JP2020145257A - Plasma processing apparatus and plasma processing method - Google Patents

Abstract

To provide a plasma processing apparatus and a plasma processing method capable of making pressure in a region for generating a plasma product and pressure in a region for processing an object to be processed differ from each other.SOLUTION: A plasma processing apparatus according to an embodiment comprises: a chamber capable of maintaining an atmosphere decompressed more than the ambient pressure; an exhaust unit capable of decompressing the inside of the chamber to predetermined pressure; a loading unit that is provided inside the chamber and can be loaded with an object to be processed; a discharge tube that has a region for generating a plasma product therein and is provided at a position separated from the chamber; a plasma generation unit capable of generating plasma in the region for generating a plasma product; a transport tube connecting the discharge tube with the chamber; and a pressure control unit that is provided at the transport pipe and can make pressure inside the discharge tube differ from pressure inside the chamber using conductance.SELECTED DRAWING: Figure 1

Description

The present invention relates to a plasma processing apparatus and a plasma processing method.

Dry processes using plasma are used in a wide range of technical fields such as manufacturing of semiconductor devices, surface hardening of metal parts, surface activation of plastic parts, and chemical-free sterilization. For example, in the manufacture of semiconductor devices and the like, plasma treatment such as etching treatment is performed. The dry process using plasma is low cost and short processing time. It is also advantageous in that environmental pollution can be reduced because no chemicals are used.

In such plasma treatment, the generated plasma excites and activates the process gas to generate plasma products such as radicals, ions, and electrons. Then, the plasma treatment (for example, etching treatment) is performed by supplying the plasma product to the surface of the processed product.

Physical processing can be performed by supplying ions and electrons to the surface of the processed object. However, if ions or electrons are supplied to the surface of the processed product, the processed product may be damaged. Therefore, a plasma processing apparatus capable of attenuating ions and electrons and mainly performing chemical treatment using radicals has been put into practical use.
For example, a plasma processing apparatus has been proposed in which a region for producing a plasma product by plasma and a region for processing a processed product using the plasma product are separated, and these regions are connected by a transport pipe (for example,). See Patent Document 1).
In such a plasma processing apparatus, ions and electrons are attenuated inside the transport tube, so that radicals mainly reach the surface of the processed material. Therefore, it is possible to perform a chemical treatment that causes less damage than a physical treatment using ions or electrons.

Japanese Unexamined Patent Publication No. 10-46372

An object to be solved by the present invention is to provide a plasma processing apparatus and a plasma processing method capable of different pressures in a region where a plasma product is generated and a pressure in a region where a processed product is processed. Is.

The plasma processing apparatus according to the embodiment is provided with a chamber capable of maintaining an atmosphere depressurized from atmospheric pressure, an exhaust portion capable of depressurizing the inside of the chamber to a predetermined pressure, and a processed object provided inside the chamber. Plasma is generated in a discharge tube provided at a position separated from the chamber and a region for generating the plasma product, which has a mounting portion on which the plasma product can be placed and a region for generating the plasma product inside. A plasma generating unit capable of causing the plasma to be generated, a transport pipe connecting the discharge pipe and the chamber, and a transport pipe provided in the transport pipe, the pressure inside the discharge pipe is measured inside the chamber by conduction. It is provided with a pressure control unit that can be different from the pressure.

According to the present invention, there is provided a plasma processing apparatus and a plasma processing method capable of making the pressure in a region where a plasma product is generated different from the pressure in a region where a processed product is processed.

It is a schematic cross-sectional view for exemplifying the plasma processing apparatus which concerns on this embodiment. It is a flowchart for exemplifying the plasma processing method which concerns on this Embodiment.

Hereinafter, embodiments of the present invention will be illustrated with reference to the drawings.

(Plasma processing equipment)
FIG. 1 is a schematic cross-sectional view for exemplifying the plasma processing apparatus 1 according to the present embodiment. The plasma processing apparatus 1 illustrated in FIG. 1 is a microwave excitation type plasma processing apparatus generally called a “CDE (Chemical Dry Etching) apparatus”. That is, the plasma processing device 1 is a remote plasma processing device in which a region for generating a plasma product and a region for processing the processed product are separated from each other.

As shown in FIG. 1, the plasma processing apparatus 1 may be provided with a generation unit 10, a processing unit 20, a transport pipe 30, an exhaust unit 40, a pressure control unit 50, and a controller 60.
The generation unit 10 generates plasma and excites and activates the process gas G by the generated plasma to generate plasma products such as radicals, ions, and electrons.
The generation unit 10 can be provided with a microwave generation unit 11, a discharge tube 12, an introduction waveguide 13, and a gas supply unit 14.

The microwave generation unit 11 can be provided at the end of the introduction waveguide 13 on the side opposite to the discharge tube 12 side. The microwave generation unit 11 can generate a microwave M having a predetermined frequency (for example, 2.45 GHz) and radiate it inside the introduction waveguide 13.

The discharge tube 12 has a tubular shape and may have a region (a region for generating a plasma product) for generating plasma P inside. The discharge tube 12 can be provided at a position separated from the chamber 21 described later. The discharge tube 12 can be formed from a material that has high transmittance for microwave M and is not easily etched by plasma products. For example, the discharge tube 12 can be formed of a dielectric such as aluminum oxide or quartz.

The introduction waveguide 13 has a tubular shape, propagates the microwave M radiated from the microwave generation unit 11, and introduces the microwave M into the region inside the discharge tube 12 where the plasma P is generated.
A shielding portion 13a can be provided at the connection portion of the introduction waveguide 13 with the discharge tube 12. The shielding portion 13a has a tubular shape and can be provided so as to cover the outer peripheral surface of the discharge pipe 12. The shielding portion 13a may extend in a direction substantially orthogonal to the direction in which the discharge pipe 12 extends. The shielding portion 13a can be provided so as to be substantially coaxial with the discharge pipe 12. A predetermined gap can be provided between the inner peripheral surface of the shielding portion 13a and the outer peripheral surface of the discharge pipe 12. The gap is sized so that the microwave M does not leak. Therefore, it is possible to prevent the microwave M from leaking due to the shielding portion 13a.

A matching device 13b can be provided at the end of the introduction waveguide 13 opposite to the microwave generating portion 11 side. A stub tuner 13c can be provided between the shielding portion 13a and the microwave generating portion 11 of the introduction waveguide 13.

An annular slot 13a1 can be provided in the shielding portion 13a. The microwave M propagating inside the introduction waveguide 13 is introduced into the inside of the discharge tube 12 via the slot 13a1. Plasma P is generated inside the discharge tube 12 by the introduced microwave M. In this case, the position inside the discharge tube 12 facing the slot 13a1 is substantially the center of the region where the plasma P is generated.
In the plasma processing apparatus 1 according to the present embodiment, the microwave generation unit 11 and the introduction waveguide 13 are plasma generation units capable of generating plasma P in the region where the plasma product is generated.

The gas supply unit 14 can supply the process gas G to the region where the plasma P is generated inside the discharge pipe 12.
The gas supply unit 14 may be provided with a storage unit 14a and a flow rate control unit 14b. The storage unit 14a can store the process gas G. Further, the storage unit 14a can supply the process gas G to the inside of the discharge pipe 12. The storage unit 14a can be, for example, a cylinder containing the process gas G, a factory pipe, or the like. The process gas G is not particularly limited, and can be appropriately selected depending on the content of the treatment, the material of the treated portion of the processed product W, and the like.

The flow rate control unit 14b can be provided between the storage unit 14a and the discharge pipe 12. The flow rate control unit 14b can control the flow rate (supply amount) of the process gas G supplied to the inside of the discharge pipe 12. The flow rate control unit 14b can be, for example, an MFC (Mass Flow Controller) or the like.

The processing unit 20 may be provided with a chamber 21, a mounting unit 22, and a straightening vane 23.
The chamber 21 can have an airtight structure capable of maintaining an atmosphere depressurized from atmospheric pressure. The chamber 21 may be cylindrical, for example. A top plate 21a can be integrally provided at the upper end of the chamber 21. A bottom plate 21b can be integrally provided at the lower end of the chamber 21.

On the side wall of the chamber 21, a carry-in / carry-out port (not shown) for carrying in / out the processed material W can be provided. The carry-in / carry-out outlet can be opened / closed by, for example, a gate valve (not shown). The chamber 21 can be formed from, for example, an aluminum alloy.

The mounting portion 22 is inside the chamber 21 and can be provided on the bottom plate 21b of the chamber 21. The mounting portion 22 can be provided between the straightening vane 23 and the bottom plate 21b. The processed material W can be placed on the upper surface of the mounting portion 22.
The mounting portion 22 may be provided with an electrostatic chuck (not shown). If the electrostatic chuck is provided, the placed processed object W can be held. The processed product W may have a plate shape, for example. The processed material W can be, for example, a semiconductor wafer, a glass substrate, or the like. However, the processed product W is not limited to the illustrated one.

Further, the mounting portion 22 may be provided with a heating portion 22a. The heating unit 22a can heat the processed product W placed on the upper surface of the mounting unit 22. For example, the heating unit 22a may use Joule heat or may circulate the heated heat medium.

The straightening vane 23 can be provided inside the chamber 21 and above the mounting portion 22. The straightening vane 23 can face the upper surface of the mounting portion 22. The straightening vane 23 can be provided below the connection portion between the transport pipe 30 and the side wall of the chamber 21. The rectifying plate 23 rectifies the flow of gas containing radicals introduced from the transport pipe 30. By rectifying the flow of the gas containing radicals, the distribution of the amount of radicals on the surface of the processed product W can be made uniform.

The straightening vane 23 has a plate shape and can have a plurality of holes 23a penetrating in the thickness direction. The straightening vane 23 can be fixed to the inner wall of the chamber 21. The area between the straightening vane 23 and the upper surface (mounting surface) of the mounting portion 22 is the processing space 24 in which the processing object W is processed. The surface of the straightening vane 23 can be covered with a material that does not easily react with radicals (for example, tetrafluorinated resin (PTFE) or ceramics such as aluminum oxide).

The transport pipe 30 can be tubular. One end of the transport pipe 30 can be connected to the end of the discharge pipe 12 opposite to the gas supply part 14 side. The other end of the transport pipe 30 can be connected to the side wall of the chamber 21. That is, the transport pipe 30 can connect the discharge pipe 12 and the chamber 21. The transport pipe 30 can be formed of a material that does not easily react with radicals, such as quartz, stainless steel, ceramics, and tetrafluorinated resin.

The exhaust unit 40 can reduce the pressure inside the chamber 21 to a predetermined pressure.
The exhaust unit 40 may be provided with an exhaust pump 41, a pressure control unit 42, and a pressure measurement unit 43.
The exhaust pump 41 can exhaust the gas inside the chamber 21. The exhaust pump 41 can be, for example, a dry pump or the like. Further, when processing is performed at a lower pressure, the exhaust pump 41 may be, for example, a turbo molecular pump (TMP) or the like.

The pressure control unit 42 can be provided between the chamber 21 and the exhaust pump 41. The pressure control unit 42 can be connected to the bottom plate 21b of the chamber 21. The pressure control unit 42 can control the pressure inside the chamber 21 to be a predetermined pressure. The pressure control unit 42 may be, for example, an automatic pressure controller (APC).
The pressure measuring unit 43 can measure the pressure in the region where the processed object W is processed (the pressure inside the chamber 21) and convert the measured pressure into an electric signal. The pressure measuring unit 43 can be, for example, a vacuum gauge or the like.

The pressure control unit 50 can be provided in the transport pipe 30. Due to conductance, the pressure control unit 50 makes the pressure in the region where the plasma product is generated (the pressure inside the discharge tube 12) different from the pressure in the region where the processed product W is processed (the pressure inside the chamber 21). can do. For example, the pressure control unit 50 can make the pressure inside the discharge tube 12 higher than the pressure inside the chamber 21.

The radicals generated inside the discharge pipe 12 are supplied to the inside of the chamber 21 together with the residual process gas G via the transport pipe 30. Since the pressure control unit 50 is provided in the transport pipe 30, gas containing radicals passes through the inside of the pressure control unit 50. Therefore, the portion of the pressure control unit 50 that comes into contact with the gas containing radicals can be formed of a material that is less likely to be damaged by radicals and is less likely to be inactivated by radicals. For example, the portion of the pressure control unit 50 that comes into contact with a gas containing radicals can be formed of tetrafluorinated resin, ceramics (for example, aluminum oxide), or coated with these materials.

Further, the pressure measuring unit 51 can be provided as needed. The pressure measuring unit 51 can be provided in the transport pipe 30 that connects the discharge pipe 12 and the pressure control unit 50. The pressure measuring unit 51 can measure the pressure in the region where the plasma product is generated (the pressure inside the discharge tube 12) and convert the measured pressure into an electric signal. The pressure measuring unit 51 can be, for example, a vacuum gauge or the like.

Here, if the pressure in the region where the processed product W is processed becomes low, the volatile product produced by reacting with radicals is likely to be released to the outside of the processed product W. Therefore, it is possible to improve the etching rate and, by extension, speed up the processing. Further, in recent years, the aspect ratio of trenches and holes tends to increase. For example, in the manufacture of an image sensor or the like, the aspect ratio of a trench or a hole may be 50 or more. In the manufacture of semiconductor memories and the like, the aspect ratio of trenches and holes may be 100 or more. The higher the aspect ratio, the less likely it is that volatile products inside trenches, holes, etc. will be released to the outside. In this case, if the pressure in the region where the processed product W is processed is made lower than before, the volatile products inside such as trenches and holes are likely to be released to the outside.

Since the region for processing the processed product W and the region for producing the plasma product are connected via the transport pipe 30, when the pressure in the region for processing the processed product W is lowered, the plasma product is generated. The pressure in the area is also low. However, when the pressure in the region where the plasma product is generated becomes low, the plasma P is less likely to be generated, the plasma density becomes low, and the generation of the plasma product may be hindered.

Therefore, the plasma processing device 1 according to the present embodiment is provided with a pressure control unit 50.
The pressure control unit 50 may have the conductance controlled by the controller 60 based on, for example, the output from the pressure measurement unit 51.
Further, the pressure control unit 50 may have, for example, a predetermined conductance. The pressure control unit 50 may be, for example, a fixed throttle or the like. In this case, the conductance can be determined in advance by conducting an experiment or a simulation.
Further, the pressure control unit 50 may manually change the conductance, for example. In this case, the operator can operate the pressure control unit 50 based on the output from the pressure measurement unit 51. The pressure control unit 50 can be, for example, a variable throttle valve or the like.
That is, the conductance of the pressure control unit 50 can be constant.
The conductance of the pressure control unit 50 can also be variable. In this case, the conductance of the pressure control unit 50 can be changed according to the pressure inside the discharge pipe 12. Further, the conductance of the pressure control unit 50 can be changed based on the value measured by the pressure measurement unit 51.

If a pressure control unit 50 having conductance is provided between the region for generating the plasma product and the region for processing the processed product W, the pressure inside the discharge tube 12 is higher than the pressure inside the chamber 21. Can also be made higher. Therefore, even if the pressure inside the chamber 21 is set to a low pressure suitable for volatilizing the product generated by radicals, the pressure inside the discharge tube 12 can be maintained at a high pressure suitable for generating plasma P. ..
For example, even if the pressure inside the chamber 21 is 30 Pa or less, preferably 20 Pa or less, the pressure inside the discharge tube 12 can be maintained at 30 Pa or more.
Furthermore, by increasing the supply amount of the process gas G, it is possible to easily increase the pressure in the region where the plasma product is generated.

The controller 60 may be provided with a processor such as a CPU (Central Processing Unit) and a storage unit such as a memory.
The processor controls the operation of each element provided in the plasma processing device 1 based on the control program stored in the storage unit. For example, the processor can control the operation of each element to perform the etching process on the processed object W.
At this time, the processor can control the pressure control unit 42 based on the output from the pressure measurement unit 43 so that the pressure inside the chamber 21 becomes a predetermined pressure.
Further, the processor can control the pressure control unit 50 based on the output from the pressure measurement unit 51 so that the pressure inside the discharge tube 12 becomes a predetermined pressure.

(Plasma processing method)
Next, the plasma processing method according to the present embodiment will be illustrated.
The plasma processing method according to the present embodiment can be used, for example, for manufacturing a finely processed product such as a semiconductor device. Further, the plasma treatment method according to the present embodiment is suitably used for removing, for example, a damaged layer on an inner wall surface such as a trench or a hole that opens on the surface of the processed material W (for example, the surface of a semiconductor wafer). be able to.

For example, when manufacturing a semiconductor device, trenches or holes that open on the surface of the semiconductor wafer may be formed. Generally, trenches and holes are formed by RIE (Reactive Ion Etching). By driving ions into a semiconductor wafer by RIE, trenches and holes having a high aspect ratio can be formed. However, when forming a trench or a hole, ions are driven into the inner wall surface of the trench or the hole, so that a damaged layer containing surface roughness or crystal defects may be generated on the inner wall surface. The damaged layer becomes a factor that deteriorates the electrical characteristics of the semiconductor device. Therefore, in general, the damaged layer is removed by performing a treatment using radicals that generate less damage.

When radicals are supplied to the damaged layer, the damaged layer reacts with the radicals, and the damaged layer is volatilized and removed. As described above, when the pressure in the region where the processed product W is processed becomes low, the generated volatile product is likely to be released to the outside such as a trench or a hole. Here, in recent years, the aspect ratio of trenches and holes tends to increase. The higher the aspect ratio, the less likely it is that volatile products inside trenches, holes, etc. will be released to the outside. Therefore, it is preferable to further reduce the pressure in the region where the processed product W is processed.

In this case, in general, the pressures of the region for processing the processed product W and the region for producing the plasma product are substantially the same. Therefore, when the pressure in the region where the processed product W is processed is lowered, the pressure in the region where the plasma product is generated is also lowered. When the pressure in the region where the plasma product is generated becomes low, the plasma P is less likely to be generated, the plasma density becomes low, and the generation of the plasma product may be hindered.

In this case, an exhaust device can be provided in the region where the processed product W is processed, another exhaust device can be provided in the region where the plasma product is generated, and the pressure in each region can be controlled individually. However, in this way, a part of the radicals generated in the region where the plasma product is generated is released to the outside by the exhaust device, and the amount of radicals supplied to the region where the processed product W is processed is reduced by that amount. ..
Therefore, in the plasma treatment method according to the present embodiment, the plasma treatment is performed as follows.

FIG. 2 is a flowchart for exemplifying the plasma processing method according to the present embodiment.
First, the pressure in the region where the processed product W is processed and the pressure in the region where the plasma product is generated connected to the region where the processed product W is processed are reduced to a predetermined pressure. (Step S1)
Next, due to the conductance provided at the connection portion between the region for processing the processed product W and the region for producing the plasma product, the pressure in the region for producing the plasma product is the region for processing the processed product W. Make it different from the pressure. (Step S2)
For example, the pressure in the region where the plasma product is generated is set to be higher than the pressure in the region where the processed product W is processed. For example, the pressure in the region where the processed product W is processed can be 30 Pa or less, preferably 20 Pa or less. The pressure in the region where the plasma product is generated can be 30 Pa or more.
In this way, it becomes easy to release the volatile products inside such as trenches and holes to the outside. Moreover, plasma P can be stably generated. In addition, since the plasma density is increased, the production efficiency of plasma products can be improved.

As mentioned above, the conductance may be constant or may be changed based on the pressure in the region where the plasma product is produced. Furthermore, by increasing the supply amount of the process gas G, it is possible to easily increase the pressure in the region where the plasma product is generated.

Next, the plasma P is generated in the region where the plasma product is generated, and the process gas G is excited and activated to generate the plasma product containing radicals. (Step S3)
The process gas G is not particularly limited and may be appropriately selected depending on the material of the processed portion of the processed product W.

Next, the plasma product is supplied to the region where the processed product W is processed via the connection portion described above. (Step S4)
At this time, the ions and electrons contained in the plasma product are attenuated until they reach the region where the processed product W is processed, so that radicals are mainly supplied to the region where the processed product W is processed. ..

Next, radicals are supplied to the surface of the processed product W to perform the desired treatment. (Step S5)
At this time, the temperature of the processed product W can be raised. The higher the temperature of the processed product W, the easier it is to release the volatile products inside such as trenches and holes to the outside. The temperature of the processed product W is preferably 100 ° C. or higher, for example.
As described above, the processed product W can be subjected to a desired treatment.
According to the plasma treatment method according to the present embodiment, appropriate treatment can be applied to trenches and holes having a high aspect ratio. In addition, the generation efficiency of plasma products can be improved by stabilizing the generation of plasma P and increasing the plasma density.

The embodiment of the present embodiment has been illustrated above. However, the present invention is not limited to these descriptions.
With respect to the above-described embodiment, those skilled in the art with appropriate design changes are also included in the scope of the present invention as long as they have the features of the present invention.
For example, the shape, dimensions, materials, arrangement, and the like of each element included in the plasma processing apparatus 1 are not limited to those illustrated, and can be appropriately changed.

1 Plasma processing device, 10 generating section, 11 microwave generating section, 12 discharge tube, 13 introduction waveguide tube, 14 gas supply section, 20 processing section, 21 chamber, 22 mounting section, 30 transport tube, 40 exhaust section, 41 Exhaust pump, 42 Pressure control unit, 43 Pressure measurement unit, 50 Pressure control unit, 51 Pressure measurement unit, 60 Controller, W processed product

Claims (8)

A chamber that can maintain an atmosphere decompressed from atmospheric pressure,
An exhaust unit that can reduce the pressure inside the chamber to a predetermined pressure,
A mounting portion provided inside the chamber on which the processed material can be mounted,
A discharge tube having a region for generating plasma products inside and provided at a position separated from the chamber,
A plasma generating unit capable of generating plasma in the region where the plasma product is generated,
A transport pipe connecting the discharge pipe and the chamber,
A pressure control unit provided in the transport pipe and capable of making the pressure inside the discharge pipe different from the pressure inside the chamber by conductance.
Plasma processing equipment equipped with. The plasma processing apparatus according to claim 1, wherein the pressure control unit makes the pressure inside the discharge tube higher than the pressure inside the chamber. The plasma processing apparatus according to claim 1 or 2, wherein the conductance of the pressure control unit is constant. The plasma processing apparatus according to claim 1 or 2, wherein the conductance of the pressure control unit is variable. The plasma processing apparatus according to claim 4, wherein the conductance of the pressure control unit can be changed according to the pressure inside the discharge tube. A pressure measuring unit for measuring the pressure inside the discharge tube is further provided.
The plasma processing apparatus according to claim 4 or 5, wherein the conductance of the pressure control unit can be changed based on a value measured by the pressure measurement unit. A step of reducing the pressure in the region for processing the processed material and the pressure in the region for producing the plasma product connected to the region for processing the processed material to a predetermined pressure.
Due to the conductance provided at the connection portion between the region for processing the processed product and the region for producing the plasma product, the pressure in the region for producing the plasma product is the pressure in the region for processing the processed product. And the process of making it different from
A step of supplying the generated plasma product to a region for processing the processed product via a connecting portion between a region for processing the processed product and a region for producing the plasma product.
Plasma processing method equipped with. In the step of making the pressure in the region where the plasma product is generated different from the pressure in the region where the processed product is processed, the pressure in the region where the plasma product is generated is changed to the pressure in the region where the processed product is processed. 7. The plasma treatment method according to claim 7.

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