JP6843396B2 - Plasma etching processing method for multi-component materials - Google Patents

Description

The present invention relates to a plasma etching processing method for a multi-component material, which can suppress deterioration of surface roughness in the processing of the multi-component material.

Reaction Sintered Silicon Carbide (RS-SiC), which is a multi-component material, has excellent corrosion resistance, heat resistance, and abrasion resistance, and has properties such as high rigidity, high thermal conductivity, low thermal expansion, and low specific gravity. Therefore, it is a material suitable for a mold material for a glass mold.

However, since it has high hardness and is chemically inert, scratches and formation of a work-altered layer become a problem in grinding using diamond abrasive grains. Further, in CMP (Chemical Mechanical Polishing) used in the polishing process, good surface roughness without damage can be obtained, but the processing speed is slow and the polishing liquid called slurry used for polishing is used to prevent aggregation and the like. Since maintenance is difficult and the purchase price and industrial waste treatment cost are high, the development of an alternative technology is desired (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2003-197574

Therefore, what the present invention seeks to solve in view of the above-mentioned situation is that even if the material is a multi-component material with high hardness and chemically inertness, there is no scratching or formation of a work-affected layer, and the cost is efficiently low. The point is to provide a processing method that can obtain uniform and good surface roughness without damage.

The present inventor has focused on plasma etching processing. In the case of plasma etching processing, even if the material has high hardness and is chemically inert, it can be processed efficiently and at low cost without scratching or forming a processing alteration layer. In particular, if atmospheric-pressure plasma chemical vaporization machining (AP-PCVM) known as a highly efficient chemical damage-free processing method is used, processing can be performed more efficiently and at low cost.

However, although plasma etching processing can obtain good surface roughness in the case of single component materials such as Si, SiC, and quartz wafers, the surface roughness is poor in the case of multi-component materials, and good surface roughness is obtained. In addition, the processing amount (etching rate) in the processing region was not uniform, and a good processed surface could not be obtained.

Therefore, as a result of further diligent studies by the present inventor, the difference in the reactivity of each component constituting the multi-component material due to plasma is the cause of the deterioration of the surface roughness and the non-uniformity of the processing amount. It has been found that the surface roughness can be made good and the amount of processing in the processing region can be made uniform by considering the reactivity by plasma, and the present invention has been completed.

That is, the present invention includes the following inventions.
(1) In the plasma etching processing method for a multi-component material, the plasma generation condition is set to a plasma generation condition within a range in which the etching rate of the material composed of each component constituting the multi-component material is almost the same. , A plasma etching processing method characterized in that a multi-component material is plasma-etched using the plasma generation conditions.

(2) The plasma etching processing method according to (1), wherein the plasma generation condition is a mixing ratio of reaction gases.
(3) The multi-component material is RS-SiC, the reaction gas is _{a mixed gas of CF 4} and O ₂ , and the mixing ratio of the reaction gas is set to 80 to 90% of the _{O 2 gas, and plasma etching is performed (} 2) The plasma etching processing method described.

(4) The machining gap is set to a machining gap within a range in which the shape of the machining mark of the material composed of each component constituting the multi-component material is substantially circular or elliptical, and the multi-component is set under the machining gap. The plasma etching processing method according to any one of (1) to (3), wherein the material is plasma-etched. The "machining mark" referred to in the present invention is a static machining mark.

(5) In a plasma etching processing method for a multi-component material, the processing gap is set within a range in which the shape of the processing mark of the material composed of each component constituting the multi-component material is substantially circular or elliptical. A plasma etching processing method characterized by setting and plasma etching a multi-component material under the processing gap.

According to the present invention as described above, the plasma generation condition is set to a plasma generation condition within a range in which the etching rate of the material composed of each component constituting the multi-component material is substantially the same, and the plasma generation condition is set. By plasma etching the multi-component material using the above, unevenness due to the difference in the etching rate of each component does not occur, and good surface roughness can be obtained efficiently and at low cost without damage.

In particular, as the plasma generation condition, the mixing ratio of the reaction gas, which greatly affects the etching rate, is set to a mixing ratio within a range in which the etching rate of the material composed of each component is the same, so that it is more efficient and good. Surface roughness can be obtained. For example, when the multi-component material is RS-SiC, the reaction gas is _{a mixed gas of CF 4} and O ₂ , and the mixing ratio of the reaction gas is set to 80 to 90% of the _{O 2 gas to achieve good surface roughness efficiency.} You can get it well.

Further, the shape of the processing mark of the material composed of each component constituting the multi-component material is set to a processing gap within a range of being substantially circular or elliptical, and the multi-component material is plasma-etched under the processing gap. By doing so, uniform processing can be performed without causing non-uniformity of the processing amount (etching rate) due to the deviation of the etching rate in the processing region of each component.

(A) and (b) are explanatory views which show the plasma etching processing apparatus which concerns on the typical embodiment of this invention. (A) is a scanning white light interferometer (SWLI) image showing the processing marks of each component material in the processing gap of 3.0 mm and the processing marks of the multi-component material in the same gap, and (b) is the processing gap. SWLI image showing the processing marks of each component material at 6.0 mm and the processing marks of the multi-component material at the same gap. The graph which shows the relationship between the mixing ratio of a reaction gas and the etching rate of each component material. (A) is a SWLI image showing the processing marks of the multi-component material according to the reaction gas composition (mixing ratio is 80% oxygen) of FIG. 3A, and the graph showing the surface shape of the ab cross section, (b) is. The SWLI image showing the processing marks of the multi-component material according to the reaction gas composition (mixing ratio: oxygen 85%) of B in FIG. 3 and the graph showing the surface shape of the ab cross section, (c) is the graph of C in FIG. The SWLI image showing the processing marks of the multi-component material due to the reaction gas composition (mixing ratio of 90% oxygen) and the graph showing the surface shape of the ab cross section, (d) is the reaction gas composition (mixing) of FIG. 3D. A SWLI image showing processing marks of a multi-component material with a ratio of 50% oxygen) and a graph showing the surface shape of ab cross sections. (A) is a scanning electron microscope (SEM) image of the processed surface of the multi-component material according to the reaction gas composition of C in FIG. 3 (mixing ratio is 90% oxygen), and (b) is the reaction gas of D in FIG. SEM image of the processed surface of a multi-component material according to the composition (mixing ratio is 50% oxygen). (A) is a SWLI image showing a processing mark of a multi-component material for 30 seconds according to the reaction gas composition (mixing ratio of oxygen is 50%) of FIG. 3D, and (b) is a SWLI image showing a processing mark of the same 60 seconds. , (C) is a graph showing the surface shape of the ab cross section in each case. (A) is a SWLI image showing a processing mark of a multi-component material for 60 seconds according to the reaction gas composition (mixing ratio of 90% oxygen) of C in FIG. 3, and (b) is a SWLI image showing a processing mark of the same 120 seconds. , (C) is a graph showing the surface shape of the ab cross section in each case. (A) is a diagram showing an atomic force microscope (AFM) image of the surface of a multi-component material having a diamond wrap finish before plasma etching processing and a cross-sectional shape between A and B thereof, and FIG. 3 (b) is a diagram showing a cross-sectional shape between A and B. The figure showing the AFM image of the processed surface of the multi-component material by the reaction gas composition of D (mixing ratio is 50% oxygen) and the cross-sectional shape between A and B thereof, (c) is the reaction gas composition of C of FIG. The figure showing the AFM image of the processed surface of the multi-component material with (mixing ratio of 90% oxygen) and the cross-sectional shape between A and B thereof, (d) shows the multi-component material with a reaction gas composition having a mixing ratio of 95% oxygen. The figure which shows the AFM image of the processed surface and the cross-sectional shape between AB. (A) is a schematic view showing a cross-sectional structure of a multi-component material that has been diamond-wrapped before plasma etching, and (b) is a poly-based reaction gas composition (mixing ratio of 50% oxygen) of FIG. 3D. Schematic diagram showing the cross-sectional structure of the component material after processing, (c) is a schematic view showing the cross-sectional structure of the multi-component material after processing according to the reaction gas composition (mixing ratio of 90% oxygen) of C in FIG. d) is a schematic view showing a cross-sectional structure of a multi-component material after processing with a reaction gas composition having a mixing ratio of 95% oxygen.

Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In the plasma etching processing method for a multi-component material of the present invention, the etching rate of the material composed of each component constituting the multi-component material is set to a condition within a range in which the etching rate is substantially the same for the plasma generation condition, and this condition is set. It is characterized in that a multi-component material is plasma-etched by using the material, whereby unevenness due to a difference in etching rate of each component does not occur, and good surface roughness can be obtained.

Such plasma generation conditions include the mixing ratio of the reaction gas, the flow rate of the process gas including the reaction gas, the electric energy, the processing gap, and the like. In particular, the mixing ratio of the reaction gas greatly affects the etching rate. It is most effective to set this mixing ratio so that the etching rates of the respective component materials are substantially the same.

Further, the present invention is a plasma etching processing method for a multi-component material, in which the processing gap is within a range in which the shape of the processing mark of the material composed of each component constituting the multi-component material is substantially circular or elliptical. It is also characterized by setting a processing gap and plasma-etching a multi-component material under the processing gap, so that the processing amount (etching rate) is not large due to the deviation of the etching rate in the processing region of each component. Uniform processing can be performed without homogenization.

In the following embodiments, in addition to setting the plasma generation conditions so that the etching rates of the materials composed of each component are substantially the same, as a preliminary step, the shape of the processing marks of the material composed of each component is substantially circular or. Although the processing gap is set within the range of elliptical shape, the present invention is not limited to using both settings in combination, and the plasma generation condition is such that only one of them, that is, the etching rate is almost the same. However, the shape of the processing marks of the material composed of each component does not become almost circular or elliptical, and vice versa.

As the "multi-component material" to be processed in the present invention, a multi-component material capable of plasma etching processing can be widely applied, and is particularly suitable for processing ceramic materials. Among ceramic materials, it is effective to target reaction-sintered ceramic materials that are damage-free and difficult to obtain good surface roughness. Hereinafter, an example in which reaction-sintered silicon carbide (RS-SiC) is plasma-etched using an atmospheric pressure plasma CVM (AP-PCVM) apparatus will be described.

FIG. 1 shows a schematic configuration of the AP-PCVM device 1 used in the present embodiment. A ceramic tube 2 for supplying argon gas as a carrier gas is provided in the central portion, and a cavity resonator 3 is arranged around the ceramic tube 2. A microwave electric field having a frequency of 2.45 GHz is applied to the cavity resonator 3 so that an electric field having the maximum strength is generated near the tip of the ceramic tube 2 (the tip position of the inner conductor 30 of the cavity resonator 3). .. Argon plasma P1 is generated inside the vicinity of the tip of the ceramic tube 2 by this microwave.

_{Further, argon, CF 4} , and O ₂ gas are supplied as process gases from the side supply port 11 into the cavity resonator 3 facing the tip opening of the ceramic tube 2, and the active argon in the argon plasma is discharged. By colliding with the reaction gas components CF ₄ and O ₂ in the process gas, a secondary plasma P2 that generates F radicals and active oxygen that contribute to etching is generated and discharged from the nozzle 4 at the tip of the cavity resonator 3. First, the surface of the workpiece 9 is etched.

The etching process of RS-SiC by the plasma P2 is carried out by an oxidation process of Si and SiC constituting RS-SiC and an etching process of _{Si, SiC and oxide SiO 2.} Oxidation process
SiC + 4O * → SiO ₂ + CO ₂ ↑
Si + 2O * → SiO ₂
Each reaction occurs, and the etching process is
SiO ₂ + 4F * → SiF ₄ ↑ + O ₂ ↑
SiC + 2O * + 4F * → SiC ₄ ↑ + CO ₂ ↑
Si + 4F * → SiF ₄ ↑
Each reaction occurs. O * indicates active oxygen and F * indicates F radical.

The cavity resonator 3 is supported on an XYZ table (not shown) and is numerically controlled by a computer (CNC) to adjust the machining gap between the tip of the nozzle 4 and the workpiece and move it in the lateral direction. The above device configuration is an example, and of course other device configurations may be used. Further, the types of carrier gas and process gas are not limited to the above gases, and suitable ones can be selected according to the workpiece. RS-SiC, which is the workpiece 9 of the present embodiment, was diamond-wrapped as a pre-processing before being processed by the AP-PCVM device 1.

In the present embodiment, when plasma etching the RS-SiC, the processing gap is first set to an optimum value. The SWLI image at the right end of FIG. 2 (a) shows the processing marks on the RS-SiC surface at the processing gap of 3.0 mm, and the SWLI image at the right end of FIG. 2 (b) shows the RS-SiC surface at the processing gap of 6.0 mm. The processing marks on the SiC surface are shown. The processing time was 60 seconds, and the mixing ratio (ratio of flow rate (sccm)) of _{the reaction gas (CF 4} , O ₂ gas) to the O _{2 gas was set to 50%.} The surface roughness is not good in either case, but when the machining gap is 3.0 mm, the etching rate in the machining area (machining mark) is biased to the left half region, and the machining amount (etching rate) becomes non-uniform. On the other hand, when the machining gap is 6.0 mm, it can be seen that the machining amount (etching rate) in the machining region (machining mark) is uniform.

Then, for the SWLI images at the left end and the center of FIG. 2A, each component material (SiC (single crystal SiC) and Si (single crystal Si)) constituting the multi-component material (RS-SiC) is prepared. The processing marks on the surface of the material processed under the same processing gap of 3.0 mm and other same conditions are shown. For the SWLI images at the left end and the center of FIG. 2B, each component material (SiC (single crystal SiC) and Si (single crystal Si)) constituting the multi-component material (RS-SiC) is prepared and the same. The processing gap is 6.0 mm, and the processing marks on the surface of the material processed under the same conditions are shown.

From this result, when the processing gap is 3.0 mm, the processing of the Si component has a distorted shape that is offset to the left as shown by the SWLI image in the center of FIG. 2 (a). It can be seen that the processing amount of is also biased toward the left half area. On the other hand, when the processing gap is 6.0 mm, as shown in FIG. 2 (b), the shape of the processing marks is almost circular or elliptical and uniform for both SiC (single crystal SiC) and Si (single crystal Si) materials. As a result, it can be seen that the processing of RS-SiC is also uniform.

As described above, if the shape of the processing mark of the material composed of each component constituting the multi-component material is set to the processing gap within the range of being substantially circular or elliptical, uniform processing can be performed. If the processing gap G becomes too large, the processing rate drops. Therefore, in the processing of RS-SiC by the AP-PCVM device using the _{reaction gases CF 4} and O _{2 gas as in the present embodiment, 5.0 mm to 7.} The machining gap is set to 0 mm, preferably 6.0 mm.

Next, the mixing ratio (ratio of flow rate (sccm)) of the O ₂ gas of the reaction gas (CF ₄ , O _{2 gas) is set.} 4 (a) to 4 (d) are a SWLI image showing processing marks when the mixing ratios are 80%, 85%, 90%, and 50% oxygen, respectively, and a graph showing the surface shape of the ab cross section. Is. The image of the 50% processed mark is almost the same as the image at the right end of FIG. 2B processed under the same conditions. From this result, _{it can be seen that if the mixing ratio of O 2} gas is set to 80 to 90%, processing with good surface roughness can be performed.

Then, in FIG. 3, each component material (SiC (single crystal SiC) and Si (single crystal Si)) constituting the multi-component material (RS-SiC) is prepared, and _{the mixing ratio of O 2} gas is changed for each. It is a graph which shows the etching rate at the time of processing. In the graph, A, B, C, and D _{indicate the positions where the O 2} gas mixing ratios are 80%, 85%, 90%, and 50%, respectively. _{As can be seen from this graph, the O 2} gas mixing ratios of 80 to 90% (A to C) subjected to the above-mentioned good surface roughness processing are the respective component materials (SiC (single crystal SiC) and Si (single crystal). It can be seen that the etching rate of Si)) is a mixing ratio in a range in which the etching rate is almost the same.

As described above, if the etching rate of the material composed of each component constituting the multi-component material is set to the mixing ratio of the reaction gas within a range of substantially the same rate, processing with good surface roughness can be performed. It is. In the processing of RS-SiC by the AP-PCVM apparatus using the _{reaction gases CF 4} and O ₂ gas as in the present embodiment _{, as described above, the O 2} gas mixing ratio is preferably 80 to 90%, more preferably. It is set to 85-90%.

FIG. 5 (a) is _{an SEM image of the processed surface of RS-SiC when the O 2} gas mixing ratio is 90%, and FIG. 5 (b) is the processed surface of RS-SiC when the _{O 2 gas mixing ratio is 50%.} It is an SEM image of. When the O ₂ gas mixing ratio is 90%, the surface is smooth, but when the O ₂ gas mixing ratio is 50%, the etching rate of Si is high, and the surface is uneven with SiC greatly exposed.

6 (a) is, _{O 2} SWLI shows a machining mark of 30 seconds RS-SiC when the gas mixing ratio of 50% image, (b) the SWLI image also shows a machining mark of 60 seconds, (c ) Is a graph showing the surface shape of the ab cross section in each case. As can be seen from FIG. 6, the O ₂ gas mixture ratio of 50%, the processing time of the surface becomes rough be doubled (only Si proceeds to process, a perforated state) only proportional to the machining depth is time do not do.

On the other hand, FIG. 7 (a), _{O 2} SWLI shows a machining mark of 60 seconds RS-SiC when the gas mixing ratio of 90% image, (b) the SWLI image also shows the processing marks 120 seconds, (c ) Is a graph showing the surface shape of the ab cross section in each case. As can be seen from FIG. 7, when the O ₂ gas mixing ratio is 90%, the surface is slightly roughened by doubling the processing time, but the processing depth proportional to the time can be obtained. From this, if the etching rate of the material composed of each component constituting the multi-component material is set to the mixing ratio of the reaction gas within a range of substantially the same rate, it is possible to perform processing with good surface roughness. It can be seen that the processing efficiency can also be improved.

FIG. 8 (a) shows an atomic force microscope (AFM) image of the RS-SiC surface finished with diamond wrap before plasma etching, and a cross-sectional shape between A and B thereof. FIG. 8 (b) is O. _The figure showing the AFM image of the processed surface of RS-SiC when the 2 gas mixing ratio is 50% and the cross-sectional shape between A and B thereof, (c) shows _{the RS-SiC when the O 2} gas mixing ratio is 90%. shows AFM images of the work surface and the cross-sectional shape between the a-B, (d) is, _{O 2} gas mixture ratio of 95% and the AFM image and the processed surface of RS-SiC time between the a-B It is a figure which shows the cross-sectional shape.

As shown in FIG. 8A, the diamond wrap finish has a good surface roughness, but a work-altered layer is formed on the entire surface, and scratches are unavoidable. As shown in FIG. 8 (b), _{O 2} gas mixture ratio of 50%, the large etching rate of Si, the surface becomes rough. As shown in FIG. 8C, good surface roughness can be obtained _{when the O 2 gas mixing ratio is 90%.} As shown in FIG. 8D, when the O ₂ gas mixing ratio is 95%, on the contrary, the etching rate of SiC is large and the surface is roughened in the form of protruding Si.

FIG. 9 shows this in a schematic view of the cross-sectional structure. (A) to (d) correspond to (a) to (d) of FIG. The black-painted portion of the surface in (a) in the figure represents the processed alteration layer. In particular, as shown in (b) to (d), it is the imbalance of the etching rate of each component material that makes it difficult to improve the surface roughness by plasma etching of the multi-component material, so that this becomes the same. By setting the plasma generation conditions (O ₂ gas mixing ratio in this example), the good surface roughness as shown in (c) can be obtained.

RS-SiC has excellent corrosion resistance, heat resistance, and wear resistance, and has characteristics such as high rigidity, high thermal conductivity, low thermal expansion, and low specific gravity. Therefore, it is efficiently processed into good surface roughness at low cost without damage. According to the present invention, RS-SiC can be used, for example, in a mirror for a space telescope, a mold for a glass-molded aspherical lens, and the like, which greatly contributes to the development of industry.

Although the embodiments of the present invention have been described above, the present invention is not limited to these examples, and it goes without saying that the present invention can be implemented in various forms without departing from the gist of the present invention.

1 AP-PCVM device 2 Ceramic tube 3 Cavity resonator 4 Nozzle 9 Work piece 30 Inner conductor 11 Supply port G Machining gap P1, P2 Plasma

Claims (2)

It is a plasma etching processing method for multi-component materials.
Set the plasma generation conditions to the plasma generation conditions within the range where the etching rate of the material composed of each component constituting the multi-component material is almost the same.
It is a plasma etching processing method in which a multi-component material is plasma-etched using the plasma generation conditions.
The plasma generation condition is the mixing ratio of the reaction gas.
The multi-component material is RS-SiC.
The reaction gas was a mixed gas of CF ₄ and O _2, and Help plasma etching method the mixing ratio is set to O ₂ gas 80-90% to plasma etching of the reaction gas. The processing gap is set to a processing gap within a range in which the shape of the processing mark of the material composed of each component constituting the multi-component material is approximately circular or elliptical.
The original working gap, plasma etching method of claim 1 Symbol mounting the multi-component material is plasma etched.