JP7610122B2 - Plasma source and plasma processing device - Google Patents

Description

The present invention relates to a plasma source for generating plasma in a vacuum vessel, and a plasma processing apparatus equipped with this plasma source.

Plasma processing equipment has been proposed that generates an inductively coupled plasma (ICP) by passing a high-frequency current through an antenna and using the resulting induced electric field to process a substrate or other workpiece.

As such a plasma processing apparatus, Patent Document 1 discloses one in which an antenna is placed outside a vacuum vessel, and a high-frequency magnetic field generated from the antenna is transmitted into the vacuum vessel through a magnetic field transmission window provided to block an opening in the side wall of the vacuum vessel, thereby generating plasma in the processing chamber. In this plasma processing apparatus, a metal plate with multiple slits (hereinafter also referred to as a slit plate) is provided to block the opening of the vacuum vessel, and a dielectric plate is provided to block the multiple slits from the outside of the vacuum vessel, so that the slit plate and the dielectric plate function as a magnetic field transmission window. This allows the thickness of the magnetic field transmission window to be smaller than when only the dielectric plate functions as a magnetic field transmission window, and also shortens the distance from the antenna to the inside of the vacuum vessel, allowing the high-frequency magnetic field generated by the antenna to be efficiently supplied into the vacuum vessel.

JP 2020-198282 A

In the plasma processing apparatus described above, a sealing member such as an O-ring is provided between the slit plate and the dielectric plate to ensure a seal between them. Here, it is desirable to provide a groove or the like in the slit plate to fit the sealing member so that the sealing member is not drawn in and deformed when the vacuum vessel is evacuated, thereby reducing the sealing performance. However, depending on the shape and arrangement of the slit, it may not be possible to process such a groove. It is also possible to ensure a seal without providing an O-ring or groove by applying an adhesive such as grease between the slit plate and the dielectric plate, but this is not preferable because the adhesive may be sucked into the vacuum vessel when it is evacuated, gradually reducing the sealing performance.

The present invention was made to solve such problems, and its main objective is to suppress deformation of the sealing member and improve the sealing performance of the magnetic field transmission window in a plasma processing apparatus in which an antenna is placed outside the vacuum vessel.

That is, the plasma source according to the present invention is a plasma source that generates plasma in a vacuum vessel by passing a high-frequency current through an antenna provided outside the vacuum vessel, and is characterized in that it comprises a slit plate that closes an opening formed in the vacuum vessel at a position facing the antenna, a dielectric plate that closes a slit formed in the slit plate from the outside of the vacuum vessel, a seal member that is sandwiched between the dielectric plate and the slit plate so as to surround the slit, and a spacer member that is provided in the space surrounded by the seal member and that contacts the inner peripheral surface of the seal member to suppress deformation of the seal member.

The plasma source configured in this manner is equipped with a spacer member that contacts the inner peripheral surface of the seal member to suppress deformation, so that even if the seal member tries to deform inward as if being drawn into the slit when the vacuum vessel is evacuated, the spacer member that contacts the inner peripheral surface can push it back outward. This suppresses deformation of the seal member and improves the sealing performance of the magnetic field transmission window. In this way, the spacer member is used to suppress inward deformation of the seal member caused by evacuation, so there is no need to provide a groove or the like in the slit plate or dielectric plate to fit the seal member into.

In the above-mentioned plasma processing apparatus, the seal member may be exposed to the plasma generated in the vacuum chamber, which may cause the seal member to be thermally deteriorated.
Therefore, it is preferable that the spacer member of the plasma source is plate-shaped and is provided so as to close the slit.
In this way, by blocking the slits with the spacer members, the seal members are not directly exposed to plasma, so that thermal deterioration of the seal members can be suppressed.

In addition, when the slit is closed by the spacer member, the plasma source is preferably such that the spacer member is made of a dielectric material.
In this way, the spacer member allows the high frequency magnetic field to pass therethrough efficiently, so that the high frequency magnetic field generated by the antenna can be efficiently supplied into the vacuum vessel.

When a seal is provided between the slit plate and the dielectric plate to ensure the seal between them, stress is concentrated at the contact points of the dielectric plate with the seal, which may cause the dielectric to crack. One possible method to prevent such cracks in the dielectric would be to make the dielectric plate thicker, but this is not preferable because it would increase the distance from the antenna to the inside of the vacuum vessel.
Therefore, the plasma source is preferably configured such that, when the vacuum vessel is evacuated, the dielectric plate is in contact with and supported by the spacer member.
In this way, the dielectric plate is supported by not only the sealing member but also the spacer member, which reduces stress concentration, making it possible to prevent cracking of the dielectric plate and to make the dielectric plate thinner. As a result, the distance from the antenna to the inside of the vacuum vessel can be shortened, and the high frequency magnetic field generated by the antenna can be supplied to the inside of the vacuum vessel more efficiently.
Here, from the viewpoint of ensuring sufficient sealing performance, it is preferable that the dielectric plate and the spacer member are not in contact with each other in an atmospheric pressure state (i.e., a state in which the vacuum container is not evacuated).

When the dielectric plate is supported by the spacer member, the mechanical strength required for the dielectric plate is lowered, and therefore the thickness of the dielectric plate can be reduced. Therefore, in the plasma source, it is preferable that the thickness of the dielectric plate is smaller than the thickness of the spacer member.
In this way, the distance from the antenna to the inside of the vacuum vessel can be shortened, and the high-frequency magnetic field generated by the antenna can be supplied to the inside of the vacuum vessel more efficiently.

In addition, in the plasma source, it is preferable that the shape of the inner circumferential surface of the seal member and the shape of the outer circumferential surface of the spacer member facing the inner circumferential surface are substantially the same in plan view.
With this configuration, when the vacuum container is evacuated, the spacer member can be in contact with most of the inner circumferential surface of the seal member, so that deformation of the seal member can be more efficiently suppressed and sealing performance can be improved.

The plasma source is preferably such that the slit plate is formed in a convex shape from the antenna side toward the vacuum vessel side.
In this configuration, by forming the slit plate to have a convex shape from the antenna side toward the vacuum vessel side, the distance between the slit plate and the antenna can be reduced compared to when the slit plate is flat, which makes it possible to increase the plasma density in the direction perpendicular to the antenna and broaden the distribution of the plasma density generated in the vacuum vessel compared to when a flat slit plate is used.
In this way, when the slit plate has a convex shape toward the vacuum vessel side, the mounting surface of the slit plate for the seal member has a concave shape, making it difficult to process a groove or step into which the seal member is fitted. However, with the plasma source of the present invention described above, there is no need to process a groove or step into the slit plate, so even if the slit plate has a convex shape toward the vacuum vessel side, deformation of the seal member can be suppressed and sealing performance can be improved.

The present invention also includes a plasma processing apparatus equipped with a vacuum container and the above-mentioned plasma source, and such a plasma processing apparatus can achieve the same effects as the above-mentioned plasma source.

The present invention configured in this way makes it possible to suppress deformation of the sealing member and improve the sealing performance of the magnetic field transmission window in a plasma processing apparatus in which an antenna is disposed outside the vacuum vessel.

1 is a vertical cross-sectional view illustrating a configuration of a plasma processing apparatus according to an embodiment; FIG. 2 is a cross-sectional view illustrating a schematic configuration of the plasma processing apparatus according to the embodiment. FIG. 4 is a cross-sectional view showing a peripheral structure of an opening of the vacuum vessel in the embodiment. FIG. 4 is a plan view showing a schematic configuration of a slit plate, a seal member, and a spacer member in the embodiment. FIG. 11 is a plan view showing a schematic configuration of a slit plate, a seal member, and a spacer member in another embodiment. FIG. 11 is a plan view showing a schematic configuration of a slit plate, a seal member, and a spacer member in another embodiment. FIG. 11 is a cross-sectional view showing a peripheral structure of an opening of a vacuum vessel in another embodiment. FIG. 11 is a cross-sectional view showing a peripheral structure of an opening of a vacuum vessel in another embodiment.

Below, an embodiment of the plasma source and plasma processing device according to the present invention will be described with reference to the drawings.

<Device Configuration>
The plasma processing apparatus 100 of this embodiment processes a substrate S by using an inductively coupled plasma P. Here, the substrate S is, for example, a substrate for a flat panel display (FPD) such as a liquid crystal display or an organic EL display, a flexible substrate for a flexible display, etc. The processing performed on the substrate S is, for example, film formation by a plasma CVD method, etching, ashing, sputtering, etc.

This plasma processing apparatus 100 is also called a plasma CVD apparatus when film formation is performed by plasma CVD, a plasma etching apparatus when etching is performed, a plasma ashing apparatus when ashing is performed, and a sputtering apparatus when sputtering is performed.

Specifically, as shown in Figures 1 and 2, the plasma processing apparatus 100 comprises a vacuum vessel 1 which is evacuated and into which gas G is introduced, and a plasma source 200 which generates plasma inside the vacuum vessel 1. The plasma source 200 comprises an antenna 2 provided outside the vacuum vessel 1, and a high-frequency power supply 3 which applies high-frequency waves to the antenna 2. In this configuration, by applying high-frequency waves from the high-frequency power supply 3 to the antenna 2, a high-frequency current IR flows through the antenna 2, generating an induced electric field inside the vacuum vessel 1 and generating an inductively coupled plasma P.

The vacuum vessel 1 is, for example, a metal vessel, and an opening 1x is formed in its wall (here, the upper wall 1a) that penetrates in the thickness direction. The vacuum vessel 1 is electrically grounded here, and its interior is evacuated by a vacuum exhaust device 4.

In addition, gas G is introduced into the vacuum vessel 1 via, for example, a flow rate regulator (not shown) or one or more gas inlets 11 provided in the vacuum vessel 1. The gas G may be selected according to the processing contents to be performed on the substrate S. For example, when a film is formed on the substrate by plasma CVD, the gas G is a raw material gas or a gas obtained by diluting the raw material gas with a dilution gas (for example, H ₂ ). To give a more specific example, when the raw material gas is SiH ₄ , a Si film can be formed on the substrate, when the raw material gas is SiH ₄ +NH ₃ , a SiN film can be formed, when the raw material gas is SiH ₄ +O ₂ , a SiO ₂ film can be formed, and when the raw material gas is SiF ₄ +N ₂ , a SiN:F film (fluorinated silicon nitride film) can be formed.

Inside this vacuum vessel 1, a substrate holder 5 is provided to hold a substrate S. As in this example, a bias voltage may be applied to the substrate holder 5 from a bias power supply V. The bias voltage may be, for example, a negative DC voltage, a negative bias voltage, etc., but is not limited to these. By using such a bias voltage, for example, it is possible to control the energy when positive ions in the plasma P are incident on the substrate S, thereby controlling the crystallinity of the film formed on the surface of the substrate S. A heater 51 for heating the substrate S may be provided inside the substrate holder 5.

As shown in Figures 1 and 2, the antenna 2 is arranged to face the opening 1x formed in the vacuum vessel 1. Note that the number of antennas 2 is not limited to one, and multiple antennas 2 may be provided.

As shown in FIG. 2, one end of the antenna 2, the power supply end 2a, is connected to a high-frequency power source 3 via a matching circuit 31, and the other end, the termination end 2b, is directly grounded. The termination end 2b may also be grounded via a capacitor or a coil, etc.

The high-frequency power source 3 can pass a high-frequency current IR through the antenna 2 via a matching circuit 31. The frequency of the high-frequency current is, for example, a typical 13.56 MHz, but is not limited to this and may be changed as appropriate.

Here, the plasma source 200 of this embodiment further includes a slit plate 6 that blocks the opening 1x formed in the wall (upper wall 1a) of the vacuum vessel 1 from outside the vacuum vessel 1, a dielectric plate 7 that blocks the slit 6x formed in the slit plate 6 from outside the vacuum vessel 1, and a seal member 8 sandwiched between the slit plate 6 and the dielectric plate 7.

The slit plate 6 has slits 6x formed through it in the thickness direction, which allows the high-frequency magnetic field generated by the antenna 2 to pass through the vacuum vessel 1 while preventing an electric field from entering the inside of the vacuum vessel 1 from outside the vacuum vessel 1.

Specifically, as shown in Figures 3 and 4, the slit plate 6 is a flat plate with multiple parallel slits 6x formed therein, and preferably has a higher mechanical strength than the dielectric plate described below, and preferably has a greater thickness than the dielectric plate.

To explain more specifically, the slit plate 6 is manufactured by rolling (e.g., cold rolling or hot rolling) a metal material such as one metal selected from the group including Cu, Al, Zn, Ni, Sn, Si, Ti, Fe, Cr, Nb, C, Mo, W, or Co, or an alloy thereof (e.g., stainless steel alloy, aluminum alloy, etc.), and has a thickness of, for example, about 5 mm. However, the manufacturing method and thickness are not limited to this and may be changed appropriately depending on the specifications.

As shown in FIG. 3, the slit plate 6 is larger than the opening 1x of the vacuum vessel in a plan view, and is supported by the upper wall 1a to close the opening 1x. A sealing member Q such as an O-ring or gasket is interposed between the slit plate 6 and the upper wall 1a, creating a vacuum seal between them.

The dielectric plate 7 is provided on the outward surface of the slit plate 6 (the back surface of the inward surface facing the inside of the vacuum vessel 1) and covers the slits 6x of the slit plate 6.

The dielectric plate 7 is a flat plate made entirely of a dielectric material, such as ceramics such as alumina, silicon carbide, and silicon nitride, inorganic materials such as quartz glass and non-alkali glass, and resin materials such as fluororesin (e.g., Teflon). From the viewpoint of reducing dielectric loss, the material constituting the dielectric plate 7 preferably has a dielectric dissipation factor of 0.01 or less, and more preferably 0.005 or less.

Here, the thickness of the dielectric plate 7 is made smaller than the thickness of the slit plate 6, but this is not limiting, and it is sufficient if the plate has a strength that can withstand the pressure difference between the inside and outside of the vacuum vessel 1 received through the slits 6x when the vacuum vessel 1 is evacuated, and may be set appropriately according to the specifications such as the number and length of the slits 6x. However, from the viewpoint of shortening the distance between the antenna 2 and the vacuum vessel 1, a thinner plate is preferable.

The sealing member 8 seals the gap between the slit plate 6 and the dielectric plate 7, and is provided so as to surround the slits 6x between the slit plate 6 and the dielectric plate 7. This sealing member 8 is provided so as to surround all of the multiple slits 6x, in other words, the entire slit group consisting of the multiple slits 6x.

Specifically, the seal member 8 is made of an elastic material such as rubber and has a certain mechanical strength, and is, for example, a gasket or an O-ring. In a plan view, the seal member 8 is annular (here, rectangular annular), and the annular inner circumferential surface 81 surrounds the slits 6x. Here, the inner circumferential surface 81 surrounds multiple slits 6x.

The opposing surfaces (also called sealing surfaces) 6s and 7s of the slit plate 6 and the dielectric plate 7 that sandwich the sealing member 8 are both flat surfaces. In other words, the opposing surfaces 6s and 7s do not have any grooves or steps into which the sealing member 8 fits.

With this configuration, the slit plate 6 and the dielectric plate 7 function as a magnetic field transmission window W that allows the magnetic field to pass through. In other words, when a high frequency is applied from the high frequency power supply 3 to the antenna 2, the high frequency magnetic field generated from the antenna 2 passes through the magnetic field transmission window W consisting of the slit plate 6 and the dielectric plate 7 and is formed (supplied) inside the vacuum vessel 1. As a result, an induced electric field is generated in the space inside the vacuum vessel 1, and an inductively coupled plasma P is generated.

In the plasma source 200 of this embodiment, as shown in Figures 3 and 4, a spacer member 9 that suppresses deformation of the seal member 8 is provided in the space 8x between the slit plate 6 and the dielectric plate 7 and surrounded by the inner surface 81 of the seal member 8.

The spacer member 9 is a flat plate placed on the outward surface of the slit plate 6, and its outer peripheral surface 91 is in contact with the inner peripheral surface 81 of the seal member 8 to suppress deformation of the seal member 8 along the in-plane direction of the seal surfaces 6s and 7s. The thickness of the spacer member 9 is smaller than that of the seal member 9 in an atmospheric pressure state (i.e., a state in which the vacuum vessel 1 is not evacuated). In this embodiment, even when the vacuum vessel 1 is evacuated, the thickness of the spacer member 9 is smaller than that of the seal member 8. In other words, the thickness of the spacer member 9 is smaller than the shortest distance between the inward surface of the dielectric plate 7 and the outward surface of the slit plate 6, so that the spacer member 9 and the dielectric plate 7 do not come into contact.

In plan view, the spacer member 9 is configured so that the entire outer edge of its outer periphery 91 is located outside (i.e., surrounds) the outer edge of the group of slits 6x that is surrounded by the inner periphery 81 of the seal member 8. In plan view, the shape of the outer periphery 91 is substantially the same as the shape of the inner periphery 81 of the seal member 8. In this embodiment, the spacer member 9 is configured so that the entire outer periphery 91 contacts the inner periphery 81 of the seal member 8 under atmospheric pressure.

In this embodiment, the spacer member 9 is provided so that its inward surface (surface facing the inside of the vacuum vessel 1) blocks the slits 6x. The spacer member 9 in this embodiment is provided so as to block all of the multiple slits 6x. Here, the spacer member 9 is entirely made of a dielectric material so that the high-frequency magnetic field generated by the antenna 2 can pass through into the vacuum vessel 1. The spacer member 9 may be made of the same material as the dielectric plate 7, or may be made of a different material.

<Effects of this embodiment>
According to the plasma processing apparatus 100 and the plasma source 200 of the present embodiment configured as described above, the spacer member 9 is provided to suppress the deformation of the seal member 8 by contacting the inner peripheral surface of the seal member 8, so that even if the seal member 8 tries to deform inward so as to be drawn into the slit 6x when the vacuum vessel 1 is evacuated, the spacer member 9 contacting the inner peripheral surface 81 of the seal member 8 can push it back outward. This suppresses the deformation of the seal member 8, and improves the sealing performance of the magnetic field transmission window W. Since the spacer member 9 suppresses the inward deformation of the seal member 8 caused by the evacuation, there is no need to provide a groove or the like in the slit plate 6 or the dielectric plate 7 to fit the seal member 8. Furthermore, since the spacer member 9 is plate-shaped and is provided to block all the slits 6x, the seal member 8 is not directly exposed to the plasma, and thermal deterioration of the seal member 8 can be suppressed.

<Other Modified Embodiments>
The present invention is not limited to the above-described embodiment.

For example, the spacer member 9 in the above embodiment is plate-shaped and covers all of the slits 6x, but is not limited to this. In other embodiments, the spacer member 9 does not have to be provided to cover the slits 6x. For example, as shown in FIG. 5, the spacer member 9 is frame-shaped with an opening in the center, and may be placed on the slit plate 6 so as to surround the slits 6x in a plan view. In this case, the spacer member 9 does not have to be made of a dielectric material.

Also, as shown in FIG. 6, the sealing member 8 may be provided between adjacent slits 6x. In this case, a plurality of spaces 8x surrounded by the inner circumferential surface 81 of the sealing member 8 are formed between the slit plate 6 and the dielectric plate 7. A spacer member 9 may be provided in each of the plurality of spaces 8x.

In other embodiments, the sealing surfaces of the slit plate 6 and the dielectric plate 7 may be formed with a groove or step into which the sealing member 8 fits.

In the above embodiment, the spacer member 9 is provided so that the entire outer circumferential surface 91 contacts the inner circumferential surface 81 of the seal member 8 under atmospheric pressure, but this is not limited to the above. In other embodiments, the entire or part of the outer circumferential surface 91 of the spacer member 9 may not contact the inner circumferential surface 81 of the seal member 8 under atmospheric pressure. If the entire or part of the outer circumferential surface 91 of the spacer member 9 contacts the inner circumferential surface 81 of the seal member 8 under the condition in which the vacuum vessel 1 is evacuated, the above-mentioned effects of the present invention can be achieved.

In another embodiment of the plasma processing apparatus 100, as shown in FIG. 7, the slit plate 6 may be formed to have a convex shape toward the vacuum vessel at a position facing the antenna 2. More specifically, when viewed from the longitudinal direction of the antenna 2, the slit plate 6 protrudes toward the vacuum vessel 2 and surrounds at least a part of the side surface of the antenna 2, forming a roughly V-shape so as to accommodate it inside. Specifically, the slit plate 6 has a pair of side wall portions 61 facing each other across the antenna 2, and a bottom portion 62 connecting the lower ends (here, the ends on the vacuum vessel side) of each side wall portion 61. The pair of side wall portions 61 are formed with an inclination so as to approach each other toward the vacuum vessel 1 side. Each side wall portion 61 has a slit 6x formed therein. A dielectric plate 7 is provided so as to close each slit 6x, and a seal member 8 is sandwiched between each dielectric plate 7 and each side wall portion 61 so as to surround the slit 6x. A spacer member 9 may be provided in each of the multiple spaces 8x surrounded by the inner circumferential surface 81 of each seal member 8.

In addition, in the plasma processing apparatus 100 of the above embodiment, the spacer member 9 and the dielectric plate 7 are configured not to come into contact with each other when the vacuum vessel 1 is evacuated, but this is not limited thereto. In other embodiments, as shown in FIG. 8, the spacer member 9 and the dielectric plate 7 may come into contact with each other when the vacuum vessel 1 is evacuated, and the dielectric plate 7 may be supported by the spacer member 9. That is, the thickness dimension of the spacer member 9 may be the same as the shortest distance dimension between the slit plate 6 and the dielectric plate 7. In this case, the thickness dimension of the dielectric plate 7 may be smaller than the thickness dimension of the spacer member 9.

It goes without saying that the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the invention.

REFERENCE SIGNS LIST 100: Plasma processing apparatus W: Substrate P: Inductively coupled plasma 2: Vacuum vessel 3: Antenna 6: Slit plate 6x: Slit 7: Dielectric plate 8: Seal member 81: Inner circumferential surface 9: Spacer member

Claims (8)

A plasma source that generates plasma within a vacuum vessel by passing a high-frequency current through an antenna provided outside the vacuum vessel,
a slit plate for closing an opening formed in the vacuum vessel at a position facing the antenna;
a dielectric plate that closes the slits formed in the slit plate from the outside of the vacuum vessel;
a seal member sandwiched between the dielectric plate and the slit plate so as to surround the slit;
a spacer member that is provided in a space surrounded by the seal member and that suppresses deformation of the seal member by contacting an inner circumferential surface of the seal member. The plasma source according to claim 1, wherein the spacer member is plate-shaped and is arranged to close the slit. The plasma source of claim 2, wherein the spacer member is made of a dielectric material. The plasma source according to any one of claims 1 to 3, wherein the dielectric plate is supported in contact with the spacer member when the vacuum vessel is evacuated. The plasma source of claim 4, wherein the thickness of the dielectric plate is smaller than the thickness of the spacer member. The plasma source according to any one of claims 1 to 5, wherein, in a plan view, the shape of the inner circumferential surface of the seal member and the shape of the outer circumferential surface of the spacer member facing the inner circumferential surface are substantially the same. The plasma source according to any one of claims 1 to 6, wherein the slit plate is formed to have a convex shape from the antenna side toward the vacuum vessel side. A vacuum vessel;
A plasma processing apparatus comprising the plasma source according to any one of claims 1 to 7.