JP4135173B2 - Plasma processing apparatus and plasma processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma processing apparatus, and more particularly to a plasma processing apparatus and a plasma processing method for performing plasma processing such as etching on a substrate to be processed such as a semiconductor wafer.
[0002]
[Prior art]
Conventionally, in the field of semiconductor device manufacturing, plasma is generated in a processing chamber, and this plasma is applied to a substrate to be processed such as a semiconductor wafer disposed in the processing chamber to perform predetermined processing such as etching or film formation. There is known a plasma processing apparatus for performing the above.
[0003]
In order to perform good processing in such a plasma processing apparatus, it is necessary to maintain the plasma state in a good state suitable for plasma processing. For this reason, a magnetic field for controlling plasma has conventionally been used. A plasma processing apparatus having a magnetic field forming mechanism to be formed is used.
[0004]
As a magnetic field forming mechanism, a substrate to be processed such as a semiconductor wafer disposed horizontally with a processing surface facing upward is arranged so that N and S magnetic poles are alternately adjacent so as to surround the periphery of the semiconductor substrate. A multi-pole type is known in which a magnetic field is not formed above a wafer, but a multi-pole magnetic field is formed so as to surround the periphery of the wafer. The number of poles of the multipole is an even number of 4 or more, and the number of poles is preferably selected between 8 and 32 so that the magnetic field strength around the wafer matches the processing conditions.
[0005]
[Problems to be solved by the invention]
In this way, plasma processing is performed in which a predetermined multipole magnetic field is formed around a substrate to be processed such as a semiconductor wafer in the processing chamber, and plasma processing such as etching processing is performed while controlling the plasma state by the multipole magnetic field. The apparatus is known. However, according to studies by the present inventors, it has been found that in plasma processing, for example, plasma etching, the in-plane uniformity of the etching rate changes depending on the strength of the multipole magnetic field.
[0006]
Here, if the above-described magnetic field forming mechanism is composed of an electromagnet, control of formation and extinction of the magnetic field can be easily performed. However, the use of an electromagnet causes a problem of increased power consumption, so that in many devices, a permanent magnet is generally used. However, when a permanent magnet is used, control such as “forming” or “not forming” the magnetic field requires that the magnetic field forming means itself be attached to or removed from the device. For this reason, there is a problem that a large apparatus is required for attaching and detaching the magnetic field forming means, and there is a problem that it takes a long time for the work, and accordingly, there is a problem that the work efficiency of the entire semiconductor processing is lowered.
[0007]
The present invention has been made to solve such a conventional problem, and can be controlled and set to an appropriate multipole magnetic field state according to the type of plasma processing process. It is an object of the present invention to provide a plasma processing apparatus that can be performed easily and easily.
[0008]
[Means for Solving the Problems]
The present invention includes a processing chamber that accommodates a substrate to be processed, a mechanism that is provided in the processing chamber and that generates plasma for performing a predetermined plasma process on the substrate to be processed, and a plurality of magnet segments made of permanent magnets. And a magnetic field forming mechanism provided outside the processing chamber and forming a predetermined multipole magnetic field around the substrate to be processed in the processing chamber, wherein the magnetic field forming mechanism and the processing A ring of conductor is arranged between the chamber and the ring of conductor is rotatable about the vertical central axis of the ring. Furthermore, the present invention makes it possible to control the intensity of the multipole magnetic field by changing the number of rotations of the ring of the conductor. Furthermore, in the plasma processing apparatus according to the present invention, plasma is applied to the substrate to be processed. The etching process is performed by acting.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0010]
FIG. 1 schematically shows a configuration when an embodiment according to the present invention is applied to a plasma etching apparatus for etching a semiconductor wafer. In the figure, reference numeral 1 denotes a cylindrical vacuum chamber made of aluminum, for example, and constitutes a plasma processing chamber. The vacuum chamber 1 has a stepped cylindrical shape composed of a small-diameter upper portion 1a and a large-diameter lower portion 1b, and is connected to a ground potential. A support table (susceptor) 2 is provided inside the vacuum chamber 1 to support a semiconductor wafer W as a substrate to be processed substantially horizontally with its surface to be processed facing upward.
[0011]
The support table 2 is made of a material such as aluminum, and is supported by a conductor support 4 via an insulating plate 3 made of ceramic or the like. A focus ring 5 made of a conductive material or an insulating material is provided on the outer periphery above the support table 2.
[0012]
An electrostatic chuck 6 for electrostatically attracting the semiconductor wafer W is provided on the mounting surface of the semiconductor wafer W of the support table 2. The electrostatic chuck 6 is configured by disposing an electrode 6a between insulators 6b, and a DC power source 13 is connected to the electrode 6a. By applying a voltage from the power source 13 to the electrode 6a, the semiconductor wafer W is attracted to the support table 2 by Coulomb force.
[0013]
Furthermore, a coolant channel (not shown) for circulating the coolant is supplied to the support table 2 and He gas is supplied to the back surface of the semiconductor wafer W in order to efficiently transfer the cold heat from the coolant to the semiconductor wafer W. A gas introduction mechanism (not shown) is provided so that the semiconductor wafer W can be controlled to a desired temperature.
[0014]
The support table 2 and the support table 4 can be moved up and down by a pole screw mechanism including a ball screw 7, and a drive portion below the support table 4 is covered with a stainless steel (SUS) bellows 8. A bellows cover 9 is provided on the outside.
[0015]
A power supply line 12 for supplying high-frequency power is connected to substantially the center of the support table 2. A matching box 11 and a high frequency power source 10 are connected to the feeder line 12. From the high frequency power supply 10, high frequency power in the range of 13.56 to 150 MHz (preferably 13.56 to 100 MHz), for example, 100 MHz, is supplied to the support table 2.
[0016]
In order to increase the etching rate, it is preferable to superimpose a high frequency for plasma generation and a high frequency for drawing ions in the plasma, and a high frequency power source (not shown) for ion drawing (bias voltage control). In this case, those having a frequency in the range of 500 KHz to 13.56 MHz are used. This frequency is preferably 3.2 MHz when the etching target is a silicon oxide film, and 13.56 MHz when a polysilicon film or an organic material film is used.
[0017]
Further, a baffle plate 14 is provided outside the focus ring 5. The baffle plate 14 is electrically connected to the vacuum chamber 1 through the support 4 and the bellows 8. On the other hand, a shower head 16 is provided on the top wall portion of the vacuum chamber 1 above the support table 2 so as to face the support table 2 in parallel, and the shower head 16 is grounded. Accordingly, the support table 2 and the shower head 16 function as a pair of electrodes.
[0018]
A large number of gas discharge holes 18 are provided in the shower head 16, and a gas introduction part 16 a is provided above the shower head 16. A gas diffusion gap 17 is formed between the shower head 16 and the top wall of the vacuum chamber 1. A gas supply pipe 15a is connected to the gas introduction part 16a, and a processing gas supply system 15 for supplying a processing gas composed of a reactive gas for etching and a dilution gas is connected to the other end of the gas supply pipe 15a. is doing.
[0019]
As the reaction gas, for example, a halogen-based (fluorine-based, chlorine-based) or hydrogen-based gas can be used, and as a dilution gas, a gas usually used in this field such as Ar gas, He gas, or the like is used. Can do. Such a processing gas reaches the gas diffusion gap 17 above the shower head 16 from the processing gas supply system 15 through the gas supply pipe 15a and the gas introduction portion 16a, and is discharged from the gas discharge hole 18 to the semiconductor wafer W. It is supplied to the etching of the formed film.
[0020]
An exhaust port 19 is formed on the side wall of the lower portion 1 b of the vacuum chamber 1, and an exhaust system 20 is connected to the exhaust port 19. By operating a vacuum pump provided in the exhaust system 20, the inside of the vacuum chamber 1 can be depressurized to a predetermined degree of vacuum. Further, a gate valve 24 that opens and closes the loading / unloading port of the semiconductor wafer W is provided on the upper side wall of the lower portion 1 b of the vacuum chamber 1.
[0021]
On the other hand, an annular magnetic field forming mechanism (ring magnet) 21 is disposed concentrically with the vacuum chamber 1 around the outside of the upper portion 1 a of the vacuum chamber 1, and a processing space between the support table 2 and the shower head 16. A magnetic field is formed around the. The entire magnetic field forming mechanism 21 can be rotated around the vacuum chamber 1 by a rotation mechanism 25 at a predetermined rotation speed, preferably 10 to 20 rpm.
[0022]
As shown in FIG. 2, the magnetic field forming mechanism 21 includes a plurality of magnet segments 22 (16 in the case of FIG. 2) supported by a support member (not shown) as main components, and the plurality of magnet segments 22. Are arranged such that the magnetic poles facing the vacuum chamber 1 side are S, N, S, N,. The outer periphery of the segment magnet 22 is preferably surrounded by a ring 23 made of a magnetic material (for example, iron) in order to increase the magnetic efficiency.
[0023]
That is, in the state shown in FIG. 2, in the magnetic field formation mechanism 21, it arrange | positions so that the direction of the magnet of the adjacent magnet segment 22 may be mutually opposite in radial direction. Accordingly, magnetic field lines are formed between the adjacent magnet segments 22 in the chamber 1 as shown in the drawing, and are 0.02 to 0.2 T (200 to 2000 G), for example, in the periphery of the processing space, that is, in the vicinity of the inner wall of the vacuum chamber 1. A magnetic field of 0.03 to 0.045 T (300 to 450 G) is formed, and the central portion of the semiconductor wafer W is formed with a weak multipole magnetic field.
[0024]
The reason why the magnetic field strength range is defined in this way is that if the magnetic field strength is too strong, magnetic flux leakage may occur, and if it is too weak, the effect of plasma confinement may not be obtained. Therefore, such a numerical value is an example determined by the structure (material) of the apparatus, and is not necessarily limited to this numerical range.
[0025]
In addition, it is desirable that the magnetic field at the central portion of the semiconductor wafer W described above is weak in nature, but it is desirably zero T (Tesla). However, a magnetic field that affects the etching process is not formed on the portion where the semiconductor wafer W is disposed, so Any value that does not affect the wafer processing can be used. In the state shown in FIG. 2, a magnetic field having a magnetic flux density of 420 μT (4.2 G) or less, for example, is applied to the periphery of the wafer, thereby exhibiting the function of confining plasma.
[0026]
Further, in the present embodiment, a non-magnetic conductor ring 26 made of aluminum or the like is disposed between the magnetic field forming mechanism 21 and the vacuum chamber 1, and the conductor ring 26 is fixed to a predetermined state by the rotating mechanism 27. It can be rotated at a rotational speed (preferably 30 to 300 rpm). The rotational speed here refers to a relative speed with respect to the magnetic field forming mechanism 21.
[0027]
When the conductor ring 26 rotates, an eddy current is generated so as to prevent the magnetic flux from the magnetic field forming mechanism 21 from passing through the conductor ring 26 by interlinking the conductor ring 26. As a result, the conductor The magnetic field strength inside the ring 26 is weakened according to the number of rotations of the conductor ring 26.
[0028]
That is, the magnetic field strength in the chamber 1 can be controlled by changing the rotation speed of the conductor ring 26. In FIG. 3, the vertical axis represents the magnetic field strength, the horizontal axis represents the distance from the center of the semiconductor wafer W disposed in the vacuum chamber 1, and the magnetic field strength 0.033T (330G) in the chamber 1 when the conductor ring 26 is not rotating. ) To the state where the rotational speed of the conductor ring 26 is increased to 200 rpm to 0.017T (170G).
[0029]
Thus, in the present embodiment, by controlling the number of rotations of the conductor ring 26, a state in which a multipole magnetic field is formed around the semiconductor wafer W in the vacuum chamber 1 and the semiconductor in the vacuum chamber 1 are obtained. The multi-pole magnetic field is configured to be substantially weakened around the wafer W (preferably about half).
[0030]
Therefore, for example, when etching the above-described silicon oxide film or the like, etching is performed by forming a multipole magnetic field around the semiconductor wafer W in the vacuum chamber 1, whereby the etching rate within the surface of the semiconductor wafer W is increased. Can improve the uniformity. On the other hand, when the organic low dielectric constant film (Low-K) or the like is etched, the multi-pole magnetic field is not substantially formed (weakened) around the semiconductor wafer W in the vacuum chamber 1. Thus, the uniformity of the etching rate within the surface of the semiconductor wafer W can be improved.
[0031]
4 to 6 show the results of examining the uniformity of the etching rate in the surface of the semiconductor wafer W, where the vertical axis is the etching rate (etching rate) and the horizontal axis is the distance from the center of the semiconductor wafer. 4 to 6, when the curve A forms a 0.03 T (300 G) multipole magnetic field in the vacuum chamber 1, the curve B shows a 0.08 T (800 G) multipole magnetic field in the vacuum chamber 1. Shown if formed.
[0032]
4 shows a case where a silicon oxide film is etched with C ₄ F ₈ gas, FIG. 5 shows a case where a silicon oxide film is etched with CF ₄ gas, and FIG. 6 shows an organic low dielectric constant with a mixed gas containing N ₂ and H _2. The case where the film (Low-K) is etched is shown. As shown in FIGS. 4 and 5, when the silicon oxide film is etched with a gas containing C and F, such as C ₄ F ₈ or CF ₄ gas, the etching is performed in the vacuum chamber 1 with a weak multipole magnetic field. It can be seen that the in-plane uniformity of the etching rate can be improved by performing. In addition, as shown in FIG. 6, when an organic low dielectric constant film (Low-K) is etched with a mixed gas containing N ₂ and H ₂ , etching is performed in a vacuum chamber 1 with a weak multipole magnetic field. It can be seen that the in-plane uniformity of the etching rate can be improved by performing.
[0033]
As described above, in the present embodiment, the state of the multipole magnetic field in the vacuum chamber 1 can be easily controlled by rotating the conductor ring 26, and the optimum multipole magnetic field can be determined depending on the process to be performed. Good processing can be performed in this state.
[0034]
The material of the conductor ring 26 is not limited to aluminum, and may be a nonmagnetic material having good conductivity, such as copper or brass. The thickness of the ring is such a dimension that sufficient eddy current is generated and sufficient mechanical strength is obtained, and it may be, for example, about 5 to 20 mm.
[0035]
Next, processing in the plasma etching apparatus configured as described above will be described.
[0036]
First, the gate valve 24 is opened, and the semiconductor wafer W is loaded into the vacuum chamber 1 by a transfer mechanism (both not shown) through a load lock chamber disposed adjacent to the gate valve 24, and is previously set in a predetermined position. Is placed on the support table 2 that has been lowered. Next, when a predetermined voltage is applied from the DC power supply 13 to the electrode 6a of the electrostatic chuck 6, the semiconductor wafer W is attracted to the support table 2 by Coulomb force.
[0037]
Thereafter, after the transfer mechanism is retracted to the outside of the vacuum chamber 1, the gate valve 24 is closed to raise the support table 2 to the position shown in FIG. 1, and the vacuum chamber is exhausted via the exhaust port 19 by the vacuum pump of the exhaust system 20. 1 is exhausted.
[0038]
After the inside of the vacuum chamber 1 reaches a predetermined degree of vacuum, a predetermined processing gas is introduced into the vacuum chamber 1 from the processing gas supply system 15 at a flow rate of, for example, 100 to 1000 sccm, and the inside of the vacuum chamber 1 has a predetermined pressure. For example, 1.33 to 133 Pa (10 to 1000 mTorr), preferably 2.67 to 26.7 Pa (20 to 200 mTorr).
[0039]
In this state, a high frequency power having a frequency of 13.56 to 150 MHz, for example, 100 MHz and a power of 100 to 3000 W is supplied from the high frequency power supply 10 to the support table 2. In this case, by applying high frequency power to the support table 2 that is the lower electrode as described above, a high frequency electric field is generated in the processing space between the shower head 16 that is the upper electrode and the support table 2 that is the lower electrode. As a result, the processing gas supplied to the processing space is turned into plasma, and a predetermined film on the semiconductor wafer W is etched by the plasma.
[0040]
At this time, as described above, the rotation of the conductor ring 26 is rotated at zero or a predetermined number of rotations (for example, 30 to 300 rpm) to form a multipole magnetic field having a predetermined strength in the vacuum chamber 1 or substantially In the vacuum chamber 1, the multipole magnetic field is set to a substantially half state.
[0041]
When a multipole magnetic field is formed, there is a possibility that a portion corresponding to the magnetic pole of the side wall portion (depot shield) of the vacuum chamber 1 (for example, a portion indicated by P in FIG. 2) is locally scraped. On the other hand, since the magnetic field forming mechanism 21 is rotated around the vacuum chamber 1 by the rotating mechanism 25 having a driving source such as a motor, the magnetic pole moves with respect to the wall portion of the vacuum chamber 1. It is possible to prevent the wall portion of the chamber 1 from being locally cut.
[0042]
When a predetermined etching process is performed, the supply of high-frequency power from the high-frequency power supply 10 is stopped, the etching process is stopped, and then the semiconductor wafer W is unloaded from the vacuum chamber 1 in the reverse procedure to the above-described procedure.
[0043]
In the above-described embodiment, the case where the present invention is applied to an etching apparatus for etching a semiconductor wafer has been described. However, the present invention is not limited to such a case. For example, the present invention can be applied to an apparatus for processing a substrate other than a semiconductor wafer, and can also be applied to a film processing apparatus such as plasma processing other than etching, for example, CVD.
[0044]
【The invention's effect】
As described above, according to the present invention, the state of an appropriate multipole magnetic field can be easily controlled and set according to the type of plasma processing process, and good plasma processing can be easily performed.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a plasma processing apparatus to which the present invention is applied.
FIG. 2 is a schematic diagram for explaining the embodiment of the present invention in more detail.
FIG. 3 is a diagram showing the relationship between the rotation of the conductor ring shown in FIGS. 1 and 2 and the magnetic field strength in the chamber.
FIG. 4 is a diagram showing an example of the relationship between the in-plane distribution of the semiconductor wafer and the magnetic field at the etching rate according to the embodiment of the present invention.
FIG. 5 is a diagram showing an example of the relationship between the in-plane distribution of the semiconductor wafer at the etching rate and the magnetic field according to the embodiment of the present invention.
FIG. 6 is a view showing an example of the relationship between the in-plane distribution of the semiconductor wafer at the etching rate and the magnetic field according to the embodiment of the present invention.
[Sharpness of sign]
DESCRIPTION OF SYMBOLS 1 ... Vacuum chamber, 2 ... Support table, 3 ... Insulating plate, 4 ... Support stand, 5 ... Focus ring, 6 ... Electrostatic chuck, 7 ... Ball screw, 8 ... Bellows, 9 ... Bellows cover, 10 ... High frequency power supply DESCRIPTION OF SYMBOLS 11 ... Matching box, 12 ... Feed line, 13 ... DC power supply, 14 ... Baffle plate, 15 ... Process gas supply system, 16 ... Shower head, 17 ... Gas diffusion space, 18 ... Gas discharge hole, 19 ... Exhaust port , 20 ... exhaust system, 21 ... magnetic field forming mechanism, 22 (22a, 22b) ... magnet segment, 24 ... gate valve, 25 ... rotating mechanism of magnetic field generating mechanism, 26 ... conductor ring, 27 ... rotating mechanism of conductor ring .

Claims (3)

A processing chamber that accommodates a substrate to be processed; a mechanism that is provided in the processing chamber to generate plasma for performing a predetermined plasma treatment on the substrate to be processed; and a plurality of magnet segments made of permanent magnets, A plasma processing apparatus provided with a magnetic field forming mechanism provided outside the processing chamber and forming a predetermined multipole magnetic field around the substrate to be processed in the processing chamber;
A plasma processing apparatus, wherein a ring of a conductor is disposed between the magnetic field forming mechanism and the processing chamber, and the ring of the conductor is rotatable about a central axis of the ring. 2. The plasma processing apparatus according to claim 1, wherein the number of rotations of the conductor ring is controllable. A plasma processing method using the plasma processing apparatus according to claim 1 or 2, wherein plasma is applied to the substrate to be processed to perform an etching process.

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