JP7204105B2 - Processing method and processing equipment - Google Patents

Description

The present invention relates to a processing method and processing apparatus. More specifically, the present invention relates to a processing method and processing apparatus capable of realizing highly efficient and highly accurate processing in dry polishing for processing GaN, SiC, and the like.

GaN (gallium nitride), SiC, and the like have a wide bandgap and are excellent in dielectric breakdown field, charge mobility, and the like, and are therefore expected to be promising materials for next-generation power semiconductor devices.

In order to fabricate a semiconductor device using GaN or the like, it is said that a processing technique for finishing the substrate surface, which is the base of the device, to be smooth and undisturbed at the atomic level is essential.

However, GaN, SiC, and the like have high hardness and are chemically stable, and therefore are extremely difficult to process, and the development of processing technology has become a technical issue.

For example, as a conventional processing method, a processing of chemically removing by polishing using abrasive grains such as chemical mechanical polishing is known. However, since the chemical reaction in the abrasive is used, the removal rate is slow, and the processing efficiency is insufficient.

Under these circumstances, the inventors of the present application have attempted to develop a machining method and a machining apparatus capable of realizing high-efficiency and high-precision machining with a simple configuration. and processing equipment.

In the processing method described in Patent Document 1, a processing member made of a metal oxide and a workpiece are brought into contact with each other, and while ozone gas containing water or an alkaline solution is supplied to the contact portion, the processing member is applied to the workpiece. Machining is performed by displacing while in contact.

In the processing method described in Patent Document 1, it was possible to improve the surface roughness of the workpiece and the processing efficiency as compared with conventional processing methods.

WO2017/141918

However, in the processing method described in Patent Document 1, a portion of the substrate surface that has been damaged by lapping in the manufacturing process of the substrate is more difficult to process due to tribochemical reaction than other substrate surfaces. was there.

As a result, on the surface of the substrate after processing, particularly on the surface of the GaN substrate, linear bumps in which the damaged portion remains in a convex shape occur, leaving room for improvement in processing accuracy of the substrate surface. In addition, this linear protuberance shape is more pronounced in processing in which ozone gas containing water or alkaline solution is supplied than in processing in which ozone gas containing no water or alkaline solution is supplied. was particularly noticeable in the processing in which the was supplied.

The present invention has been devised in view of the above points, and aims to provide a processing method and processing apparatus capable of realizing highly efficient and highly accurate processing in dry polishing for processing GaN, SiC, and the like. It is intended. A further object of the present invention is to provide a processing method and processing apparatus capable of realizing a surface free of linear protuberances after processing.

[About processing method]
In order to achieve the above object, the processing method of the present invention comprises bringing a processing member made of a metal oxide having light transmittance into contact with a workpiece, and applying ozone gas containing water or an alkaline solution to the contact portion. At the same time, while irradiating the workpiece with ultraviolet light from the surface of the workpiece opposite to the surface in contact with the workpiece, the workpiece is displaced while the workpiece is in contact with the workpiece. It comprises a step of causing

In the processing according to the present invention, surface modification of the surface to be processed of the workpiece and surface removal for removing the modified portion are performed simultaneously, so that the surface to be processed is processed and flattened.

In addition, the surface modification in the processing in the present invention includes surface modification by tribochemical reaction occurring on the friction surface of the workpiece and the workpiece, and the modification of the surface of the workpiece by the irradiation of ultraviolet light and the ultraviolet light. It is done by surface modification by chemical reaction.

Further, the surface removal in the machining in the present invention is performed by physically and chemically removing the surface-modified modified portion of the workpiece surface of the workpiece with the workpiece. Furthermore, surface removal is also performed by etching of the modified portion, which will be described later.

Here, by bringing the processing member into contact with the workpiece and supplying ozone gas to the contact portion, the contact portion can be placed in an ozone gas environment. That is, although ozone gas is an unstable molecule, by supplying ozone gas to the contact portion, it becomes possible to localize the ozone gas in the same region.

In addition, by the step of displacing the processing member in contact with the workpiece, it is possible to generate frictional heat at the contact portion. This frictional heat thermally decomposes the supplied ozone gas to generate atomic oxygen from the ozone gas. The generated atomic oxygen suppresses the binding of carboxyl groups, etc. to the OH groups on the outermost surface of the workpiece, which is responsible for the chemical reaction (processing) with the workpiece in an atmospheric environment, that is, the contamination derived from organic matter. do. Atomic oxygen decomposes and cleans dirt derived from organic substances, and hydrophilization is performed by exposing OH groups on the surface of the workpiece, which stabilizes and promotes the tribochemical reaction and solid phase reaction, and the workpiece is processed. It enables stable and highly efficient physical and chemical processing of objects.

Further, as described above, since the contact portion is in an ozone gas environment, it is possible to secure atomic oxygen necessary for stable processing.

In addition, while supplying ozone gas containing water or an alkaline solution to the contact portion and irradiating the workpiece with ultraviolet light, the workpiece after machining is displaced while being in contact with the workpiece. It is possible to suppress the formation of linear protuberances on the processing surface of the workpiece. In addition, photoexcitation of ultraviolet light can promote surface modification of the processed surface of the workpiece. Furthermore, irradiation with ultraviolet light promotes the generation of atomic oxygen from ozone gas, and can further stabilize and promote tribochemical reactions and solid-phase reactions. In addition, the irradiation of ultraviolet light makes the surface of the member to be processed hydrophilic and exposes OH groups, thereby further increasing the efficiency of processing the workpiece. In addition, contamination originating from organic matter on the surface of the workpiece can be removed by irradiating the workpiece with ultraviolet light.

In addition, the processing member is made of a metal oxide having light transmittance, and by irradiating the processing member with ultraviolet light from the side opposite to the surface in contact with the processing member, the It becomes easy to directly irradiate the processing surface of the workpiece with the ultraviolet light through the processing member from the arrangement position or the position where interference with the position of the ozone gas supply source can be easily avoided. As a result, it becomes easier to increase the illuminance of the ultraviolet light with which the processing surface of the workpiece is irradiated, and various effects of ultraviolet light irradiation that contribute to the processing of the workpiece can be improved.

In addition, by containing water or an alkaline solution, the ozone gas accelerates the tribochemical reaction that occurs on the friction surface of the workpiece and the workpiece, generates oxides on the machining surface of the workpiece, and preferentially It can be removed. As a result, in addition to processing using atomic oxygen generated by thermal decomposition of ozone gas, processing by tribochemical reaction is promoted, and the accuracy of surface roughness can be further increased, and processing efficiency can be improved. The alkaline solution referred to herein is, for example, alkaline electrolyzed water, NaOH, KOH, or other alkaline solution.
The ozone gas containing water or alkaline solution includes ozone gas containing water having vapor pressure and ozone gas accompanied by mist of water or alkaline solution.

Further, the processed member is made of any one of single crystal sapphire composed of Al ₂ O ₃ , corundum, sapphire glass, sapphire crystal, and glass mainly composed of SiO ₂ , and the work piece is If it is made of any one of SiC, GaN, AlN, diamond, polycrystalline diamond, CVD diamond, and DLC film, the processing surface of the workpiece can be made a sufficiently high-precision surface, and the processing efficiency can be improved. can.

Further, when the member to be processed is made of synthetic quartz, the transmittance of ultraviolet light in the member to be processed is high. Various effects of ultraviolet light irradiation that contribute to processing can be improved.

Moreover, when the alkaline solution is a KOH aqueous solution, it is possible to promote the tribochemical reaction with ozone gas containing the KOH aqueous solution. In addition, the KOH aqueous solution makes it possible to remove the surface-modified portion of the workpiece by etching, thereby increasing the efficiency of surface removal without damaging the surface to be processed. As a result, the machined surface of the workpiece can be made to be a highly accurate surface, and the machining efficiency can be improved.

In addition, when the ultraviolet light has a wavelength of 365 nm and an illuminance of 10 mW/cm ² or more, the chemical reaction (oxidation) with the substrate surface is promoted by the ultraviolet light, and the processing accuracy and processing efficiency of the substrate surface are improved. sufficient, and the formation of linear protuberances can be suppressed. Further, the illuminance is more preferably 100 mW/cm ² or more, and more preferably 300 mW/cm ² or more.

In addition, when the ultraviolet light has energy equal to or greater than the bandgap of the workpiece, the chemical reaction (oxidation) between the workpiece and the ultraviolet light is accelerated, further enhancing the working surface of the workpiece. can be made into a highly accurate surface, and processing efficiency can be improved.

Further, when the workpiece is made of GaN and the ultraviolet light includes a substance with a wavelength of 365 nm or less, the chemical reaction (oxidation) with the substrate surface of the GaN substrate is promoted by the ultraviolet light, and the GaN substrate is exposed to the substrate surface. Machining accuracy and machining efficiency can be made sufficient.
If the wavelength of the ultraviolet light is short, the ultraviolet light will be easily absorbed by the workpiece and the air, and the irradiation of the ultraviolet light to the workpiece will be insufficient. preferably included.

In addition, in order to promote hydrophilic treatment on the surface of the processing member and the surface of the workpiece, when atomic oxygen is generated from ozone gas and supplied to the contact portion of the processing member and the workpiece. Therefore, the machining surface of the workpiece can be sufficiently machined.

[About processing equipment]
In order to achieve the above objects, a processing apparatus according to the present invention holds a processing member made of a metal oxide having optical transparency and a predetermined workpiece in contact with the processing member. An ozone gas supply unit that supplies ozone gas containing water or an alkaline solution to a contact portion between the holding mechanism, the processing member and the work piece, and a surface of the processing member that is opposite to the surface that contacts the work piece. An ultraviolet light irradiation unit for irradiating the workpiece with ultraviolet light from the surface side, and a driving unit for displacing the workpiece while the workpiece and the workpiece are in contact with each other.

Here, the contact portion is placed in an ozone gas environment by a holding mechanism that holds a predetermined workpiece in contact with the workpiece and an ozone gas supply section that supplies ozone gas to the contact portion between the workpiece and the workpiece. can be done. That is, although ozone gas is an unstable molecule, by supplying ozone gas to the contact portion, it becomes possible to localize the ozone gas in the same region.

In addition, while the processing member and the workpiece are in contact with each other, the drive section that displaces the processing member can generate frictional heat at the contact portion. This frictional heat thermally decomposes the supplied ozone gas to generate atomic oxygen from the ozone gas. The generated atomic oxygen is bound to the hydroxyl group (OH group) on the outermost surface of the workpiece, which is responsible for the chemical reaction (processing) with the workpiece in an atmospheric environment. Suppress nations. Atomic oxygen decomposes and cleans dirt derived from organic substances, and hydrophilization is performed by exposing hydroxyl groups (OH groups) on the surface of the processed member, thereby stabilizing and promoting tribochemical reactions and solid-phase reactions. , stable and highly efficient physical and chemical processing of the workpiece is possible.

Further, as described above, since the contact portion is in an ozone gas environment, it is possible to secure atomic oxygen necessary for stable processing.

Further, an ozone gas supply unit that supplies ozone gas containing water or an alkaline solution to a contact portion between the processing member and the work piece, an ultraviolet light irradiation unit that irradiates the work piece with ultraviolet light, and the processing member and the work piece. It is possible to suppress the formation of linear protuberances on the processing surface of the workpiece after processing by the drive unit that displaces the processing member while the object is in contact with the object. In addition, photoexcitation by ultraviolet light can promote surface modification of the processed surface of the workpiece. Furthermore, irradiation with ultraviolet light promotes the generation of atomic oxygen from ozone gas, and can further stabilize and promote tribochemical reactions and solid-phase reactions. In addition, the irradiation of ultraviolet light makes the surface of the member to be processed hydrophilic, thereby further increasing the efficiency of processing the workpiece. In addition, contamination originating from organic matter on the surface of the workpiece can be removed by irradiating the workpiece with ultraviolet light.

Further, by a processing member made of a metal oxide having optical transparency and an ultraviolet light irradiation unit that irradiates the work piece with ultraviolet light from the side opposite to the surface of the processing member that contacts the work piece, It is easy to directly irradiate the processing surface of the workpiece with ultraviolet light through the workpiece from a position where interference with the position of the workpiece or the position of the ozone gas supply source can be easily avoided. As a result, it becomes easier to increase the illuminance of the ultraviolet light with which the processing surface of the workpiece is irradiated, and various effects of ultraviolet light irradiation that contribute to the processing of the workpiece can be improved.

In addition, by containing water or an alkaline solution, the ozone gas accelerates the tribochemical reaction that occurs on the friction surface of the workpiece and the workpiece, generates oxides on the machining surface of the workpiece, and preferentially It can be removed. As a result, in addition to processing using atomic oxygen generated by thermal decomposition of ozone gas, processing by tribochemical reaction is promoted, and the accuracy of surface roughness can be further increased, and processing efficiency can be improved. The alkaline solution referred to herein is, for example, alkaline electrolyzed water, NaOH, KOH, or other alkaline solution.
The ozone gas containing water or alkaline solution includes ozone gas containing water having vapor pressure and ozone gas accompanied by mist of water or alkaline solution.

Further, the processed member is made of any one of single crystal sapphire composed of Al ₂ O ₃ , corundum, sapphire glass, sapphire crystal, and glass mainly composed of SiO ₂ , and the work piece is If it is made of any one of SiC, GaN, AlN, diamond, polycrystalline diamond, CVD diamond, and DLC film, the processing surface of the workpiece can be made a sufficiently high-precision surface, and the processing efficiency can be improved. can.

Further, when the member to be processed is made of synthetic quartz, the transmittance of ultraviolet light in the member to be processed is high. Various effects of ultraviolet light irradiation that contribute to processing can be improved.

Moreover, when the alkaline solution is a KOH aqueous solution, it is possible to promote the tribochemical reaction with ozone gas containing the KOH aqueous solution. In addition, the KOH aqueous solution makes it possible to remove the surface-modified portion of the workpiece by etching, thereby increasing the efficiency of surface removal without damaging the surface to be processed. As a result, the machined surface of the workpiece can be made to be a highly accurate surface, and the machining efficiency can be improved.

In addition, when the ultraviolet light has energy equal to or greater than the bandgap of the workpiece, the chemical reaction (oxidation) between the workpiece and the ultraviolet light is accelerated, further enhancing the working surface of the workpiece. can be made into a highly accurate surface, and processing efficiency can be improved.

In addition, when the ultraviolet light has a wavelength of 365 nm and an illuminance of 10 mW/cm ² or more, the chemical reaction (oxidation) with the substrate surface is promoted by the ultraviolet light, and the processing accuracy and processing efficiency of the substrate surface are improved. sufficient, and the formation of linear protuberances can be suppressed. Further, the illuminance is more preferably 100 mW/cm ² or more, and more preferably 300 mW/cm ² or more.

Further, when the workpiece is made of GaN and the ultraviolet light includes a substance with a wavelength of 365 nm or less, the chemical reaction (oxidation) with the substrate surface of the GaN substrate is promoted by the ultraviolet light, and the GaN substrate is exposed to the substrate surface. Machining accuracy and machining efficiency can be made sufficient. Furthermore, when the wavelength of 200 nm or more is included, ultraviolet light can pass through the workpiece and air.

In addition, in order to promote hydrophilic treatment on the surface of the processing member and the surface of the workpiece, when atomic oxygen is generated from ozone gas and supplied to the contact portion of the processing member and the workpiece. Therefore, the machining surface of the workpiece can be sufficiently machined.

The processing method and processing apparatus to which the present invention is applied can provide a processing method and processing apparatus capable of realizing highly efficient and highly accurate processing in dry polishing for processing GaN, SiC, and the like.

It is a schematic diagram for demonstrating the processing apparatus to which this invention is applied. FIG. 2 is a schematic diagram (left) showing a UV irradiation range on a surface of a workpiece, and a diagram (right) showing the surface to be processed after processing in Example 1. FIG. Data obtained by measuring the surface roughness of a part of the processed region of the processed surface of the workpiece with a non-contact shape measuring machine, (a) showing the processed region of the processed surface before processing, and (b) indicates the processed region of the UV irradiated range after processing in Example 1, and (c) indicates the processed region of the UV non-irradiated range after processing in Example 1. FIG. FIG. 10 is a schematic diagram (left) showing a UV irradiation range on the surface of a workpiece, and a diagram (right) showing the surface to be processed after processing in Example 2. FIG. Data obtained by measuring the surface roughness of a part of the processed region of the processed surface of the workpiece with a non-contact shape measuring machine, (a) showing the processed region of the processed surface before processing, and (b) indicates the processed region of the UV irradiated range after processing in Example 2, and (c) indicates the processed region of the UV non-irradiated range after processing in Example 2. FIG. It is data obtained by measuring the surface roughness of a part of the processed region of the processed surface of the workpiece with a non-contact shape measuring machine, and (a) shows the UV irradiation range after processing of Example 2 (synthetic quartz). The processed region is shown, and (b) shows the processed region of the UV irradiation range after processing of Example 1 (soda-lime glass). It is data obtained by measuring the surface roughness of a part of the processed region of the processed surface of the workpiece with a non-contact shape measuring machine, and (a) shows the processed region of the processed surface after processing in Comparative Example 1. , (b) shows the processed region of the processed surface after processing in Comparative Example 2, and (c) shows the processed region of the processed surface after processing in Example 3. FIG. 4 is a graph showing evaluation results of machining efficiency in Example 1, Comparative Example 1, and Comparative Example 2. FIG.

[Embodiment of the Invention]
EMBODIMENT OF THE INVENTION Hereafter, the form for implementing this invention (it is hereafter called "embodiment of invention") is demonstrated.
FIG. 1 is a schematic diagram for explaining a processing apparatus to which the present invention is applied. The processing apparatus 1 shown here holds a processing table 2, a synthetic quartz platen 3, and a GaN substrate 5 as a workpiece. It has a sample holder 4 for The synthetic quartz surface plate 3 is an example of a member to be processed, and the GaN substrate 5 is an example of a workpiece.

The processing apparatus 1 also has an ozone supply unit 6 that supplies ozone gas containing a KOH aqueous solution to a contact portion between the synthetic quartz surface plate 3 and the GaN substrate 5 .

The processing apparatus 1 also has an ultraviolet light irradiation unit 7 that irradiates the surface of the GaN substrate 5 to be processed with ultraviolet light (UV).

In this processing apparatus 1, a GaN substrate 5 as a workpiece is brought into contact with the upper surface (upper surface in FIG. 1) of a synthetic quartz surface plate 3, and the surface to be processed (substrate surface) of the GaN substrate 5 is polished. Become.

More specifically, the processing in the processing apparatus 1 simultaneously performs surface modification on the surface to be processed of the GaN substrate 5 and surface removal for removing the modified portion, thereby progressing the processing of the surface to be processed. flattened.

Further, the surface modification of the GaN substrate 5 includes surface modification by a tribochemical reaction that occurs on the friction surface between the synthetic quartz surface plate 3 and the GaN substrate 5, and surface modification of the surface to be processed of the GaN substrate 5 by irradiation of ultraviolet light. It is performed by surface modification by chemical reaction with

The surface of the GaN substrate 5 is removed by physically and chemically removing the surface-modified portion of the GaN substrate 5 with the synthetic quartz surface plate 3 . Furthermore, surface removal is also performed by etching the modified portion with a KOH aqueous solution contained in ozone gas.

The ozone supply unit 6 is arranged above the synthetic quartz platen 3 . The tip of the ozone supply part 6 , that is, the part from which ozone gas is discharged is directed to the contact part between the synthetic quartz surface plate 3 and the GaN substrate 5 . As a result, the contact portion is placed in an ozone environment.

In addition, the ozone gas is thermally decomposed by frictional heat generated between the synthetic quartz surface plate 3 and the GaN substrate 5 at the contact portion to generate atomic oxygen, which stabilizes and promotes the tribochemical reaction and the solid-phase reaction, thereby facilitating GaN. Stable and highly efficient physical and chemical processing of the substrate 5 is possible.

In addition, since the ozone gas containing the KOH aqueous solution is supplied, the tribochemical reaction that occurs on the friction surface of the workpiece and the workpiece is promoted, and oxides on the machining surface of the workpiece can be generated and removed preferentially. become a thing. Furthermore, the modified portion of the GaN substrate 5 can be etched with a KOH aqueous solution to promote surface removal.

The ultraviolet light irradiation unit 7 is arranged on the bottom side of the synthetic quartz surface plate 3 . The ultraviolet light (UV) emitted from the ultraviolet light irradiation unit 7 is transmitted through the synthetic quartz surface plate 3 and is applied to the contact portion between the synthetic quartz surface plate 3 and the GaN substrate 5, that is, the surface of the GaN substrate 5 to be processed. directed towards. Moreover, the ultraviolet light irradiation unit 7 is a light source capable of irradiating ultraviolet light having a wavelength of 365 nm or less. Furthermore, the ultraviolet light irradiation unit 7 is a light source that can irradiate ultraviolet light with an illuminance of 10 mW/cm ² or more at a wavelength of 365 nm. Further, the illuminance is more preferably 100 mW/cm ² or more, and more preferably 300 mW/cm ² or more.

The processing table 2 is formed as a frame-like body that supports the synthetic quartz surface plate 3, and the ultraviolet light emitted from the ultraviolet light irradiation unit 7 passes between the frame members forming the processing table 2. , and is incident on the synthetic quartz surface plate 3 .

In addition, it is possible to prevent the surface of the GaN substrate 5 after processing from being linearly protuberant due to the irradiation of the ultraviolet light by the ultraviolet light irradiation unit 7 . In addition, surface modification of the GaN substrate 5 can be promoted by photoexcitation of ultraviolet light. Furthermore, irradiation with ultraviolet light promotes the generation of atomic oxygen from ozone gas, and can further stabilize and promote tribochemical reactions and solid-phase reactions.

Moreover, the efficiency of processing the GaN substrate 5 can be increased by making the surface of the processing member hydrophilic by irradiating the ultraviolet light. In addition, contamination derived from organic matter remaining on the surface of the synthetic quartz surface plate 3 can be removed by irradiation with ultraviolet light.

Further, since the GaN substrate 5 can be irradiated with ultraviolet light through the synthetic quartz surface plate 3 from the bottom side of the synthetic quartz surface plate 3 , the ultraviolet light is positioned so as not to interfere with the sample holder 4 and the ozone supply unit 6 . A light irradiation unit 7 can be arranged. Therefore, the processed surface of the GaN substrate 5 can be directly irradiated with ultraviolet light.

In addition, since the distance between the ultraviolet light irradiation unit 7 and the processing surface of the GaN substrate 5 can be reduced, the illuminance of the ultraviolet light can be easily increased, and various effects of ultraviolet light irradiation that contribute to the processing of the GaN substrate 5 can be improved. be able to

Here, in the present embodiment, the case where the workpiece is formed of the synthetic quartz surface plate 3 is described as an example, but a metal having light transmittance and capable of processing the workpiece is used. An oxide is sufficient, and it is not necessarily required to be formed on the synthetic quartz surface plate 3 .

The processed member may be made of, for example, single crystal sapphire composed of Al ₂ O ₃ , corundum, sapphire glass, sapphire crystal, glass containing SiO ₂ as a main component, and constituent materials thereof. Absent. Further, synthetic quartz, fused quartz, soda-lime glass, borosilicate glass, and the like can be used as glass containing SiO ₂ as a main component.

The synthetic quartz surface plate 3 is fixed on the processing table 2 whose rotational speed is controllable, and the rotation of the processing table 2 allows the synthetic quartz surface plate 3 to rotate in the direction indicated by reference numeral R1 in FIG. ing.

Further, the sample holder 4 is configured to be rotatable in the direction indicated by symbol R2 in FIG. In this state, the GaN substrate 5 and the synthetic quartz surface plate 3 are lowered from above to a position where they come into contact with each other. The symbol P in the drawing indicates the direction in which the load is applied.

In this embodiment, the GaN substrate 5 is used as an example of the workpiece held by the sample holder 4, but the workpiece is not limited to the GaN substrate 5. Diamond-related materials such as diamond, single-crystal diamond, polycrystalline diamond, CVD diamond, and DLC films, and hard and brittle materials such as SiC, AlN, sapphire, SiC ceramics, _{Si3N4 ceramics} , and glass may be used.

Moreover, the alkaline solution to be contained in the ozone gas is not limited to the aqueous KOH solution as long as it is alkaline. For example, an alkaline solution such as NaOH or alkaline electrolyzed water can be contained in ozone gas and used for processing. However, a corrosive aqueous solution is preferable from the viewpoint of etching the modified portion of the surface of the workpiece.

As for the wavelength of the ultraviolet light emitted from the ultraviolet light irradiation unit 7, it is preferable to use ultraviolet light having energy equal to or greater than the bandgap of the workpiece. In other words, the wavelength of the ultraviolet light is selected according to the bandgap of the workpiece.

For example, if the band gap of GaN (about 3.42 eV), ultraviolet light with a wavelength of about 365 nm or less is selected, and if the band gap of SiC (about 3.26 eV), ultraviolet light with a wavelength of about 380 m or less is selected. be done.

A processing method using the processing apparatus 1 configured as described above will be described below. That is, an example of a processing method to which the present invention is applied will be described.

In one example of the processing method to which the present invention is applied, ozone gas is supplied from the ozone supply unit 5 to the contact portion between the synthetic quartz surface plate 3 and the GaN substrate 5 while rotating the synthetic quartz surface plate 3 . Further, ultraviolet light is irradiated from the ultraviolet light irradiation unit 7, and the ultraviolet light transmitted through the GaN substrate 5 is irradiated toward the surface of the GaN substrate 5 to be processed.

In this processing method, on the surface to be processed of the GaN substrate 5, tribochemical reaction occurs at the friction surface between the synthetic quartz surface plate 3 and the GaN substrate 5, and the surface to be processed of the GaN substrate 5 and the ultraviolet light are caused by the irradiation of ultraviolet light. This chemical reaction promotes surface modification of the surface to be processed.

Then, the synthetic quartz surface plate 3 physically and chemically removes the surface-modified portion of the surface to be processed of the GaN substrate 5 to remove the surface.

Further, in the modified portion of the surface to be processed of the GaN substrate 5, the surface is removed by etching the modified portion with the KOH aqueous solution contained in the ozone gas.

By rotating the synthetic quartz surface plate 3 and the GaN substrate 5 while they are in contact with each other, the surface to be processed of the GaN substrate 5 is simultaneously modified and removed. The surface to be processed of the GaN substrate 5 is removed physically and chemically, and the surface to be processed is planarized.

Further, while supplying ozone gas to the contact portion between the synthetic quartz surface plate 3 and the GaN substrate 5, the ozone gas is thermally decomposed by frictional heat generated at the contact portion to generate atomic oxygen. Further, the generation of atomic oxygen from ozone gas is promoted by irradiation with ultraviolet light from the ultraviolet light irradiation unit 7 .

Atomic oxygen generated from this ozone gas stabilizes and promotes tribochemical reactions and solid-phase reactions, enabling stable and highly efficient physical and chemical processing of the GaN substrate 5 .

In addition, by irradiating with ultraviolet light, it is possible to prevent the surface of the GaN substrate 5 after processing from forming linear protuberances. In addition, surface modification of the GaN substrate 5 can be promoted by photoexcitation of ultraviolet light. Furthermore, irradiation with ultraviolet light promotes the generation of atomic oxygen from ozone gas, and can further stabilize and promote tribochemical reactions and solid-phase reactions.

Moreover, the efficiency of processing the GaN substrate 5 can be increased by making the surface of the processing member hydrophilic by irradiating the ultraviolet light. In addition, contamination derived from organic matter remaining on the surface of the synthetic quartz surface plate 3 can be removed by irradiation with ultraviolet light.

[effect]
A processing method and processing apparatus to which the present invention is applied supplies ozone gas containing water or an alkaline solution to a contact portion of a member to be processed and a workpiece, and irradiates the surface of the workpiece to be processed with ultraviolet light. Therefore, it is possible to achieve stable, high-precision and high-efficiency machining while suppressing the formation of linear protuberances.

EXAMPLES Examples and comparative examples of the present invention will be described below. In addition, the embodiment shown here is an example and does not limit the present invention.

[Example 1]
As the processing method of Example 1 of the present invention, processing was performed under the following conditions. First, as the processing method of Example 1 of the present invention, GaN (10 mm×10 mm) as a workpiece was pressed against a soda-lime glass platen with a load of 0.5 kg, and the soda-lime glass platen was rotated at 200 rpm. The sample holder was rotated at 31.25 rpm while rotating at a rocking distance of 3 mm and a rocking speed of 0.1 mm/s. Further, an ozone gas (5 L/min) containing a KOH aqueous solution (0.1 mol/L, pH 12.6) was supplied from an ozone supply unit to the contact portion between the soda-lime glass platen and GaN. Further, ultraviolet light (UV irradiation distance: 22 mm, UV illuminance: 1075 mW/cm ² ) was irradiated from the ultraviolet light irradiation unit toward a certain range of the processed surface of GaN. Processing was performed for 1 hour under these conditions.
In Example 1, the surface roughness of GaN after processing was observed with a metallurgical microscope and measured with a non-contact shape measuring machine (scanning white light interferometer, Zygo NewView7300) for evaluation. In FIG. 2, the left diagram is a diagram for distinguishing between the UV-irradiated area and the UV-unirradiated area, and the right diagram is a slope image (differential image).

As shown in the diagram on the left side of FIG. 2, the inside of the circular range indicated by symbol C of GaN is the UV irradiation range (symbol X1) irradiated with ultraviolet light on the surface to be processed, and the circular range indicated by symbol C. is a UV unirradiated range (symbol X2) on the surface to be processed that is not irradiated with ultraviolet light.

Further, as a result of the processing of Example 1, as shown on the right side of FIG. It was confirmed that the formation of linear protuberances was suppressed as compared with the area outside the circular range.

3 shows the result of measuring the surface roughness of a part of the processed region of the surface to be processed with a non-contact shape measuring machine for the processing of Example 1. As shown in FIG. In FIG. 3, the upper stage shows a height image, and the lower stage shows a slope image (differential image).

As is clear from FIG. 3A, which is the processed region before processing, and FIG. As a result, the processed surface of the workpiece was processed with high accuracy, and the arithmetic mean roughness (Ra) value in the measurement range of the processed surface was 0.155 nm, and the formation of linear bumps was not confirmed, and the surface was smooth. was found to have been processed into The value of arithmetic mean roughness (Ra) in the measurement range of the surface to be processed before processing was 1.942 nm. Further, as is clear from FIG. 3C, which is the processed region of the UV non-irradiated range after processing in Example 1, in the UV non-irradiated range, the range without linear protuberances is processed smoothly. However, as a result, remarkable formation of linear protuberances was confirmed.

[Example 2]
In the processing method of Example 2 of the present invention, processing was performed by changing the type of processing member from the soda-lime glass of Example 1 to a synthetic quartz surface plate. The processing conditions in Example 2 were that the type of processing member was changed from the processing conditions in Example 1, and the UV illuminance of the ultraviolet light was 1332 mW/cm ² . The reason why the UV illuminance of the ultraviolet light in Example 2 is higher than the UV illuminance of the ultraviolet light in Example 1 is that the soda-lime glass surface plate and the synthetic quartz surface plate have different transmittances of ultraviolet light. are doing.
In Example 2 above, the surface roughness of GaN after processing was evaluated by observing it with a metallurgical microscope and measuring it with a non-contact shape measuring machine. In FIG. 4, the left figure is a diagram for distinguishing between the UV-irradiated area and the UV-unirradiated area, and the right figure is a Slope image (differential image).

As shown in the diagram on the left side of FIG. 4, the inner side of the circular range indicated by symbol C of GaN is the UV irradiation range (symbol X1) irradiated with ultraviolet light on the surface to be processed, and the circular range indicated by symbol C. is a UV unirradiated range (symbol X2) on the surface to be processed that is not irradiated with ultraviolet light.

Further, as a result of the processing of Example 2, as shown on the right side of FIG. It was confirmed that the formation of linear protuberances was suppressed as compared with the area outside the circular range.

5 shows the result of measuring the surface roughness of a part of the processed region of the surface to be processed with a non-contact shape measuring machine for the processing of Example 2. As shown in FIG. In FIG. 5, the upper image shows the height image, and the lower image shows the slope image (differential image).

As is clear from FIG. 5A, which is the processed region before processing, and FIG. As a result, the processed surface of the workpiece was processed with extremely high accuracy, and the arithmetic mean roughness (Ra) value in the measurement range of the processed surface was 0.169 nm, and the formation of linear bumps was confirmed. It was found that the surface was processed smoothly. The arithmetic mean roughness (Ra) in the measurement range of the surface to be processed before processing was 1.535 nm. Further, as is clear from FIG. 5C, which is the processed region of the UV non-irradiated range after processing in Example 2, in the UV non-irradiated range, the range without linear protuberances is processed smoothly. However, the result confirmed the formation of linear protuberances.

Moreover, the processing efficiency in Example 2 was 4282 nm/h, indicating sufficient processing efficiency. The processing efficiency is obtained by forming a groove having a predetermined depth in the GaN to be processed, and calculating the processing efficiency from the amount of change in the depth of the groove before and after processing.

In addition, FIG. 6 shows the results of measuring the surface roughness of the surface to be processed in the UV irradiation range with a non-contact shape measuring machine for Examples and Example 2 described above. In FIG. 6, the upper image shows the height image, and the lower image shows the slope image (differential image). As is clear from FIG. 6, it is clear that both the processing of Example 1 using soda-lime glass and the processing of Example 2 using a synthetic quartz surface plate as a processing member can provide a highly accurate processed surface. became.

In order to confirm the effect of ultraviolet light irradiation in the present invention, studies were conducted using Example 3 and Comparative Examples 1 and 2 below.

Here, in Example 3, processing was performed under the same conditions as in Example 2 described above, and a synthetic quartz surface plate was employed as the processing member, and ozone gas containing a KOH aqueous solution was supplied and ultraviolet light was applied. Is going. On the other hand, in Comparative Example 1, under the conditions of Example 3, the ozone gas containing the KOH aqueous solution was not supplied, and ultraviolet light irradiation was performed. Comparative Example 2 is a process in which ozone gas containing a KOH aqueous solution is supplied under the conditions of Example 3, and ultraviolet light irradiation is not performed.

7 shows the results of measurement of the surface roughness of a part of the processed region of the surface to be processed with a non-contact shape measuring machine for the processing of Example 3, Comparative Examples 1 and 2. As shown in FIG. The upper image shows the height image, and the lower image shows the slope image (differential image).
As is clear from FIG. 7(c), which is the processing area in the UV irradiation range after processing in Example 3, the processed surface of the workpiece can be processed with very high precision by the processing in Example 3 in the UV irradiation range. The processed surface had an arithmetic mean roughness (Ra) value of 0.169 nm in the measurement range, indicating that the surface was processed smoothly with no formation of linear bumps. Further, as is clear from FIG. 7A showing the results of Comparative Example 1 and FIG. 7B showing the results of Comparative Example 2, the ozone gas containing the KOH aqueous solution was not supplied, and the ultraviolet light was irradiated. A high-precision surface could not be obtained in the processing performed, or in the processing in which the ozone gas containing the KOH aqueous solution was supplied and the ultraviolet light irradiation was not performed.

Further, as shown in FIG. 8, the processing efficiency in Example 3 was 4282 nm/h, indicating sufficient processing efficiency. On the other hand, the processing efficiency of Comparative Example 1 was 2247 nm/h, and the processing efficiency of Comparative Example 2 was 2558 nm/h.

REFERENCE SIGNS LIST 1 processing device 2 processing table 3 synthetic quartz surface plate 4 sample holder 5 GaN substrate 6 ozone supply section 7 ultraviolet light irradiation section

Claims (12)

A processing member made of a metal oxide having optical transparency is brought into contact with a work piece, an ozone gas containing water or an alkaline solution is supplied to the contact portion, and the surface of the processing member that comes into contact with the work piece. A processing method by tribochemical reaction comprising a step of displacing the processing member in contact with the workpiece while irradiating the same workpiece with ultraviolet light from the opposite surface side,
The workpiece is made of GaN,
The ultraviolet light has a wavelength of 365 nm and an illuminance of 10 mW/cm ² or more, and the ultraviolet light has a wavelength of 365 nm or less.
processing method. The processing according to claim 1, wherein the processing member is made of any one of single-crystal sapphire composed of _{Al2O3 ,} corundum, sapphire glass, sapphire crystal, and glass mainly composed of _SiO2 . Method. 3. The processing method according to claim 1, wherein the processing member is made of synthetic quartz. The processing method according to any one of claims 1 to 3, wherein the ozone gas is ozone gas accompanied by a mist of water or an alkaline solution. The processing method according to any one of claims 1 to 4, wherein the alkaline solution is a KOH aqueous solution. In order to promote hydrophilic treatment on the surface of the processing member and the surface of the workpiece, atomic oxygen is generated from the ozone gas, and the atomic oxygen is transferred to the contact portion of the processing member and the workpiece. 6. The processing method according to any one of claims 1 to 5. a processed member made of a metal oxide having optical transparency;
a holding mechanism that holds a predetermined workpiece in contact with the workpiece;
an ozone gas supply unit that supplies ozone gas containing water or an alkaline solution to a contact portion between the processing member and the workpiece;
an ultraviolet light irradiation unit that irradiates the workpiece with ultraviolet light from the side opposite to the surface of the workpiece that contacts the workpiece;
A processing apparatus using a tribochemical reaction, comprising a driving unit that displaces the processing member while the processing member and the workpiece are in contact with each other,
The workpiece is made of GaN,
The ultraviolet light has a wavelength of 365 nm and an illuminance of 10 mW/cm ² or more, and the ultraviolet light has a wavelength of 365 nm or less.
processing equipment. The processing according to claim 7, wherein the processing member is made of any one of single-crystal sapphire made of _{Al2O3 ,} corundum, sapphire glass, sapphire crystal, and glass mainly composed of _SiO2 . Device. 9. The processing apparatus according to claim 7, wherein the processing member is made of synthetic quartz. The processing apparatus according to any one of claims 7 to 9, wherein the ozone gas is ozone gas accompanied by a mist of water or an alkaline solution. The processing apparatus according to any one of claims 7 to 10, wherein the alkaline solution is a KOH aqueous solution. In order to promote hydrophilic treatment on the surface of the processing member and the surface of the workpiece, atomic oxygen is generated from the ozone gas, and the atomic oxygen is transferred to the contact portion of the processing member and the workpiece. 12. The processing apparatus according to any one of claims 7 to 11, which supplies to the.

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