JP3591407B2 - Local processing unit - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surface treatment technique for etching, ashing, modifying, or forming a thin film on a surface of an object to be treated, and in particular, locally using an excited active species generated in a plasma at or near atmospheric pressure. The present invention relates to a local processing apparatus for performing a surface treatment on an object.
[0002]
[Prior art]
Conventionally, by using excited active species generated by plasma discharge under a pressure near the atmospheric pressure, a surface capable of variously treating the surface of an object to be processed at low cost without requiring vacuum equipment. Processing techniques are known. For surface treatment with plasma under atmospheric pressure, a gas discharge is directly generated between the electrode and the object to be processed, and the plasma is directly exposed to the generated plasma. And an indirect discharge method in which an object to be processed is exposed to excited active species generated thereby.
[0003]
The indirect discharge method requires a high output because the processing rate is lower than that of the direct discharge method. However, the indirect discharge method is advantageous in that there is no risk of damage to the workpiece due to charge-up. A typical example of a surface treatment apparatus suitable for local surface treatment for such atmospheric pressure plasma is disclosed in Japanese Patent Application Laid-Open No. 9-232293. This conventional device includes, for example, a thin discharge tube made of a dielectric material such as glass having a narrow cross section having an inner diameter of 1 mm or less, and a pair of electrodes arranged to face each other so as to sandwich the discharge tube. The nozzle portion is arranged facing the surface of the workpiece. A reactive gas containing excited active species generated by generating a gas discharge between both electrodes while introducing a predetermined gas from a gas supply source into a discharge tube is converted into a thin gas flow from a nozzle portion on the surface of the workpiece. Spray.
[0004]
[Problems to be solved by the invention]
However, conventionally, there were the following problems.
[0005]
As described above, a discharge tube having a small diameter of 1 mm or less is used. For this reason, it is common to provide a casing for taking the discharge tube inside. In general, the casing is formed of a metal material and electromagnetically shields the outside. Further, in order to protect the discharge tube provided in the casing from vibrations or the like, it is preferable to cover the periphery of the discharge tube by filling the casing with a protective member made of a dielectric material.
[0006]
However, in such a case, when a high-frequency voltage is applied to the electrode, high-frequency power leaks to the casing via the protective member, causing a considerable amount of loss in the high-frequency power transmitted to the electrode. Since the loss of the high-frequency power applied to the electrodes also reduces the surface treatment efficiency due to gas discharge, it has been desired to prevent the high-frequency power from leaking to the casing.
[0007]
An object of the present invention is to provide a local processing apparatus capable of performing stable gas discharge while minimizing loss of high-frequency power.
[0008]
[Means for Solving the Problems]
In order to maintain the insulation of the conduction path, it is conceivable to cover the periphery with the above-described dielectric. However, the relative permittivity of the dielectric (insulator) is several times or more higher than that in the air atmosphere. For this reason, the inventor of the present application has noticed that leakage of high-frequency power can be more effectively prevented by bringing the inside of the casing closer to the atmosphere than by using a structure in which the inside of the casing is filled with a dielectric.
[0009]
The local processing apparatus according to the present invention is made based on the above-mentioned knowledge, and includes a discharge tube for flowing a processing gas in a casing forming an electromagnetic shield, and a protection made of a dielectric material around the discharge tube. A member is arranged, a pair of electrodes are arranged on both sides of the discharge tube, a lead is connected to one of the electrodes, and a conduction path and a protection member formed by the one electrode and the lead A hollow portion is formed between the casing and the casing.
[0010]
Therefore, when the high-frequency voltage is transmitted to the conduction path, insulation between the conduction path and the protection member and the casing is effectively maintained, and leakage current can be minimized. Thereby, gas discharge can be generated stably.
Moreover, since the local exhaust device according to the present invention has a detachable nozzle tip at the tip of the discharge tube, the local exhaust device can be replaced with one having a different hole diameter and the area to be surface-treated can be adjusted.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the local processing apparatus of the present invention will be described in detail with reference to the drawings.
[0012]
FIG. 1 is a cross-sectional view of the local processing apparatus 20 according to the present embodiment. The local processing apparatus 20 according to the present embodiment has a casing member 21. The casing member 21 is formed of an upper casing member 22, a middle casing member 24, a lower casing member 26, and a bottom casing member 28. Each of the upper to lower casing members 22, 24, 26, and 28 is formed by hollowing out a center portion of a substantially prismatic block body into a substantially cylindrical shape. The casing member 21 is in close contact with the hollow portions of the top to bottom casing members 22, 24, 26, and 28 by centering. For this reason, since the casing member 21 can omit or add a part of the casing members 22, 24, 26, and 28, the size can be adjusted according to the members to be inserted into the casing member 21. In the present embodiment, the casing member 21 is formed of aluminum. Therefore, it is possible to shield the electromagnetic wave to the outside of the casing member 21. The material of the casing member 21 is not limited to aluminum, but may be any material having a shielding function.
[0013]
A straight discharge tube 40 is disposed on the axis of the casing member 21. The discharge tube 40 has an upper end located on the axis of the upper casing member 22 and a lower end facing the inner wall surface of the bottom casing member 28. On the other hand, a nozzle tip 44 is detachably provided on the surface of the bottom casing member 28 facing the lower end of the discharge tube 40 so as to protrude to the outside, and the lower end of the discharge tube 40 is attached to the nozzle tip 44. Inlaid. As described above, since the discharge tube 40 and the nozzle tip 44 are formed so as to be separable, the nozzle tip 44 can be replaced with one having a different hole diameter. For this reason, the area to be surface-treated can be adjusted. As a material of the nozzle tip 44, stainless steel (SUS) or aluminum is preferable.
[0014]
The nozzle tip 44 has an upper end projecting into the bottom casing member 28. The upper end of the nozzle tip 44 is screwed and fixedly held on a nozzle holder 42 formed in a substantially cylindrical shape. The material of the nozzle holder 42 is preferably stainless steel (SUS) or aluminum.
[0015]
The discharge tube 40 is covered with a protection member 36 around a surface facing the lower casing member 26. The protection member 36 has an inverted T-shape in which a partition portion 39 is integrally provided at the center of the receiving portion 37. The protection member 36 protects the discharge tube 40 by passing the discharge tube 40 through the central axis of the partition 39. The protection member 36 has the lower surface of the receiving portion 37 in contact with the upper surface of the nozzle holder 42 and is supported by the nozzle holder 42.
[0016]
A pair of rod-shaped electrodes 46 and 48 are in contact with the upper and lower centers of both surfaces 39a and 39b of the partition 39 of the protection member 36 as shown in FIG. The pair of rod-shaped electrodes 46 and 48 each have a substantially rectangular shape, and are opposed to each other so as to be linear when viewed from above, with the partition 39 of the protection member 36 interposed therebetween as shown in FIG. I have. The discharge tube 40 penetrates in the vertical direction through the axial center of the partition 39 sandwiched between the rod-shaped electrodes 46 and 48, and causes gas discharge in the penetrating portion of the discharge tube 40. As described above, the pair of rod-shaped electrodes 46 and 48 are arranged near the nozzle tip 44. As a result, excited active species such as plasma can be immediately released from the nozzle tip 44 to the outside. For this reason, sufficient excited active species can reach the surface of the object.
[0017]
The length of the receiving portion 37 in the longitudinal direction is longer than the length of the rod-shaped electrodes 46 and 48 in the longitudinal direction. Thereby, the installation area of both electrodes 46 and 48 is secured. In particular, since the rod-shaped electrode 46 to which the high-frequency voltage is applied does not linearly face the bottom casing member 28, it is possible to prevent discharge from occurring between the rod-shaped electrode 46 and the bottom casing member 28. The protection member 36 is made of alumina or quartz, and keeps the electrodes 46 and 48 insulated. The material of the protection member 36 is not limited to this as long as it is an insulator material.
[0018]
The height of the partition 39 of the protection member 36 is higher than the rod electrodes 46 and 48 as shown in FIG. 2B. The partition portions 39a and 39b of the protection member 36 are formed sufficiently long in the thickness direction of the rod-shaped electrodes 46 and 48. Thereby, the rod-shaped electrodes 46 and 48 are prevented from linearly facing each other. When the rod-shaped electrodes 46 and 48 are linearly facing each other, there is a possibility that a creeping discharge that is conducted along the surface (creeping surface) of the protection member 36 when applying the voltage to the rod-shaped electrodes 46 and 48 may occur. When the creeping discharge occurs, the gas discharge in the discharge tube 40 does not occur or the generated gas discharge is stopped. As described above, since the partition 39 of the protective member 36 is formed sufficiently long in the thickness direction of the rod-shaped electrodes 46 and 48, creeping discharge can be prevented. For this reason, the gas discharge through the inside of the discharge tube 40 can be reliably generated, and the generated gas discharge can be stably maintained. The rod-shaped electrodes 46 and 48 are formed of aluminum, and each surface is plated with gold. Thereby, corrosion and oxidation of the rod-shaped electrodes 46 and 48 can be prevented. Since gold has high conductivity, the conduction efficiency of the rod-shaped electrode can be improved. In addition, the performance of the rod-shaped electrodes 46 and 48 can be prevented from deteriorating.
[0019]
A holder member 50 is interposed between the back surface of the rod-shaped electrode 46 and the inner wall surface of the casing member 21. The holder member 50 has a base end in contact with the inner wall surface of the lower casing member 26 and a distal end of the holder member 50 in contact with the back surface of the rod-shaped electrode 46. Thus, the rod-shaped electrode 46 is positioned and held on the protection member 36 side. As a material of the holder member 50, alumina or quartz can be preferably used, but is not limited to this as long as it is an insulator material.
[0020]
On the other hand, the other rod-shaped electrode 48 is integrally connected to the extension electrode 49 exposed to the outer surface of the lower casing member 21. The extension electrode 49 is connected to a ground path (not shown). Thus, the grounding of the rod-shaped electrode 48 is ensured.
[0021]
A substantially cylindrical intermediate member 34 is disposed on the protection member 36. The intermediate member 34 is disposed such that a side surface portion faces the inner wall surface of the middle casing member 24. The lower surface of the intermediate member 34 is in contact with the upper surface of the partition 39 of the protection member 36, thereby positioning the protection member 36. Further, a through-hole is provided in the central shaft portion of the intermediate member 34, and the discharge tube 40 is inserted into the through-hole to protect the discharge tube 40. The intermediate member 34 is preferably made of Teflon or mica ceramics, but is not limited to this as long as it is an insulator material.
[0022]
An insulating member 32 is disposed above the intermediate member 34. The insulating member 32 has a substantially cylindrical shape corresponding to a hollow portion of the upper casing member 22. The insulating member 32 is fitted in a hollow portion of the upper casing member 32. Thereby, the casing member 21 is sealed in the upper surface direction, and a sealed space can be formed inside the casing member 21. The upper surface of the insulating member 32 is formed in a concave shape in cross section, and the bottom surface of the concave portion is formed so as to correspond to the upper surface of the intermediate member 34. The lower surface of the insulating member 32 is formed in a downwardly projecting cross-sectional inverted convex shape, and the lower surface of the inverted convex portion is in contact with the upper surface of the intermediate member 34. The insulating member 32 has a gas inflow hole 33 opened on the peripheral surface. A gas inflow pipe 62 connected to a gas supply source (not shown) is also provided on one side surface of the upper casing member 22, and a tip of the gas inflow pipe 62 corresponds to an upper opening of the gas inflow hole 33. I have. The gas inflow hole 33 extends from the upper opening toward the axial center of the insulating member 32 and is bent downward along the axis at the axial center. The gas inlet 33 reaches the lower surface of the insulating member 32 and has a lower opening at the lower surface. The upper end of the discharge tube 40 is inserted into the lower opening of the gas inflow hole 33 on the lower surface of the insulating member 32. Therefore, the processing gas flowing from the gas inflow pipe 62 is sent out to the upper portion of the discharge tube 40 through the gas inflow hole 33. A cylindrical pressing member 35 is formed on the inner wall surface of the lower opening of the gas inflow hole 33. The holding member 35 has an inner flange formed thereon, and the inner flange contacts the upper portion of the discharge tube 40 and urges the discharge tube 40 downward. Therefore, the discharge tube 40 can be positioned. The insulating member 32 is made of Teflon, and performs insulation holding. The insulating member 32 is not limited to this as long as it is an insulator material.
[0023]
A lead 30 is inserted and arranged from the axial center direction of the upper surface of the upper casing member 22. The lead 30 is bent in the diameter direction near the upper surface of the insulating member 32. Then, it descends along the inner wall surface of the upper surface concave portion of the insulating member 32 and penetrates the insulating member 32. As described above, since the bottom surface of the concave portion of the upper surface of the insulating member 32 is formed so as to correspond to the upper surface of the intermediate member 34, the lead 30 penetrating the insulating member 32 descends so as to contact the side surface of the intermediate member 34. Thus, the lead 30 can be protected by the intermediate member 34. The lead 30 extends further downward and connects to the rod-shaped electrode 46. As a result, electrical conduction between the lead 30 and the rod-shaped electrode 46 is ensured. The lower end of the lead 30 contacts the receiving portion 37a of the protection member 36, thereby improving the conduction efficiency.
[0024]
The lead 30 is formed of a plurality of plate members, and the plurality of plate members are stacked and arranged. In the present embodiment, the lead 30 is formed by laminating three plate members. In the present embodiment, the upper end of the lead 30 is connected to a high-frequency power source (not shown). In the present embodiment, a high frequency voltage having a frequency of 40.68 MHz is used. High-frequency power generated by a high-frequency power supply (not shown) is transmitted from the upper end of the lead 30, but such high-frequency power is transmitted to the rod-shaped electrode 46 not through the inside of the lead 30 but through the surface of the lead 30. As described above, the lead 30 has a plurality of plate-like members stacked and arranged, but the high-frequency power is transmitted through the surface of the lead 30 through the gap between the plate-like members. In the present embodiment, since the three plate-shaped members are arranged in a stacked manner, the conduction efficiency of the high-frequency power can be tripled. Thus, a high-frequency voltage can be efficiently applied to the rod-shaped electrode 46, and gas discharge can be performed with the high-frequency voltage. By applying a high-frequency voltage to the rod-shaped electrode 46 in this manner, electrons are oscillated at a high frequency between the rod-shaped electrodes 46 and 48, and the collision of the electrons turns the processing gas into plasma to become excited active species. Therefore, high-density plasma can be generated at a high generation rate, and abnormal discharge can be suppressed. Further, even if the volume of the entire lead 30 is reduced, the power is efficiently transmitted by increasing the surface area of the lead 30 and the local processing apparatus 20 can be made compact. Further, by using the high frequency voltage having a frequency of 30 MHz or more, the electrons oscillate between the rod electrodes 46 and 48 while maintaining the conduction efficiency of the high frequency voltage. Therefore, high-density plasma can be generated without causing damage, and processing efficiency can be improved.
[0025]
The lead 30 is made of copper and has a gold plated surface. Accordingly, the lead 30 can be prevented from being oxidized, and the high-frequency power can be stably conducted.
[0026]
The local processing apparatus 20 provides a hollow region 60 between the conductive path (lead 30, the bar-shaped electrode 46) and the protection member (the protection member 36, the intermediate member 34), and the inside of the casing member 21 to form an insulating space. Has formed. A form in which the periphery of the conduction path is surrounded by a dielectric such as mica-based ceramics and insulated is also conceivable. However, as shown in FIG. 3B, the relative permittivity of the mica-based ceramic, which is a dielectric (insulator), is at least five times higher than that in the air atmosphere. As described above, the present inventor has paid attention to the fact that it is possible to more effectively maintain insulation by forming a hollow region and setting it in an air atmosphere than by forming a structure surrounding the conduction path with a dielectric. Since the hollow region 60 is formed in this manner, insulation between the conduction path (lead 30, the bar-shaped electrode 46) and the protection member (the protection member 36, the intermediate member 34) and the inside of the casing member 21 is effectively performed. , Leakage current can be minimized. Thereby, gas discharge can be stably generated.
[0027]
An air supply pipe 52 projects from one side of the lower casing member 26, and an air discharge pipe 54 projects from the other side of the lower casing member 26. The cooling air is guided from the air supply pipe 52 into the casing member 21. Then, heat exchange inside the casing member 21 is performed through the hollow region 60 in the casing member 21, and the heat is released to the outside of the casing member 21 from the air discharge pipe 54. Thus, an overheating state of the electrode during the plasma generation process can be prevented, the temperature inside the casing member 21 can be kept constant, and the discharge can be stabilized. Damage due to thermal expansion or the like of the electrode portion can be prevented. Note that the structure is not particularly limited to the above structure as long as the electrode portion in the casing member 21 can be air-cooled.
[0028]
The operation of the local processing device 20 configured as described above is as follows. The local processing apparatus 20 has a tip of the nozzle tip 44 facing above a workpiece (not shown).
[0029]
The processing gas flows into the opening of the discharge tube 40 provided on the side wall of the upper casing member 22. The processing gas advances in the discharge tube 40 and descends in the casing member 21. In the lower casing member 26, a high-frequency voltage is applied to the rod-shaped electrodes 46 and 48, and gas discharge occurs in the discharge tube 40. In the present embodiment, since a voltage is applied at a high frequency, a high-density excited active species can be generated. Since the excited active species is immediately sent out from the nozzle tip 44 onto the workpiece, a sufficient amount of the excited active species can be delivered onto the workpiece to perform surface treatment. The object to be processed includes a semiconductor chip and a wafer. The processing step includes, for example, etching, ashing, modification, or thin film formation, but the application is not particularly limited to this.
[0030]
FIG. 3A shows a comparison diagram of the ashing rate between the local processing device 20 of the embodiment and the local processing device of the comparative example. The local processing apparatus of the comparative example has mica ceramics disposed in the hollow region 60. As processing conditions, the He flow rate is 2 l / min, and the O ₂ flow rate is 30 ml / min. The distance from the tip of the nozzle tip to the workpiece is about 0.5 mm. The outer diameter of the nozzle tip is 3.0 mm and the inner diameter is 1.5 mm. Comparing the ashing rates of the embodiment and the comparative example under the above-mentioned processing conditions, as shown in FIG. 3A, it was found that the processing efficiency could be increased three times or more even with the same output.
[0031]
【The invention's effect】
In the local processing apparatus according to the present invention, a discharge tube that circulates a processing gas is formed in a casing that forms an electromagnetic shield, and a protective member made of a dielectric is disposed around the discharge tube. A pair of electrodes are arranged on both sides of the discharge tube, a lead is connected to one of the electrodes, and a hollow is formed between the one electrode and the conductive path formed by the lead and the protective member and the casing. Since the portion is formed, insulation between the conduction path and the protection member and the casing is effectively maintained, and leakage current can be minimized. Thereby, gas discharge can be stably generated.
[0032]
[Brief description of the drawings]
FIG. 1 is a sectional view showing a local processing apparatus according to an embodiment of the present invention.
FIG. 2 is a top view and a perspective view of a main part of the local processing apparatus according to the embodiment of the present invention.
FIG. 3 is an explanatory diagram showing the processing efficiency and relative permittivity of a material of the local processing apparatus according to the present invention.
[Explanation of symbols]
20 Local surface treatment device 21 Casing member 22 Upper casing member 24 Middle casing member 26 Lower casing member 28 Bottom casing member 30 Lead 32 ... Insulating member 33 ... Gas inflow hole 34 ... Intermediate member 35 ... Pressing member 36 ... Protective member 37 ... Receiving part 39 ... Partition part 40 ... Discharge tube 42 ... Nozzle holder 44 Nozzle tip 46 Rod electrode 48 Rod electrode 49 Extension electrode 50 Holder member 52 Air supply pipe 54 Air discharge pipe 60 Hollow area 62 ... Gas inflow pipe

Claims (2)

In a casing that forms an electromagnetic shield, a discharge tube that allows a processing gas to flow is formed, and a protective member made of a dielectric material is arranged around the discharge tube.The protective member, on both sides of the discharge tube, A local processing apparatus in which a pair of electrodes is arranged, an excited active species is obtained by a high-frequency voltage applied to the electrodes, and is sent out from a nozzle onto an object to be processed.
The casing encloses the discharge tube, the protection member, and the pair of electrodes, and provides a pipe and an opening for wiring , then closes a body and a bottom surface, and further closes an upper portion with an insulating material,
A lead is connected to one of the pair of electrodes, and the other electrode is connected to a ground path,
A space is provided between the electrode to which the lead is connected and the body of the casing, and a space is also provided between the conduction path formed by the lead and the body of the casing,
A local processing apparatus, wherein a space is provided between the protection member and a body of the casing, and a space is also provided between the protection member and a bottom of the casing. A local processing apparatus comprising a detachable nozzle tip at a tip of the discharge tube according to claim 1.

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