducing lattice defects or a thermally deteriorated layer on a processing surface of a workpiece has been proposed. For example, a suspension in which ultra fine 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 in a substantially unloaded state. We already know the processing by so-called EEM (Elastic Emission Machining), which removes and processes the workpiece surface atoms on the order of atomic units by the interaction (a kind of chemical bond) at the interface between the ultrafine powder and the workpiece surface. (Patent Documents 1 to 3).

The 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 ultra-pure water supplies fine particles such as SiO _{2 with} a particle size of about 0.1 μm to the surface, and the processing proceeds as atoms on the surface of the fine particles and atoms on the surface of the workpiece are chemically bonded. It is. At this time, the fine particles are supplied along the surface to be processed by the shear flow of ultrapure water, and the fine protrusions on the surface to be processed are selectively removed, so that the atomic arrangement is flat without disturbing the atomic arrangement. It is possible to create a 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 to form a non-disturbed surface by the chemical action. For example, as shown in Patent Document 4, a method of polishing a diamond thin film while immersing a diamond thin film in an oxidizing polishing liquid in which abrasive grains having an oxidation catalytic action are dispersed and rubbing the surface of the thin film with abrasive grains is disclosed. 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, Patent Document 5 describes that a polishing cloth used for CMP has a catalytic function for promoting the oxidizing power of an oxidizing agent contained in a CMP slurry. This catalytic action exhibits a catalytic effect from the moment when the slurry and the polishing cloth come into contact until the slurry reaches the object to be processed. Specifically, hydrogen peroxide, persulfate, excess At least one kind of iodine hydrochloric acid is used, and a metal composed of iron, silver, titanium, ruthenium and platinum is used as a component having a catalytic action. Here, the catalytic component is present in a predetermined shape of the polishing cloth in the form of a lattice or a donut, or is uniformly present in all areas of the polishing cloth.

Patent Document 6 discloses that CMP is performed using a polishing pad containing at least one soluble metal catalyst having a plurality of oxidation states, using a solution containing hydrogen peroxide as an oxidizing agent and alumina or silica as an abrasive. The points to do are described. Specifically, it is disclosed that the most preferable catalyst is a compound of iron, copper, silver having a plurality of oxidation states and any combination thereof, and a particularly preferable catalyst is ferric nitrate.
Japanese Patent Publication No. 2-25745 Japanese Patent Publication No. 7-16870 JP 2000-167770 A Japanese Patent No. 3734722 JP 2002-299294 A Special table 2004-526302 gazette

  The above-mentioned EEM processing method provides a crystallographically excellent processing surface, but is a very soft processing method by a kind of chemical reaction between the fine particles and the surface atoms of the workpiece, so the processing speed is slow, In particular, it is not suitable for the processing of SiC and GaN, which are becoming increasingly important as materials for electronic devices in recent years. Further, in CMP, polishing is basically performed by pressing the work surface with a polishing pad, so that it is inevitable that scratches are caused by abrasive grains or slurry.

  Therefore, in view of the above-mentioned situation, the present invention is to propose a new processing method capable of processing difficult work, particularly SiC, GaN, etc., with high processing efficiency and high accuracy. With the goal. That is, the present invention is a catalyst using magnetic fine particles that can obtain a crystallographically excellent processed surface based on a processing principle using a catalytic action capable of chemical reaction without introducing lattice defects on the surface of the workpiece. A chemical processing method and apparatus are proposed.

  In order to solve the above-described problems, the present invention provides a workpiece to be placed in an oxidizer solution, restrained by a magnetic field on a surface plate or a machining head, and magnetic particles of a transition metal controlled spatially. The work surface of the workpiece is brought into contact with the workpiece under an extremely low load, and the work surface and the magnetic fine particles are relatively displaced, and the oxidizing power generated on the surface of the magnetic fine particles is generated by the catalytic action of the magnetic fine particles. Provided is a catalytic chemical processing method using magnetic fine particles characterized in that a workpiece is processed by removing or eluting a compound generated by a chemical reaction between an active species having and a surface atom of the workpiece ( Claim 1).

Here, it is preferable that the oxidizing agent is H ₂ O ₂ (claim 2). The magnetic fine particles are preferably made of one or a combination of two or more selected from Fe, Ni and Co, or a compound or alloy containing Fe, Ni or Co. (Claim 3) The workpiece is preferably one selected from crystalline SiC, sintered SiC, GaN, sapphire, ruby, diamond, and glass.

More preferably, the oxidizing agent is H ₂ O ₂ , the magnetic fine particles are Fe, the workpiece is SiC, GaN, or diamond, and processing is performed using the Fenton reaction.

  The present invention also provides a processing tank containing an oxidant, a magnet surface plate that is provided on the bottom surface of the processing tank and capable of rotating or eccentric movement, and the magnet surface plate facing the magnet surface plate in the processing tank. A workpiece holder having a rotation axis that is eccentric with respect to the rotation axis of the magnet surface plate, and a magnetic fine particle of a transition metal constrained on the surface of the magnet surface plate by a magnetic field, and held by the holder. The work surface of the work piece is brought into contact with the magnetic fine particles under an extremely low load, and both or one of the magnet surface plate and the holder is rotated to flatten the work surface of the work piece. A catalytic chemical processing apparatus using the characteristic magnetic fine particles was constructed (claim 6).

  In addition, the present invention provides a processing tank containing an oxidant, a bottom of the processing tank, a workpiece holding holder, and a workpiece holder that can reciprocate or rotate in a plane, A magnet processing head that is arranged to face the holder in a processing tank and is rotatable, and a magnetic fine particle of a transition metal is constrained by a magnetic field on the surface of the magnet processing head, and a workpiece to be processed held by the holder is processed. A surface is brought into contact with the magnetic fine particles under an extremely low load, and the holder is reciprocated or rotated while rotating the magnet processing head to process the workpiece surface of the workpiece into an arbitrary free-form surface shape. A catalytic chemical processing apparatus using magnetic fine particles is configured (claim 7).

  In the processing apparatus, the selection conditions for the oxidizing agent and the magnetic fine particles are the same as those in the processing method, and the types of workpieces to be processed are also the same.

  The catalytic chemical processing method and apparatus using the magnetic fine particles according to the present invention as described above is a processing method for processing a magnetic fine particle of a transition metal, which is constrained by a magnetic field on a platen or a processing head, and which is spatially controlled. Since the surface is brought into contact under an extremely low load, no scratches are caused by the magnetic fine particles on the surface to be processed, and active species having a strong oxidizing power generated from an oxidizing agent on the fine particle surface are brought into contact with the fine particles. Since a chemical reaction is performed with surface atoms in the immediate vicinity of the processed workpiece, and the compound formed thereby is removed or eluted, the processed surface excellent in crystallography can be obtained.

  The present invention has the greatest feature in utilizing the catalytic action by fine particles made of a transition metal, the restriction by a magnetic field by using magnetic fine particles, and the space controllability. The magnetic fine particles are self-aligned like a spike along the magnetic field lines coming out from the surface plate or processing head, cover the surface of the surface plate or processing head, and bring the workpiece into contact with the magnetic fine particles in such a state. Therefore, a contact state with an extremely low load can be realized.

  Further, by relatively displacing the work surface and the magnetic fine particles, the amount of work on the work surface is spatially averaged, so that a very flat work surface can be obtained, and surface atoms and active species can be obtained. Since the oxide of the work surface generated by the chemical reaction with the above is removed and a new work surface always appears, the processing speed is increased. Here, since the active species generated on the catalyst surface are inactivated rapidly when they are separated from the catalyst surface, the active species are present only on the catalyst surface as a reference surface or in the immediate vicinity of the surface. Therefore, it can be processed in a spatially controlled state.

  The catalytic chemical processing method and apparatus using the magnetic fine particles of the present invention enables high-precision processing of SiC, GaN, sapphire, ruby, diamond, and glass, which has been difficult to process so far, and further provides a semiconductor manufacturing process. May also be used to planarize semiconductors, metal layers or metal thin films.

  Next, the present invention will be described in more detail based on embodiments. The processing principle of the present invention is that a catalyst composed of a workpiece and a transition metal is placed in an oxidizer, the workpiece and the catalyst are brought into contact, and at that time, active species generated from molecules in the oxidizer on the catalyst. The surface to be processed is oxidized by removing the oxide and the oxide is removed or eluted. Here, the greatest feature of the present invention resides in that magnetic fine particles made of a transition metal are used as a catalyst, the magnetic fine particles are constrained by a magnetic field, and spatially controlled.

  In other words, the catalytic chemical processing method using the magnetic fine particles of the present invention includes a workpiece in an oxidant solution, restrained by a magnetic field on a surface plate or processing head, and spatially controlled transition metal magnetism. The fine particles are brought into contact with the work surface of the work piece under an extremely low load, and the work surface and the magnetic fine particles are relatively displaced and generated on the surface of the magnetic fine particles by the catalytic action of the magnetic fine particles. It is characterized in that the workpiece is processed by removing or eluting a compound generated by a chemical reaction between the active species having the oxidizing power and the surface atoms of the workpiece.

  FIG. 1 shows a catalytic chemical processing apparatus (polishing apparatus) using the magnetic fine particles of the present invention. The polishing apparatus 1 includes a processing tank 3 containing an oxidant 2, a magnet surface plate 4 which is provided on the bottom surface of the processing tank 3, a rotatable surface plate 4, and the magnet surface plate 4 facing the inside of the processing tank 3. The holder 8 of the workpiece 7 having the rotating shaft 6 eccentric with respect to the rotating shaft 5 of the magnet surface plate 4 and the magnetic fine particles 9 of the transition metal on the surface of the magnet surface plate 4 by a magnetic field. The work surface of the work 7 held by the holder 8 is brought into contact with the magnetic fine particles 9 under an extremely low load, and both or one of the magnet surface plate 4 and the holder 8 is rotated and swung. Thus, the work surface of the work 7 is flattened. Here, the magnet surface plate 4 may be capable of eccentric movement as well as rotation.

  More specifically, in the present embodiment, the magnet surface plate 4 is provided integrally with the bottom surface portion of the processing tank 3 and has a structure in which the processing tank 3 is rotated by the rotating shaft 5 of the bottom surface portion. The magnet surface plate 4 is configured by fixing a permanent magnet to the bottom surface of the processing tank 3. Here, the processing tank 3 and the holder 8 are preferably made of a non-magnetic material so as not to disturb the magnetic lines of force of the magnet surface plate 4. A permanent magnet plate 10 magnetized in the front and back direction or a ferromagnetic plate such as iron is disposed in the bottom surface of the processing tank 3 in parallel with the magnet surface plate 4, and the magnetic field strength of the magnet surface plate 4 is increased. It is also preferable to enhance the ratio.

  As described above, when an appropriate amount of the magnetic fine particles 9 are sprinkled on the surface of the magnet surface plate 4 in the processing tank 3 filled with the oxidant 2, the magnetic fine particles 9 are aligned along the magnetic line density distribution, and adjacent magnetic fine particles are arranged. Since the columns are of the same polarity, they repel each other and become independent like a head. In this state, the holder 8 holding the workpiece 7 is lowered from above, the position is set so that the workpiece 7 contacts the tip of the head of the magnetic fine particle 9, and then the magnet is fixed together with the processing tank 3. The panel 4 is rotated and swung, and the holder 8 is rotated.

  Moreover, the form which turned the position of the magnet surface plate 4 and the holder 8 upside down with respect to FIG. 1 may be sufficient. In that case, the processing tank 3 is kept stationary, and the magnet surface plate 4 and the holder 8 are rotated by different rotating shafts in the oxidant 2. In this case, since the spikes of the magnetic fine particles 9 hang down from the magnet surface plate 4 disposed above, the tip of the magnetic fine particles 9 is received by the processing surface of the workpiece 7 and lightly brought into contact therewith.

  Moreover, the conceptual diagram of NC processing apparatus 11 which can process arbitrary free-form surface shape is shown in FIG. The processing apparatus 11 is provided in a processing tank 13 containing an oxidant 12 and a bottom surface in the processing tank 13, holds the workpiece 7, and can be reciprocated or rotated in a plane. The holder 14, the holder 14 in the processing tank 13 so as to face the holder 14, the magnet processing head 15 that can be rotated, and the magnetic fine particles 9 of transition metal on the surface of the magnet processing head 15 are restrained by a magnetic field, The processing surface of the workpiece 7 held by the holder 14 is brought into contact with the magnetic fine particles 9 under an extremely low load, and the holder 14 is reciprocated or rotated while rotating the magnet processing head 15. The processing surface of the workpiece 7 is processed into an arbitrary free-form surface shape.

  More specifically, in the present embodiment, the holder 14 is constituted by an XY stage that reciprocates in a horizontal plane, the magnet processing head 15 is rotationally symmetric, and a cylindrical permanent magnet at the tip of the rotating shaft 16. Is fixed. When the magnetic fine particles 9 are attracted to the surface of the magnet processing head 15, the magnetic fine particles 9 hang down from the head, and the processing surface of the processing object 7 held by the holder 14 is brought into contact with the tip portion thereof. Then, while rotating the magnet processing head 15, the workpiece 7 is moved horizontally by the holder 14, the contact time with the magnetic fine particles 9 is controlled to adjust the processing amount spatially, and an arbitrary free-form surface It is processed into a shape.

  In this embodiment, iron powder is used for the magnetic fine particles as the catalyst, and a hydrogen peroxide solution stock solution having a concentration of 40% is used as the oxidizing agent. In this case, OH radicals (hydroxyl radicals) are generated as active species on the Fe surface by the Fenton reaction represented by the following [Chemical Formula 1] and [Chemical Formula 2]. OH radicals (dots are displayed on the right side of OH in the chemical formula) have a short lifetime but a very strong oxidizing power.

In general, it is known that OH radicals are generated by redox decomposition of H ₂ O ₂ . That is, the decomposition of H ₂ O ₂ by the Harber-Waiss mechanism, and OH by one-electron reduction with low-valent transition metals (Fe ²⁺ , Ti ³⁺ , Cr ²⁺ , Cu ⁺ etc.). A radical is generated. In particular, the reaction with Fe ²⁺ is well known as the Fenton reaction. H ₂ O ₂ reacts with a low-valent metal ion capable of performing a redox reaction to generate OH radicals. Here, Fe ²⁺ has a catalytic action.

Here, when the workpiece is SiC, as shown in the following [Chemical Formula 3], the SiC surface is oxidized by OH radicals and dissolved oxygen in H ₂ O ₂ , and the portion is preferentially processed. I guess.

  Such a feature of the present invention is that reactive species are created only on the catalyst, and the reactive species are rapidly deactivated when separated from the catalyst. As a result, unlike chemical etching, processing can be performed without being affected by the surface index of the surface, and the processing region can be controlled spatially, and flattening at the atomic scale as seen in EEM can be expected. . In addition, since free magnetic fine particles are constrained by a magnetic field and spatially controlled, the magnetic fine particles can be brought into contact with only a necessary portion of the workpiece with an extremely low load. That is, it is considered that the catalytic chemical processing method and apparatus using the magnetic fine particles of the present invention may be an efficient ultraprecision processing method.

Here, examples of the oxidizing agent include H ₂ O _2, but are not limited to H ₂ O ₂ , and persulfate and periodic hydrochloric acid can also be used depending on a combination of a workpiece, a catalyst, processing conditions, and the like. Further, the magnetic fine particles 9 may be made of one or a combination of two or more selected from Fe, Ni and Co, or a compound or alloy containing Fe, Ni or Co. Examples of the object to be processed include crystalline SiC, sintered SiC, GaN, sapphire, ruby, diamond, and glass.

  A commercially available SiC wafer (single crystal SiC (0001), as-slice plane) was smoothed by the polishing apparatus 1 shown in FIG. The processing conditions are shown in Table 1 below.

  Figure 1 shows the results of observing the surface of single crystal 4H-SiC (0001) that is generally marketed for devices and the surface of single crystal SiC (0001) obtained by this processing method using an AFM (atomic force microscope). 3 and FIG. FIG. 3A is an AFM image of the surface of single crystal SiC (0001) commercially available for a device, and FIG. 3B is a cross section taken along the observation line (center portion) shown in FIG. Shows the profile. 4A is an AFM image of the surface of the processed single crystal SiC (0001), and FIG. 4B shows a cross-sectional profile along the observation line (center portion) shown in FIG. Show. Table 2 shows the measurement results of the surface roughness of both surfaces.

  FIG. 5 shows digital microscope images of the single crystal SiC (0001) surface (as-slice plane) before and after processing. FIG. 5 (a) is the surface before processing, and FIG. 5 (b) is after processing. The surface of each is shown.

From these results, it was possible to easily process SiC, which is generally difficult to chemically etch, by simply contacting and rubbing SiC in H ₂ O ₂ . Moreover, the surface roughness after processing was improved by about one digit in each evaluation, and the effectiveness of the present invention could be shown. Moreover, since H ₂ O ₂ is inexpensive and relatively easy to handle, it can be said that the present invention is useful from a practical viewpoint.

1 shows a simplified cross-sectional view of a catalytic chemical processing apparatus using magnetic fine particles of the present invention. It is a conceptual diagram of the processing apparatus which can process an arbitrary free-form surface shape by numerically controlling the processing head. The surface state of single crystal SiC (0001) marketed for devices is shown, (a) shows the AFM image of the surface, and (b) shows the cross-sectional profile along the observation line shown in (a). The surface state after processing single crystal SiC (0001) in H ₂ O ₂ using Fe fine particles is shown, (a) shows the AFM image of the surface, (b) shows the observation line shown in (a). The cross-sectional profile in is shown. The digital microscope image before and after processing of the single crystal SiC (0001) surface (as-slice plane) is shown, (a) shows the surface before processing, and (b) shows the surface after processing.

Explanation of symbols

1 Polishing device,
2 oxidizing agents,
3 Processing tank,
4 Magnet surface plate,
5 rotation axis,
6 rotation axis,
7 Workpiece,
8 holders,
9 Magnetic fine particles,
10 Permanent magnet plate,
11 NC processing equipment,
12 Oxidizing agent,
13 Processing tank,
14 holders,
15 Magnet processing head,
16 Axis of rotation.

Claims (11)

  A workpiece is placed in an oxidizer solution, restrained by a magnetic field on a platen or machining head, and magnetic particles of a spatially controlled transition metal are applied to the workpiece surface with a very low load. The surface of the work piece and the active species having the oxidizing power generated on the surface of the magnetic fine particle by the catalytic action of the magnetic fine particle are displaced by relatively displacing the work surface and the magnetic fine particle. A catalytic chemical processing method using magnetic fine particles, wherein a workpiece is processed by removing or eluting a compound generated by a chemical reaction. The catalytic chemical processing method using magnetic fine particles according to claim 1, wherein the oxidizing agent is H ₂ O ₂ .   3. Catalytic chemical processing using magnetic fine particles according to claim 1 or 2, wherein the magnetic fine particles comprise one or a combination of two or more selected from Fe, Ni and Co, or a compound or alloy containing Fe, Ni or Co. Method.   The catalytic chemistry using magnetic fine particles according to any one of claims 1 to 3, wherein the workpiece is one selected from crystalline SiC, sintered SiC, GaN, sapphire, ruby, diamond, and glass. Processing method. The catalytic chemical processing method using magnetic fine particles according to claim 1, wherein the oxidizing agent is H ₂ O ₂ , the magnetic fine particles are Fe, the workpiece is SiC, GaN, or diamond, and processing is performed using the Fenton reaction. A processing tank containing an oxidizing agent,
A magnet surface plate that is provided on the bottom surface in the processing tank and is capable of rotating or eccentric movement;
A holder for a workpiece having a rotation axis that is eccentric with respect to the rotation axis of the magnet surface plate, arranged facing the magnet surface plate in the processing tank,
The magnetic fine particles of transition metal are restrained by the magnetic field on the surface of the magnet surface plate, the work surface of the work piece held by the holder is brought into contact with the magnetic fine particles under an extremely low load, and the magnet surface plate A catalytic chemical processing apparatus using magnetic fine particles, characterized in that both or one of the holders is rotated to flatten a processing surface of a workpiece. A processing tank containing an oxidizing agent,
Provided on the bottom surface in the processing tank, holding the workpiece, holder of the workpiece that can be reciprocated or rotated in a plane,
A magnet processing head that is arranged to face the holder in the processing tank and is rotatable;
A magnetic fine particle of a transition metal is constrained by a magnetic field on the surface of the magnet machining head, a work surface of a work piece held on the holder is brought into contact with the magnetic fine particle under an extremely low load, and the magnet machining head is A catalytic chemical processing apparatus using magnetic fine particles, wherein the processing surface of a workpiece is processed into an arbitrary free-form surface shape by reciprocating or rotating the holder while rotating. The catalytic chemical processing apparatus using magnetic fine particles according to claim 6 or 7, wherein the oxidizing agent is H ₂ O ₂ .   The magnetic fine particles according to any one of claims 1 to 3, wherein the magnetic fine particles comprise one or a combination of two or more selected from Fe, Ni, and Co, or a compound or alloy containing Fe, Ni, or Co. Catalytic chemical processing equipment.   The catalytic chemistry using magnetic fine particles according to any one of claims 6 to 10, wherein the workpiece is one selected from crystalline SiC, sintered SiC, GaN, sapphire, ruby, diamond, and glass. Processing equipment. The catalytic chemical processing apparatus using magnetic fine particles according to claim 6 or 7, wherein the oxidizing agent is H ₂ O ₂ , the magnetic fine particles are Fe, the workpiece is SiC, GaN, or diamond, and is processed using a Fenton reaction. .