JPWO2017150308A1 - Processing method and apparatus using radical adsorption transport - Google Patents

Abstract

[PROBLEMS] To use radicals rich in chemical reactivity to process Si, SiC, GaN, diamond and other wide bandgap semiconductors with high efficiency, and in a dry state, the device configuration is simple. The present invention provides a processing method and apparatus using radical adsorption transport that is easy and safe to handle. In the vicinity of a movable tool having a surface having corrosion resistance and adsorption ability against radicals, a reactive gas plasma in which a gas containing at least a radical generating element or a substituent group and a rare gas are mixed is generated. The radicals generated in the plasma generation region are adsorbed on the tool surface to give reactive active species, and the reactive active species are transported to the workpiece surface by the movement of the tool and react with atoms on the workpiece surface in contact with the tool. The reaction product produced by the chemical reaction with the active species is removed, and the workpiece surface is etched using the tool surface as the machining reference surface.

Description

  The present invention relates to a processing method and apparatus using radical adsorption transport, and more specifically, it is possible to flatten or process an arbitrary shape of wide band gap semiconductor substrates such as Si, SiC, GaN, and diamond. The present invention relates to a processing method and apparatus using radical adsorption transport.

  Currently, Si is mainly used in semiconductor devices, but its performance is approaching the limit due to the physical properties of Si. Therefore, wide band gap semiconductors represented by silicon carbide (SiC), gallium nitride (GaN), and diamond are attracting attention. Since these power semiconductor device materials have physical properties such as band gap, dielectric breakdown electric field value, thermal conductivity, and electron mobility several times to several tens of times larger than Si, power devices are fabricated using these materials. In this case, it is possible to achieve high voltage resistance, low power consumption, high speed operation, and the like. Because of these advantages, wide band gap semiconductors are expected as materials that will drive the field of next-generation power semiconductor devices.

  However, planarization of a semiconductor substrate where surface crystallinity is important in manufacturing a semiconductor power device is essential, and wide band gap semiconductor substrates such as SiC, GaN, and diamond are hard and brittle. High-efficiency flattening is difficult in processing without causing damage. P-CVM (Plasma Chemical Vaporization Machining) is a chemical processing method using plasma in an atmospheric pressure atmosphere, and can be processed with high efficiency and no damage to the crystal due to its high radical density. (Patent Documents 1 and 2). However, processing by plasma is essentially isotropic etching, and the entire surface direction is processed, so that it is not suitable for flattening the surface of an uneven workpiece with high efficiency.

  Therefore, we proposed the Catalyst-Referred Etching (CARE) method, which improved the drawback of chemical polishing by the use of a reference surface catalyst on the polishing platen. (Patent Document 3). In the CARE method, a catalytic action is added by using Ni or Pt for the polishing surface plate serving as a reference surface, and an etching reaction is induced with the help of halogen radicals generated only in the vicinity of the polishing surface plate. Can be selectively processed. Further, since the processing proceeds only by the etching reaction, no damage can be entered in principle, and the reference surface shape can be transferred chemically. To date, SiC or GaN step terrace structures have been realized by CARE processing, and it has been confirmed that the substrate surface can be planarized to the atomic level. However, since the CARE method described in Patent Document 3 uses a processing liquid in which halogen-containing molecules are dissolved, for example, hydrofluoric acid, it must be handled with great care. However, there is a problem that the apparatus configuration is complicated.

  In addition, essentially using only water as the working fluid, the potential of the workpiece relative to the working fluid is controlled, and OH radicals generated by the dissociation of water molecules by the action of the catalyst are adsorbed on the surface of the workpiece, resulting in hydrolysis. The Water-CARE method is capable of processing difficult-to-work products such as solid oxide, wide band gap semiconductor substrates such as SiC and GaN, etc., by the processing principle of removing the decomposition products from the workpiece surface and proceeding with the processing. It has been proposed (Patent Documents 4 and 5). However, these Water-CARE methods are excellent processing methods that do not use any abrasives or abrasive grains, and are easy to treat waste liquid, but the processing speed is slow, especially the processing speed for diamond is almost low. Could not process. Moreover, since the process is basically performed in a wet state, there is a particular problem as compared with the process in a dry state.

Japanese Patent No. 2521127 Japanese Patent No. 2962583 JP 2006-114632 A International Publication No. 2013/084934 Japanese Patent Laying-Open No. 2015-173216

  Therefore, in view of the above-described situation, the present invention intends to solve difficult-to-work products such as wide band gap semiconductor substrates such as Si, SiC, GaN, and diamond using radicals rich in chemical reactivity. Disclosed is a processing method and apparatus that uses radical adsorption transport that is simple and easy to handle because it is a process in a dry state despite the fact that it can be processed with high efficiency. In the point.

  In order to solve the above-mentioned problems, the present invention has constituted a processing method and a processing apparatus that use the following radical adsorption transport.

(1)
Plasma composed of a reactive gas in which a gas containing at least the above-described element or substituent that generates radicals and a rare gas are mixed in the vicinity of a movable tool having a surface having corrosion resistance and adsorption ability for radicals rich in chemical reactivity. The radicals generated in the plasma generation region are adsorbed to the tool surface to give reactive active species, and the reactive active species are transported to the workpiece surface by the movement of the tool and contact with the tool. Radiation adsorption transport, characterized in that the workpiece surface is etched using the tool surface as a processing reference plane by removing a reaction product generated by a chemical reaction between an atom and a reactive species on the workpiece surface. Is a processing method.

(2)
The processing method using radical adsorption transport according to (1), wherein the element that generates the radical is a halogen element of F or Cl, and the radical is an F radical or a Cl radical.

(3)
The processing method using radical adsorption transport according to (1), wherein the substituent that generates the radical is an OH group, and the radical is an OH radical.

(4)
The processing method using the radical adsorption transport according to any one of (1) to (3), wherein at least a surface of the tool is formed of Ni.

(5)
The processing method using the radical adsorption transport according to any one of (1) to (3), wherein the surface of the tool is an alumina or yttria coating layer.

(6)
The processing method according to (1), wherein the tool is a rotary surface plate tool, and the surface of the workpiece is flattened using the surface of the rotary surface plate tool as a processing reference surface.

(7)
The tool is a spherical rotary tool having a rotary shaft, and plasma is generated in the vicinity of the outer peripheral portion of the spherical rotary tool, and radicals are adsorbed on the outer peripheral portion of the spherical rotary tool, thereby generating plasma of the spherical rotary tool. The outer peripheral portion different from the region is rotated while being brought into contact with the workpiece surface at a predetermined pressure, and the contact portion is numerically scanned on the workpiece surface to be processed into an arbitrary shape (1). Is a processing method.

(8)
A rotating surface plate tool having a surface with corrosion resistance and adsorption capacity for radicals rich in chemical reactivity;
An electrode head disposed with a predetermined gap with respect to the surface of the rotating surface plate tool;
A gas supply means for supplying a reactive gas obtained by mixing a gas containing at least an element that generates radicals or a substituent and a rare gas to the electrode head;
A high frequency power source that generates a plasma in the gap by applying a high frequency electric field to the electrode head;
The workpiece is held in front of the rotating surface of the rotating surface plate tool to which the radicals generated in the plasma generation region are adsorbed and the reactive species are applied, and the workpiece is placed on the surface of the rotating surface plate tool at a predetermined pressure. A work holder to be contacted,
And processing the surface of the workpiece using the rotary surface plate tool surface as a processing reference surface.

(9)
A spherical rotary tool that has a rotary shaft and has corrosion resistance and adsorption capacity for radicals rich in chemical reactivity on at least the outer peripheral surface;
An electrode arranged with a predetermined gap with respect to the outer periphery of the spherical rotary tool;
A gas supply means for supplying a reactive gas obtained by mixing a gas containing an element or substituent that generates at least the radical to the electrode and a rare gas;
A high frequency power source for generating a plasma in the gap by applying a high frequency electric field to the electrode;
The spherical rotation is performed in a state where an outer peripheral portion different from the plasma generation region of the spherical rotary tool to which the reactive species are attached by adsorbing radicals generated in the plasma generation region is in contact with the workpiece surface at a predetermined pressure. Scanning means for relatively numerically controlling scanning of the tool and the workpiece;
Radical adsorbing and transporting, wherein the contact portion between the spherical rotary tool and the workpiece is numerically controlled and scanned on the surface of the workpiece to process the spherical rotary tool surface into a desired shape Assisted processing equipment.

(10)
The processing apparatus using radical adsorption transport according to (8) or (9), wherein the element that generates the radical is a halogen element of F or Cl, and the radical is an F radical or a Cl radical.

(11)
The processing apparatus using radical adsorption transport according to (8) or (9), wherein the substituent that generates the radical is an OH group, and the radical is an OH radical.

(12)
The processing apparatus using radical adsorption transport according to (8) or (9), wherein at least a surface of the rotary surface plate tool or the spherical rotary tool is formed of Ni.

(13)
The processing apparatus using radical adsorption transport according to (8) or (9), wherein a surface of the rotary surface plate tool or the spherical rotary tool is an alumina or yttria coating layer.

  According to the processing method and apparatus using the radical adsorption transport of the present invention as described above, dry etching using the tool surface on which radicals are adsorbed as a processing reference surface is realized. There is no other technique having such a processing reference surface in the dry etching technique. According to the present invention, it is possible to expect a strain-free flattening of a single crystal material with high efficiency. For example, it is possible to expect higher quality and lower cost of next-generation semiconductor substrates such as wide band gap semiconductor substrates such as SiC, GaN and diamond. Furthermore, even in the case of a substrate or a polycrystalline substrate having a crystallinity non-uniformity caused by crystal growth, which is difficult to process uniformly in the prior art, the present invention can perform uniform processing by the effect of the processing reference surface. There is a possibility that it can be realized. In the present invention, since the plasma does not directly contact the surface of the workpiece, it is considered that processing is possible even for a material having a low heat resistance temperature.

It is a conceptual diagram of the processing apparatus which used the radical adsorption transport of this invention. It is the simplified perspective view of the processing apparatus which also used the radical adsorption transport of this invention. It is a simple perspective view of the planarization processing apparatus of 1st Embodiment of this invention. Similarly, a part of the flattening apparatus of the first embodiment is shown, (a) is a perspective view of the electrode head, (b) is a partial cross-sectional view showing the relationship between the electrode head and the workpiece. The concept of the numerical control processing apparatus of 2nd Embodiment of this invention is shown, (a) is a front view, (b) is a side view. The processing experiment 1 is a white interferometer image showing a result of a planarization processing experiment of a Si substrate and showing a surface state under conditions where plasma is not generated for each place and time. The processing experiment 1 is a white interferometer image showing a result of a planarization processing experiment using an F radical of a Si substrate, and showing a surface state under conditions where plasma is generated for each place and time. It is the white interferometer image which showed the result of the planarization process experiment of a SiC substrate as the process experiment 2, and showed the surface state before a process and after a process. It is a conceptual diagram of the processing apparatus in the case of using the mixed gas of He and water vapor | steam as reaction gas. As processing experiment 3, the result of the flattening processing experiment of the Si substrate is shown, and is a white interferometer image showing the surface state under conditions where plasma is not generated for each place and time. As processing experiment 3, the result of the flattening processing experiment by the OH radical of the Si substrate is shown, and it is a white interferometer image showing the surface state under the condition where plasma is generated for each place and time. As processing experiment 4, the result of the flattening processing experiment of the Si substrate using the rotating surface plate tool in which the alumina coating layer is formed is shown, and is a white interferometer image of the surface state under the condition that plasma is not generated. As the processing experiment 4, the result of the planarization processing experiment by the F radical of the Si substrate using the rotating surface plate tool on which the alumina coating layer is formed is shown, and the surface condition under the condition where the plasma is generated is shown for each place and time. White interferometer image.

  Next, the present invention will be described in more detail based on the embodiments shown in the accompanying drawings. 1 and 2 are conceptual diagrams of a processing apparatus using radical adsorption transport according to the present invention, where W is a workpiece, 1 is a rotating surface plate tool, 2 is an electrode head, 3 is a gas supply means, 4 is A high frequency power source and 5 indicate work holders.

  The processing principle of the present invention is as follows. First, in the vicinity of a movable tool (rotary surface plate tool 1) having a surface having corrosion resistance and adsorption ability against free radicals with high chemical reactivity (hereinafter simply referred to as “radicals”), at least the radicals are introduced. A plasma composed of a reaction gas in which a gas containing an element or substituent to be generated and a rare gas are mixed is generated, and a radical R is generated in the plasma generation region P. When the surface of the movable tool passes through the plasma generation region P, the radical R is highly coordinated to atoms on the tool surface or excessively adsorbed to become a reactive species, and the workpiece is processed by the movement of the tool. It is transported to the surface of the object W. The reactive species transported to the surface of the workpiece W in contact with the tool moves to the surface atom side of the workpiece W, weakens the back bonds of the surface atoms, and bonds to the reaction product. Become. This reaction product is removed from the surface of the workpiece W, whereby surface atoms of the workpiece W are removed, that is, etched.

Here, examples of the element that generates the radical include a halogen element of F or Cl. Specifically, the halogen element-containing gas includes SF ₆ , CF ₄ , NF _{3, and the} like that contain the F element. there are _{Cl 2,} CCl _4, PCl 4 such as those containing the element Cl. Here, O ₂ gas may be used as the gas for generating the radical. Further, as the substituent for generating the radical, it includes OH groups, typically as a gas containing OH groups is H _{2 O.} In addition, the said substituent shows the partial structure of a molecule | numerator and respond | corresponds to the said free radical. And as a noble gas, helium gas and argon gas are mentioned. A small amount of a third gas may be added to the reaction gas in addition to the radical generating gas and the rare gas. Here, the pressure P _G in the reaction gas is a basic atmospheric pressure may be reduced pressure state or a vacuum state, but in this case, reactive species which radicals R are formed on the tool surface by adsorption Immediate removal from the tool surface must be avoided.

  The surface of the rotating surface tool 1 is a processing reference surface. The material that can be used for the surface of the rotary surface plate tool 1 is required to have corrosion resistance and adsorption ability against radicals, and various metal materials such as Ni can be used. Alternatively, a coating layer may be formed by spraying alumina or yttria. In this embodiment, the surface of the rotary surface plate tool 1 is formed by forming a 20 μm thick Ni layer 6 by electroless Ni plating, or by forming an alumina coating layer by thermal spraying. Here, the Ni layer 6 may be formed by electrolytic plating or vacuum deposition in addition to electroless plating. Further, the tool 1 itself may be made of bulk Ni.

  An electrode head 2 is arranged with a predetermined gap G with respect to the surface of the rotary surface plate tool 1, and at least radicals are generated from the gas supply means 3 in the gap between the electrode head 2 and the surface of the rotary surface plate tool 1. A reactive gas in which a gas containing an element or a substituent to be mixed with a rare gas is supplied. The electrode head 2 forms a gas flow path constituting the gas supply means 3 at the center, is connected to a gas cylinder (not shown) by a gas supply pipe, and injects a reactive gas toward the tip.

  Then, a high-frequency electric field is applied to the electrode head 2 from a high-frequency power source 4 to generate atmospheric pressure plasma composed of the reaction gas in the gap G. The rotating surface plate tool 1 and the electrode head 2 may be housed in a chamber and plasma may be generated in a reduced pressure atmosphere. Usually, the high frequency power source 4 uses an RF power source having a frequency of 13.56 MHz, but a frequency up to about 200 MHz can be used.

Here, the radical R generated in the plasma generation region P is highly coordinated to Ni atoms in the Ni layer 6 on the surface when the surface of the rotary platen tool 1 passes through the plasma generation region P. Or it adsorb | sucks excessively and it becomes a reactive species, and it is transported to the rotation direction front with the rotation. A workpiece W held by a work holder 5 is brought into contact with a surface in front of the rotation direction of the plasma generation region of the rotary surface plate tool 1 at a predetermined pressure. This was the contact pressure P _L, it distinguishes a pressure P _G in the processing atmosphere. Thereby, the reactive species derived from the radicals R adsorbed on the Ni layer 6 in the plasma generation region and transported by the rotation of the rotary platen tool 1 are formed on the surface of the workpiece W and the rotary platen tool 1. The reaction product is generated by weakening and bonding the back bonds of the constituent atoms of the workpiece W at the contact portion with the workpiece, and the reaction product is volatilized or removed by an appropriate method. The surface of the object W is processed. Since the workpiece W is selectively processed from the convex portion that is in contact with the surface of the rotary surface plate tool 1, the workpiece W is flattened using the Ni layer 6 as a processing reference surface. In this case, if the work holder 5 is rotated about an axis in the same direction as the rotation axis of the rotary platen tool 1, the processing is averaged, so that the flatness is further increased.

  As described above, the main configuration of the present invention includes plasma generation means (electrode head 2, gas supply means 3, high-frequency power supply 4) for generating radicals, and a tool (rotary surface plate tool) for transporting radicals by adsorbing them on the surface. 1) and a work holder 5 that holds the workpiece W and keeps contact with the tool. According to the present invention, it is possible to selectively dry-etch only the portion in contact with the radical adsorption tool, which is extremely innovative. F radicals, Cl radicals, O radicals, OH radicals and the like, which are the main reactive species in atmospheric pressure plasma etching, are generated in the plasma generation region and adsorbed on the surface of the tool (rotating platen tool). The surface on which these radicals are adsorbed is in a highly coordinated state rich in reactivity. Then, reactive species derived from radicals adsorbed by the movement of the tool are transported to the surface of the workpiece W, and the surface atoms of the workpiece W in contact with the tool react with the reactive species on the tool surface by a chemical reaction. The surface of the workpiece is etched by becoming a product and being removed.

A planarization processing apparatus according to the first embodiment of the present invention is shown in FIGS. The flattening apparatus of the present embodiment is provided with an opening 7 at the center, a horizontal rotary surface plate tool 1 having a surface having corrosion resistance and adsorption ability against radicals, and the surface of the rotary surface plate tool 1 An electrode head 2 arranged with a predetermined gap with respect to the gas head, a gas supply means 3 for supplying a reactive gas in which a gas containing at least a radical generating element or a substituent and a rare gas are mixed to the electrode head 2; A high-frequency power source 4 that generates a plasma in the gap by applying a high-frequency electric field to the electrode head 2, and a surface of the surface of the rotating surface plate tool 1 to which radicals generated in the plasma generation region P are adsorbed and reactive species are applied. holding the workpiece W forward in the rotational direction, the work holder 5 is brought into contact with the workpiece W on the rotating surface plate surface of the tool 1 at a predetermined pressure (contact pressure P _L), comprising a workpiece The surface of those to be processed flattened. Here, the pressure P _G in the processing atmosphere is the basic atmospheric pressure, may be a reduced pressure atmosphere.

  A Ni layer 6 is formed on the surface of the rotary surface plate tool 1 by electroless Ni plating. Here, the rotary surface plate tool 1 is grounded, and the Ni layer 6 serving as a machining reference surface is at ground potential. A base portion of the electrode head 2 is supported by a vertical shaft at the center of the opening 7 of the rotary surface plate tool 1 so that the head portion can be swung horizontally. As shown in FIGS. 4A and 4B, the electrode head 2 holds the base portion of the horizontal arm portion 8 with a rotary joint 9, and the head portion 10 is placed on the surface of the rotary surface plate tool 1 with a predetermined amount. Arranged in a gap. Further, the electrode head 2 has a gas flow path 11 formed continuously from the rotary joint 9 to the arm portion 8 and the head portion 10, and constitutes a part of the gas supply means 3. Since the head portion 10 of the electrode head 2 is worn out by being exposed to plasma, it is preferable to have a replaceable structure. The electrode head 2 can adjust the distance from the workpiece W held by the work holder 5 by changing the rotation angle around the rotary joint 9.

  The rotational drive mechanism of the rotary surface plate tool 1 and the drive mechanism of the work holder 5 have the same structure as a conventional polishing apparatus, and the conventional polishing apparatus includes the electrode head 2, the gas supply means 3, and the high-frequency power source 4. The planarization apparatus of the present invention can be configured only by adding. In addition, since the present invention is dry etching, a structure around water is unnecessary, and the apparatus configuration can be simplified.

A numerically controlled machining apparatus according to the second embodiment of the present invention is shown in FIG. The numerically controlled processing apparatus according to the present embodiment includes a rotary shaft 20, a spherical rotary tool 21 that has corrosion resistance and adsorption ability against radicals at least on the outer peripheral surface, and an outer peripheral portion 22 of the spherical rotary tool 21. And an electrode 23 arranged with a predetermined gap G, and a gas supply means (not shown) for supplying a reactive gas obtained by mixing a rare gas and a gas containing at least a radical generating element or a substituent to the electrode 23. A plasma of the high-frequency power source 24 that generates a plasma in the gap G by applying a high-frequency electric field to the electrode 23 and a plasma of the spherical rotary tool 21 to which a radical generated in the plasma generation region P is adsorbed and a reactive species is applied. the outer peripheral portion 22 which is different from the generation region P, being in contact with a predetermined pressure to the surface of the workpiece W (contact pressure P _L), and the spherical rotary tool 21 Scanning means (not shown) for relatively numerically scanning the workpiece W, and numerically scanning the contact portion C between the spherical rotary tool 21 and the workpiece W on the surface of the workpiece W Then, it is processed into an arbitrary shape. In this case, reactive species derived from radicals adsorbed on the outer peripheral portion 22 of the spherical rotary tool 21 are transported to the contact portion C with the workpiece W as the spherical rotary tool 21 rotates. The pressure P _G in the processing atmosphere in the present embodiment, although the basic atmospheric pressure, may be a reduced pressure atmosphere.

  The spherical rotary tool 21 is not limited to a literal spherical shape, and may be any shape as long as the disk-shaped or tire-shaped outer peripheral portion 22 has an arc surface. In order to machine the surface of the workpiece W into an arbitrary shape, a profile of the unit machining trace formed at the contact portion C by the spherical rotary tool 21 is acquired, and local machining on the surface of the workpiece W is performed. Based on the amount data, the staying time of the contact portion C is defined. Actually, since the scanning is repeated, the staying time is controlled by changing the scanning speed. The numerical control scanning is performed by driving either the spherical rotary tool 21 or the workpiece W.

<Processing experiment 1 to verify the processing principle>
Next, an experiment for demonstrating the processing principle of the present invention was performed using the flattening apparatus. In other words, a basic experiment was conducted to confirm whether radicals generated in the plasma were adsorbed on the rotating platen and the reactive species provided on the surface of the rotating platen were supplied to the contact area with the workpiece. The results are shown.

Using a rotating plate tool with electroless Ni plating applied to a thickness of 20 μm as a radical adsorption tool, He: SF ₆ = 99: 1 reaction gas (pressure P _G : large) at a position about 15 mm upstream of the sample (silicon substrate). The change in the surface of the sample when the plasma (atmospheric pressure) was generated and when it was not generated was compared. As a sample, a surface having a poor surface roughness of a 10 mm square substrate of Si was used. Sample rotates only the rotating platen tool without rotating, in that the rotational speed is 10 rpm, the contact pressure P _L for pressing the sample into rotary platen tool is 3 kPa. Table 1 shows experimental conditions for generating plasma. The surface roughness of the sample surface was evaluated every hour. As an evaluation method of the surface roughness, four observation points were measured in a range of 64 × 48 (μm ² ) using a white interferometer (NewView 200 manufactured by Zygo).

  First, FIG. 6 shows the results of processing in a state where plasma is not generated (no voltage applied, no reactant gas supplied). The sample was processed under a rotational speed of 10 rpm and a pressure of 3 kPa, and the surface roughness was measured every hour. Figure 6 shows white interferometer (Zygo NewView 200) images from before processing to processing for 3 hours at the center, top, right, and left of the substrate, indicated by a circle in the left column of FIG. Show. The upper part of the Si substrate is a part close to the electrode head 2, and so on. Since no improvement in surface roughness was observed at any of the observation points, it was confirmed that there was no machining effect under the processing conditions of a rotational speed of 10 rpm and a contact pressure of 3 kPa.

  Next, FIG. 7 shows the result of processing in a state where plasma is generated (with voltage applied and with reactive gas supplied). With the plasma generated under the conditions shown in Table 1, the sample was processed under a rotational speed of 10 rpm and a contact pressure of 3 kPa, and the surface roughness was measured every hour. Fig. 7 shows white interferometer images (Zygo's NewView 200) from 4 points before and after 3 hours of processing at the center, top, right and left of the substrate, indicated by ○ in the left column of Fig. 7. Show. Due to the action of reactive species derived from F radicals, the surface roughness (rms) at any observation point has been reduced from more than 400 nm before processing to 10 nm or less after processing for 3 hours, and a significant improvement is seen. It was.

  Since the surface roughness was not improved in the processing without plasma generation, it is considered that the machining action does not work, so the radicals generated in the plasma generation region are adsorbed on the surface of the polishing platen, It was confirmed that was supplied to the sample surface with the rotation of the polishing platen. In plasma etching where the sample surface is directly exposed to plasma, the removal rate is isotropic, so flattening is not possible. However, by generating plasma between the rotating platen tool and the electrode, F radicals are adsorbed to the rotating platen tool. The surface of the sample was flattened by supplying the reactive species derived from the F radicals to the sample surface as the rotary surface plate tool rotated. In this experiment, it became clear that reactive species derived from F radicals were supplied to the sample surface, and that the Si substrate was planarized.

<Processing experiment 2 to verify the processing principle>
Next, FIG. 8 shows the results of a similar experiment using a SiC substrate as a workpiece using the planarization apparatus. Plasma generation conditions are the same as those shown in Table 1, the contact pressure P _L of the SiC substrate in this case is 5 kPa. By the planarization process for 3 hours, the surface roughness (rms) of the SiC substrate was planarized from more than 100 nm before the process to 10 nm or less. It was confirmed that the SiC substrate was flattened similarly to the Si substrate by the action of the F radical.

<Processing experiment 3 to verify the processing principle>
Next, a reactive gas (pressure P _G : atmospheric pressure) of He and H ₂ O (water vapor) is used as a reactive gas, and the Si substrate (area: 0.59 cm) is processed using the planarization apparatus. The surface of ² ) was processed. Table 2 shows plasma generation conditions and processing conditions. In this case as well, a rotating surface plate tool with electroless Ni plating applied to a thickness of 20 μm was used. Contact pressure _{P L} of the Si substrate is 3.4 kPa. As shown in FIG. 9, the reaction gas containing water vapor was used by putting water in a sealed container, blowing out He gas in water, and collecting the reaction gas of He and water vapor in the gas phase. The gap G between the rotary platen tool 1 and the electrode head 2 was 200 μm, and the distance L from the electrode head 2 to the downstream Si substrate was 15 mm.

  First, FIG. 10 shows the result of processing in a state where plasma is not generated (no voltage applied, no reaction gas supplied). In FIG. 10, the upper part is the upper part of the Si substrate and the lower part is a white interferometer (Zygo NewView 200) image of the central part of the Si substrate. It shows after processing. Also in this case, it can be seen that there is almost no change in the surface of the Si substrate even after 1 hour.

  Next, FIG. 11 shows the result of processing in a state where plasma is generated (with voltage applied and with reactive gas supplied). In FIG. 11, the upper row is the white interferometer (Zygo NewView 200) image of the upper portion of the Si substrate and the lower row is the center portion of the Si substrate. It shows after processing, after processing for 1.5 hours, after processing for 2 hours, and after processing for 3 hours. In the upper part of the Si substrate, the surface roughness (rms) before processing was 167 nm before processing, but it is improved to 22 nm after processing for 1 hour and 16 nm after processing for 3 hours. . On the other hand, in the central part of the Si substrate, the surface roughness (rms) before processing was 184 nm before processing, but improved to 48 nm after processing for 1 hour and 16 nm after processing for 3 hours. I understand that. It is considered that the generation of water vapor plasma generated OH radicals, which contributed to the processing of the Si substrate surface.

<Processing experiment 4 to prove the processing principle>
Finally, using the planarizing apparatus, a rotating surface plate tool in which the surface of a conductive substrate is coated with alumina (Al ₂ O ₃ ) is used, and a Si substrate (area: 0.78 cm ² ) is processed as a workpiece. The surface was processed. Table 3 shows plasma generation conditions and processing conditions. In this case is substantially the same as the conditions shown in Table 1, it is as large as 5.1kPa contact pressure P _L of the Si substrate with respect to the rotating surface plate tool. The gap G between the rotary surface plate tool and the electrode head was 600 μm, and the distance L from the electrode head to the downstream Si substrate was 15 mm.

First, FIG. 12 shows the result of processing in a state where plasma is not generated (no voltage application, no reaction gas supply). In this case, the contact pressure P _L is mechanical processing line is generated even 1 kPa, was found not able to completely flattening. It can be inferred that the reason why the processing line is generated is that the fine Si scrap generated by chipping the edge of the Si substrate is sandwiched between the rotary surface plate tool and the Si substrate and damages the surface of the Si substrate.

  Next, FIG. 13 shows the result of processing in a state where plasma is generated (with voltage applied and with reactive gas supplied). In FIG. 13, the upper row is the white interferometer (Zygo NewView 200) image of the upper part of the Si substrate, and the lower row is the lower part of the Si substrate. After, 1.5 hours after processing is shown. On the upper part of the Si substrate, the surface roughness (rms) before processing was 547 nm before processing, but it was greatly improved to 72 nm after processing for 30 minutes, and after processing for 1 hour, 21 nm, 1. It turns out that it has improved to 24 nm after processing for 5 hours. On the other hand, in the lower part of the Si substrate, the surface roughness (rms) before processing was 592 nm before processing, but it has not improved much to 470 nm after processing for 30 minutes, but after processing for 1 hour. It can be seen that after processing at 80 nm for 1.5 hours, the thickness is improved to 40 nm.

This machining experiment shows that the Si substrate could be planarized even using an alumina tool. An alumina tool is advantageous in practical use because it has excellent surface stability and little deterioration with time. Incidentally, even 5.1kPa contact pressure P _L of the Si substrate with respect to the rotating surface plate tool, the mechanical machining line does not occur, the fine Si debris adhering to the rotating platen tool plasma generation region When passing, it can be assumed that it was removed by plasma etching.

  In the above examples, examples of application to flattening processing and numerical control processing using a spherical rotating tool have been shown, but other applications such as grooving using a wire traveling tool are also possible depending on the shape of the radical adsorption tool. It is done. In addition, diamond tools and gemstones can be processed into a flat surface or an acute angle shape.

1 rotary surface plate tool,
2 electrode heads,
3 gas supply means,
4 High frequency power supply,
5 Work holder,
6 Ni layer,
7 opening,
8 Arm part,
9 Rotary joint,
10 head,
11 Gas flow path,
20 rotation axis,
21 Spherical rotary tool,
22 outer periphery,
23 electrodes,
24 high frequency power supply,
W Workpiece,
G gap,
P plasma generation region,
The R radical,
C contact part,

Claims (13)

  Plasma composed of a reactive gas in which a gas containing at least the above-described element or substituent that generates radicals and a rare gas are mixed in the vicinity of a movable tool having a surface having corrosion resistance and adsorption ability for radicals rich in chemical reactivity. The radicals generated in the plasma generation region are adsorbed to the tool surface to give reactive active species, and the reactive active species are transported to the workpiece surface by the movement of the tool and contact with the tool. Radiation adsorption transport, characterized in that the workpiece surface is etched using the tool surface as a processing reference plane by removing a reaction product generated by a chemical reaction between an atom and a reactive species on the workpiece surface. Is a processing method.   2. The processing method using radical adsorption transport according to claim 1, wherein the element that generates the radical is a halogen element of F or Cl, and the radical is an F radical or a Cl radical.   The processing method using radical adsorption transport according to claim 1, wherein the substituent that generates the radical is an OH group, and the radical is an OH radical.   The processing method using radical adsorption transport according to any one of claims 1 to 3, wherein at least a surface of the tool is formed of Ni.   The processing method using radical adsorption transport according to any one of claims 1 to 3, wherein a surface of the tool is an alumina or yttria coating layer.   The processing method using radical adsorption transport according to claim 1, wherein the tool is a rotary surface plate tool, and the surface of the workpiece is flattened using the surface of the rotary surface plate tool as a processing reference surface.   The tool is a spherical rotary tool having a rotary shaft, and plasma is generated in the vicinity of the outer peripheral portion of the spherical rotary tool, and radicals are adsorbed on the outer peripheral portion of the spherical rotary tool, thereby generating plasma of the spherical rotary tool. 2. The radical adsorption transport according to claim 1, wherein an outer peripheral portion different from the region is rotated while being brought into contact with the workpiece surface at a predetermined pressure, and the contact portion is numerically scanned on the workpiece surface to be processed into an arbitrary shape. Is a processing method. A rotating surface plate tool having a surface with corrosion resistance and adsorption capacity for radicals rich in chemical reactivity;
An electrode head disposed with a predetermined gap with respect to the surface of the rotating surface plate tool;
A gas supply means for supplying a reactive gas obtained by mixing a gas containing at least an element that generates radicals or a substituent and a rare gas to the electrode head;
A high frequency power source that generates a plasma in the gap by applying a high frequency electric field to the electrode head;
The workpiece is held in front of the rotating surface of the rotating surface plate tool to which the radicals generated in the plasma generation region are adsorbed and the reactive species are applied, and the workpiece is placed on the surface of the rotating surface plate tool at a predetermined pressure. A work holder to be contacted,
And processing the surface of the workpiece using the rotary surface plate tool surface as a processing reference surface. A spherical rotary tool that has a rotary shaft and has corrosion resistance and adsorption capacity for radicals rich in chemical reactivity on at least the outer peripheral surface;
An electrode arranged with a predetermined gap with respect to the outer periphery of the spherical rotary tool;
A gas supply means for supplying a reactive gas obtained by mixing a gas containing an element or substituent that generates at least the radical to the electrode and a rare gas;
A high frequency power source for generating a plasma in the gap by applying a high frequency electric field to the electrode;
The spherical rotation is performed in a state where an outer peripheral portion different from the plasma generation region of the spherical rotary tool to which the reactive species are attached by adsorbing radicals generated in the plasma generation region is in contact with the workpiece surface at a predetermined pressure. Scanning means for relatively numerically controlling scanning of the tool and the workpiece;
Radical adsorbing and transporting, wherein the contact portion between the spherical rotary tool and the workpiece is numerically controlled and scanned on the surface of the workpiece to process the spherical rotary tool surface into a desired shape Assisted processing equipment.   10. The processing apparatus using radical adsorption transport according to claim 8, wherein the element that generates the radical is a halogen element of F or Cl, and the radical is an F radical or a Cl radical.   The processing apparatus using radical adsorption transport according to claim 8 or 9, wherein the substituent that generates the radical is an OH group, and the radical is an OH radical.   The processing apparatus using radical adsorption transport according to claim 8 or 9, wherein at least a surface of the rotary surface plate tool or the spherical rotary tool is formed of Ni.   The processing apparatus using radical adsorption transport according to claim 8 or 9, wherein a surface of the rotary surface plate tool or the spherical rotary tool is an alumina or yttria coating layer.

Images