JP2020202393A - Plasma processing method and plasma processing apparatus - Google Patents

Abstract

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 of the present invention relate to a plasma processing method and a plasma processing apparatus.

A semiconductor device using silicon carbide (SiC) instead of silicon (Si) has been proposed in order to reduce switching loss and improve electrical characteristics in a high temperature region.
Similar to the semiconductor device using silicon, in the semiconductor device using silicon carbide, trenches and holes are formed by RIE (Reactive Ion Etching).
By driving ions into the substrate by RIE, a trench having a high aspect ratio can be formed.

However, when forming a trench, if ions are injected into a portion not covered with a resist or a hard mask such as the side surface or the bottom surface of the trench, damage such as surface roughness or crystal defects may occur.
In addition, the light generated when reaction products such as ions and radicals are generated using plasma includes ultraviolet rays having a short wavelength. When ultraviolet rays enter a portion of the substrate that is not covered with a resist or a hard mask, the ultraviolet rays may be absorbed by the substrate and cause damage.

Damage caused by ions and ultraviolet rays is a factor that deteriorates the electrical characteristics of semiconductor devices. Therefore, in the case of a semiconductor device using silicon, the damaged surface region is removed by performing a treatment using radicals that cause less damage, and the surface region is exposed when the surface region is removed. It suppresses the occurrence of damage to the lower layer.
Further, even in the case of a semiconductor device using silicon carbide, it has been proposed to remove a damaged surface region by performing a treatment using radicals (see, for example, Patent Document 1). ..

However, silicon carbide has a higher bond strength between elements than silicon. Therefore, it has been difficult to remove the damaged surface region by simply performing the treatment using radicals.

Japanese Patent No. 5732790

The problem to be solved by the present invention is that it is possible to remove a surface region containing silicon carbide and causing damage, and it is possible to suppress damage to the lower layer exposed when the surface region is removed. It is to provide a plasma processing method capable of, and a plasma processing apparatus.

The plasma treatment method according to the embodiment is a step of irradiating a damaged surface region of a substrate containing silicon carbide with ultraviolet rays, and a gas using plasma in an atmosphere separated from the atmosphere on which the substrate is placed. It includes a step of generating a radical from the surface region and a step of supplying the radical to the surface region irradiated with the ultraviolet rays to remove the surface region irradiated with the ultraviolet rays.

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

It is a schematic cross-sectional view for exemplifying the formation of a trench 110. It is a schematic cross-sectional view for exemplifying the plasma processing apparatus 1 which concerns on 2nd Embodiment. (A) to (d) are schematic views for exemplifying the movement of the position of the plasma P. (A) and (b) are schematic views for exemplifying the discharge tube 11a supported by being inclined. (A) and (b) are schematic views for exemplifying a bent discharge tube 11a. (A) and (b) are schematic views for exemplifying a connecting tube 11a having a linear shape and a connecting tube 14b having a refracting shape.

Hereinafter, embodiments will be illustrated with reference to the drawings. In each drawing, similar components are designated by the same reference numerals and detailed description thereof will be omitted as appropriate.

(First Embodiment)
The substrate 100 processed by the plasma processing method according to the present embodiment contains silicon carbide. The substrate 100 can be, for example, a SiC wafer used in the manufacture of semiconductor devices. However, the substrate 100 is not limited to the SiC wafer, and may be at least one in which a layer made of silicon carbide is exposed 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 adopted. In the trench gate structure, the gate electrode is provided inside the trench formed on the surface of the substrate 100.

Generally, trenches are formed by RIE.
FIG. 1 is a schematic cross-sectional view for exemplifying the formation of the trench 110.
The process of forming 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 102a 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.
Since known techniques can be applied to the formation of the hard mask 101, the resist mask 102, and the trench 110, detailed description thereof will be omitted.

Here, if ions are driven 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 injected into the wall surface (side surface and bottom surface) of the trench 110, damage such as surface roughness and crystal defects may occur.

Further, the light generated when the processing gas is excited in the treatment by RIE to generate a reaction product such as an ion or a radical contains ultraviolet rays having a short wavelength. When ultraviolet rays enter the wall surface of the trench 110, the ultraviolet rays may be absorbed by the wall surface of the trench 110 and damage the wall surface of the trench 110.

Similar damage may occur when 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.
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 a gate electrode is formed inside the trench. Therefore, if there is a damaged surface region on the wall surface of the trench 110, it becomes a factor of deteriorating the electrical characteristics of the semiconductor device.

Here, if the surface region 100a in which damage is generated is removed by performing a treatment using radicals that generate less physical damage, such as CDE (Chemical Dry Etching), the surface region 100a is removed. It is possible to suppress the occurrence of damage to the lower layer that is exposed when the etching 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 which is an object to be etched, and silicon carbide has a higher bond strength between elements than silicon, so that it is simply , It was difficult to remove the damaged surface region 100a only by performing the treatment using radicals.

Therefore, in the plasma treatment method according to the present embodiment, the surface region 100a in which damage is generated is removed as follows.
First, ultraviolet rays are applied to the damaged surface region 100a of the substrate 100 containing silicon carbide.
The ultraviolet rays can be irradiated by, for example, an ultraviolet irradiation device equipped with an ultraviolet lamp or the like.

When the damaged surface region 100a is irradiated with ultraviolet rays, the ultraviolet rays are absorbed by the 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 is weakened, 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. After that, radicals are supplied to the surface region 100a irradiated with ultraviolet rays to remove the surface region 100a irradiated with ultraviolet rays.
For example, in an atmosphere separated from the atmosphere on which the substrate 100 is placed, plasma P is used to generate radicals from the gas G, which is a processing gas, and the radicals are transported to the atmosphere in which the substrate 100 is placed, and the transported radicals are transported. The surface region 100a irradiated with ultraviolet rays is removed by a chemical reaction with.

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

The gas containing a fluorine atom can be, for example, CHF3, CF4, C4F8 or the like. However, the gas containing a fluorine atom is not limited to the example. The gas containing a fluorine atom may be any gas capable of generating fluorine radicals.
Oxygen gas is added to extend the life of the fluorine radicals. Oxygen gas is not always necessary.

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

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

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 generated from gas G. The radical generated from Gus G is a fluorine radical in the case of this embodiment.
On the other hand, the lower layer of the surface region 100a irradiated with ultraviolet rays is not exposed to the above-mentioned irradiation of ultraviolet rays or ions until the surface region 100a is removed, so that the bond strength between Si and C remains high. Therefore, it is difficult to remove by fluorine radicals. Therefore, it is possible to prevent the trench hole diameter and other dimensions from becoming unnecessarily large due to overetching.

In the case of the above-mentioned case, after irradiating the damaged surface region 100a with ultraviolet rays, the radicals generated from the gas G were supplied, but the damaged surface region is as follows. It is also possible to remove 100a.
First, the surface region 100a where damage is generated 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 radicals may be continuously supplied from the step of irradiating the ultraviolet rays to the step of supplying the radicals.

Further, instead of or in combination with the irradiation of ultraviolet rays, hydrogen radicals can be supplied to the surface region 100a where damage is generated.
That is, a step of supplying hydrogen radicals to the surface region 100a can be further provided.
By supplying hydrogen radicals to the surface region 100a, the Si—C bond in the surface region 100a can be changed to a Si—H bond. Since hydrogen has a small mass, it is easy to remove the surface region 100a if it can be converted into a Si—H bond.

Here, as described above, the light generated when the gas G, which is a processing gas, is excited to generate a reaction product such as an ion or a radical contains ultraviolet rays.
Therefore, it is also possible to irradiate the damaged surface region 100a with the ultraviolet rays generated when the reaction product is generated.
In this case, the damaged surface region 100a can be removed as follows.

First, radicals are generated from gas G using plasma P in an atmosphere separated from the atmosphere on which the substrate 100 containing silicon carbide is placed.
Next, the surface region 100a in which the substrate 100 is damaged is irradiated with ultraviolet rays generated when radicals are generated.
For example, in the vicinity of the damaged surface region 100a (near the substrate 100), the plasma P is used to generate a reaction product from the gas G. 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 driven into the surface region 100a. However, even if ions are driven into the surface region 100a and damage occurs, the surface region 100a is removed, so there is no problem. Further, since the ions are driven into the surface region 100a, the removal of the surface region 100a by radicals becomes easier.

In addition, radicals reach the surface region 100a. Therefore, the treatment of the surface region 100a by ultraviolet rays and the removal of the surface region 100a by 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 determined in consideration of the spread of the plasma from the position of the portion of the plasma P having the highest plasma density.
The position of the portion of the plasma P having the highest plasma density can be obtained in advance by experiments or simulations, or can be regarded as the position facing the slot 11b2 in the discharge tube.
If the distance between the plasma P and the surface region 100a becomes long, it becomes difficult for ions having a shorter lifetime than radicals to reach the surface region 100a (substrate 100). Further, if the distance between the plasma P and the surface region 100a becomes long, it becomes difficult for ultraviolet rays 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 for ultraviolet rays and ions to reach the exposed lower layer, it is possible to suppress damage to the lower layer due to ultraviolet rays and ions.

The appropriate distance between the plasma P and the surface region 100a can be appropriately determined by conducting an experiment or a simulation.

The distance between the plasma P and the surface region 100a can be changed by moving the position of the plasma P.
3 (a) to 3 (d) are schematic views for exemplifying the movement of the position of the plasma P.
For example, when irradiating the surface region 100a 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. 3 (a)).
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. 3 (b)).
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, the surface region 100a is easily irradiated 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 for ultraviolet rays and ions to irradiate the surface region 100a. 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 plasma P is set to the first magnitude (FIG. 3C).
When removing the surface region 100a irradiated with ultraviolet rays, the spread of the plasma P is set to a second size smaller than the first size (FIG. 3 (d)).

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

Further, the step of irradiating the ultraviolet rays and the step of supplying radicals described above can be performed once or repeatedly.
Further, 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 treatment method according to the present embodiment, the surface region 100a in which damage is generated is irradiated with ultraviolet rays so that the surface reaction in the surface region 100a is promoted.
Therefore, even if the surface region 100a contains silicon carbide having a higher bond strength between elements than silicon, it can be easily removed by radicals.
Further, since the surface region 100a is removed by using radicals that generate less damage, it is possible to suppress the occurrence of damage to the lower layer exposed when the surface region 100a is removed.

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

As shown in FIG. 2, the plasma processing apparatus 1 includes a processing container 10, a plasma generating unit 11, a decompression unit 12, a gas supply unit 13, a connecting pipe 14, a moving unit 15, an ultraviolet irradiation unit 16, and a control unit 17. It is provided.
The processing container 10 has an airtight structure capable of maintaining an atmosphere depressurized from atmospheric pressure.
The processing container 10 is provided with a carry-in / carry-out port (not shown) so that the substrate 100 can be carried in and out through a carry-in / carry-out port (not shown).

A mounting portion 10a on which the substrate 100 is mounted is provided inside the processing container 10. An electrostatic chuck (not shown) can be incorporated in the mounting portion 10a. Further, the mounting portion 10a may be provided with a heating device (not shown) for controlling the temperature of the substrate 100.
A straightening vane 10b is provided inside the processing container 10 and above the mounting portion 10a. The rectifying plate 10b rectifies the flow of the gas containing radicals introduced from the connecting pipe 14 so that the amount of radicals above the substrate 100 becomes uniform. The region between the straightening vane 10b and the upper surface (mounting surface) of the mounting portion 10a is the processing space 10c where the etching process for the substrate 100 is performed.

Further, the ultraviolet rays generated when the reaction product is generated are irradiated to the surface region 100a of the substrate 100 through the plurality of holes 10b1 provided in the straightening vane 10b.

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

The introduction waveguide 11b propagates the microwave M radiated from the microwave generation unit 11c to introduce the microwave M into the region where the plasma P is generated.
The introduction waveguide 11b has a tubular shape. The microwave M emitted from the microwave generation unit 11c propagates in the space inside the introduction waveguide 11b.
A microwave generation unit 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 a shielding portion 11b1. Further, an annular slot 11b2 is provided at a connecting portion between the introduction waveguide 11b and the shielding portion 11b1. The microwave M propagating inside the introduction waveguide 11b is introduced into the inside of the discharge tube 11a via the slot 11b2.

The microwave generation unit 11c generates a microwave M having a predetermined frequency (for example, 2.45 GHz) and radiates it toward the introduction waveguide 11b.
The depressurizing 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 or the like. The pressure reducing 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 the end of the discharge pipe 11a on the side opposite to the connection pipe 14 side via the flow 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 to the inside of the discharge pipe 11a. The supply amount of the gas G supplied to the inside of the discharge pipe 11a is controlled by the flow rate control unit 13a.
When a plurality of types of gases are supplied to the inside of the discharge pipe 11a, a flow rate control unit can be provided for each of the plurality of types of gases.

The connection pipe 14 connects the discharge pipe 9 and the processing container 10.
One end of the connecting pipe 14 is connected to the end of the discharge pipe 11a on the side opposite to the gas supply portion 13 side. The other end of the connecting tube 14 is connected to the processing container 10.
The connecting pipe 14 is not always necessary. For example, the discharge pipe 11a and the processing container 10 may be connected.
Further, the arrangement position of the connecting pipe 14 in the processing container 10 is not particularly limited, but it is preferably directly above the mounting 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 produced.
The shape of the connecting pipe 14 is not particularly limited, but it is preferably a straight line, that is, a straight tubular 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 produced. In addition, it becomes easy to supply radicals to the surface region 100a of the substrate 100.

The moving unit 15 moves the position of the introduction waveguide 11b 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 generating unit 11c along the discharge tube 11a.
In this case, the moving portion 15 may also move the shielding portion 11b1, the slot 11b2, and the introduction waveguide 11b along the discharge tube 11a. In this case, a flexible tubular body can be provided between the microwave generation unit 11c and the introduction waveguide 11b.
The moving unit 15 may be provided with, for example, a control motor such as a servomotor, a guide mechanism such as a linear motion bearing, and a conduction mechanism such as a ball screw.
If the moving portion 15 is provided, it becomes easy to control the distance between the plasma P and the surface region 100a described above.
The distance between the plasma P and the surface region 100a is a distance on the path from the plasma P generation region to the reaction product or ultraviolet rays reaching the surface region 100a.
That is, the distance from the plasma P generation region to the end of the discharge pipe 11a opposite to the gas supply portion 13 side, the axial length of the connection pipe 14, and the connection between the connection pipe 14 and the processing container 10. It can be the sum of the lengths from the portion to the surface region 100a. For example, when the shape of the connecting tube 14 is refracted, the refracted length is included.
When the distance between the plasma P and the surface region 100a is changed by changing the spread of the plasma P, the moving portion 15 can be omitted.
Further, it is also possible to control the position of the plasma P by the moving unit 15 and control the spread of the plasma P by the decompression unit 12, the gas supply unit 13, and the like.

The ultraviolet irradiation unit 16 irradiates the surface region 100a of the substrate 100 with ultraviolet rays.
The ultraviolet irradiation unit 16 can be, for example, an ultraviolet irradiation device provided with an ultraviolet lamp or the like.
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 or the like 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.
When the ultraviolet rays generated when the reaction product is produced are used, the ultraviolet irradiation unit 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 device 1 based on the control program stored in the storage unit. Since known techniques can be applied to the control program that controls the operation of each element, detailed description thereof will be omitted.

In addition, the control unit 17 can perform the following control.
The control unit 17 controls the moving unit 15 to control the position of the plasma P.
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, so that ultraviolet rays and ions irradiate the lower layer exposed when the surface region 100a is removed. Avoid being done.
For example, the control unit 17 controls the moving unit 15 to move the shielding unit 11b1, the slot 11b2, the introduction waveguide 11b, and the microwave generating unit 11c along the discharge tube 11a to move the plasma P and the surface region. By setting the distance to and from the 100a to 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 introduction waveguide 11b, and the microwave generating unit 11c along the discharge tube 11a to move the plasma P and the surface region 100a. By setting the distance between them to a second distance longer than the first distance, it is possible to prevent ultraviolet rays from being applied to the lower layer exposed when the surface region 100a is removed.

The control unit 17 controls at least one of the decompression unit 12, the microwave generation unit 11c, and the gas supply unit 13 to control the spread of the plasma P.
The control unit 17 controls the decompression unit 12 to reduce the processing pressure and thereby increase the spread of the plasma P. The control unit 17 controls the decompression unit 12 to increase the processing pressure and thereby reduce the spread of the plasma P.
For example, the control unit 17 controls the decompression unit 12 to set the pressure inside 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 the irradiation of ultraviolet rays.

The control unit 17 controls the microwave generation unit 11c to increase the output, thereby increasing the spread of the plasma P. The control unit 17 controls the microwave generation unit 11c to reduce the output, thereby reducing the spread of the plasma P.
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, so that the lower layer exposed when the surface region 100a is removed. Suppresses the irradiation of ultraviolet rays.

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

The plasma processing apparatus 1 removes the damaged surface region 100a as follows, for example.
First, the substrate 100 is placed on the mounting portion 10a by a transport device (not shown).
Next, the ultraviolet irradiation unit 16 irradiates the surface region 100a of the substrate 100 with ultraviolet rays.
Next, the pressure reducing unit 12 reduces the pressure inside the processing container 10 to a predetermined pressure.
Next, a predetermined flow rate of gas G is supplied from the gas supply unit 13 to the discharge pipe 11a via the flow rate control unit 13a. On the other hand, a microwave M having a predetermined power is radiated into the introduction waveguide 11b from the microwave generating unit 11c. The radiated microwave M propagates in the introduction waveguide 11b and is radiated toward the discharge tube 11a via 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. Plasma P is generated by the energy of the microwave M radiated into the discharge tube 11a in this way. Then, when the electron density in the generated plasma P becomes equal to or higher than the 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. It will be 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 reflecting 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 the plasma excitation plane, the gas G is excited and activated to generate plasma products such as radicals and ions.

The gas containing the generated plasma product is conveyed into the processing container 10 via the connecting 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 is rectified by the rectifying plate 10b and reaches the surface region 100a 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 the case where the ultraviolet irradiation unit 16 irradiates the surface region 100a with ultraviolet rays, but the surface region 100a may be irradiated with the ultraviolet rays generated when the reaction product is generated.
For example, the moving portion 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, at least one of the decompression unit 12, the microwave generation unit 11c, and the gas supply unit 13 increases the spread of the plasma P so that the surface region 100a is irradiated with ultraviolet rays.
Since the position control of the plasma P and the control of the spread of the plasma P can be the same as those described above, 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 connecting pipe 14 is linear and is provided directly above the processing container 10, but the present invention is not limited to this.
4 (a) and 4 (b) are schematic views for exemplifying the discharge tube 11a supported by being inclined.
As shown in FIGS. 4A and 4B, for example, the connecting pipe 14 may be provided so that the shaft of the discharge pipe 11a is supported by being inclined with respect to the outer wall surface of the processing container 10. In this case, the first distance in the process of irradiating the ultraviolet rays is that the substrate exists on an extension line 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. It can be set to a distance (Fig. 4 (a)). Further, the second distance during the step of removing the surface region irradiated with ultraviolet rays is set from the position where the plasma P2 is generated from the position where the plasma P2 is generated in order to suppress the ultraviolet rays and ions from reaching the surface region 100a of the substrate. The distance can be set so that the substrate does not exist in the extension direction of the shaft (FIG. 4 (b)).
5 (a) and 5 (b) are schematic views for exemplifying a bent discharge tube 11a.
As shown in FIGS. 5A and 5B, for example, the discharge pipe 11a is inclined with respect to the straight line portion 11a1 provided perpendicular to the outer wall surface of the processing container 10 and the straight line portion 11a1. It can also have a bent portion 11a2 (the angle of intersection with 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 according to the process. In this case, the moving unit 15 can be omitted. For example, in the step of irradiating ultraviolet rays, microwaves are applied to the first slot 11b2 provided in the straight line portion 11a1 so that the distance between the plasma P and the surface region becomes the first distance. Plasma P1 is generated in (FIG. 5 (a)). During the step of removing the surface region irradiated with ultraviolet rays, microwaves are 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. 5 (b)).
6 (a) and 6 (b) are schematic views for exemplifying a connecting tube 11a having a linear shape and a connecting tube 14b having a refracting shape.
As shown in FIGS. 6A and 6B, for example, a connecting pipe 14a having a linear shape and a connecting pipe 14b having a refracting shape are provided, and a discharge pipe is connected to each of them, and the discharge pipe is connected according to the process. The position of the plasma P can be selectively moved. For example, when performing the step of irradiating ultraviolet rays, the plasma P1 is set so that the distance between the plasma P and the surface region is the first distance in one of the discharge tubes connected to the linear connecting tube 14a. (Fig. 6 (a)). During the step of removing the surface region irradiated with ultraviolet rays, the distance between the plasma P and the surface region is set to the second distance in the other discharge tube connected to the connecting tube 14b having a refracting shape. , Plasma P2 is generated (FIG. 6 (b)). In this case as well, a plurality of shielding portions 11b1 and slots 11b2 may be provided and selectively used depending on the process, and the moving portion 15 can be omitted.
With respect to the above-described embodiment, those skilled in the art appropriately adding, deleting or changing the design of components, or adding, omitting or changing the conditions of processes also have the features of the present invention. As long as it is included in 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, and can be appropriately changed.
In addition, the elements included in each of the above-described embodiments can be combined as much as possible, and the combination thereof is also included in the scope of the present invention as long as the features of the present invention are included.

1 Plasma processing device, 10 processing container, 10a mounting part, 11 plasma generating part, 11a discharge tube, 11b introduction waveguide, 11c microwave generating part, 12 decompression part, 13 gas supply part, 14 connecting pipe, 15 moving Unit, 16 UV irradiation unit, 17 Control unit, 100 substrate, 100a surface area, G gas, M microwave, P plasma

The plasma processing apparatus according to the embodiment is provided inside the processing container, a processing container capable of maintaining an atmosphere depressurized from atmospheric pressure, a decompression unit that depressurizes the inside of the processing container to a predetermined pressure, and A mounting portion on which the substrate is mounted, a discharge tube having a region for generating plasma inside and being provided at a position separated from the processing container, a microwave generating portion for generating microwaves, and the micro An introduction waveguide that propagates waves and introduces the microwave into the region where the plasma is generated, a gas supply unit that supplies gas to the region that generates the plasma, and a control unit that controls the gas supply unit. The substrate contains silicon carbide and has a damaged surface region, and the control unit emits ultraviolet rays generated when a radical is generated from the gas by using the plasma. After irradiating the region, the composition of the gas is changed so as to reduce the spread of the plasma, and the ultraviolet rays radiated to the surface region are suppressed.

Claims (13)

The process of irradiating the damaged surface area of the substrate containing silicon carbide with ultraviolet rays,
A step of generating radicals from gas using plasma in an atmosphere isolated from the atmosphere on which the substrate is placed, and
A step of supplying the radical to the surface region irradiated with ultraviolet rays to remove the surface region irradiated with ultraviolet rays, and a step of removing the surface region.
Plasma processing method equipped with. A process of generating radicals from gas using plasma in an atmosphere isolated from the atmosphere on which a substrate containing silicon carbide is placed, and
A step of irradiating the damaged surface region of the substrate with ultraviolet rays generated when the radicals are generated, and
A step of supplying the radical to the surface region irradiated with ultraviolet rays to remove the surface region irradiated with ultraviolet rays, and a step of removing the surface region.
Plasma processing method equipped with. The plasma treatment 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 to the substrate is suppressed. When irradiating the surface region with ultraviolet rays generated when the radicals are generated, the distance between the plasma and the surface region is set to the first distance.
The plasma treatment according to claim 3, wherein when removing the surface region irradiated with ultraviolet rays, the distance between the plasma and the surface region is set to a second distance 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 the first magnitude.
The plasma treatment method according to claim 3 or 4, wherein when the surface region irradiated with ultraviolet rays is removed, the spread of the plasma is set to a second magnitude smaller than the first magnitude. The plasma treatment method according to any one of claims 1 to 5, further comprising a step of supplying hydrogen radicals to the surface region.
A processing container that can maintain an atmosphere decompressed from atmospheric pressure,
A decompression unit that decompresses the inside of the processing container to a predetermined pressure,
A mounting portion provided inside the processing container on which the substrate is mounted,
A discharge tube having a region for generating plasma inside and provided at a position separated from the processing container,
A microwave generator that generates microwaves and
An introduction waveguide that propagates the microwave and introduces the microwave into the region where the plasma is generated,
A gas supply unit that supplies gas to the region where plasma is generated, and
With
The substrate contains silicon carbide and has a surface area where damage has occurred.
A plasma processing apparatus in which the surface region is irradiated with ultraviolet rays generated when radicals are generated from the gas using the plasma. Further provided with a moving portion for moving the position of the introduced waveguide with respect to the discharge tube.
The moving portion sets the distance between the plasma and the surface region to the first distance so that the ultraviolet rays are irradiated to the surface region.
By setting the distance between the plasma and the surface region to a second distance longer than the first distance, the ultraviolet rays are applied to the lower layer exposed when the surface region is removed. 7. The plasma processing apparatus according to claim 7. The decompression unit sets the pressure inside the processing container to the first pressure so that the ultraviolet rays are irradiated to the surface region.
A claim that suppresses the irradiation of the ultraviolet rays to the 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 7. The plasma processing apparatus according to Item 7. The microwave generating unit sets the power of the microwave to the first power so that the ultraviolet rays are irradiated to the surface region.
Claim 7 that by setting the power of the microwave to a second power lower than the first power, the ultraviolet rays are suppressed from being irradiated to the lower layer exposed when the surface region is removed. 9. The plasma processing apparatus according to any one of 9. The gas supply unit corresponds to any one of claims 7 to 10 so that the surface region is irradiated with the ultraviolet rays by adding at least one of an inert gas and a nitrogen gas to the gas. The described plasma processing apparatus. The gas supply unit supplies a gas containing hydrogen to the region where the plasma is generated, hydrogen radicals are generated from the hydrogen-containing gas supplied by the plasma, and the generated hydrogen radicals are transferred to the surface region. The plasma processing apparatus according to any one of claims 7 to 11 to be supplied. The plasma processing apparatus according to any one of claims 7 to 12, further comprising an ultraviolet irradiation unit that irradiates the surface region with ultraviolet rays.

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