Plasma CVM processing method and device therefor

Abstract

To provide a plasma CVM processing method and a device therefor that can suppress an increase in surface roughness of a surface to be processed when etching a single crystal semiconductor wafer, a dielectric substrate of crystal or the like, or an X-ray mirror material by a plasma CVM process using a nozzle-type electrode under high pressure.SOLUTION: A plasma CVM processing method in which high-frequency power is applied to a nozzle-type electrode disposed facing a processing surface of a workpiece to generate plasma based on a process gas under high pressure, and neutral radicals generated in the plasma are caused to act on the surface of the workpiece to remove a volatile substance generated by a chemical reaction between the neutral radicals and a workpiece constituent element during processing. The method comprises a steps of simultaneously performing: a step of sucking in the process gas supplied to a periphery of the nozzle-type electrode from a gas suction port opened in the nozzle-type electrode on the workpiece-processing surface side; and a step of applying a positive bias voltage to a conductive workpiece holder that holds the workpiece.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a plasma chemical vapor deposition (PCD) processing method and apparatus that suppresses an increase in surface roughness of single crystal semiconductor wafers, dielectric substrates such as quartz crystal, or X-ray mirror materials. [Background technology]

[0002] A method of processing materials using a localized plasma generated by using a process gas under high pressure is known as plasma CVM (Chemical Vaporization Machining) and is well known (Patent Document 1 and Patent Document 2). The processing principle of this plasma CVM is as follows. When a plasma is generated at a processing electrode installed near a workpiece under high pressure and a highly electronegative reactive gas such as a halogen is supplied to this plasma, the reactive gas dissociates and generates highly reactive, high-density neutral radicals. The surface of the workpiece is processed by reacting these neutral radicals with the surface of the workpiece and continuously vaporizing the products generated by the reaction. The high-frequency plasma generated under high pressure near atmospheric pressure is localized near the electrode, and the neutral radicals generated by this are also only present in a limited space, so processing with excellent spatial control is possible. In addition, since the mean free path is short under high pressure, there are few ions with high energy, and it is generally believed that damage to the surface of the workpiece caused by ions hardly occurs, but it cannot be denied that ion acceleration caused by an ion sheath near the surface may have a negative effect on the surface.

[0003] Patent Document 3 discloses high-pressure plasma CVM in which reactive gas is blown out from the central hole of a nozzle-type electrode to generate plasma in the space between the electrode and the workpiece, and although it enables machining with high spatial resolution, it presents the problem of increased surface roughness around the electrode. Based on the knowledge that the cause of increased surface roughness around the electrode is the rapid decrease in gas flow rate with increasing distance from the electrode, a structure with a circular plate provided around the tip of the electrode has been proposed as a means of preventing the decrease in gas flow rate.

[0004] Patent Document 4 presents issues with high-pressure plasma CVM, in which reactive gas is blown out from the central hole of a nozzle-type electrode and plasma is generated in the space between the electrode and the workpiece, such as the machining marks being large compared to the electrode diameter, making precise machining impossible, and the machining rate at the center of the electrode being lower than around it.In response to these issues, a method is proposed to improve the machining profile by sucking out the reactive gas supplied from the periphery through the central hole of the electrode.

[0005] Patent Document 5 proposes a technique for applying a negative bias voltage of 50 V or more to the workpiece (workpiece holder) in a method for plasma etching in which etching gas plasma is sprayed onto the workpiece, although this is a low-pressure plasma technique of around 1 Torr. However, the purpose of applying a negative bias voltage to the workpiece is to increase the ion density in the vicinity of the workpiece to improve the etching rate, and damage to the workpiece due to ion bombardment is unavoidable. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 01-125829 [Patent Document 2] Japanese Patent Application Publication No. 04-246184 [Patent Document 3] Japanese Patent Application Publication No. 09-115692 [Patent Document 4] Japanese Patent Application Publication No. 09-063791 [Patent Document 5] Japanese Patent Application Publication No. 09-115887 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in conventional plasma chemical vapor deposition (PCD) using a nozzle-type electrode (a pipe-shaped machining electrode) under high pressure, machining while ejecting reactive gas from the tip of the nozzle-type electrode causes the surface roughness of the workpiece around the electrode to deteriorate, i.e., the surface becomes rough. It is presumed that the cause of this deterioration in surface roughness is that ions in the plasma collide with the electrode, and the electrode material atoms released into the gas phase by sputtering lose their kinetic energy through collisions with other particles, and are blown onto the workpiece surface by the gas flow and adhere to it. In other words, the electrode material adhering to the workpiece surface acts as a mask, causing uneven etching, and the workpiece surface becomes uneven, causing the surface roughness to deteriorate. In the case of dielectric substrates such as single crystal semiconductor wafers and quartz, the roughness of the workpiece surface reduces the characteristics of the devices manufactured using them, and in the case of X-ray mirror materials, it leads to a deterioration in the focusing characteristics due to wavefront disturbance.

[0008] In view of the above, the present invention aims to provide a plasma CVM processing method and apparatus that can suppress an increase in surface roughness of the processed surface when etching single crystal semiconductor wafers, dielectric substrates such as quartz, or X-ray mirror materials by plasma CVM using a nozzle-type electrode under high pressure. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the present invention provides a plasma CVM processing method and an apparatus therefor, which are configured as follows.

[0010] [Configuration 1] A plasma CVM processing method comprising the steps of: applying high frequency power to a nozzle-type electrode disposed opposite to a processing surface of a workpiece; generating plasma based on a process gas under high pressure; and causing neutral radicals generated in the plasma to act on the surface of the workpiece; and removing volatile substances generated by chemical reactions between the neutral radicals and the constituent elements of the workpiece, a step of sucking in a process gas supplied to the periphery of the nozzle-type electrode through a gas suction port that opens on the processing surface side of the workpiece of the nozzle-type electrode; applying a positive bias voltage to a conductive work holder that holds the work; The steps include simultaneously carrying out Plasma CVM processing method.

[0011] [Configuration 2] The machining is performed under the condition that the average flow velocity of the process gas in the machining gap between the workpiece and the nozzle-type electrode is 2.08 m / s or more and the bias voltage is 50 V or more, or the average flow velocity is 1.04 m / s or more and the bias voltage is 300 V or more; The workpiece after processing is evaluated by the arithmetic mean roughness (Ra) measured by an atomic force microscope (AFM) in a range of 500 nm x 500 nm, and the roughness change Δ obtained by subtracting the surface roughness before processing from the surface roughness after processing of the workpiece is 0.3 nmRa or less. 2. The plasma CVM processing method according to claim 1.

[0012] [Configuration 3] The machining is performed under the condition that the average flow velocity of the process gas in the machining gap between the workpiece and the nozzle-type electrode is 2.6 m / s or more and the bias voltage is 150 V or more, or the average flow velocity is 1.04 m / s or more and the bias voltage is 300 V or more; The roughness change amount Δ is 0.1 nmRa or less; The plasma CVM processing method according to configuration 2.

[0013] [Configuration 4] The nozzle-type electrode and the workpiece are moved relative to each other to control the dwell time of the nozzle-type electrode on the machining surface of the workpiece. 4. A plasma CVM processing method according to configuration 1, 2 or 3.

[0014] [Configuration 5] The process gas is a mixture of a carrier gas and a reactive gas, and has a pressure of 10 to 110 kPa. 4. A plasma CVM processing method according to configuration 1, 2 or 3.

[0015] [Configuration 6] A plasma CVM processing device applies high frequency power to an electrode facing a workpiece, generates plasma based on a process gas under high pressure, and causes neutral radicals generated in the plasma to act on the surface of the workpiece, thereby removing volatile substances generated by chemical reactions between the neutral radicals and the constituent elements of the workpiece, thereby processing the workpiece. A chamber; A conductive work holder that holds the work placed in the chamber; A nozzle-type electrode disposed in the chamber so as to face the processing surface of the workpiece; A gas supply means for supplying a process gas into the chamber; a gas exhaust means for sucking in a process gas supplied to the periphery of the nozzle-type electrode through a gas suction port that opens on the processing surface side of the nozzle-type electrode; a main power source that applies high frequency power to the nozzle-type electrode; a bias power supply that applies a positive bias voltage to the work holder; Equipped with Plasma CVM processing equipment.

[0016] [Configuration 7] The machining is performed under the condition that the average flow velocity of the process gas in the machining gap between the workpiece and the nozzle-type electrode is 2.08 m / s or more and the bias voltage is 50 V or more, or the average flow velocity is 1.04 m / s or more and the bias voltage is 300 V or more; The workpiece after processing is evaluated by the arithmetic mean roughness (Ra) measured by an atomic force microscope (AFM) in a range of 500 nm x 500 nm, and the roughness change Δ obtained by subtracting the surface roughness before processing from the surface roughness after processing of the workpiece is 0.3 nmRa or less. 7. The plasma CVM processing apparatus according to configuration 6.

[0017] [Configuration 8] The machining is performed under the condition that the average flow velocity of the process gas in the machining gap between the workpiece and the nozzle-type electrode is 2.6 m / s or more and the bias voltage is 150 V or more, or the average flow velocity is 1.04 m / s or more and the bias voltage is 300 V or more; The roughness change amount Δ is 0.1 nmRa or less; 8. The plasma CVM processing apparatus according to configuration 7.

[0018] [Configuration 9] The apparatus further includes an XY stage that holds the work holder via an insulator, and the XY stage is driven to relatively move the nozzle-type electrode and the workpiece, thereby controlling the dwell time of the nozzle-type electrode with respect to the machining surface of the workpiece to perform machining. The plasma CVM processing apparatus according to configuration 6, 7 or 8.

[0019] [Configuration 10] The process gas is a mixture of a carrier gas and a reactive gas, and has a pressure of 10 to 100 kPa. The plasma CVM processing apparatus according to configuration 6, 7 or 8. Effect of the Invention

[0020] The plasma CVM processing method and apparatus of the present invention described above have the following advantages.

[0021] In the present invention, by sucking in the process gas supplied around the nozzle-type electrode from the gas inlet opening on the machining surface side of the nozzle-type electrode, even if the electrode material atoms are sputtered by ions in the plasma and released into the gas phase, they are removed from the gas inlet of the nozzle-type electrode by the gas flow, so that the amount of atoms that reach and adhere to the surface of the workpiece can be reduced, thereby suppressing the deterioration of the surface roughness. Furthermore, although the effect of suppressing the deterioration of the surface roughness can be increased by increasing the flow rate (flow velocity) of the process gas, this alone is not sufficient. In addition, by applying a positive bias voltage to the conductive work holder that holds the workpiece, the positive ions in the plasma are prevented from reaching the workpiece surface in a high-energy state, and the deterioration of the surface roughness due to ion bombardment can be effectively suppressed. Note that neutral radicals are not affected by the application of a bias voltage and contribute to the machining of the workpiece.

[0022] In the present invention, by adjusting the range of the gas suction flow rate (flow velocity) of the nozzle-type electrode and the range of the positive bias voltage applied to the work holder, the arithmetic mean roughness (Ra) of a 500 nm x 500 nm area of ​​the work after machining is measured with an atomic force microscope (AFM), and the roughness change amount Δ, obtained by subtracting the surface roughness of the work before machining from the surface roughness after machining, can be reduced to 0.3 nmRa or less.Furthermore, by specifying the optimal range for both, the roughness change amount Δ can be reduced to 0.1 nmRa or less, which means that the deterioration of surface roughness due to plasma CVM processing can be significantly suppressed. [Brief description of the drawings]

[0023] [Figure 1] 1 is a conceptual diagram of a plasma CVM processing apparatus according to the present invention. [Diagram 2] FIG. 2 shows the relationship between the nozzle-type electrode and the workpiece, where (a) is a cross-sectional view and (b) is an explanatory diagram showing the space between the tip of the nozzle-type electrode and the workpiece. [Diagram 3] The figures show AFM images and surface roughness of quartz before and after processing under various conditions. [Figure 4] 1 is a graph showing the change Δ in surface roughness before and after processing of a processed surface of quartz crystal obtained by changing the flow rate (flow speed) of the process gas and the bias voltage. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Next, the present invention will be described in more detail based on the embodiment shown in the attached drawings. Figure 1 shows a conceptual diagram of the plasma CVM processing apparatus of the present invention, in which W denotes a workpiece, 1 denotes a chamber, 2 denotes a workpiece holder, 3 denotes a nozzle-type electrode, 4 denotes a gas supply means, 5 denotes a gas exhaust means, 6 denotes a main power supply, 7 denotes a bias power supply, and 8 denotes an XY stage.

[0025] The plasma CVM processing apparatus of the present invention operates on the processing principle of applying high-frequency power to an electrode facing the workpiece W, generating plasma based on a process gas under high pressure, and causing neutral radicals generated in the plasma to act on the surface of the workpiece, thereby removing volatile substances generated by chemical reactions between the neutral radicals and the workpiece constituent elements.

[0026] Specifically, the plasma CVM processing equipment has the following features: Chamber 1; A conductive work holder 2 that holds the work W placed in the chamber 1; A nozzle-type electrode 3 is disposed in the chamber 1 so as to face the processing surface of the workpiece W; A gas supply means 4 for supplying a process gas into the chamber 1; a gas exhaust means 5 for sucking in a process gas supplied to the periphery of the nozzle-type electrode from a gas suction port 15 opened on the processing surface side of the nozzle-type electrode 3 for the workpiece W; A main power source 6 that applies high frequency power to the nozzle-type electrode 3; a bias power supply 7 for applying a positive bias voltage to the work holder 2; It is equipped with:

[0027] The plasma CVM machining apparatus further comprises an XY stage 8 which holds the work holder 2 via an insulator 9, and the XY stage 8 is driven to move the nozzle-type electrode 3 and the work W relatively to each other, thereby controlling the residence time of the nozzle-type electrode 3 on the machining surface of the work W for machining. The XY stage 8 is composed of a fixed part 10 which is fixed in the chamber 1 and a movable part 11 which moves in the XY directions relative to the fixed part, and the movable part 11 is grounded together with the chamber 1 and is at earth potential. The work holder 2 is attached to the movable part 11 of the XY stage 8 via the insulator 9.

[0028] Here, the workpiece holder 2 adsorbs and holds the workpiece W by using a vacuum chuck method. To set the vacuum chuck to a predetermined negative pressure state, a process gas is sucked in by a pressure reducing pump 12. The sucked process gas is returned to the chamber 1 again, thereby suppressing pressure fluctuations in the chamber 1 and achieving effective use of the process gas. In this embodiment, the adsorption differential pressure of the vacuum chuck is set to 15 kPa.

[0029] The process gas is a mixture of a carrier gas and a reactive gas. In the present invention, high pressure means a pressure near atmospheric pressure, specifically a pressure of 10 to 100 kPa (reduced pressure state), preferably a pressure of 15 to 50 kPa. In this embodiment, the pressure in the chamber 1 is set to 30 kPa. The gas supply means 4 mixes the gases at a predetermined concentration from the carrier gas cylinder 13 and the reactive gas cylinder 14 via MFCs (mass flow controllers) and supplies them into the chamber 1. The process gas in the chamber 1 is exhausted by a vacuum pump through a gas exhaust path 16 that passes through the inside of the nozzle-type electrode 3 from the gas suction port 15 and continues to the outside of the chamber 1. These constitute the gas exhaust means 5. The process gas sucked in by the gas exhaust means 5 also contains volatile substances generated by the reaction and electrode element components scattered by sputtering of the electrode, and are collected by an appropriate filter.

[0030] In this embodiment, since the workpiece W is a quartz wafer, SF6, which generates fluorine radicals, is used as the reactive gas, but it can be selected according to the processing material, and multiple types of gases can be mixed and used. For example, halogen gas, oxygen gas, ozone gas, etc. are used as the reactive gas. Halogen gas includes fluorine gas and chlorine gas. Fluorine gas includes F2, CF4, C2F6, C3F6, C4F8, SF6, etc. Chlorine gas includes Cl2, BCl3, CCl4, etc. There is also CClF3, which contains both fluorine and chlorine. SF6 is selected even if the processing target material is silicon or germanium, and SF6 or O2 is selected if it is diamond. In this embodiment, He is used as the carrier gas, but Ar can also be used. In that case, a stabilizing gas, such as ethanol or ammonia, that is added to add a gas with a smaller ionization potential than the metastable level of Ar and ionized by the Penning effect to generate electrons necessary for generating and maintaining the plasma may be added.

[0031] While supplying the above-mentioned process gas, high frequency power is supplied from the main power supply 6 to the nozzle-type electrode 3 via a matching unit 17, and plasma is generated in a machining gap set between the nozzle-type electrode 3 and the workpiece W. Here, the main power supply 4 has a frequency of 13.56 MHz and a rated output of 300 W. A positive DC bias voltage is applied to the workpiece holder 2 by a bias power supply 7.

[0032] FIG. 2(a) shows the relationship between the tip of the nozzle-type electrode 3 and the workpiece W. The nozzle-type electrode 3 is made of aluminum, has an outer diameter of 4 mmφ (radius R = 2 mm), an inner diameter of 0.5 mmφ (radius r = 0.25 mm), and a machining gap of 1.5 mm. The surface of the nozzle-type electrode 3 is preferably anodized. Plasma is generated in a plasma generation space P surrounded by the outer periphery of the tip of the nozzle-type electrode 3 and the surface of the workpiece W. In the present invention, the average flow rate of the process gas in this plasma generation space P is calculated and defined from the flow rate sucked in from the gas suction port 15 of the nozzle-type electrode 3.

[0033] If there is no gas leak into the vacuum system including the chamber 1, and the pressure inside the chamber 1 is kept constant, the flow rate of the process gas supplied from the gas supply means 4 (volumetric flow rate at 1 atmospheric pressure) and the flow rate of the process gas sucked out by the gas exhaust means 5 (volumetric flow rate at 1 atmospheric pressure) will be the same, and the corresponding mass flow rate should be equal to the mass flow rate sucked out from the gas suction port 15 of the nozzle-type electrode 3, but it is desirable to monitor and accurately control the flow rate of the process gas in the gas exhaust path 16.

[0034] The average flow velocity in the plasma generation space P mentioned above is calculated as follows. As shown in Figure 2(b), a cylindrical space with a diameter of 4 mm and a height of 1.5 mm (volume V [m 3 ]) First, the flow rate at 1 atmosphere (101.3 kPa) is Q [sccm], and the pressure inside the chamber 1 is P [kPa]. The flow rate Q' at the tip of the nozzle-type electrode 3 is Q´=101.3×(Q / P)[sccm] =1.689×10 -6 ×(Q / P)[m 3 / s] This can be expressed as: The time T [s] for this flow rate Q' to pass through volume V is: T=V / Q´ It becomes. The average radial flow velocity v [m / s] is defined as the radial distance (Rr) divided by the time T to pass the flow. v = (Rr) / T =(Rr) × (Q´ / V) =1.689×10 ―6 (Rr)Q / (PV) This is added to the above. Rr=2[mm]-0.25[mm] =1,75[mm](=1.75×10 -3 [m]) V = πR 2 ×1.5 =18.84[mm 3 ](=18.84×10 -9 [m 3]) Substituting, v = 0.156 × (Q / P) [m / s] (1) is obtained. Here, if P = 30 kPa, v = 0.0052 × Q [m / s] (2) It becomes.

[0035] <Comparative experiment> Figure 3A The workpiece W is a quartz wafer (4 inches, surface roughness Ra: 0.091 nm). Before processing, a 500 nm x 500 nm area on the surface of the quartz wafer was measured with an atomic force microscope (AFM), and the surface roughness was found to be 0.091 nmRa and 0.11 nmRms. Here, Ra is the arithmetic mean height, and Rms is the root mean square height, which correspond to ISO Sa and Sq, respectively.

[0036] Figure 3B First, the conventional method of blowing process gas from a nozzle-type electrode was used for processing, and the surface roughness after processing was measured with an AFM (500 nm x 500 nm). The processing conditions in this case were that the process gas was blown from a nozzle-type electrode, and no bias voltage was applied. The processing conditions are shown in Table 1.

[0037] [Table 1]

[0038] Figure 3 C Next, in addition to the conventional processing conditions in Table 1, a positive bias voltage (200V) was applied and the surface roughness was measured with an AFM (500nm x 500nm). The other processing conditions are as shown in Table 1. In other words, the processing conditions in this case are a method in which the process gas is blown out from a nozzle-type electrode and a bias voltage is applied.

[0039] D in Figure 3 Next, processing was performed under the conventional processing conditions in Table 1, with the process gas sucked in through the nozzle-type electrode, and the surface roughness after processing was measured with an AFM (500 nm x 500 nm). In other words, the processing conditions in this case were such that the process gas was sucked in through the nozzle-type electrode, and no bias voltage was applied.

[0040] Figure 3E Then, under the processing conditions (invention method) of Table 2, the process gas was sucked from the nozzle-type electrode (flow rate 500sccm) while applying a bias voltage (200V) and the surface roughness was measured with an AFM (500nm x 500nm). In other words, the processing conditions in this case are a method in which the process gas is sucked from the nozzle-type electrode and a bias voltage is applied.

[0041] [Table 2]

[0042] In this comparative experiment, in the conventional plasma CVM processing method in which the process gas is blown out from the nozzle-type electrode without applying a bias voltage, the surface roughness significantly deteriorated from 0.091 nmRa before processing to 3.34 nmRa after processing (Fig. 3B). In contrast, when the process gas is blown out from the nozzle-type electrode but a bias voltage is applied, the surface roughness was 2.55 nmRa, and it was found that the deterioration of the surface roughness could be suppressed somewhat (Fig. 3C). On the other hand, when the process gas is sucked in from the nozzle-type electrode and processing is performed without applying a bias voltage, the surface roughness was 0.48 nmRa, and the deterioration of the surface roughness was significantly suppressed, but it was still insufficient (Fig. 3D). Furthermore, it was found that when the process gas is sucked in from the nozzle-type electrode and a bias voltage is applied, the surface roughness was significantly improved to 0.14 nmRa (Fig. 3E).

[0043] As described above, in conventional plasma CVM processing, the modification of simply sucking in process gas from the nozzle-type electrode or simply applying a positive bias voltage was not able to sufficiently suppress the deterioration of surface roughness. However, it was confirmed that by sucking in process gas from the nozzle-type electrode and applying a positive bias voltage, the deterioration of surface roughness after processing can be significantly suppressed. EXAMPLES

[0044] Finally, in order to find the optimal processing conditions in the plasma CVM processing method according to the present invention, processing experiments were carried out with the flow rate of the process gas (average flow rate in the plasma generation space) and the value of the positive bias voltage as parameters. The workpiece was a quartz wafer (3 inch, t80 μm). The processing conditions were as shown in Table 2, with the scanning method being raster scan, the scanning speed being 1000 mm / min, and the scan pitch being 0.5 mm. Then, the arithmetic mean roughness (Ra) of a 500 nm × 500 nm area of ​​the processed workpiece was measured with an atomic force microscope (AFM), and the roughness change amount Δ was calculated by subtracting the surface roughness of the workpiece before processing from the surface roughness of the workpiece after processing. Note that the flow rate of the process gas is a parameter that changes depending on the specifications of the device, particularly the nozzle-type electrode and the processing gap, so the more universal average flow rate (defined by formula (1) or formula (2)) in the plasma generation space (the space between the outer periphery of the tip of the nozzle-type electrode and the workpiece) was used as a parameter. In the experiment, the flow rate, which is easy to control, was changed and converted into an average flow velocity that reflected the device specifications. The experimental results are shown in Table 3 and Figure 4.

[0045] [Table 3]

[0046] The experimental results show that, for the same flow rate, the higher the bias voltage, the smaller the change in surface roughness Δ tends to be, and, for the same bias voltage, the higher the flow rate, the smaller the change in surface roughness Δ tends to be. Therefore, the optimal range of processing conditions is determined by the lower limit of the flow rate and bias voltage.

[0047] As a result, the machining conditions under which the change in surface roughness Δ is 0.3 nmRa or less are conditions in which the average flow velocity of the process gas in the machining gap between the workpiece and the nozzle-type electrode is 2.08 m / s (400 sccm) or more and the bias voltage is 50 V or more, or conditions in which the average flow velocity is 1.04 m / s (200 sccm) or more and the bias voltage is 300 V or more.

[0048] Furthermore, the machining conditions under which the change in surface roughness Δ becomes 0.1 nmRa or less are conditions in which the average flow velocity of the process gas in the machining gap between the workpiece and the nozzle-type electrode is 2.6 m / s (500 sccm) or more and the bias voltage is 150 V or more, or conditions in which the average flow velocity is 1.04 m / s or more (200 sccm) and the bias voltage is 300 V or more.

[0049] As the flow rate and bias voltage both tend to become saturated as their effects increase, it is necessary to define practical upper limits. First, it is desirable that the bias voltage does not exceed the voltage of the high frequency power source supplied to the nozzle-type electrode. In addition, the upper limit of the flow rate (flow velocity) is limited by the set pressure P of the plasma generation space and the exhaust capacity from the nozzle-type electrode, but in this embodiment, even at 500 sccm (2.6 m / s), the change in surface roughness before and after processing Δ can be achieved to be 0.1 nmRa or less, and a sufficient roughness suppression effect can be obtained even at a lower flow rate (flow velocity) by applying a bias voltage, so the upper limit is set to 600 sccm (3.1 m / s). Note that a higher flow rate increases the consumption of process gas, which is a factor of higher costs, so a lower flow rate is preferable. [Explanation of symbols]

[0050] W work, P plasma generation space, 1 chamber, 2 work holder, 3 Nozzle type electrode, 4 gas supply means; 5 Gas exhaust means, 6 Mains power; 7 Bias power supply, 8 XY Stage 9 Insulators, 10 Fixed part, 11 moving parts, 12 Pressure reducing pump, 13 Carrier gas cylinder, 14 Reactive gas cylinders, 15 Gas inlet, 16 Gas exhaust passage, 17 matching units.

Claims

1. A plasma CVM processing method comprising the steps of: applying high frequency power to a nozzle-type electrode disposed opposite to a processing surface of a workpiece; generating plasma based on a process gas under high pressure; and causing neutral radicals generated in the plasma to act on the surface of the workpiece; and removing and processing volatile substances generated by chemical reactions between the neutral radicals and elements constituting the workpiece, the method comprising the steps of: a step of sucking in a process gas supplied to the periphery of the nozzle-type electrode through a gas suction port that opens on the processing surface side of the workpiece of the nozzle-type electrode; applying a positive bias voltage to a conductive work holder that holds the work; The steps include simultaneously carrying out Plasma CVM processing method.

2. The machining is performed under the condition that the average flow velocity of the process gas in the machining gap between the workpiece and the nozzle-type electrode is 2.08 m / s or more and the bias voltage is 50 V or more, or the average flow velocity is 1.04 m / s or more and the bias voltage is 300 V or more; The workpiece after processing is evaluated by the arithmetic average roughness (Ra) measured by an atomic force microscope (AFM) in a range of 500 nm x 500 nm, and the roughness change Δ obtained by subtracting the surface roughness before processing from the surface roughness after processing of the workpiece is 0.3 nmRa or less. The plasma CVM processing method according to claim 1.

3. The machining is performed under the condition that the average flow velocity of the process gas in the machining gap between the workpiece and the nozzle-type electrode is 2.6 m / s or more and the bias voltage is 150 V or more, or the average flow velocity is 1.04 m / s or more and the bias voltage is 300 V or more; The roughness change Δ is 0.1 nmRa or less; The plasma CVM processing method according to claim 2.

4. The nozzle-type electrode and the workpiece are moved relative to each other to control the dwell time of the nozzle-type electrode on the machining surface of the workpiece.

4. The plasma CVM processing method according to claim 1, 2 or 3.

5. The process gas is a mixture of a carrier gas and a reactive gas, and has a pressure of 10 to 100 kPa.

4. The plasma CVM processing method according to claim 1, 2 or 3.

6. A plasma CVM processing device applies high frequency power to an electrode facing a workpiece, generates plasma based on a process gas under high pressure, and causes neutral radicals generated in the plasma to act on the surface of the workpiece, thereby removing volatile substances generated by chemical reactions between the neutral radicals and elements constituting the workpiece, thereby processing the workpiece, A chamber; A conductive work holder that holds the work placed in the chamber; A nozzle-type electrode disposed in the chamber so as to face the processing surface of the workpiece; A gas supply means for supplying a process gas into the chamber; a gas exhaust means for sucking in a process gas supplied to the periphery of the nozzle-type electrode through a gas suction port that opens on the processing surface side of the nozzle-type electrode; a main power source that applies high frequency power to the nozzle-type electrode; a bias power supply that applies a positive bias voltage to the work holder; Equipped with Plasma CVM processing equipment.

7. The machining is performed under the condition that the average flow velocity of the process gas in the machining gap between the workpiece and the nozzle-type electrode is 2.08 m / s or more and the bias voltage is 50 V or more, or the average flow velocity is 1.04 m / s or more and the bias voltage is 300 V or more; The workpiece after processing is evaluated by the arithmetic average roughness (Ra) measured by an atomic force microscope (AFM) in a range of 500 nm x 500 nm, and the roughness change Δ obtained by subtracting the surface roughness before processing from the surface roughness after processing of the workpiece is 0.3 nmRa or less.

7. The plasma CVM processing apparatus according to claim 6.

8. The machining is performed under the condition that the average flow velocity of the process gas in the machining gap between the workpiece and the nozzle-type electrode is 2.6 m / s or more and the bias voltage is 150 V or more, or the average flow velocity is 1.04 m / s or more and the bias voltage is 300 V or more; The roughness change Δ is 0.1 nmRa or less; The plasma CVM processing apparatus according to claim 7.

9. The apparatus further includes an XY stage that holds the work holder via an insulator, and the XY stage is driven to relatively move the nozzle-type electrode and the workpiece, thereby controlling the dwell time of the nozzle-type electrode with respect to the machining surface of the workpiece to perform machining.

9. The plasma CVM processing apparatus according to claim 6, 7 or 8.

10. The process gas is a mixture of a carrier gas and a reactive gas, and has a pressure of 10 to 100 kPa.

9. The plasma CVM processing apparatus according to claim 6, 7 or 8.

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