JP2003323999A - High frequency inductively coupled plasma generating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high frequency inductively coupled plasma generating device allowing the formation of uniform plasma. <P>SOLUTION: A magnetic path structure 7 of a soft magnetic material is provided to encircle a plasma chamber body 3 and an exciting coil 6. A flux line can be uniformly distributed in the plasma chamber body 3 over its wider internal space region by the magnetic path structure 7 to form uniform plasma in the wider space region. Furthermore, the magnetic path structure 7 consists of a plurality of blocks 71-77 formed of soft magnetic materials and a spacer block 82 formed of a non-magnetic material. The flux distribution in the plasma chamber body 3 is therefore easily controlled by removing part of the blocks 71-77 or replacing it with the spacer block 82. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency inductively coupled plasma generator.

[0002]

2. Description of the Related Art As a substrate processing apparatus for performing processing such as etching, film formation, and sputtering on a silicon wafer or a glass substrate, there is a substrate processing apparatus that uses plasma to perform such processing. As one of the plasma generation devices used in these substrate processing apparatuses, there is an inductively coupled plasma generation device that generates plasma by an inductively coupled plasma excitation method. In the inductively coupled plasma generation device, a high frequency current is passed through an excitation coil provided near the plasma generation chamber to generate a high frequency magnetic field in the plasma generation chamber. The high frequency magnetic field induces a high frequency induction electric field in the plasma generation chamber, and the induction electric field ionizes the gas in the plasma generation chamber to generate plasma.

FIG. 7 shows an example of a conventional plasma generator, FIG. 7 (a) uses a solenoid type coil 100 as an exciting coil, and FIG. 7 (b) shows a plane type coil 104. It is used. In the apparatus of FIG. 7 (a), the solenoid coil 100 is arranged in such a manner that it is wound around the tubular chamber 103 that constitutes the plasma generation chamber. A high-frequency current from a high-frequency power supply 102 is supplied to the solenoid coil 100 via a matching device 101, and a high-frequency magnetic field parallel to the central axis of the coil 100 is formed inside the tubular chamber 103. As a result, plasma P is generated in the tubular chamber 103.

On the other hand, in the apparatus shown in FIG. 7B, a high frequency introduction window 106 is provided on the upper end surface of the chamber 105, and a flat coil 104 is provided outside the high frequency introduction window 106. The high-frequency magnetic field generated by the planar coil 104 enters the chamber 105 through the high-frequency introduction window 106, and plasma P is generated in the space area in the chamber 105 near the high-frequency introduction window 106.

[0005]

By the way, in a substrate processing apparatus in which such a plasma generating apparatus is used, the diameter of the substrate is increasing, and a larger plasma area is required for the plasma generating apparatus. Is required to be generated. Therefore, in the case of the device using the solenoid type coil 100 of FIG. 7A, the coil diameter is increased in order to cope with a large-diameter substrate, and the number of coil turns is accordingly increased in order to secure a sufficient magnetic flux density. I need to do a lot.

However, the expansion of the coil shape is accompanied by an increase in inductance and an increase in loss resistance due to an increase in the length of the winding. If the frequency is constant, the increase in inductance acts as a current blocking reactance, so that matching is performed by the matching device 101 to correct this. Since this correction is performed by reducing the capacitance C of the capacitor provided in the matching device 101, it is easily affected by the parasitic capacitance. That is, the matching condition changes in a direction that deviates from the stable adjustment range, and plasma generation tends to be unstable.

On the other hand, in the apparatus of FIG. 7 (b), even if the number of turns is increased and the coil diameter is increased, the magnetic field strength at the central portion of the coil is increased, and the plasma region is expanded as expected. There is a problem that the uniformity cannot be achieved and the uniformity is deteriorated. In addition, the planar coil 104
In this case, since a magnetic field is formed not only in the chamber space below the coil but also in the space above the coil, the efficiency of energy transfer to the plasma is poor.

An object of the present invention is to provide a high frequency inductively coupled plasma generator capable of forming a uniform plasma in a larger area.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the invention will be described in association with FIGS. (1) In the high frequency inductively coupled plasma generation apparatus according to the invention of claim 1, a cylindrical plasma generation chamber 2 in which plasma is formed, an excitation coil 6 that forms a high frequency magnetic field, and a plurality of separable soft magnetic material blocks. The magnetic path structure 7 configured by 71 to 77 for uniformly distributing the magnetic flux of the high frequency magnetic field formed by the excitation coil 6 in the plasma generation chamber 2 achieves the above-mentioned object. (2) In the high frequency inductively coupled plasma generating apparatus according to the invention of claim 2, a cylindrical plasma generating chamber 2 in which plasma is formed, an exciting coil 6 for forming a high frequency magnetic field, and a plurality of separable soft magnetic material blocks. 71 to 77 and at least one spacer block 82 having a magnetic permeability smaller than that of the soft magnetic material blocks 71 to 77, the magnetic flux of the high frequency magnetic field formed by the excitation coil 6 is uniformly distributed in the plasma generation chamber 2. The road structure 7 is provided to achieve the above-mentioned object.

In the section of the means for solving the above problems, the drawings of the embodiments of the present invention are used to make the present invention easy to understand, but the present invention is limited to the embodiments of the present invention. Not something.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a high frequency inductively coupled plasma generation apparatus according to the present invention. Figure 1
Shows a schematic configuration of the plasma generation apparatus, and the portion B above the dashed line constitutes the plasma generation apparatus 1. A plasma chamber body 3 that forms a plasma chamber 2 of the plasma generation apparatus 1 is provided above the vacuum chamber 12 that is a process chamber. The plasma chamber body 3 is formed of ceramics or the like like the high frequency introduction window of the conventional device, and the high frequency magnetic field penetrates into the plasma chamber 2 through the plasma chamber body 3. The vacuum chamber 12 is evacuated by a vacuum pump (not shown) connected to the exhaust port 12a.

In the plasma generator 1 shown in FIG. 1, the plasma chamber body 3 has a cylindrical shape, and the excitation coil 6 is provided outside the plasma chamber body 3 so as to face the end face of the cylinder.
Is provided. The excitation coil 6 is a 2-turn solenoid type coil, and an RF power source 9 is connected via a matching unit 8. In the present embodiment, the excitation coil 6 is a solenoid type coil, but may be, for example, a one-turn flat type coil. As the frequency of the RF power source 9,
Although about 1 MHz to 100 MHz is used in consideration of economy, a high frequency power supply of 13.56 MHz is used in the present embodiment.

The matching box 8 is provided with a capacitor for impedance matching, and the matching condition can be adjusted by adjusting the capacitance of this capacitor. At the time of generating plasma, argon gas or the like is introduced into the plasma chamber 2. A magnetic path structure 7 is provided around the plasma chamber body 3 so as to cover the plasma chamber body 3.
Is provided. The magnetic path structure 7 constitutes a magnetic flux return circuit formed by the excitation coil 6 as described later, and is formed of a soft magnetic material having good high frequency characteristics, that is, excellent loss characteristics in the excitation frequency range. To be done. For example, iron, nickel, cobalt or the like is used. further,
The magnetic path structure 7 is composed of a large number of divided blocks,
Inner plasma chamber body 3 and outer frame member 1
3 keeps a constant shape.

A conductive grid-type aperture 4 is provided between the plasma chamber 2 and the vacuum chamber 12. A voltage Vacc is applied to the aperture 4 by a power supply 5. The aperture 4 closes the plasma in the plasma chamber 2, and the ions extracted from the plasma are accelerated downward in the figure by the acceleration voltage Vacc. As a result, the ion beam is extracted from the plasma generation device 1 and used for various processes. 10 is
It is a Faraday cup for measuring the current density of the ion beam extracted from the plasma generation device 1. The Faraday cup 10 has a structure capable of scanning the inside of the vacuum chamber 12 in the horizontal direction, and the ion current detected by the Faraday cup 10 is measured by a minute ammeter 11.

FIG. 2 is a diagram for explaining a high frequency magnetic field formed in the plasma chamber 2. In FIG. 2, (a) shows magnetic flux lines in the plasma generator 1, and (b) shows
Shows the magnetic flux lines of a conventional device using a planar coil. Further, FIG. 2 (c) qualitatively shows the distribution of the plasma density, and the horizontal axis represents the radial position of the plasma chamber.

As shown in FIG. 2A, the magnetic path structure 7 is functionally composed of three parts. The first is a core portion 7A that is arranged inside the excitation coil 6 to collect the magnetic flux in the central portion of the coil and to make the distribution uniform. The magnetic flux lines 20 enter the plasma chamber 2 from the lower end surface of the core portion 7A. The second is a magnetic flux line 2 which is provided on the outer peripheral portion of the excitation coil 6 and the plasma chamber body 3 and exits from the end face of the core portion 7A.
It is a side surface return portion 7B that guides 0 to the side surface portion of the plasma chamber body 3. The magnetic flux lines 20 passing through the side surface portion of the plasma chamber body 3 enter the cylindrical side surface return portion 7B. Thirdly, the magnetic flux lines 20 that have entered the side return portion 7B.
Is a back-side return portion 7C for returning to the core portion 7A.

In the plasma generator 1 of the present embodiment,
By providing the side surface return portion 7B and guiding the magnetic flux lines 20 extending from the lower end surface of the core portion 7A toward the side surface return portion 7B, it is possible to form a magnetic field that is uniform in strength throughout the plasma chamber 2. The high frequency energy is radiated from the excitation coil 6 as induction magnetic field energy and supplied to the plasma in the plasma chamber 2.

On the other hand, FIG. 2 (b) shows the state of magnetic flux lines when the conventional planar coil is used. The high-frequency magnetic field formed by the coil 21 is largely distributed not only inside the plasma chamber 23 but also in the outer space, as indicated by the magnetic flux lines 22. On the other hand, in the plasma generator 1 shown in FIG. 2A, most of the magnetic flux lines 20 that have exited the lower end surface of the core portion 7A enter the side surface return portion 7B, and they are the side surface return portion 7B and the back surface return portion. It passes through the inside of the portion 7C and enters the other end surface of the core portion 7A. That is, the magnetic flux lines 20 are inside the magnetic path structure 7 except the plasma space, and the magnetic flux lines 20 do not leak to the space outside the device as in the conventional device shown in FIG. 2B. Therefore, the efficiency of energy transfer to plasma is improved.

Furthermore, the magnetic flux density in the plasma chamber 2 becomes uniform by guiding the magnetic flux lines 20 in the lateral direction of the plasma chamber by the side surface return portion 7B. As a result, uniform plasma can be formed over a wide area in the plasma chamber 2. FIG. 2C qualitatively shows the plasma density distribution, and the horizontal axis represents the radial position of the plasma chamber. In the case of the present embodiment, a uniform distribution is obtained as indicated by the curve L1 for the reasons described above. on the other hand,
In the apparatus using the planar coil shown in FIG. 2B, the magnetic field strength in the central portion of the coil is large, so that the distribution in the central portion becomes larger than the other portions as indicated by L2, and the uniformity is poor.

Since the magnetic path structure 7 is provided,
The magnetic flux lines 20 of the high frequency magnetic field formed by the excitation coil 6 are
The side return part 7 of the magnetic path structure 7 through the plasma space
Guided in the B direction. Therefore, it is possible to guide the magnetic flux lines 20 to the entire plasma region without increasing the diameter of the excitation coil 6 in accordance with the required size of the plasma region. The fact that the diameter of the excitation coil 6 does not have to be changed means that it is possible to avoid a change in reactance due to the length of the coil winding and a resistance loss, and prevent unstable impedance matching. You can

<< Detailed Description of Magnetic Path Structure 7 >> Next, the detailed structure of the magnetic path structure 7 will be described. As previously mentioned,
The magnetic path structure is composed of a large number of divided blocks, an example of which is shown in FIG. In the case of the magnetic path structure 7 shown in FIG. 3, it is composed of seven types of soft magnetic blocks 71 to 77. In FIG. 3, (a) is a plan view and (b) is a cross-sectional view taken along line CC of (a). As shown in FIG. 3A, six fan-shaped blocks 74 are circumferentially arranged around the cylindrical block 75 in the central portion. Block 7
Reference numerals 5 and 74 have the same thickness, and four layers are provided in the vertical direction as shown in FIG.

On the outer side of the block 74, six arc-shaped blocks 73 arranged in the circumferential direction are arranged.
6 arcuate blocks 7 arranged in the circumferential direction on the outside of the
2 are arranged, and further, six arc-shaped blocks 71 arranged in the circumferential direction are arranged outside the block 72. The blocks 73, 72, 71 are arranged in the radial direction, their thickness is equal to that of the blocks 75, 74, and each block 73, 72, 71 is provided with only two layers. Below the block 72, three layers of arc-shaped blocks 77 having the same plan view and a large thickness are arranged. Further, on the lower side of the block 71, three layers of arc-shaped blocks 76 having the same plan view and a large thickness are arranged. The thickness of the blocks 77 and 76 is set to be twice that of the blocks 72 and 71.

No block is provided between the block 74 and the block 77, and a ring-shaped space 80 is formed. The two-turn excitation coil 6 is arranged in the space 80. The shape of the magnetic path structure 7 including the blocks 71 to 77 is held by the plasma chamber body 3 and the frame member 13. Each block 71-7
7 is made of a soft magnetic material, and the frame member 13 is made of non-magnetic material such as ceramics or plastics.

As described above, in the present embodiment, the magnetic path structure 7 is composed of the small blocks 71 to 77. Therefore, by removing some blocks or replacing them with blocks made of different materials, the magnetic flux distribution , That is,
The plasma distribution can be changed subtly. Since each block 71 to 77 is made of a soft magnetic material,
This is because when the arrangement of blocks is changed and the shape of the magnetic path structure 7 is changed, the magnetic flux distribution is also changed.

FIG. 4A shows the magnetic path structure 7 shown in FIG.
The distribution of the ion beam current density in the case of is shown. On the other hand, FIG. 4B shows the ion beam current density in the magnetic path structure 7 shown in FIG. 3 excluding the fourth layer block D (75) among the four layers of blocks 75. It shows the distribution of. In FIG. 4, the vertical axis represents the ion beam current density and the unit is an arbitrary unit (AU).
I am trying. The horizontal axis represents the position from the center of the plasma chamber 2. Note that these distributions are obtained by scanning the Faraday cup 10 in FIG. 1 in the horizontal direction in the figure and detecting the ion beam current.

In the case of the distribution shown in FIG. 4 (a), there is a peak P1 in the central portion, and the current density is maximum in the central portion. Then, the current density gradually decreases with distance from the center, and sharply decreases outside the region E. On the other hand, in the case of FIG. 4B in which the block D is removed, there are peaks P2 and P3 at symmetrical positions apart from the central portion. The current density at the central portion is smaller than the current densities of the peaks P2 and P3. Assuming that the widths of the current values in the region E are ΔI1 and ΔI2, respectively, ΔI2 <ΔI1, and it can be seen that the plasma distribution is more uniform in the case of FIG. 4B.

As described above, since the magnetic path structure 7 is composed of the plurality of blocks 71 to 77, the plasma distribution can be easily adjusted by changing the blocks. Although the magnetic flux distribution is changed and the matching parameter is changed by removing the block D (75), such a change in the matching parameter can be dealt with by matching the matching device 8. Further, the shape maintenance may be ensured by disposing a non-magnetic spacer block in the portion where the block D (75) is removed. The material of the spacer block may be non-magnetic, for example,
If it is a metal, aluminum or copper can be used, and if it is a non-metal, fluororesin such as PTFE or ceramics can be used.

In addition, it is practically difficult to form all of the components forming the plasma generating apparatus 1 in axial symmetry, and in such a case, the magnetic path structure 7 must be asymmetrical. Asymmetry tends to occur in the magnetic flux distribution. In this embodiment, the magnetic path structure 7 can be made substantially symmetrical by replacing the soft magnetic material block with a non-magnetic spacer block.

For example, in the excitation coil 6, the wiring for supplying electric power has to be drawn out to the outside of the magnetic path structure 7, and the symmetry is broken because a hole or the like of the drawn portion is formed in the magnetic path structure 7. I will end up. FIG. 5 is a diagram when the excitation coil 6 is drawn out above the magnetic path structure 7, and FIG. 5A is a plan view,
(B) is a GG sectional view. As shown in FIG. 5, two layers of the block 72 corresponding to the reference numeral F are removed in the extraction portion of the excitation coil 6 to the outside. In this case,
The blocks 72 (for two layers) at three positions that are axially symmetric with respect to the part denoted by the symbol F are replaced with spacer blocks 82. By this replacement, the symmetry of the magnetic path structure 7 can be maintained, and the magnetic flux density distribution becomes symmetric. As the material of the spacer block 82, a material having a magnetic permeability substantially equal to the magnetic permeability of the space F may be used. Instead of replacing the spacer block 82, the space of the spacer block 82 may be a void in which no block is arranged.

Further, even in the plasma generators 1 having the same design, in reality, there are subtle differences between the devices. Such variations among devices can also be adjusted by changing the block configuration. In such a case, not only the non-magnetic spacer block 82 may be used, but also magnetic material having different magnetic permeability may be used as the material of the spacer block 82.

Another advantage of the magnetic path structure 7 having the divided block structure is that the same plasma generating apparatus 1 can be mounted on various substrate processing apparatuses. That is, even if the plasma conditions are different for each substrate processing apparatus, the substantial shape of the magnetic path structure 7 can be changed by changing the configuration of the block, so that it is possible to meet each condition. as a result,
It is not necessary to design and manufacture a plasma generation apparatus for each substrate processing apparatus, and it is possible to reduce the cost and shorten the number of manufacturing days by making the plasma generation apparatus common.

The division shape when dividing the magnetic path structure 7 into a large number of blocks is not limited to those shown in FIGS. 3 and 5, and for example, a block as shown in FIG. 6 may be used. good. In the example shown in FIG. 6, all the soft magnetic blocks have the same cylindrical shape. In this case, a cylindrical soft magnetic block 83 is laid in the frame member 13 to form the magnetic path structure 7.
To form. When such a soft magnetic block 83 is used, it is easy to deal with the magnetic path structure 7 having various shapes, and since the blocks 83 have the same shape, the manufacturing cost of the block 83 can be reduced. it can. Further, even when a part is replaced with the cylindrical spacer block, there is an advantage that it can be replaced more finely.

In the embodiment described above, the shape of the magnetic path structure 7 is held by providing the frame member 13 to the magnetic path structure 7 composed of blocks, but the holding method is not limited to this. . Further, although there is a difficulty in reassembling the blocks, the blocks may be fixed to each other by adhering them with an adhesive.

[0034]

As described above, according to the present invention,
By providing the magnetic path structure, the magnetic flux can be uniformly distributed in a wide area in the plasma generation chamber, and plasma can be formed in a larger area. Furthermore, since the magnetic path structure is composed of multiple separable blocks,
By removing a part of the soft magnetic material block or replacing it with a spacer block, the magnetic flux distribution can be finely adjusted, and a desired magnetic flux distribution can be formed more accurately.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a high-frequency inductively coupled plasma generation device according to the present invention.

FIG. 2 is a diagram showing a state of a high-frequency magnetic field in comparison with a conventional device, in which (a) shows the high-frequency magnetic field of the present embodiment,
(B) is a figure which shows the high frequency magnetic field of the conventional planar coil, (c) is a figure which shows a plasma density distribution.

FIG. 3 is a diagram showing a detailed structure of a magnetic path structure 7,
(A) is a top view of the magnetic path structure 7, (b) is CC sectional drawing.

FIG. 4 is a diagram showing a distribution of an ion beam current density,
(A) shows the distribution in the case of the magnetic path structure 7 of FIG.
(B) is a block D (7) of the fourth layer from the magnetic path structure of FIG.
The distribution when 5) is removed is shown.

FIG. 5 is a diagram showing a magnetic path structure 7 in which some of blocks 71 to 77 are replaced with spacer blocks 82;
(A) is a top view and (b) is a BB sectional view.

FIG. 6 is a perspective view when a large number of cylindrical blocks 83 having the same shape are used as soft magnetic blocks.

FIG. 7 is a diagram showing a conventional plasma generation device,
(A) is an apparatus using a solenoid type coil, and (b) is an apparatus using a plane type coil.

[Explanation of symbols]

1 Plasma generator 2,23 Plasma chamber 3 Plasma chamber body 4 Grid type aperture 6 excitation coil 7 Magnetic path structure 7A core part 7B Side return part 7C Rear return section 8 Matching device 9 RF power supply 12 vacuum chamber 13 Frame member 20,22 magnetic flux lines 71-77,83 Soft magnetic block 82 Spacer block

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 21/3065 H01L 21/302 101C F term (reference) 4G075 AA24 AA30 BC02 BC06 CA14 CA25 CA42 DA02 EA01 EB01 EB44 EE31 FC20 5C030 DD01 DE07 DG07 5F004 AA16 BA20 BB07 BD04 BD05

Claims (2)

[Claims] 1. A cylindrical plasma generation chamber in which plasma is formed, an excitation coil for forming a high-frequency magnetic field, and a plurality of separable soft magnetic material blocks, and a high-frequency magnetic field formed by the excitation coil is formed. A high frequency inductively coupled plasma generation apparatus comprising: a magnetic path structure that uniformly distributes magnetic flux in the plasma generation chamber. 2. A cylindrical plasma generation chamber in which plasma is formed, an excitation coil for forming a high-frequency magnetic field, a plurality of separable soft magnetic material blocks, and at least one having a magnetic permeability smaller than that of the soft magnetic material blocks. A high frequency inductively coupled plasma generation apparatus comprising: a spacer structure block; and a magnetic path structure that uniformly distributes a magnetic flux of a high frequency magnetic field formed by the excitation coil in the plasma generation chamber.