US20060037702A1

US20060037702A1 - Plasma processing apparatus

Info

Publication number: US20060037702A1
Application number: US11/203,204
Authority: US
Inventors: Daisuke Hayashi; Shigetoshi Kimura; Nobuhiro Iwama
Original assignee: Tokyo Electron Ltd
Current assignee: Tokyo Electron Ltd
Priority date: 2004-08-20
Filing date: 2005-08-15
Publication date: 2006-02-23

Abstract

A plasma processing apparatus includes a processing chamber having a ceiling and a sidewall, a susceptor, disposed in the processing chamber, for mounting thereon an object to be processed, a processing gas supply mechanism for supplying a processing gas through the ceiling to generate a plasma, an exhaust plate that is disposed between the susceptor and the sidewall and has a plurality of holes, a gas exhaust unit for exhausting a gas from under the susceptor through the exhaust plate, and a fin structure having plural fins arranged at regular intervals, which is disposed as protruded from the sidewall, at least, in a region extending from a top end portion of the sidewall to a region of a same height as that of a mounting surface of the susceptor for mounting the object thereon.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This document claims priority to Japanese Patent Application Number 2004-241264, filed Aug. 20, 2004 and U.S. Provisional Application No. 60/608,415, filed Sep. 10, 2004, the entire content of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a plasma processing apparatus for performing an etching process or the like on an object to be processed by using a plasma.

BACKGROUND OF THE INVENTION

Conventionally, in a semiconductor device manufacturing process and the like, a plasma processing apparatus for converting a processing gas into a plasma and performing a specified process, e.g., an etching process, on an object to be processed by using the plasma has been widely employed.
Generally, such a plasma processing apparatus includes a susceptor for mounting thereon an object to be processed which is installed in a cylindrical processing chamber made of metal such as aluminum, wherein a processing gas is supplied through a port disposed above the susceptor into the processing chamber to generate a plasma and, then, exhausted through a port disposed under the susceptor. Further, commonly, an exhaust plate having a plurality of through holes for gas exhaustion is provided around the susceptor, which also prevents a plasma from leaking between the susceptor and a sidewall of the processing chamber. As one of such exhaust plates, there is an exhaust plate configured to form a curved gas exhaust path in order to definitely prevent the plasma from leaking (e.g., see Reference 1). Further, there is a movable exhaust plate surrounding a plasma generation region, which is able to change the volume of the plasma generation region (e.g., see Reference 2).

- [Reference 1] Japanese Patent Laid-open Publication No. H10-70109
- [Reference 2] Japanese Patent Laid-open Publication No. H10-321605

In the above-mentioned plasma processing apparatus, the size of the susceptor for mounting thereon an object to be processed such as a semiconductor wafer is restricted by the diameter of the semiconductor wafer and is determined accordingly. Further, the inner diameter of the processing chamber needs to be larger than the diameter of the susceptor, and it is necessary to increase the inner diameter of the processing chamber to some extent in order to secure a sufficient conductance even when a flow rate of the processing gas is large.
On the other hand, as the inner diameter of the processing chamber is increased, the volume of a plasma generation region formed above the susceptor is also enlarged, so that a plasma density is decreased since the plasma is diffused; and an operating cost is increased since a high frequency power required for generating the plasma becomes larger.
Therefore, conventionally, the inner diameter of the processing chamber is determined by taking into consideration both a conductance required for a gas flow and a volume of a plasma generation region, and it was difficult to reduce the volume of the plasma generation region while securing the conductance required for the gas flow.
Further, in case that a movable exhaust plate surrounding a plasma generation region is employed to make the volume of the plasma generation region changeable, it is difficult to control the temperature of the exhaust plate. Consequently, lots of deposits are attached to the exhaust plate. Additionally, it is difficult to stably maintain a ground potential of the exhaust plate, thereby causing a plasma leak.

SUMMARY OF THE INVENTION

The present invention has been developed to ameliorate the above drawbacks of the conventional processing apparatus; and it is, therefore, an object of the present invention to provide a plasma processing apparatus capable of securing a conductance for a gas flow while at the same time reducing the volume of a plasma generation region compared to a conventional one and preventing a plasma from leaking or deposits from being generated therein.
In accordance with a preferred embodiment of the present invention, there is provided a plasma processing apparatus, including a processing chamber having a ceiling and a sidewall; a susceptor, disposed in the processing chamber, for mounting thereon an object to be processed; a processing gas supply mechanism for supplying a processing gas through the ceiling to generate a plasma; an exhaust plate that is disposed between the susceptor and the sidewall and has a plurality of holes; a gas exhaust unit for exhausting a gas from under the susceptor through the exhaust plate; and a fin structure having plural fins arranged at regular intervals, which is disposed as protruded from the sidewall, at least, in a region extending from a top end portion of the sidewall to a region of a same height as that of a mounting surface of the susceptor for mounting the object thereon.
Further, preferably, the exhaust plate has a plate-shaped upper part having a plurality of openings, a plate-shaped lower part having a plurality of openings, which is spaced apart from the upper part thereunder, and side surfaces that are coupled to the upper part and the lower part to provide an enclosed space. Furthermore, the upper part, the lower part, and the side surfaces are formed of a conductive material, so that they are electrically connected to each other, thereby having a same potential.
Further, preferably, the upper part, the lower part, and the side surfaces have a ground potential.
Further, preferably, the upper part and the lower part are disposed parallel to each other at a specified interval x, and the side surfaces are two members disposed parallel to each other at a specified interval y. Furthermore, it is preferable that x/y and y/x are not integers.
In accordance with another preferred embodiment of the present invention, there is provided a plasma processing apparatus including a processing chamber having a ceiling and a sidewall; a susceptor, disposed in the processing chamber, for mounting thereon an object to be processed; a processing gas supply mechanism for supplying a processing gas through the ceiling to generate a plasma; a gas exhaust unit for exhausting a gas from under the susceptor; and a fin structure having plural fins arranged at regular intervals, which is disposed as protruded from the sidewall in a region extending from a top end portion of the sidewall to a region positioned lower than a mounting surface of the susceptor for mounting the object thereon.
Further, preferably, the fin structure is configured such that plural slots are formed in an annular member and capable of being attached to or detached from the ceiling.
Further, preferably, a specified gap between the fins of the fin structure is set to be narrower than a width of a plasma sheath formed near the fin structure.
Further, preferably, the plasma processing apparatus includes a temperature controlling mechanism for controlling a temperature of the fin structure.
In accordance with still another preferred embodiment of the present invention, there is provided a plasma processing apparatus including a plasma diffusion preventing member in a processing chamber for generating a plasma, wherein the plasma diffusion preventing member has a plate-shaped upper part having a plurality of openings, which is disposed at an upper flow side of a plasma diffusion path; a plate-shaped lower part having a plurality of openings, which is disposed at a lower flow side of the plasma diffusion path; and side surfaces that are coupled to the upper part and the lower part to provide an enclosed space, wherein the upper part, the lower part, and the side surfaces are formed of a conductive material, so that they are electrically connected to each other, thereby having a same potential.
Further, preferably, the upper part, the lower part, and the side surfaces have a ground potential.
Further, preferably, the upper part and the lower part are disposed parallel to each other at a specified interval x, and the side surfaces are two members disposed parallel to each other at a specified interval y. Furthermore, it is preferable that the x and y are determined such that x/y and y/x are not integers.
In accordance with the present invention, it is possible to provide a plasma processing apparatus capable of securing a conductance for a gas flow while at the same time reducing the volume of a plasma generation region compared to a conventional one and preventing a plasma from leaking or deposits from being generated therein.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments, given in conjunction with the accompanying drawings, in which:
FIG. 1 shows a schematic configuration of a plasma processing apparatus in accordance with a first embodiment of the present invention;
FIG. 2 illustrates a principal part of the plasma processing apparatus shown in FIG. 1;
FIG. 3 depicts the principal part of the plasma processing apparatus shown in FIG. 1;
FIG. 4 shows a schematic configuration of a plasma processing apparatus in accordance with a second embodiment of the present invention;
FIG. 5 shows a schematic configuration of a plasma processing apparatus in accordance with a third embodiment of the present invention; and
FIG. 6 illustrates a principal part of the plasma processing apparatus shown in FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows a schematic configuration of a whole plasma processing apparatus (etching apparatus) for use in a first embodiment of the present invention. A cylindrical processing chamber (vacuum chamber) 1 illustrated in FIG. 1 is made of, e.g., aluminum and airtightly sealed.
The processing chamber 1 is connected to a ground potential. Further, installed inside the vacuum chamber 1 is a susceptor 2 also serving as a lower electrode, which is made of a conductive material, e.g., aluminum, and is of a shape of a block.
The susceptor 2 is supported via an insulating plate 3 made of ceramic and the like in the vacuum chamber 1. An electrostatic chuck 4 is disposed in an upper portion of the susceptor 2, which serves as a mounting surface for the semiconductor wafer W. The electrostatic chuck 4 includes an insulating film 4 b made of an insulating material and an electrostatic chuck electrode 4 a embedded in the insulating film 4 b, and the electrostatic chuck electrode 4 a is connected to a DC power supply 5.
Further, installed inside the susceptor 2 are a heat transfer medium path 6 for circulating an electrically insulating fluid serving as a heat transfer medium for a temperature control and a gas channel 7 for supplying a gas such as He gas to be used for a temperature control to a backside surface of the semiconductor wafer W.
Further, the susceptor 2 can be controlled to be maintained at a specified temperature by circulating an insulating fluid, which is controlled to be kept at a specified temperature by a chiller 6 a, in the heat transfer medium path 6. Furthermore, a gas to be used for temperature control is supplied between the susceptor 2 and the backside surface of the semiconductor wafer W via the gas channel 7, whereby heat exchange therebetween can be facilitated. Accordingly, the semiconductor wafer W can be efficiently and accurately controlled to be maintained at a predetermined temperature.
Further, a focus ring 8 formed of either a conductive material or an insulating material is disposed around the upper portion of the susceptor 2, and a feeder line 9 for supplying a high frequency power is connected to the susceptor 2 at a nearly central portion thereof. The feeder line 9 is connected to a matching box 10 and a high frequency power supply 11, wherein a high frequency power of a specified frequency, e.g., ranging from 13.56 MHz to 150 MHz, is supplied to the susceptor 2 from the high frequency power supply 11.
Further, an annular exhaust plate 12 having a plurality of exhaust holes is installed outside the focus ring 8, and a processing space inside the vacuum chamber 1 is exhausted via the exhaust plate 12 to vacuum by a gas exhaust unit 14 connected to a gas exhaust port 13. Furthermore, the gas exhaust unit 14 includes a vacuum pump for exhausting a gas, a pressure control unit (APC) for controlling a pressure, and so forth.
Meanwhile, at the ceiling portion of the processing chamber 1 above the susceptor 2, a shower head 15 is installed such that it faces in parallel the susceptor 2, wherein the shower head 15 is grounded. Thus, it is designed such that the shower head 15 and the susceptor 2 function as a pair of electrodes (an upper electrode and a lower electrode).
A plurality of gas discharge holes 16 are formed on the lower surface of the shower head 15, and a gas inlet 17 is disposed at an upper portion thereof. Also, a gas diffusion space 18 is formed inside the shower head 15. The gas inlet 17 is connected to a gas supply line 19, and a processing gas supply system 20 is connected to the other end of the gas supply line 19. The processing gas supply system 20 includes mass flow controllers (MFC) 20 a and 20 b for controlling respective gas flow rates flowing therethrough; processing gas supply sources 20 c and 20 d for supplying, e.g., various kinds of processing gases for etching and the like; and so forth.
In the meantime, an annular magnetic field forming mechanism (ring magnet) 21 is disposed around the peripheral portion of the processing chamber 1, concentrically with the processing chamber 1, so that a magnetic field can be formed in a processing space between the susceptor 2 and the shower head 15. The entire magnetic field forming mechanism 21 can rotate around the vacuum chamber 1 at a predetermined angular velocity by a rotation unit 22.
Further, in the first preferred embodiment, a fin structure 23 is installed in an inner sidewall of the processing chamber 1. The fin structure 23 is formed of the same material as the processing chamber 1, e.g., aluminum having an anodic oxide film on its surface. As shown in FIGS. 2 and 3, the fin structure 23 is configured such that slots 23 a of a specified width are formed at regular intervals in an annular member.
Further, the fin structure 23 is installed to be inserted between the sidewall 1 a and the ceiling 1 b of the processing chamber 1, and it can be separated by detaching the ceiling 1 b from the processing chamber 1. The fin structure 23 is attached to the processing chamber 1 such that each fin thereof is aligned along a radial direction having the center of the semiconductor wafer W as its origin of the radial direction and stands vertically to the surface of the semiconductor wafer W. By arranging respective fins of the fin structure 23 as described above, an exhaust flow around the semiconductor wafer W can be rectified, thereby facilitating improvement of conductance. Further, slots, i.e., the fin structure 23, may be prepared directly in the sidewall 1 a of the processing chamber 1.
Further, the fin structure 23 is installed to be electrically connected to the processing chamber 1, whereby it has a same potential as the processing chamber 1, i.e., a ground potential. By employing such a configuration, even when a plasma is generated, the fin structure 23 is stabilized to be maintained at the ground potential. Since the potential of the fin structure 23 is stably maintained at the ground potential, the plasma can be stabilized.
As shown in FIG. 1, the fin structure 23 is configured to be extended from a top end portion of the sidewall 1 a to reach a region having at least a same height as that of a mounting surface of the semiconductor wafer W. Further, a specified width (gap between two neighboring fins of the fin structure) of the slots 23 a is set to be narrower than a width of a plasma sheath formed in the fin structure 23, whereby the plasma is prevented from entering into the slots 23 a. Accordingly, the plasma generation area formed above the susceptor 2 is substantially restricted to an inner area surrounded by the fin structure 23. Namely, as shown by an arrow in FIG. 3, an electrical inner diameter for the plasma corresponds to a diameter of the inner area surrounded by the fin structure 23.
On the other hand, a processing gas can easily penetrate into the slots 23 a of the fin structure 23, whereby it is configured to secure a conductance required for a gas flow. Namely, as shown by a diametric line in FIG. 3, an inner diameter of gas conductance for a gas flow is substantially extended to an outer edge of the fin structure 23.
Further, the processing chamber 1 is provided with a temperature controlling mechanism 24 for controlling the temperature of the sidewall 1 a and the fin structure 23, so that the sidewall 1 a and the fin structure 23 can be maintained at a specified temperature. Accordingly, it prevents deposits from being attached to the sidewall 1 a and the fin structure 23.
An etching sequence performed by using the above-mentioned etching apparatus will be described. First, a gate valve (not shown) installed in the processing chamber 1 is opened, and a semiconductor wafer W is loaded into the processing chamber 1 by a transfer mechanism (not shown) through a load-lock chamber (not shown) disposed in proximity to the gate valve to be mounted on the susceptor 2. Then, a specified voltage is applied to the electrostatic chuck electrode 4 a of the electrostatic chuck 4 from the DC power supply 5 to thereby attract toward the susceptor 2 and hold the semiconductor wafer W thereon by Coulomb force.
Thereafter, the transfer mechanism is withdrawn from the processing chamber 1 and the gate valve is closed. While the processing chamber 1 is exhausted through the gas exhaust port 13 by the vacuum pump of the gas exhaust unit 14, a pressure control is performed by the pressure control unit (APC) of the gas exhaust unit 14.
Then, after the processing chamber 1 has been exhausted to reach a predetermined vacuum level, a specified etching gas of a predetermined flow rate is introduced into the processing chamber 1 from the processing gas supply system 20, whereby a specified pressure level, e.g., approximately 1 to 133 Pa (10-1000 mTorr), is maintained in the processing chamber 1.
Under this condition, a high frequency power of a predetermined frequency (e.g., 13.56 MHz) is supplied to the susceptor 2 from the high frequency power supply 11.
In this case, a high frequency power is applied to the susceptor 2 also serving as a lower electrode, whereby a high frequency field is formed in a processing space between the shower head 15 also serving as an upper electrode and the susceptor 2. At the same time, a magnetic field is formed in the processing space by the magnetic field forming mechanism 21. Under this condition, a plasma etching is performed.
At this time, the fin structure 23 makes it possible to secure the conductance for a gas flow and at the same time reduce the volume of the plasma generation region. Thus, while a processing gas of a sufficient flow rate is supplied and power consumption is suppressed, a plasma etching processing can be performed favorably by using a high-density plasma. Further, the potential of the fin structure 23 is maintained stably at a ground potential, whereby the plasma can be stabilized and the leakage thereof can be suppressed. Furthermore, the temperature of the fin structure 23 is controlled by the temperature controlling mechanism 24, thereby preventing the deposits from being attached to the fin structure 23.
After a specified etching processing is performed, the etching processing is stopped by stopping supplying a high frequency power from the high frequency power supply 11. Then, the semiconductor wafer W is unloaded from the processing chamber 1 in a reverse order of the above-described sequence.
Hereinafter, a second preferred embodiment will be described with reference to FIG. 4. In the second preferred embodiment shown in FIG. 4, a vertically lengthened fin structure 230 is provided instead of the exhaust plate 12 in the first preferred embodiment shown in FIG. 1.
Specifically, the fin structure 230 is extended from the top end portion of the sidewall 1 a to a region positioned lower than the mounting surface of the susceptor 2 for the semiconductor wafer W, and an inner end portion thereof is disposed in proximity to the susceptor 2. Further, a specified width (gap between two neighboring fins of the fin structure) of slots 230 a is set to be narrower than a width of a plasma sheath formed in the fin structure 230, whereby a plasma cannot enter into the slots 230. On the contrary, a processing gas can easily enter the slots 230 a of the fin structure 230 to thereby secure the conductance required for a gas flow.
Also in the second embodiment, the same effect as the first embodiment can be obtained, and the exhaust plate can be omitted.
Hereinafter, a third preferred embodiment will be described with reference to FIG. 5. In the third preferred embodiment, an exhaust plate 12 a is provided instead of the exhaust plate 12 in the first preferred embodiment shown in FIG. 1.
As shown in FIG. 6, the exhaust plate 12 a includes a plate-shaped upper part 122 having a plurality of openings 121; a plate-shaped lower part 124 having a plurality of openings 123, which is spaced apart from the upper part 122 thereunder; and two side surfaces 125 and 126 that are coupled to the upper part 122 and the lower part 124, thereby providing an enclosed space. The upper part 122, the lower part 124, and the side surfaces 125 and 126 are formed of a conductive material and they are electrically connected to each other, thereby having a same potential (a ground potential in the third embodiment).
Further, as shown in FIG. 6, the upper part 122 and the lower part 124 are disposed parallel to each other at a specified interval x, and the side surfaces 125 and 126 are disposed parallel to each other at a specified interval y. Furthermore, in order to prevent resonance from occurring in the space, the intervals (distances) x and y are determined such that x/y and y/x are not integers.
In the third preferred embodiment, since the space, which is surrounded by the upper part 122, the lower part 124, and the side surfaces 125 and 126, is electrically shielded, there is no electric field in the space. Accordingly, even though a plasma leaks into the space through the openings 121 of the upper part 122, which is disposed at an upper flow side of a plasma diffusion path, since there is no electric field in the space, an energy supply is cut off and the plasma immediately disappears. Therefore, it is possible to definitely prevent a plasma from leaking from the lower part 124, which is disposed at a lower flow side of the plasma diffusion path.
Further, as described above, it is allowable that the plasma may leak somewhat through the openings 121. Thus, the size of the openings 121 can be made larger to some extent. Similarly, the size of the openings 123 can be made larger to some extent, whereby a sufficient conductance can be secured.
While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.

Claims

1. A plasma processing apparatus, comprising:

a processing chamber having a ceiling and a sidewall;

a susceptor, disposed in the processing chamber, for mounting thereon an object to be processed;

a processing gas supply mechanism for supplying a processing gas through the ceiling to generate a plasma;

an exhaust plate that is disposed between the susceptor and the sidewall and has a plurality of holes;

a gas exhaust unit for exhausting a gas from under the susceptor through the exhaust plate; and

a fin structure having plural fins arranged at regular intervals, which is disposed as protruded from the sidewall, at least, in a region extending from a top end portion of the sidewall to a region of a same height as that of a mounting surface of the susceptor for mounting the object thereon.

2. The plasma processing apparatus of claim 1, wherein the exhaust plate includes:

a plate-shaped upper part having a plurality of openings;

a plate-shaped lower part having a plurality of openings, which is spaced apart from the upper part thereunder; and

side surfaces that are coupled to the upper part and the lower part to provide an enclosed space,

wherein the upper part, the lower part, and the side surfaces are formed of a conductive material, so that they are electrically connected to each other, thereby having a same potential.

3. The plasma processing apparatus of claim 2, wherein the upper part, the lower part, and the side surfaces are maintained at a ground potential.

4. The plasma processing apparatus of claim 3, wherein the upper part and the lower part are disposed parallel to each other at a specified interval x, the side surfaces are two members disposed parallel to each other at a specified interval y, and x/y and y/x are not integers.

5. A plasma processing apparatus, comprising:

a processing chamber having a ceiling and a sidewall;

a gas exhaust unit for exhausting a gas from under the susceptor; and

a fin structure having plural fins arranged at regular intervals, which is disposed as protruded from the sidewall in a region extending from a top end portion of the sidewall to a region positioned lower than a mounting surface of the susceptor for mounting the object thereon.

6. The plasma processing apparatus of claim 1, wherein the fin structure is configured such that plural slots are formed in an annular member and capable of being attached to or detached from the ceiling.

7. The plasma processing apparatus of claim 1, wherein a specified gap between neighboring fins of the fin structure is set to be narrower than a width of a plasma sheath formed near the fin structure.

8. The plasma processing apparatus of claim 1, comprising a temperature controlling mechanism for controlling a temperature of the fin structure.

9. A plasma processing apparatus, comprising:

a plasma diffusion preventing member in a processing chamber for generating a plasma,

wherein the plasma diffusion preventing member includes:

a plate-shaped upper part having a plurality of openings, which is disposed at an upper flow side of a plasma diffusion path;

a plate-shaped lower part having a plurality of openings, which is disposed at a lower flow side of the plasma diffusion path; and

10. The plasma processing apparatus of claim 9, wherein the upper part, the lower part, and the side surfaces have a ground potential.

11. The plasma processing apparatus of claim 10, wherein the upper part and the lower part are disposed parallel to each other at a specified interval x, the side surfaces are two members disposed parallel to each other at a specified interval y, and x/y and y/x are not integers.