US20080283500A1

US20080283500A1 - Plasma processing apparatus and plasma processing method

Info

Publication number: US20080283500A1
Application number: US12/120,713
Authority: US
Inventors: Takeharu Motokawa
Original assignee: Individual
Current assignee: Toshiba Corp
Priority date: 2007-05-18
Filing date: 2008-05-15
Publication date: 2008-11-20
Also published as: JP2008288437A

Abstract

A plasma processing apparatus includes a processing chamber which has a dielectric wall partly formed of a dielectric substance and in which a to-be-processed substrate is subjected to a plasma process, an induction coil which is arranged to face the dielectric wall and generates an induction electric field to generate plasma in the processing chamber, a Faraday shield which is provided to partially have openings between the dielectric wall and the induction coil to shield an electrostatic field component and pass an electromagnetic field component, and a drive mechanism which moves the Faraday shield.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2007-132918, filed May 18, 2007, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to a plasma processing apparatus used for semiconductor etching and formation of thin films, and more particularly to a plasma processing apparatus having a Faraday shield, and further relates to a plasma processing method using the above apparatus.
2. Description of the Related Art
In a plasma processing apparatus used for semiconductor etching and formation of thin films, electromagnetic waves are applied to gas filled in a plasma processing chamber as one means for generating plasma in the plasma processing chamber. In this case, as representative means for generation of electromagnetic waves, an induction coil is used.
In the plasma generation process using the induction coil, the inner wall of the processing chamber wall (dielectric wall) that faces the induction coil is exposed to a strong electromagnetic field. Such a strong electromagnetic field damages the dielectric wall surface. In order to reduce the damage, a measure of disposing a Faraday shield between the induction coil and the dielectric wall is taken. The Faraday shield is arranged not to cover the entire surface of the dielectric wall that faces the induction coil but to cover a portion thereof. Specifically, the Faraday shield is configured by arranging metal plates around the dielectric wall at regular intervals and alternately arranging areas (shielding portions) in which the metal plates are placed and areas (opening portions) in which the metal plates are not placed. This is because electromagnetic waves cannot be introduced into the plasma processing chamber if the entire surface of the dielectric wall that faces the induction coil is covered with the shielding portion.
As documents in which the effect of the Faraday shield is explained, “IEEE Trans. Plasma Sci. PS-13 (1985) 569, 2” and “Study of Nuclear Fusion, Vol. 58, No. 1 (July, 1987), Plasma Wave Heating Antenna and Analysis of Electromagnetic Field, pp 13 to 25” are known. As given in the above documents, and also realized by the present invention, the following three effects are provided by a Faraday shield.
(Effect 1): Component of electric field in antenna axial direction is smoothly distributed
(Effect 2): Component of electric field perpendicular to antenna is shielded
(Effect 3): Component of electrostatic field is shielded
It is understood based on (Effect 1) that provision of the Faraday shield itself contributes to a reduction in the damage to the dielectric wall surface. However, (Effects 2 and 3) are different in the opening portion and shielding portion of the Faraday shield. The above difference results in the generation of local damage to the dielectric wall surface. When such local damage continues, particles are generated from the dielectric wall surface.
Thus, in the conventional plasma processing apparatus, the dielectric wall surface is subjected to local damage due to the presence of the Faraday shield disposed between the induction coil and the dielectric wall, which causes a problem that particles may be generated.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided a plasma processing apparatus including a processing chamber which has a dielectric wall partly formed of a dielectric substance and in which a to-be-processed substrate is subjected to a plasma process, an induction coil which is arranged to face the dielectric wall and generates an induction electric field to generate plasma in the processing chamber, a Faraday shield which is provided to partially have openings between the dielectric wall and the induction coil to shield an electrostatic field component and pass an electromagnetic field component, and a drive mechanism which moves the Faraday shield.
According to a second aspect of the present invention, there is provided a plasma processing method which includes preparing a plasma processing apparatus having a dielectric wall formed of a dielectric substance and partly disposed in a processing chamber used for a plasma process and a Faraday shield that is provided to partially have openings between the dielectric wall and an induction coil to shield an electrostatic field component and pass an electromagnetic field component, generating plasma in the processing chamber by supplying gas into the processing chamber and generating an induction electric field in the processing chamber by use of the induction coil, and changing a positional relation of the openings of the Faraday shield with respect to the dielectric wall by moving the Faraday shield during the plasma process by use of the plasma or moving the Faraday shield after elapse of a preset processing period of time.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a schematic configuration view showing a plasma processing apparatus according to a first embodiment of this invention.

FIG. 2 is a perspective view showing an installation example of a Faraday shield in the first embodiment.

FIGS. 3A and 3B are cross-sectional views each showing the Faraday shield as viewed from above, for illustrating the plasma processing apparatus according to the first embodiment.

FIGS. 4A and 4B are cross-sectional views each showing a Faraday shield as viewed from above, for illustrating a plasma processing apparatus according to a second embodiment of this invention.

FIG. 5 is a schematic configuration view showing a plasma processing apparatus according to a third embodiment of this invention.

FIG. 6 is a plan view showing an installation example of a Faraday shield in the third embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described below with reference to the accompanying drawings.

First Embodiment

FIG. 1 is a schematic configuration view showing a plasma processing apparatus according to a first embodiment of this invention. The apparatus is a cylinder type ICP (Inductive Coupling Plasma) etching apparatus having a Faraday shield.
A reference symbol 10 in FIG. 1 is a metal processing chamber and a conductive stage 21 on which a to-be-processed substrate 20 is placed, which is disposed in the processing chamber 10. The stage 21 is fixed above a platform 11 that is fixed on the bottom portion of the processing chamber 21 with an insulating body 22 disposed therebetween. An RF power source 24 provided outside the processing chamber 21 is connected to the stage 21.
A gas inlet port 12 is formed in the upper wall portion of the processing chamber 10 and a vacuum pump drawing passage (gas outlet port) 13 is provided in a lower portion of the processing chamber 10, lower than the stage 21. Gas used for plasma etching is introduced via the gas inlet port 12 and discharged from the gas outlet port 13.
The upper portion of the processing chamber 10 is formed with a large inside diameter and a cylindrical dielectric wall 15 is provided in a portion in which the inside diameter of the processing chamber is increased. The dielectric wall 15 is formed of a dielectric substance such as ceramic or quartz and the inside diameter is set to be substantially the same as the inside diameter of the lower portion of the processing chamber 10.
An induction coil 31 is disposed on the upper portion in which the inside diameter of the processing chamber 10 is increased to surround the outer peripheral surface of the dielectric wall 15. The induction coil 31 applies an induction electric field for plasma generation to an inside portion of the processing chamber 10 and is connected to an RF power source 32 provided outside the processing chamber 10. Thus, plasma is generated in an area 34 shown in FIG. 1 by supplying gas into the processing chamber 10 and applying the induction electric field by use of the induction coil 31.
A Faraday shield 41 that shields an electrostatic field component and permits an electromagnetic field component to pass therethrough is provided between the induction coil 31 and the dielectric wall 15. The Faraday shield 41 has openings partly formed therein and arranged along the outer peripheral surface of the dielectric wall 15.
FIG. 2 is a perspective view showing the arrangement relation between the dielectric wall 15 and the Faraday shield 41. Strip-form metal plates 41 a (shielding portions) forming the Faraday shield 41 are arranged around the outer peripheral surface of the cylindrical dielectric wall 15 in a circumferential direction at regular intervals. The metal plate 41 a has high conductivity and is formed by coating silver on the surface of a copper plate, for example. Further, the length of the metal plate 41 a in the lengthwise direction is set to be equal to the height of the cylindrical dielectric wall 15.
The regular arrangement interval of the metal plates 41 a makes a configuration in which areas (shielding portions) 41 a in which the metal plates are present and areas (opening portions) 41 b in which the metal plates are not present are alternately arranged in a circumferential direction of the dielectric wall 15. That is, in the Faraday shield 41, the shielding portions 41 a and the opening portions 41 b are alternately arranged in the circumferential direction of the dielectric wall 15. In this case, the width of the shielding portion 41 a (the length of the dielectric wall 15 in the circumferential direction) may be set to be the same as or different from the width of the opening portion 41 b. The shielding amount of the electrostatic field component and the passage amount of the electromagnetic field component can be adjusted by changing the dimensional relation between the width of the shielding portion 41 a and the width of the opening portion 41 b.
The bottom portion of the Faraday shield 41, that is, the bottom portion of each metal plate 41 a formed in a strip form is linked with a ring-form Faraday shield base 42. The Faraday shield base 42 can be rotated by a motor or actuator (not shown) and the Faraday shield 41 can also be rotated by rotating the Faraday shield base 42. The arrangement relation between the shielding portions 41 a and the opening portions 41 b of the Faraday shield 41 can be changed by rotating the Faraday shield base 42.
Next, the plasma processing method using the present apparatus is explained. First, the basic process of the plasma process by use of an ICP etching apparatus is explained.
First, gas used for plasma etching is introduced into the processing chamber 10 via the gas inlet port 12 and filled in the plasma generation area 34. Then, the pressure of the area 34 in which plasma is generated is controlled by controlling the cross-sectional area of the vacuum pump drawing passage 13.
After this, the RF power sources 24, 32 are activated to output RF powers so as to generate plasma in the processing chamber 10. The to-be-processed substrate 20 on the stage 21 is etched by use of the thus generated plasma. In this way, the plasma process is performed by the ICP etching apparatus.
Next, the arrangement relation and the operation of the Faraday shield 41, which are the features of the preset embodiment, are explained.
FIGS. 3A and 3B are cross-sectional views each showing the Faraday shield 41 shown in FIG. 2 as viewed from above. In FIGS. 3A, 3B, the Faraday shield 41 is moved to rotate around the central axis of the cylindrical dielectric wall 15. When the position shown in FIG. 3A is set as a reference, the Faraday shield 41 is moved to rotate by 15 degrees in FIG. 3B. As a result, an opening area A of FIG. 3A becomes an opening area B in FIG. 3B and an area which is an opening area in FIG. 3A becomes a shield area in FIG. 3B. When the Faraday shield base 42 is thus rotated, the arrangement of the shielding portions 41 a and the opening portions 41 b of the Faraday shield 41 can be shifted. As a result, damage to the dielectric wall 15 can be prevented, and generation of particles due to any irregularities in the dielectric wall 15 can be prevented.
Specifically, any differences between the damage of the dielectric wall 15 that faces the opening portions 41 b and the damage of the dielectric wall 15 that faces the shielding portions 41 a can be controlled by changing the arrangement relation of the opening portions 41 b of the Faraday shield 41 with respect to the dielectric wall 15. In practice, when the damage difference has reached a certain reference level, the damage difference is gradually decreased by reversely setting the positions of the opening portions 41 b and shielding portions 41 a. That is, it is understood that it is effective to change the arrangement of the opening portions 41 b of the Faraday shield 41 in order to prevent occurrence of local damage of the dielectric wall 15 that is the problem of the Faraday shield 41.
The rotation operation of the Faraday shield 41 may be performed at the same time as the plasma process or may be performed a preset period of time after the plasma process was performed. When the rotation operation of the Faraday shield 41 is performed at the same time as the plasma process, the Faraday shield may be rotated at an extremely slow speed (for example, at a speed of one rotation/hour) during the plasma process. When the rotation operation of the Faraday shield 41 is periodically performed, for example, the relation between the plasma process accumulation time and a desired number of particles with respect to the processing chamber in which the plasma process is performed is previously acquired and time at which the arrangement of the opening portions is changed may be determined based on the thus acquired relation. That is, it is important to make uniform any local damage caused by the opening portions of the Faraday shield 41 without allowing any specific local damage to worsen.
Thus, according to the present embodiment, irregularities in the damage to the dielectric wall 15 can be eliminated by rotating the Faraday shield 41 a preset period of time after the plasma process or during the process. Therefore, generation of particles due to irregularity in damage can be prevented. That is, generation of particles can be prevented by eliminating damage irregularities and controlling the damage amount. This leads to enhancement of the reliability of the plasma process and thus an extremely useful effect can be attained.

Second Embodiment

FIGS. 4A and 4B are cross-sectional views each showing a Faraday shield as viewed from above, for illustrating a plasma processing apparatus according to a second embodiment of this invention. Portions which are the same as those of FIGS. 3A and 3B are denoted by the same reference symbols and a detailed explanation thereof is omitted.
The present embodiment also relates to a cylinder type ICP (Inductive Coupling Plasma) etching apparatus as in the first embodiment, and the basic apparatus configuration is substantially the same as that of the first embodiment. The differences are in the following three items.
(1) Faraday shields are coaxially arranged in multiple stages (in two stages in this example).
(2) Respective Faraday shield bases can be independently rotated.
(3) The positional relation between the Faraday shield and the Faraday shield base can be changed.
The present embodiment is an example in which the numerical aperture of the Faraday shield is controlled by using the function (3). Two-stage Faraday shields 51, 52 are provided to surround the outer peripheral surface of a dielectric wall 15. The inner Faraday shield 51 is obtained by arranging strip-form metal plates (shielding portions) 51 a at regular intervals in the circumferential direction of the dielectric wall 15. In this case, however, unlike the first embodiment, two types of opening portions are provided, with small opening portions and large opening portions alternately arranged. The outer Faraday shield 52 is obtained by arranging strip-form metal plates 52 a at regular intervals in the circumferential direction of the dielectric wall 15. The size of the opening portions of the outer Faraday shield 52 is the same as that of the large opening portions of the inner Faraday shield 51 and the arrangement interval is set to twice that of the inner Faraday shield 51.
The Faraday shields 51, 52 are connected to a Faraday shield base (not shown) and rotated by rotating the Faraday shield base. Further, the positional relations of the Faraday shields 51, 52 with respect to the Faraday shield base can be independently changed.
As shown in FIG. 4A, in the initial condition, it is supposed that the large opening portions of the inner Faraday shield 51 are overlapped with the opening portions of the outer Faraday shield 52. At this time, if the large opening portion of the inner Faraday shield 51 is set to the same size as the opening portion 41 b of the Faraday shield 41 of FIG. 3A, the numerical aperture in the initial state is set to the same value as that of FIG. 3A. Therefore, the arrangement relation of the opening portions with respect to the dielectric wall 15 can be changed, as in the first embodiment, by rotating both of the Faraday shields 51, 52 in the same direction by driving the Faraday shield base in this state.
Next, as shown in FIG. 4B, the outer Faraday shield 52 is rotated in the circumferential direction to set and overlap the small opening portions of the inner Faraday shield 51 with the opening portions of the outer Faraday shield 52 by using the function (3). As a result, for example, the numerical aperture of 33% in the case of FIG. 4A can be reduced to 11% in the case of FIG. 4B. Thus, the arrangement relation of the opening portions with respect to the dielectric wall 15 can be changed, as in the first embodiment, by rotating both of the Faraday shields 51, 52 in the same direction by driving the Faraday shield base in this state. Additionally, the state of the small numerical aperture can be maintained.
According to this embodiment, the Faraday shields are provided in two stages and the sizes of the opening portions determined by overlapping of the two Faraday shields 51, 52 can be changed. Therefore, it is of course possible to attain the same effect as that of the first embodiment and freely adjust the passage amount of the electromagnetic field component and the shielding amount of the electrostatic field component determined by the numerical aperture of the Faraday shield. This means that the optimum numerical aperture of the Faraday shield can be selected based on a combination of the damage to the dielectric wall 15 and the strength of the electromagnetic field applied within the processing chamber 10.

Third Embodiment

FIG. 5 is a schematic configuration view showing a plasma processing apparatus according to a third embodiment of this invention. Portions which are the same as those of FIG. 1 are denoted by the same reference symbols and a detailed explanation thereof is omitted.
The present embodiment is different from the first embodiment explained before in that the induction coil 31 is not disposed on the side wall surface of the processing chamber 10 but arranged above the processing chamber 10.
The upper wall portion of the processing chamber 10 is formed of a disk-like dielectric wall 17 and the induction coil 31 is arranged above the dielectric wall 17. A Faraday shield 61 is movably provided between the induction coil 31 and the dielectric wall 17. As shown in FIG. 6, the Faraday shield 61 is formed by radially arranging fan-shaped metal plates (shielding portions) 61 a at regular intervals. That is, the Faraday shield 61 is formed by alternately arranging the shielding portions 61 a and opening portions 61 b in the circumferential direction.
The outer peripheral portion of the Faraday shield 61, that is, the outer peripheral surface of each metal plate 61 a is connected to a ring-form Faraday shield base 62. The Faraday shield base 62 can be rotated by use of a motor or actuator (not shown). Therefore, the Faraday shield 61 is rotated by rotating the Faraday shield base 62 to change the position of the opening portions of the Faraday shield 61.
With the above configuration, any irregularities in the damage of the dielectric wall 15 can be eliminated by rotating the Faraday shield base 62 to rotate the Faraday shield 61 a preset period of time after the plasma process or during the process. Therefore, the same effect as that of the first embodiment can be attained.

Modification

This invention is not limited to the above embodiments. In the first and second embodiments, the Faraday shield is configured by a plurality of strip-form metal plates and the shielding portions and opening portions are alternately arranged. However, this invention is not limited to this case and the Faraday shield can be configured by forming openings in a cylindrical metal plate at regular intervals. Further, the material and numerical aperture of the Faraday shield can be appropriately changed according to the specification. Also, the driving mechanism of the Faraday shield is not limited to the motor or actuator and can be provided by use of a hydraulic or pneumatic apparatus. In addition, the rotation direction of the Faraday shield is not limited to one direction and may be within a range of preset angles.
Further, the apparatus of the embodiments is explained as an example of the etching apparatus, but the apparatus can be used as a film formation apparatus by replacing the introduced gas. In addition, the apparatus is not limited to the etching apparatus or film formation apparatus and can be applied to various types of plasma processing apparatuses.
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

Claims

1. A plasma processing apparatus comprising:

a processing chamber which has a dielectric wall partly formed of a dielectric substance and in which a to-be-processed substrate is subjected to a plasma process,

an induction coil which is arranged to face the dielectric wall and generates an induction electric field to generate plasma in the processing chamber,

a Faraday shield which is provided to partially have openings between the dielectric wall and the induction coil to shield an electrostatic field component and pass an electromagnetic field component, and

a drive mechanism which moves the Faraday shield.

2. The plasma processing apparatus according to claim 1, wherein the dielectric wall is cylindrical, the Faraday shield is arranged to cover an outer peripheral surface of the dielectric wall and the openings of the Faraday shield are arranged in a circumferential direction of the dielectric wall at regular intervals.

3. The plasma processing apparatus according to claim 2, wherein the Faraday shield is configured by arranging strip-form metal plates in an outer peripheral direction of the dielectric wall at regular intervals.

4. The plasma processing apparatus according to claim 2, wherein the drive mechanism causes the Faraday shield to make one of a rotational movement and a reciprocal rotational movement along the outer peripheral surface of the dielectric wall.

5. The plasma processing apparatus according to claim 1, wherein the Faraday shield includes a plurality of Faraday shields coaxially overlapped in plural stages and each stage is provided to be independently moved.

6. The plasma processing apparatus according to claim 4, wherein a total numerical aperture of the Faraday shield is controlled by changing an overlapping state of the Faraday shields of the plural stages.

7. The plasma processing apparatus according to claim 1, wherein a lower portion of the processing chamber is formed of metal and an upper portion thereof is formed of the dielectric substance.

8. The plasma processing apparatus according to claim 1, wherein the processing chamber is formed to be cylindrical.

9. The plasma processing apparatus according to claim 1, wherein a gas inlet port which introduces gas used for a plasma process is provided in an upper portion of the processing chamber and a gas outlet port which discharges the gas is provided in a lower portion thereof.

10. The plasma processing apparatus according to claim 1, wherein a dielectric substance forming the dielectric wall is quartz.

11. The plasma processing apparatus according to claim 1, wherein the dielectric wall is formed in a cylindrical form to cover an upper surface of the processing chamber, the Faraday shield is arranged above the dielectric wall and the Faraday shield has shielding portions and opening portions alternately arranged in a circumferential direction.

12. The plasma processing apparatus according to claim 11, wherein the processing chamber is formed in a cylindrical form and the dielectric wall is provided to cover an opening of an upper-side portion of the processing chamber.

13. The plasma processing apparatus according to claim 11, wherein the Faraday shield is obtained by radially arranging fan-shaped metal plates used as the shielding portions at regular intervals.

14. The plasma processing apparatus according to claim 11, wherein the drive mechanism causes the Faraday shield to move coaxially with the rotation of the dielectric wall.

15. A plasma processing method comprising:

preparing a plasma processing apparatus having a dielectric wall formed of a dielectric substance and partly disposed in a processing chamber used for a plasma process and a Faraday shield which is provided to partially have openings between the dielectric wall and an induction coil to shield an electrostatic field component and pass an electromagnetic field component,

generating plasma in the processing chamber by supplying gas into the processing chamber and generating an induction electric field in the processing chamber by use of the induction coil, and

changing a positional relation of the openings of the Faraday shield with respect to the dielectric wall by moving the Faraday shield during the plasma process by use of the plasma or moving the Faraday shield after elapse of a preset processing period of time.