Plasma etching method

Abstract

The present invention reduces the possibility of the occurrence of a phenomenon in which a coating film is difficult to remove in places from a section of a surface of a processing object. This plasma etching method is for exposing a processing object (W) that is retained inside a plasma processing chamber (10) to an inductively coupled plasma that is produced using a process gas (G), to remove a coating film that has been applied to a surface of the processing object, wherein the processing object is a member that is made of metal and has had the coating film applied thereto, the process gas includes oxygen gas, and the plasma etching method includes an etching step in which plasma etching is performed under the condition that the magnitude of a negative bias voltage that is applied to the processing object is greater than 0V and less than 60V.

Description

Plasma Etching Method

[0001] The present disclosure relates to a plasma etching method.

[0002] A technique for removing a film from a processing object having a film formed thereon by performing plasma etching inside a plasma chamber is known.

[0003] Japanese Patent Application Laid-Open No. 2023-4296

[0004] In such a technique, it has been found that when the processing object is a metal member with a film applied thereto, a phenomenon may occur in which the film is partially difficult to be removed on a part of the surface of the processing object. One aspect of the present disclosure has been made in view of the above problems, and an object thereof is to realize a plasma etching method capable of reducing the possibility of a phenomenon in which the film is partially difficult to be removed on a part of the surface of the processing object.

[0005] In order to solve the above problems, a plasma etching method according to one aspect of the present disclosure is a plasma etching method for exposing a processing object held inside a plasma processing chamber to an inductively coupled plasma generated by a process gas introduced into the plasma processing chamber to remove a film applied to the surface of the processing object, wherein the processing object is a metal member with the film applied thereto, the process gas contains oxygen gas, and an etching step of performing plasma etching under a condition that the magnitude of a negative bias voltage applied to the processing object is greater than 0 V and less than 60 V is included.

[0006] Furthermore, a plasma etching method according to one aspect of the present disclosure is a plasma etching method for removing a coating applied to the surface of an object to be processed, which is held inside a plasma processing chamber, by exposing it to an inductively coupled plasma generated by a process gas introduced inside the plasma processing chamber, wherein the object to be processed is a metal member to which the coating is applied, the process gas includes oxygen gas, and the method includes a first step of performing plasma etching under the condition that the magnitude of the negative bias voltage applied to the object to be processed is a first voltage value capable of causing sputtering of the metal constituting the member, and a second step of performing plasma etching under the condition that the magnitude of the negative bias voltage applied to the object to be processed is a second voltage value smaller than the first voltage value.

[0007] According to one aspect of this disclosure, the possibility of a phenomenon occurring where the coating becomes partially difficult to remove on a portion of the surface of the object being treated can be reduced.

[0008] This is a schematic diagram showing the configuration of a film removal apparatus according to one embodiment of the present disclosure. This is a diagram showing the state in which the surface of the object to be processed is etched. This is a diagram showing the state in which the surface of the object to be processed is etched. This is a diagram showing the measurement results of bias voltage and etching rate. This is a diagram showing the measurement results when the surface of the object to be processed is etched under various conditions. This is an image diagram of the object to be processed with the film remaining. This is a diagram showing the relationship between bias voltage and etching time according to the present disclosure.

[0009] [Embodiment 1] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to Figure 1. Figure 1 is a schematic diagram showing the configuration of the film removal apparatus 1. The film removal apparatus 1 is a film removal apparatus that etches the coating on a workpiece (work W) that has a coating formed on it by exposing it to plasma. The workpiece W is a component that uses a metal part as a base material and has a coating made of inorganic material formed on its surface. The workpiece W comprises a coating 11 and a base material 12.

[0010] As a specific example, the workpiece W is a machining tool made from a cemented carbide base material, and the coating is made of DLC (Diamond-Like Carbon) or polycrystalline diamond (PCD) to enhance the durability of the machining tool. However, the present disclosure can be applied as long as the coating is made of a material that gasifies when it reacts with oxygen. For example, the coating may be a material mainly composed of carbon.

[0011] The film removal apparatus 1 comprises a gas introduction unit 2, a dielectric plate 3, an antenna 4, a matching box 5, a high-frequency power supply 6, an impedance control unit 7, a bias control unit 8, a sealing unit 9, and a plasma processing chamber 10. In Figure 1, the direction from the antenna 4 toward the plasma processing chamber 10 is the X-axis direction, the direction in which the antenna 4 extends is the Z-axis direction, and the direction perpendicular to the X-axis direction and the Z-axis direction is the Y-axis direction.

[0012] The dielectric plate 3, antenna 4, matching box 5, high-frequency power supply 6, and impedance control unit 7 constitute an ICP (Inductively Coupled Plasma) generator that generates high-density plasma in the plasma processing chamber 10 through inductive coupling, for example, 1e11 to 1e12 / cm ３ It can generate high-density plasma.

[0013] Antenna 4 generates a high-frequency magnetic field. Antenna 4 is a metal pipe antenna extending in the Z-axis direction and is arranged along the dielectric plate 3. As shown in Figure 1, the length of antenna 4 is longer than the Z-axis length of the workpiece W. This allows the workpiece W to be positioned within the plasma generation region even in the Z-axis direction, so that the entire workpiece W can be etched. By changing the length of antenna 4, the etching area can be increased, and plasma can be generated to match the size of the workpiece W. There may also be multiple antennas 4. For example, multiple antennas 4 may be arranged in a row in the Y-axis direction. This increases the etching area in the Y-axis direction. In the electrical circuit, antenna 4 is connected to a matching box 5 and an impedance control unit 7. High-frequency current can be supplied to antenna 4 from a high-frequency power supply 6 via the matching box 5.

[0014] The matching box 5 and impedance control unit 7 perform impedance matching of the antenna 4 circuits with respect to the high-frequency power supply 6.

[0015] The dielectric plate 3 introduces the high-frequency magnetic field generated by the antenna 4 into the plasma processing chamber 10 in order to generate plasma inside the plasma processing chamber 10. The dielectric plate 3 is positioned substantially parallel to the antenna 4. The dielectric plate 3 is provided to cover the opening of the plasma processing chamber 10. The dielectric plate 3 is made of a dielectric material. The material constituting the dielectric plate 3 can be, for example, ceramics or glass. Multiple metal slits may be attached to the dielectric plate 3.

[0016] The plasma processing chamber 10 holds the workpiece W inside. The inside of the plasma processing chamber 10 is evacuated by a vacuum pump (not shown), and process gas G is introduced by the gas introduction section 2. The process gas G introduced into the plasma processing chamber 10 is a gas containing oxygen gas, and becomes a plasma that etches the coating on the workpiece W. The process gas G is composed of argon Ar and oxygen O ２A mixture of gases may also be used. The plasma processing chamber 10 is, for example, a metal box-shaped container. The plasma processing chamber 10 is electrically grounded.

[0017] The sealing portion 9 is provided at the connection between the dielectric plate 3 and the plasma processing chamber 10, and improves the airtightness inside the plasma processing chamber 10. The sealing portion 9 may be, for example, an O-ring.

[0018] The gas introduction section 2 introduces process gas G into the plasma processing chamber 10. As shown in Figure 1, the gas introduction section 2 is a tube that extends in the Z-axis direction along the dielectric plate 3 and is provided with multiple holes that serve as gas outlets. This reduces the uneven distribution of process gas G and makes the plasma concentration uniform.

[0019] The bias control unit 8 applies a negative bias voltage to the workpiece W. By controlling the bias voltage, for example, the energy of ions in the plasma in the plasma processing chamber 10 when they are incident on the workpiece W, the film removal process on the workpiece W can be controlled.

[0020] <Plasma Etching> The process of removing the coating from the workpiece W will be explained using Figures 2 and 3. Figures 2 and 3 show the state in which the coating is removed from the workpiece W. Figure 2 shows a cross-section of the corner and a flat portion other than the corner of the workpiece W coated with the coating 11. The process gas G is radicalized or ionized inside the plasma processing chamber 10. Oxygen radicals and oxygen ions chemically react with the carbon C in the coating 11, producing carbon oxides (carbon monoxide CO or carbon dioxide CO). ２ It generates (etc.). The generated carbon oxides are exhausted as a gas from the plasma processing chamber 10 by a vacuum pump. The oxygen radicals generally move along the airflow within the plasma processing chamber 10.

[0021] However, compared to the flat areas, the corners of the workpiece W are more prone to airflow stagnation, making it difficult for oxygen radicals to reach them. Also, because the local surface area in the corners is larger than in the flat areas, the density of ions reaching per unit surface area is lower, resulting in a weaker sputtering effect. Therefore, as plasma etching progresses, the coating 11 remains in the corners, while the flat areas are completely decoupled.

[0022] As plasma etching progresses, as shown in Figure 3, the substrate 12 is exposed in the flat areas before the corners. Metal atoms are sputtered from the exposed surface of the substrate 12, react with oxygen ions to form metal oxides, and reattach, forming a metal oxide layer 13 that prevents the reaction between the coating 11 and oxygen.

[0023] The etching rate is affected by the magnitude of the bias voltage applied to the workpiece W. Figure 4 shows the measurement results of the relationship between the bias voltage Vb (V) and the etching rate (μm / h). The measurement conditions were an oxygen supply of 50 sccm, atmospheric pressure of 5 Pa, and high-frequency output of 1000 W. In Figure 4, the etching rate in the flat region is plotted when the bias voltage is -30 (V), -100 (V), and -250 (V). From these results, it can be seen that the etching rate increases as the bias voltage is increased in the negative direction. Therefore, in order to efficiently remove the film from the workpiece W, it is necessary to increase the absolute value of the bias voltage.

[0024] [Measurement Results] The measurement results regarding the relationship between bias voltage and etching time will be explained using Figures 5 to 7. The workpiece W used in this measurement has a coating 11 formed on its surface and has protruding parts as shown in Figure 6, with right-angled corners 15 at the base of the protruding parts. The measurement conditions were an oxygen supply of 250 sccm, atmospheric pressure of 5 Pa, and high-frequency output of 1800 W.

[0025] Figure 5 shows the measurement results when the workpiece W was etched under various conditions. At bias voltages of 0 (V), -30 (V), -50 (V), -60 (V), -80 (V), and -250 (V), it was evaluated whether the coating was removed from the flat parts (flat parts 14) and corner parts (corner parts 15) of the workpiece W. Figure 6 is an image of the workpiece W in which the coating remained at the corner parts 15 in this experiment.

[0026] At a bias voltage of -250 (V) and processing times of 8 (min) and 120 (min), the coating on the flat portion 14 was completely removed, while the coating on the corner portion 15 remained.

[0027] At a bias voltage of -80 (V) and processing times of 45 (min) and 120 (min), the coating on the flat portion 14 was completely removed, while the coating on the corner portion 15 remained.

[0028] At a bias voltage of -60 (V) and processing times of 45 (min) and 120 (min), the coating on the flat portion 14 was completely removed, while the coating on the corner portion 15 remained.

[0029] At a bias voltage of -50 (V), after a processing time of 45 (min), the coating on the flat portion 14 was completely removed, while the coating on the corner portion 15 remained. On the other hand, at a bias voltage of -50 (V), after a processing time of 60 (min), the coating on both the flat portion 14 and the corner portion 15 was completely removed.

[0030] At a bias voltage of -30 (V), after a processing time of 60 (min), the coating on the flat portion 14 was completely removed, while the coating on the corner portion 15 remained. On the other hand, at a bias voltage of -30 (V), after a processing time of 120 (min), the coating on both the flat portion 14 and the corner portion 15 was completely removed.

[0031] At a bias voltage of -0 (V), after a processing time of 60 (min), the coating on the flat portion 14 was completely removed, while the coating on the corner portion 15 remained. On the other hand, at a bias voltage of -0 (V), after a processing time of 120 (min), the coating on both the flat portion 14 and the corner portion 15 was completely removed.

[0032] The experimental results described above are summarized in Figure 7. Figure 7 shows the relationship between the strength of the bias voltage Vb and the processing time (min).

[0033] From the experimental results above, under conditions where the magnitude of the negative bias voltage Vb is greater than 0V and less than 60V, metal oxides are less likely to accumulate in the corners 15, and the coating is reliably removed, thereby reducing the possibility of the coating being difficult to remove in certain areas such as the corners 15. This is because, in the range where the magnitude of the negative bias voltage Vb is greater than 0V and less than 60V, the sputtering effect is small, and the phenomenon of metal atoms on the substrate being sputtered and reattached is less likely to occur.

[0034] Furthermore, the experimental results above confirmed that the coating could be removed even in the corners 15 when the magnitude of the negative bias voltage Vb in the etching process was 50V or less.

[0035] <Plasma Etching Method> The following describes a method for efficiently removing the film from the workpiece W. The equipment used is the same as that described above using Figure 1.

[0036] First, in the first step, plasma etching is performed under the condition that the magnitude of the negative bias voltage Vb applied to the workpiece W is a first voltage value Vb1 that can cause sputtering of the workpiece W. As shown in Figure 4, the first voltage value Vb1 at this time is set to 60V or higher when the entire surface of the workpiece W is covered with a coating, taking into consideration that the etching speed improves as the magnitude of the negative bias voltage Vb increases. The first step is terminated before the substrate is exposed on a part of the surface of the workpiece W. The duration of the first step can be set by the value of the first voltage value Vb1 and the thickness of the coating 11, etc.

[0037] Next, in the second step, plasma etching is performed under the condition that the magnitude of the negative bias voltage Vb applied to the workpiece W is a second voltage value Vb2 which is smaller than the first voltage value Vb1. In this case, the second voltage value Vb2 is such that the magnitude of the negative bias voltage Vb is greater than 0V and less than 60V.

[0038] According to the above process, it becomes difficult for the metal oxide layer 13 to form in the corners, and the possibility of a phenomenon occurring where the coating 11 is difficult to remove in parts such as the corners 15 can be reduced.

[0039] Furthermore, by performing the treatment with the first voltage value Vb1 before performing the treatment with the second voltage value Vb2, the overall processing time until the film removal is completed can be shortened.

[0040] 〔Summary〕 Aspect 1 of the plasma etching method according to the present disclosure is a plasma etching method for removing a film formed on the surface of a workpiece held inside a plasma processing chamber by exposing the workpiece to an inductively coupled plasma generated by a process gas introduced into the plasma processing chamber. The workpiece is a metal member on which the film is formed, the process gas contains oxygen gas, and the etching process includes performing plasma etching under the condition that the magnitude of the negative bias voltage applied to the workpiece is greater than 0 V and less than 60 V.

[0041] Aspect 2 of the plasma etching method according to the present disclosure is, in Aspect 1, the magnitude of the bias voltage in the etching process is 50 V or less.

[0042] Aspect 3 of the plasma etching method according to the present disclosure is, in Aspect 1 or 2, the etching process is performed in a state where a part of the surface of the workpiece exposes the metal member.

[0043] Aspect 4 of the plasma etching method according to the present disclosure is a plasma etching method for removing a film formed on the surface of a workpiece held inside a plasma processing chamber by exposing the workpiece to an inductively coupled plasma generated by a process gas introduced into the plasma processing chamber. The workpiece is a metal member on which the film is formed, the process gas contains oxygen gas, and the method includes a first step of performing plasma etching under the condition that the magnitude of the negative bias voltage applied to the workpiece is a first voltage value that can cause sputtering of the metal constituting the member, and a second step of performing plasma etching under the condition that the magnitude of the negative bias voltage applied to the workpiece is a second voltage value smaller than the first voltage value.

[0044] Aspect 5 of the plasma etching method according to the present disclosure is, in Aspect 4, the second step is performed in a state where a part of the surface of the workpiece exposes the metal member.

[0045] Aspect 6 of the plasma etching method according to the present disclosure is, in any one of Aspects 1 to 5, the film is made of a material that gasifies when reacting with oxygen.

[0046] Aspect 7 of the plasma etching method according to the present disclosure is, in any one of Aspects 1 to 6, the film contains carbon as a main component.

[0047] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure.

[0048] 1. Film removal device 2. Gas introduction part 3. Dielectric plate 4. Antenna 5. Matching box 6. High-frequency power supply 7. Impedance control part 8. Bias control part 9. Seal part 10. Plasma processing chamber 11. Film 12. Substrate 13. Metal oxide layer 14. Flat part 15. Corner part W. Work G. Process gas

Claims

1. A plasma etching method for removing a coating applied to the surface of an object to be processed, which is held inside a plasma processing chamber, by exposing the object to be processed to an inductively coupled plasma generated by a process gas introduced into the plasma processing chamber, wherein the object to be processed is a metal component to which the coating is applied, the process gas contains oxygen gas, and the method includes an etching step in which plasma etching is performed under the condition that the magnitude of the negative bias voltage applied to the object to be processed is greater than 0V and less than 60V.

2. The plasma etching method according to claim 1, wherein the magnitude of the bias voltage in the etching step is 50V or less.

3. The plasma etching method according to claim 1, wherein the etching step is performed in a state in which the metal member is exposed on a part of the surface of the object to be processed.

4. A plasma etching method for removing a coating applied to the surface of an object to be processed, which is held inside a plasma processing chamber, by exposing it to an inductively coupled plasma generated by a process gas introduced into the plasma processing chamber, wherein the object to be processed is a metal member to which the coating is applied, the process gas includes oxygen gas, and the method comprises: a first step of performing plasma etching under the condition that the magnitude of the negative bias voltage applied to the object to be processed is a first voltage value capable of causing sputtering of the metal constituting the member; and a second step of performing plasma etching under the condition that the magnitude of the negative bias voltage applied to the object to be processed is a second voltage value smaller than the first voltage value.

5. The plasma etching method according to claim 4, wherein the second step is performed in a state in which the metal member is exposed on a part of the surface of the object to be processed.

6. The plasma etching method according to any one of claims 1 to 5, wherein the coating is made of a material that gasifies when it reacts with oxygen.

7. The plasma etching method according to any one of claims 1 to 5, wherein the coating is mainly composed of carbon.

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