JP2017183607A - Plasma processing method and plasma processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma processing method capable of removing a surface region which contains a silicon carbide and in which damage occurs, and suppressing occurrence of damage in a lower layer that is exposed when the surface region is removed, and a plasma processing apparatus.SOLUTION: A plasma processing method includes the steps of: irradiating a surface region in which damage occurs, of a substrate containing a silicon carbide with ultraviolet light; generating a radical from a gas using plasma in an atmosphere isolated from an atmosphere for placing the substrate; and supplying the radical to the surface region irradiated with the ultraviolet light, thereby removing the surface region irradiated with the ultraviolet light.SELECTED DRAWING: Figure 2

Description

  Embodiments described herein relate generally to a plasma processing method and a plasma processing apparatus.

Semiconductor devices using silicon carbide (SiC) instead of silicon (Si) have been proposed to reduce switching loss and improve electrical characteristics in a high temperature region.
Similarly to a semiconductor device using silicon, in a semiconductor device using silicon carbide, trenches and holes are formed by RIE (Reactive Ion Etching).
If ions are implanted into the substrate by RIE, a trench with a high aspect ratio can be formed.

However, when forming a trench, if ions are implanted into a portion that is not covered with a resist or a hard mask, such as a side surface or a bottom surface of the trench, damage such as surface roughness or crystal defects may occur.
Further, light generated when a reaction product such as ions or radicals is generated using plasma contains ultraviolet rays having a short wavelength. When ultraviolet rays are incident on a portion of the substrate that is not covered with a resist or hard mask, the ultraviolet rays are absorbed by the substrate and damage may occur.

Damage caused by ions or ultraviolet rays is a factor that deteriorates the electrical characteristics of the semiconductor device. For this reason, in the case of a semiconductor device using silicon, by performing treatment using radicals with less damage, the surface area where damage is generated is removed and exposed when the surface area is removed. The occurrence of damage to the lower layer is suppressed.
Also in the case of a semiconductor device using silicon carbide, it has been proposed to remove a surface region where damage has occurred by performing treatment using radicals (see, for example, Patent Document 1). .

  However, silicon carbide has higher bond strength between elements than silicon. For this reason, it is difficult to remove the surface area where the damage has occurred simply by performing treatment using radicals.

Japanese Patent No. 5732790

  A problem to be solved by the present invention is that a surface region containing silicon carbide and causing damage can be removed, and the occurrence of damage to a lower layer exposed when the surface region is removed is suppressed. It is an object to provide a plasma processing method and a plasma processing apparatus.

  The plasma processing method according to the embodiment includes a step of irradiating a surface region of a substrate containing silicon carbide with ultraviolet rays and a gas using plasma in an atmosphere separated from an atmosphere in which the substrate is placed. And a step of supplying the radical to the surface region irradiated with the ultraviolet light and removing the surface region irradiated with the ultraviolet light.

  According to the embodiment of the present invention, it is possible to remove the surface region including silicon carbide and causing damage, and to suppress the occurrence of damage to the lower layer exposed when the surface region is removed. A plasma processing method and a plasma processing apparatus are provided.

4 is a schematic cross-sectional view for illustrating formation of a trench 110. FIG. It is a schematic cross section for illustrating the plasma processing apparatus 1 which concerns on 2nd Embodiment. (A)-(d) is a schematic diagram for illustrating the movement of the position of the plasma P. FIG. (A), (b) is a schematic diagram for demonstrating the discharge tube 11a supported by inclination. (A), (b) is a schematic diagram for illustrating the bent discharge tube 11a. (A), (b) is a schematic diagram for illustrating the connecting pipe 11a having a linear shape and the connecting pipe 14b having a refractive shape.

  Hereinafter, embodiments will be illustrated with reference to the drawings. In addition, in each drawing, the same code | symbol is attached | subjected to the same component and detailed description is abbreviate | omitted suitably.

(First embodiment)
Substrate 100 processed by the plasma processing method according to the present embodiment includes silicon carbide. The substrate 100 can be, for example, a SiC wafer used in manufacturing a semiconductor device. However, the substrate 100 is not limited to the SiC wafer, and may be any substrate having a layer made of silicon carbide exposed at least on the surface.

  Here, for example, in a semiconductor device using silicon carbide as well as a semiconductor device using silicon, trenches and holes are formed by RIE.

  For example, when the semiconductor device is a power semiconductor device, a trench gate structure may be employed. In the trench gate structure, a gate electrode is provided inside a trench formed on the surface of the substrate 100.

Generally, the trench is formed by RIE.
FIG. 1 is a schematic cross-sectional view for illustrating the formation of the trench 110.
The formation process of the trench 110 is as follows.
First, the hard mask 101 is formed on the substrate 100.
The hard mask 101 can be, for example, a silicon nitride film (SiN film), and can be formed by CVD (Chemical Vapor Deposition), a thermal oxidation method, or the like.

Next, a resist mask 102 having a pattern 102 a is formed on the hard mask 101.
The resist mask 102 having the pattern 102a can be formed by, for example, a photolithography method.

Next, using the resist mask 102 as an etching mask, the hard mask 101 and the substrate 100 are sequentially etched to form the trench 110.
A known technique can be applied to the formation of the hard mask 101, the formation of the resist mask 102, and the formation of the trench 110, and a detailed description thereof will be omitted.

  Here, if ions are implanted into the substrate 100 by RIE, highly anisotropic etching can be performed. Therefore, the trench 110 having a high aspect ratio can be easily formed. However, when ions are implanted into the wall surface (side surface and bottom surface) of the trench 110, damage such as surface roughness and crystal defects may occur.

  In addition, light generated when a processing gas is excited in a RIE process to generate reaction products such as ions and radicals includes ultraviolet rays having a short wavelength. When ultraviolet light is incident on the wall surface of the trench 110, the ultraviolet light is absorbed by the wall surface of the trench 110 and damage may occur on the wall surface of the trench 110.

If ions or ultraviolet rays are incident on a portion of the substrate 100 that is not covered with the resist mask 102 or the hard mask 101, such as the wall surface of the trench 110, similar damage may occur.
The wall surface of the trench 110 serves as an interface on which an oxide film serving as a gate insulating film is formed when the gate electrode is formed inside the trench. Therefore, if there is a surface region in which damage is generated on the wall surface of the trench 110, it becomes a factor of deteriorating electrical characteristics as a semiconductor device.

Here, the surface region 100a can be removed by removing the surface region 100a where the damage has occurred by performing treatment using radicals that are less likely to cause physical damage, such as CDE (Chemical Dry Etching). It is possible to suppress the occurrence of damage to the lower layer exposed when the operation is performed.
The lower layer exposed when the surface region 100a is removed is, for example, the wall surface of the trench 110 where the substrate 100 made of silicon carbide is exposed.
However, the treatment using radicals is a treatment in which etching is performed by a chemical reaction with the surface region 100a that is an object to be etched. In addition, silicon carbide has a higher bond strength between elements than silicon. It is difficult to remove the surface region 100a where the damage has occurred only by performing treatment using radicals.

Therefore, in the plasma processing method according to the present embodiment, the surface region 100a where damage has occurred is removed as follows.
First, the surface region 100a where the substrate 100 containing silicon carbide is damaged is irradiated with ultraviolet rays.
Ultraviolet rays can be irradiated, for example, by an ultraviolet irradiation device equipped with an ultraviolet lamp or the like.

  When the surface region 100a where the damage has occurred is irradiated with ultraviolet rays, the ultraviolet rays are absorbed by silicon carbide in the surface region 100a, and the bond between Si and C is excited. When the bond between Si and C is excited, the bond between Si and C weakens, so that the surface reaction can be promoted. Therefore, it becomes easy to remove (etch) the surface region 100a using radicals described later.

Next, the irradiation of ultraviolet rays is stopped. Thereafter, radicals are supplied to the surface region 100a irradiated with ultraviolet rays to remove the surface region 100a irradiated with ultraviolet rays.
For example, radicals are generated from a gas G, which is a processing gas, using plasma P in an atmosphere separated from the atmosphere on which the substrate 100 is placed, and the radicals are transported to the atmosphere on which the substrate 100 is placed. The surface region 100a irradiated with the ultraviolet rays is removed by the chemical reaction.

  The gas G can be, for example, a gas containing fluorine atoms and an oxygen gas. Note that the gas containing fluorine atoms and the oxygen gas may be supplied to a region where the plasma P is generated in a mixed state, or may be supplied separately to a region where the plasma P is generated.

The gas containing a fluorine atom can be, for example, CHF ₃ , CF ₄ , C ₄ F ₈ or the like. However, the gas containing a fluorine atom is not limited to what was illustrated. The gas containing a fluorine atom may be any gas that can generate a fluorine radical.
Oxygen gas is added to extend the lifetime of fluorine radicals. Oxygen gas is not always necessary.

When a gas containing a fluorine atom is used, the generated radical is a fluorine radical.
In this case, ions are also generated when fluorine radicals are generated.
When the generated ions reach the surface of the substrate 100, damage may occur in the lower layer exposed when the surface region 100a is removed.
Therefore, ions are prevented from reaching the surface of the substrate 100 when removing the damaged surface region 100a.

  For example, a reaction product is generated in an atmosphere (for example, in a discharge tube 11a to be described later) separated from an atmosphere (for example, a processing space 10c to be described later) on which the substrate 100 is placed, such as a remote plasma processing apparatus. The generated reaction product may be transported to the atmosphere on which the substrate 100 is placed. In this way, it is possible to prevent ions having a short lifetime from reaching the atmosphere on which the substrate 100 is placed. In this case, fluorine radicals having a longer lifetime than ions can reach the atmosphere in which the substrate 100 is placed.

The surface region 100a irradiated with the ultraviolet rays has a low bond strength between Si and C, so even if it contains silicon carbide, it can be easily removed by radicals generated from the gas G. In the present embodiment, the radicals generated from the gas G are fluorine radicals.
On the other hand, since the lower layer of the surface region 100a irradiated with ultraviolet rays is not exposed to the above-described irradiation of ultraviolet rays or ions until the surface region 100a is removed, the bond strength between Si and C remains high. Therefore, it is difficult to remove by fluorine radicals. Therefore, it is possible to suppress an unnecessary increase in dimensions such as a trench hole diameter due to overetching.

In the case of the above-described case, radicals generated from the gas G are supplied after irradiating the damaged surface region 100a with ultraviolet rays, but the damaged surface region is generated as follows. 100a can also be removed.
First, the surface region 100a where damage has occurred is irradiated with ultraviolet rays and radicals are supplied.
Next, the irradiation of ultraviolet rays is stopped.
Next, only radicals are supplied to the surface region 100a. The radical supply may be continuously performed from the step of irradiating with ultraviolet rays to the step of supplying radicals.

Further, hydrogen radicals can be supplied to the surface region 100a where damage has occurred instead of the ultraviolet irradiation or together with the ultraviolet irradiation.
That is, it is possible to further include a step of supplying hydrogen radicals to the surface region 100a.
If hydrogen radicals are supplied to the surface region 100a, the Si—C bonds in the surface region 100a can be changed to Si—H bonds. Since the mass of hydrogen is small, the surface region 100a can be easily removed if it can be changed to a Si—H bond.

Here, as described above, the light generated when the gas G, which is the processing gas, is excited to generate reaction products such as ions and radicals contains ultraviolet rays.
For this reason, the ultraviolet ray generated when the reaction product is generated can be irradiated to the surface region 100a where the damage is generated.
In this case, the surface region 100a where the damage has occurred can be removed as follows.

First, radicals are generated from the gas G using the plasma P in an atmosphere separated from the atmosphere on which the substrate 100 containing silicon carbide is placed.
Next, the surface region 100a where the substrate 100 is damaged is irradiated with ultraviolet rays generated when radicals are generated.
For example, a reaction product is generated from the gas G using the plasma P in the vicinity of the damaged surface region 100a (in the vicinity of the substrate 100). That is, the distance between the plasma P and the surface region 100a is shortened.
Since the surface region 100a is in the vicinity of the plasma P, the ultraviolet rays generated when the reaction product is generated are irradiated to the surface region 100a.

  At this time, ions are implanted into the surface region 100a. However, even if ions are implanted into the surface region 100a and damage occurs, there is no problem because the surface region 100a is removed. In addition, since ions are implanted into the surface region 100a, the removal of the surface region 100a by radicals is further facilitated.

  In addition, radicals reach the surface region 100a. Therefore, the treatment of the surface region 100a with ultraviolet rays and the removal of the surface region 100a with radicals can be performed in parallel.

Next, radicals generated from the gas G are supplied to the surface region 100a irradiated with ultraviolet rays to remove the surface region 100a irradiated with ultraviolet rays.
At this time, for example, the distance between the plasma P and the surface region 100a is made longer than when the surface region 100a is irradiated with ultraviolet rays or ions.
The distance between the plasma P and the surface region 100a can be obtained by considering the spread of the plasma from the position of the portion with the highest plasma density of the plasma P.
The position of the plasma P having the highest plasma density can be obtained in advance by experiments or simulations, or can be regarded as a position facing the slot 11b2 in the discharge tube.
If the distance between the plasma P and the surface region 100a is increased, ions having a shorter lifetime than the radicals do not easily reach the surface region 100a (substrate 100). Further, when the distance between the plasma P and the surface region 100a is increased, the ultraviolet rays are difficult to reach the surface region 100a (substrate 100).
On the other hand, since the radical can reach the surface region 100a, the surface region 100a irradiated with ultraviolet rays or ions can be removed by the radical.
When the surface region 100a is removed by radicals, the lower layer of the surface region 100a is exposed. However, since it is difficult to reach the lower layer to which ultraviolet rays or ions are exposed, it is possible to suppress damage to the lower layer due to ultraviolet rays or ions.

  Note that an appropriate distance between the plasma P and the surface region 100a can be determined as appropriate through experiments and simulations.

The distance between the plasma P and the surface region 100a can be changed by moving the position of the plasma P.
3A to 3D are schematic views for illustrating movement of the position of the plasma P. FIG.
For example, when the surface region 100a is irradiated with ultraviolet rays generated when radicals are generated, the distance between the plasma P generated at the first position and the surface region 100a is set to the first distance. (FIG. 3A).
When removing the surface region 100a irradiated with ultraviolet rays, the distance between the plasma P generated at the second position and the surface region 100a is set to a second distance longer than the first distance. (FIG. 3B).
In this case, as will be described later, the position of the plasma P can be moved by changing the position of the introduction waveguide 11b with respect to the discharge tube 11a.

Further, the distance between the plasma P and the surface region 100a can be changed by changing the spread of the plasma P.
For example, if the spread of the plasma P is increased, the distance between the plasma P and the surface region 100a can be shortened. Therefore, it becomes easy to irradiate the surface region 100a with ultraviolet rays.
If the spread of the plasma P is reduced, the distance between the plasma P and the surface region 100a can be increased. Therefore, it becomes difficult to irradiate the surface region 100a with ultraviolet rays or ions. In this case, radicals having a longer lifetime than ions can reach the surface region 100a.
For example, when the surface region 100a is irradiated with ultraviolet rays generated when radicals are generated, the spread of the plasma P is set to the first magnitude (FIG. 3C).
When removing the surface region 100a irradiated with the ultraviolet rays, the spread of the plasma P is set to a second size smaller than the first size (FIG. 3D).

The spread of the plasma P can be changed by the processing pressure, the power such as microwaves, the composition of the gas G, and the like.
For example, if the processing pressure is lowered, the spread of the plasma P can be increased. If the processing pressure is increased, the spread of the plasma P can be reduced.
If the power of microwaves or the like is increased, the spread of the plasma P can be increased. If the power of the microwave or the like is lowered, the spread of the plasma P can be reduced.
If an inert gas such as Ar, He, or Xe, nitrogen gas, or the like is added to the gas G, the spread of the plasma P can be increased.

Further, the step of irradiating with ultraviolet rays and the step of supplying radicals described above can be performed once or repeatedly.
Further, both the position and spread of the plasma may be changed by moving the position of the plasma P and changing the processing pressure, the power such as microwaves, and the composition of the gas G.

In the plasma processing method according to the present embodiment, the surface reaction in the surface region 100a is promoted by irradiating the damaged surface region 100a with ultraviolet rays.
Therefore, even if the surface region 100a contains silicon carbide having higher bond strength between elements than silicon, it can be easily removed by radicals.
In addition, since the surface region 100a is removed using radicals that cause little damage, it is possible to suppress damage from occurring in the lower layer exposed when the surface region 100a is removed.

(Second Embodiment)
FIG. 2 is a schematic cross-sectional view for illustrating the plasma processing apparatus 1 according to the second embodiment.
The plasma processing apparatus 1 can execute the plasma processing method described above.
The plasma processing apparatus 1 illustrated in FIG. 2 is a CDE apparatus that is a kind of remote plasma processing apparatus.

As shown in FIG. 2, the plasma processing apparatus 1 includes a processing vessel 10, a plasma generation unit 11, a decompression unit 12, a gas supply unit 13, a connection pipe 14, a moving unit 15, an ultraviolet irradiation unit 16, and a control unit 17. Is provided.
The processing container 10 has an airtight structure capable of maintaining an atmosphere reduced in pressure from atmospheric pressure. The processing vessel 10 is provided with a loading / unloading port (not shown) so that the substrate 100 can be loaded and unloaded via the loading / unloading port (not shown).

Inside the processing container 10, a placement unit 10 a on which the substrate 100 is placed is provided. The mounting portion 10a can incorporate an electrostatic chuck (not shown). In addition, the mounting unit 10 a can be provided with a heating device (not shown) for controlling the temperature of the substrate 100.
A rectifying plate 10b is provided inside the processing container 10 and above the mounting portion 10a. The rectifying plate 10 b rectifies the flow of the gas containing radicals introduced from the connection pipe 14 so that the amount of radicals above the substrate 100 is uniform. A region between the rectifying plate 10b and the upper surface (mounting surface) of the mounting portion 10a is a processing space 10c in which an etching process is performed on the substrate 100.

  Further, the ultraviolet light generated when the reaction product is generated is irradiated onto the surface region 100a of the substrate 100 through a plurality of holes 10b1 provided in the rectifying plate 10b.

The plasma generator 11 is provided with a discharge tube 11a, an introduction waveguide 11b, and a microwave generator 11c.
The discharge tube 11 a has a region for generating plasma P inside, and is provided at a position separated from the processing vessel 10. The discharge tube 11a has a tubular shape and is formed of a material that has a high transmittance with respect to the microwave M and is difficult to be etched. For example, the discharge tube 11a can be formed of a dielectric such as alumina or quartz.

The introduction waveguide 11b propagates the microwave M emitted from the microwave generation unit 11c and introduces the microwave M into the region where the plasma P is generated.
The introduction waveguide 11b has a cylindrical shape. The microwave M radiated from the microwave generator 11c propagates in the space inside the introduction waveguide 11b.
A microwave generator 11c is connected to one end of the introduction waveguide 11b. The other end of the introduction waveguide 11b is connected to the discharge tube 11a via the shielding part 11b1. In addition, an annular slot 11b2 is provided at a connection portion between the introduction waveguide 11b and the shielding portion 11b1. The microwave M that has propagated through the introduction waveguide 11b is introduced into the discharge tube 11a through the slot 11b2.

The microwave generator 11c generates a microwave M having a predetermined frequency (for example, 2.45 GHz) and radiates it toward the introduction waveguide 11b.
The decompression unit 12 decompresses the inside of the processing container 10 to a predetermined pressure.
The decompression unit 12 can be, for example, a turbo molecular pump. The decompression unit 12 is connected to the processing container 10 via a pressure control unit (Auto Pressure Controller: APC) 12a.

The gas supply unit 13 is connected to an end of the discharge tube 11a opposite to the connection tube 14 side via a flow rate control unit (Mass Flow Controller: MFC) 13a.
The gas supply unit 13 supplies the gas G to the region where the plasma P is generated. That is, the gas supply unit 13 supplies the gas G into the discharge tube 11a. The supply amount of the gas G supplied into the discharge tube 11a is controlled by the flow rate controller 13a.
In the case where a plurality of types of gases are supplied into the discharge tube 11a, a flow rate control unit can be provided for each of the plurality of types of gases.

The connection tube 14 connects the discharge tube 9 and the processing container 10.
One end of the connection tube 14 is connected to the end of the discharge tube 11a opposite to the gas supply unit 13 side. The other end of the connection pipe 14 is connected to the processing container 10.
The connecting pipe 14 is not always necessary. For example, the discharge tube 11a and the processing container 10 may be connected.
In addition, the position of the connection pipe 14 in the processing container 10 is not particularly limited, but is preferably directly above the placement portion 10a. In this way, it becomes easy to irradiate the surface region 100a of the substrate 100 with ultraviolet rays or ions generated when the reaction product is generated.
Further, the shape of the connecting pipe 14 is not particularly limited, but it is preferably a linear shape, that is, a straight cylindrical body. In this way, it becomes easy to irradiate the surface region 100a of the substrate 100 with ultraviolet rays or ions generated when the reaction product is generated. Further, it becomes easy to supply radicals to the surface region 100 a of the substrate 100.

The moving unit 15 moves the position of the introduction waveguide 11 b with respect to the discharge tube 9. That is, the moving unit 15 changes the position of the generated plasma P.
For example, the moving unit 15 moves the shielding unit 11b1, the slot 11b2, the introduction waveguide 11b, and the microwave generation unit 11c along the discharge tube 11a.
In this case, the moving unit 15 may move the shielding unit 11b1, the slot 11b2, and the introduction waveguide 11b along the discharge tube 11a. In this case, a flexible cylindrical body can be provided between the microwave generator 11c and the introduction waveguide 11b. The moving unit 15 may include, for example, a control motor such as a servo motor, a guide mechanism such as a linear motion bearing, and a conduction mechanism such as a ball screw.
If the moving part 15 is provided, the distance between the plasma P and the surface region 100a described above can be easily controlled.
Note that the distance between the plasma P and the surface region 100a is a distance on the path from which a reaction product or ultraviolet light reaches the surface region 100a from the generation region of the plasma P.
That is, in the discharge tube 11a, the distance from the plasma P generation region to the end opposite to the gas supply unit 13 side, the axial length of the connection tube 14, and the connection between the connection tube 14 and the processing vessel 10 The total length from the portion to the surface region 100a can be taken. For example, when the shape of the connecting pipe 14 is refracted, the refracted length is included.
Note that when the distance between the plasma P and the surface region 100a is changed by changing the spread of the plasma P, the moving unit 15 can be omitted.
Further, the position control of the plasma P by the moving unit 15 and the control of the spread of the plasma P by the decompression unit 12 or the gas supply unit 13 can be performed.

The ultraviolet irradiation unit 16 irradiates the surface region 100 a of the substrate 100 with ultraviolet rays.
The ultraviolet irradiation unit 16 can be, for example, an ultraviolet irradiation device including an ultraviolet lamp.
The ultraviolet irradiation unit 16 can be provided inside the processing container 10. The ultraviolet irradiation unit 16 can be provided in the processing space 10c, for example.
The ultraviolet irradiation unit 16 can also be provided outside the processing container 10. For example, a load lock chamber 200 may be provided between the processing container 10 and the external space. When the load lock chamber 200 or the like is provided, the ultraviolet irradiation unit 16 can be provided inside the load lock chamber 200 or the like.
In addition, when using the ultraviolet-ray generated when producing | generating a reaction product, the ultraviolet irradiation part 16 can be omitted.

The control unit 17 includes a calculation unit such as a CPU (Central Processing Unit) and a storage unit such as a memory.
The control unit 17 controls the operation of each element provided in the plasma processing apparatus 1 based on a control program stored in the storage unit. Since a known technique can be applied to the control program for controlling the operation of each element, a detailed description is omitted.

Moreover, the control part 17 can perform the following control.
The control unit 17 controls the position of the plasma P by controlling the moving unit 15.
The control unit 17 controls the moving unit 15 to shorten the distance between the plasma P and the surface region 100a so that the surface region 100a is irradiated with ultraviolet rays.
Further, the control unit 17 controls the moving unit 15 to increase the distance between the plasma P and the surface region 100a, thereby irradiating the lower layer exposed when the surface region 100a is removed with ultraviolet rays or ions. Do not be.
For example, the control unit 17 controls the moving unit 15 to move the shielding unit 11b1, the slot 11b2, the introducing waveguide 11b, and the microwave generating unit 11c along the discharge tube 11a, and the plasma P and the surface region. By setting the distance to 100a as the first distance, the surface region 100a is irradiated with ultraviolet rays.
The control unit 17 controls the moving unit 15 to move the shielding unit 11b1, the slot 11b2, the introducing waveguide 11b, and the microwave generating unit 11c along the discharge tube 11a, and the plasma P and the surface region 100a. By setting the distance between the second distance longer than the first distance, the lower layer exposed when the surface region 100a is removed is prevented from being irradiated with ultraviolet rays.

The control unit 17 controls the spread of the plasma P by controlling at least one of the decompression unit 12, the microwave generation unit 11c, and the gas supply unit 13.
The control unit 17 controls the decompression unit 12 to increase the spread of the plasma P by lowering the processing pressure. The control unit 17 controls the decompression unit 12 to increase the processing pressure, thereby reducing the spread of the plasma P.
For example, the control unit 17 controls the decompression unit 12 to set the internal pressure of the processing container 10 to the first pressure so that the surface region 100a is irradiated with ultraviolet rays.
The control unit 17 controls the decompression unit 12 to set the pressure inside the processing container 100 to a second pressure higher than the first pressure, so that the lower layer exposed when the surface region 100a is removed. Suppresses ultraviolet rays from being irradiated.

The control unit 17 controls the microwave generation unit 11c to increase the output of the plasma P by increasing the output. The control unit 17 controls the microwave generation unit 11c to reduce the spread of the plasma P by reducing the output.
For example, the control unit 17 controls the microwave generation unit 11c to set the power of the microwave M to the first power so that the surface region 100a is irradiated with ultraviolet rays.
The control unit 17 controls the microwave generation unit 11c to set the power of the microwave M to a second power lower than the first power, thereby exposing the lower layer exposed when the surface region 100a is removed. Suppresses ultraviolet rays from being irradiated.

The control unit 17 controls the gas supply unit 13 to increase the spread of the plasma P by adding an inert gas such as Ar, He, or Xe, nitrogen gas, or the like to the gas G.
That is, the control unit 17 controls the gas supply unit 13 to add at least one of an inert gas and a nitrogen gas to the gas G so that the surface region 100a is irradiated with ultraviolet rays.

For example, the plasma processing apparatus 1 removes the damaged surface region 100a as follows.
First, the board | substrate 100 is mounted on the mounting part 10a with the conveying apparatus which is not shown in figure.
Next, the ultraviolet irradiation unit 16 irradiates the surface region 100 a of the substrate 100 with ultraviolet rays.
Next, the inside of the processing container 10 is decompressed to a predetermined pressure by the decompression unit 12.
Next, a gas G having a predetermined flow rate is supplied from the gas supply unit 13 through the flow rate control unit 13a into the discharge tube 11a. On the other hand, a microwave M having a predetermined power is radiated from the microwave generator 11c into the introduction waveguide 11b. The radiated microwave M propagates in the introduction waveguide 11b and is radiated toward the discharge tube 11a through the slot 11b2.

  The microwave M radiated toward the discharge tube 11a propagates on the surface of the discharge tube 11a and is radiated into the discharge tube 11a. Thus, plasma P is generated by the energy of the microwave M radiated into the discharge tube 11a. When the electron density in the generated plasma P becomes equal to or higher than a density (cutoff density) that can shield the microwave M supplied through the discharge tube 11a, the microwave M is discharged from the inner wall surface of the discharge tube 11a. The light is reflected until it enters the space in 11a by a certain distance (skin depth). Therefore, a standing wave of the microwave M is formed between the reflection surface of the microwave M and the lower surface of the slot 11b2. As a result, the reflection surface of the microwave M becomes a plasma excitation surface, and the plasma P is stably excited and generated on this plasma excitation surface. In the plasma P excited and generated on this plasma excitation surface, the gas G is excited and activated to generate plasma products such as radicals and ions.

  The generated gas containing the plasma product is conveyed into the processing container 10 through the connection pipe 14. At this time, ions having a short life cannot reach the processing container 10, and only radicals having a long life reach the processing container 10. The gas containing radicals introduced into the processing container 10 reaches the surface region 100a that is rectified by the rectifying plate 10b and irradiated with ultraviolet rays. Since the surface region 100a irradiated with ultraviolet rays has a low bond strength between Si and C, even if it contains silicon carbide, it can be easily removed by radicals.

The above is a case where the ultraviolet ray irradiation unit 16 irradiates the surface region 100a with ultraviolet rays. However, the surface region 100a may be irradiated with ultraviolet rays generated when the reaction product is generated.
For example, the moving unit 15 shortens the distance between the plasma P and the surface region 100a so that the surface region 100a is irradiated with ultraviolet rays.
Further, the surface region 100a is irradiated with ultraviolet rays by increasing the spread of the plasma P by at least one of the decompression unit 12, the microwave generation unit 11c, and the gas supply unit 13.
Note that the control of the position of the plasma P and the control of the spread of the plasma P can be the same as those described above, and a detailed description thereof will be omitted.

The embodiment has been illustrated above. However, the present invention is not limited to these descriptions.
For example, in the second embodiment, the connection pipe 14 is linear and is provided directly above the processing container 10, but is not limited thereto.
FIGS. 4A and 4B are schematic views for illustrating the discharge tube 11a supported by being inclined.
As shown in FIGS. 4A and 4B, for example, the connection tube 14 may be provided so that the shaft of the discharge tube 11 a is supported while being inclined with respect to the outer wall surface of the processing vessel 10. In this case, the first distance during the process of irradiating with ultraviolet rays is such that the substrate exists on the extension of the axis of the discharge tube from the position where the plasma P1 is generated so that the ultraviolet rays and ions reach the surface region 100a of the substrate. The distance can be set (FIG. 4A). In addition, the second distance during the process of removing the surface region irradiated with ultraviolet rays is such that the ultraviolet ray and ions reach the surface region 100a of the substrate from the position where the plasma P2 is generated from the position where the plasma P2 is generated. The distance in which the substrate does not exist in the extending direction of the shaft can be set (FIG. 4B).
FIGS. 5A and 5B are schematic views for illustrating a bent discharge tube 11a.
As shown in FIGS. 5A and 5B, for example, the discharge tube 11a is inclined with respect to the straight portion 11a1 provided perpendicular to the outer wall surface of the processing vessel 10 and the straight portion 11a1. It is also possible to have a bent portion 11a2 (the angle intersecting the straight portion is 180 degrees or less). In this case, the position of the plasma P may be moved by having a plurality of shielding portions 11b1 and slots 11b2 and selectively using them in accordance with the process. In this case, the moving unit 15 can be omitted. For example, during the process of irradiating ultraviolet rays, a microwave is applied to the first slot 11b2 provided in the straight portion 11a1, so that the distance between the plasma P and the surface region becomes the first distance. Then, plasma P1 is generated (FIG. 5A). In the step of removing the surface region irradiated with ultraviolet rays, a microwave is applied to the second slot 11b2 provided in the bent portion 11a2, and the distance between the plasma P and the surface region is the second. Plasma P2 is generated so as to be a distance (FIG. 5B).
FIGS. 6A and 6B are schematic views for illustrating a connecting pipe 11a having a linear shape and a connecting pipe 14b having a refracting shape.
As shown in FIGS. 6A and 6B, for example, a connecting tube 14a having a linear shape and a connecting tube 14b having a refracting shape are provided, and a discharge tube is connected to each, and the discharge tube is set according to the process. The position of the plasma P can be selected and moved. For example, when performing the process of irradiating ultraviolet rays, the plasma P1 is set so that the distance between the plasma P and the surface region becomes the first distance in one discharge tube connected to the connecting tube 14a having a linear shape. Is generated (FIG. 6A). In the step of removing the surface region irradiated with ultraviolet rays, the distance between the plasma P and the surface region is the second distance in the other discharge tube connected to the connecting tube 14b having a refractive shape. Then, plasma P2 is generated (FIG. 6B). Also in this case, a plurality of shielding portions 11b1 and slots 11b2 may be provided and selectively used according to the process, and the moving portion 15 can be omitted.
Regarding the above-described embodiment, those in which those skilled in the art appropriately added, deleted, or changed the design, or added the process, omitted, or changed the conditions also have the features of the present invention. As long as it is within the scope of the present invention.
For example, the shape, size, material, arrangement, number, and the like of each element included in the plasma processing apparatus 1 are not limited to those illustrated, but can be changed as appropriate.
Moreover, each element with which each embodiment mentioned above is combined can be combined as much as possible, and what combined these is also included in the scope of the present invention as long as the characteristics of the present invention are included.

DESCRIPTION OF SYMBOLS 1 Plasma processing apparatus, 10 processing container, 10a mounting part, 11 plasma generation part, 11a discharge tube, 11b introduction waveguide, 11c microwave generation part, 12 decompression part, 13 gas supply part, 14 connection pipe, 15 movement Part, 16 ultraviolet irradiation part, 17 control part, 100 substrate, 100a surface region, G gas, M microwave, P plasma

Claims (13)

A step of irradiating a surface region where damage has occurred on a substrate containing silicon carbide with ultraviolet rays;
Generating radicals from gas using plasma in an atmosphere separated from the atmosphere on which the substrate is placed;
Supplying the radicals to the surface region irradiated with the ultraviolet rays, and removing the surface region irradiated with the ultraviolet rays;
A plasma processing method comprising: Generating radicals from gas using plasma in an atmosphere separated from an atmosphere on which a substrate containing silicon carbide is placed;
Irradiating the surface region where the damage of the substrate is generated with ultraviolet rays generated when the radicals are generated;
Supplying the radicals to the surface region irradiated with the ultraviolet rays, and removing the surface region irradiated with the ultraviolet rays;
A plasma processing method comprising:   The plasma processing method according to claim 1 or 2, wherein in the step of removing the surface region irradiated with the ultraviolet rays, the irradiation of the ultraviolet rays onto the substrate is suppressed. When irradiating the surface region with ultraviolet light generated when the radical is generated, the distance between the plasma and the surface region is set to a first distance,
The plasma processing according to claim 3, wherein when removing the surface region irradiated with ultraviolet rays, a distance between the plasma and the surface region is set to a second distance that is longer than the first distance. Method. When the surface region is irradiated with ultraviolet rays generated when the radicals are generated, the spread of the plasma is set to a first size,
5. The plasma processing method according to claim 3, wherein when the surface region irradiated with the ultraviolet rays is removed, the spread of the plasma is set to a second size smaller than the first size.   The plasma processing method according to claim 1, further comprising a step of supplying hydrogen radicals to the surface region. A treatment container capable of maintaining an atmosphere depressurized from atmospheric pressure;
A decompression section for decompressing the inside of the processing container to a predetermined pressure;
A mounting portion provided inside the processing container and for mounting a substrate;
A discharge tube provided in a position separated from the processing vessel, having a region for generating plasma inside;
A microwave generator for generating microwaves;
An introduction waveguide for propagating the microwave and introducing the microwave into a region where the plasma is generated;
A gas supply unit for supplying a gas to a region for generating the plasma;
With
The substrate comprises silicon carbide and has a surface region in which damage has occurred;
The plasma processing apparatus in which the surface region is irradiated with ultraviolet rays generated when radicals are generated from the gas using the plasma. A moving unit for moving the position of the introduction waveguide with respect to the discharge tube;
The moving unit sets the distance between the plasma and the surface region to a first distance so that the ultraviolet ray is irradiated to the surface region,
By setting the distance between the plasma and the surface region to a second distance that is longer than the first distance, the lower layer exposed when the surface region is removed is irradiated with the ultraviolet light. The plasma processing apparatus of Claim 7 which suppresses. The decompression unit is configured to irradiate the surface region with the ultraviolet ray by setting the pressure inside the processing container to a first pressure,
Claims for suppressing irradiation of the ultraviolet ray to a lower layer exposed when the surface region is removed by setting the pressure inside the processing container to a second pressure higher than the first pressure. Item 9. The plasma processing apparatus according to Item 7 or 8. The microwave generator is configured to irradiate the surface region with the ultraviolet ray by setting the microwave power to the first power,
The power of the microwave is set to a second power lower than the first power, thereby suppressing irradiation of the ultraviolet light to a lower layer exposed when the surface region is removed. The plasma processing apparatus as described in any one of -9.   The gas supply unit according to any one of claims 7 to 10, wherein the surface region is irradiated with the ultraviolet light by adding at least one of an inert gas and a nitrogen gas to the gas. The plasma processing apparatus as described.   The gas supply unit supplies a hydrogen-containing gas to a region where the plasma is generated, hydrogen radicals are generated from the supplied hydrogen-containing gas by the plasma, and the generated hydrogen radicals are generated in the surface region. The plasma processing apparatus according to any one of claims 7 to 11, which is supplied. The plasma processing apparatus according to claim 7, further comprising an ultraviolet irradiation unit that irradiates the surface region with ultraviolet rays.

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