JP2004079947A - Plasma processing apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma processing apparatus which is capable of setting the state of a multi-pole magnetic field corresponding to the kind of plasma processing and easily carrying out semiconductor processing. <P>SOLUTION: The plasma processing apparatus is equipped with a processing chamber housing substrates to be processed, a plasma generating mechanism which is provided inside the processing chamber to generate a plasma for processing the substrates as prescribed, and a magnetic field forming mechanism which is composed of a plurality of arranged permanent magnet segments and provided outside the processing chamber to form a multi-pole magnetic field around the substrates in the processing chamber. A conductor ring is arranged between the magnetic field forming mechanism and the processing chamber, and the conductor ring is set rotatable around its vertical center axis. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD 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]
2. Description of the Related 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, for example, a semiconductor wafer or the like, disposed in the processing chamber to perform a predetermined process, such as etching or film formation. Is known.
[0003]
In such a plasma processing apparatus, in order to perform good processing, it is necessary to maintain the state of plasma in a good state suitable for plasma processing. For this reason, a magnetic field for controlling plasma has conventionally been required. A plasma processing apparatus having a magnetic field forming mechanism for forming a magnetic field is used.
[0004]
As the magnetic field forming mechanism, N and S magnetic poles are arranged so as to alternately adjoin a substrate to be processed, such as a semiconductor wafer, which is horizontally disposed with the surface to be processed facing upward, so as to surround the periphery thereof. There is known a multi-pole type in which a magnetic field is not formed above a wafer and 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 preferably between 8 and 32, the number of poles is selected so that the magnetic field strength around the wafer matches the processing conditions.
[0005]
[Problems to be solved by the invention]
As described above, a plasma process in which a predetermined multipole magnetic field is formed around a substrate to be processed such as a semiconductor wafer in a processing chamber, and a plasma process such as an etching process is performed while controlling a plasma state by the multipole magnetic field. The device is known. However, according to the study by the present inventors, it has been found that in plasma processing, for example, plasma etching or the like, the in-plane uniformity of the etching rate changes depending on the intensity of the multipole magnetic field.
[0006]
Here, if the above-described magnetic field forming mechanism is configured by an electromagnet, control of forming and extinguishing a magnetic field can be easily performed. However, the use of electromagnets causes a problem of increased power consumption. Therefore, in many devices, permanent magnets are generally used. However, when a permanent magnet is used, control such as "forming" or "not forming" a 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 in that a large-scale apparatus is required for attaching and detaching the magnetic field forming means, so that a long time is required for the operation, and therefore, there is a problem that the operation efficiency of the entire semiconductor processing is reduced.
[0007]
The present invention has been made to solve such a conventional problem, and can control and set an appropriate multipole magnetic field state according to a type of a plasma processing process. An object of the present invention is to provide a plasma processing apparatus that can be easily and easily performed.
[0008]
[Means for Solving the Problems]
The present invention provides a processing chamber for accommodating a substrate to be processed, a mechanism provided in the processing chamber to generate plasma for performing a predetermined plasma processing on the substrate to be processed, and a plurality of magnet segments each including a permanent magnet. A plasma processing apparatus, comprising: a magnetic field forming mechanism arranged outside the processing chamber and configured to form a predetermined multipole magnetic field around the substrate to be processed in the processing chamber; A ring of conductor is arranged between the chamber and the ring, and the ring of conductor is rotatable about a vertical central axis of the ring. Further, the present invention is to make it possible to control the intensity of a multipole magnetic field by changing the number of revolutions of the ring of the conductor, and furthermore, in the plasma processing apparatus according to the present invention, To perform an etching process.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
[0010]
FIG. 1 schematically shows a configuration in which an embodiment according to the present invention is applied to a plasma etching apparatus for etching a semiconductor wafer. In FIG. 1, reference numeral 1 denotes a cylindrical vacuum chamber made of a material such as aluminum, which constitutes a plasma processing chamber. The vacuum chamber 1 has a stepped cylindrical shape having a small-diameter upper portion 1a and a large-diameter lower portion 1b, and is connected to a ground potential. In addition, a support table (susceptor) 2 that supports a semiconductor wafer W as a substrate to be processed substantially horizontally with its surface to be processed facing upward is provided inside the vacuum chamber 1.
[0011]
The support table 2 is made of, for example, 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 an outer periphery above the support table 2.
[0012]
An electrostatic chuck 6 for electrostatically attracting the semiconductor wafer W is provided on the surface of the support table 2 on which the semiconductor wafer W is placed. The electrostatic chuck 6 has an electrode 6a arranged between insulators 6b, and a DC power supply 13 is connected to the electrode 6a. By applying a voltage from the power supply 13 to the electrode 6a, the semiconductor wafer W is made to adhere to the support table 2 by Coulomb force.
[0013]
Further, a coolant flow path (not shown) for circulating a coolant in the support table 2 and a He gas is supplied to the back surface of the semiconductor wafer W in order to efficiently transmit 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 driving portion below the support table 4 is covered with a bellows 8 made of stainless steel (SUS). 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. The matching box 11 and the high frequency power supply 10 are connected to the power supply 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 high frequency power is supplied to the support table 2.
[0016]
In order to increase the etching rate, it is preferable that a high frequency for generating plasma and a high frequency for drawing ions in the plasma are superposed, and a high frequency power supply (not shown) for drawing ions (bias voltage control) is used. The frequency is in the range of 500 KHz to 13.56 MHz. This frequency is preferably 3.2 MHz when the etching target is a silicon oxide film, and 13.56 MHz when the etching target is a polysilicon film or an organic material film.
[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 via the support 4 and the bellows 8. On the other hand, a shower head 16 is provided on the ceiling 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. Therefore, the support table 2 and the shower head 16 function as a pair of electrodes.
[0018]
The shower head 16 is provided with a number of gas discharge holes 18, and a gas inlet 16 a is provided above the shower head 16. A gas diffusion space 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 section 16a, and a processing gas supply system 15 for supplying a processing gas including a reaction gas for etching and a diluting gas is connected to the other end of the gas supply pipe 15a. are doing.
[0019]
As a reaction gas, for example, a halogen-based (fluorine-based, chlorine-based) or hydrogen-based gas can be used, and as a diluent gas, a gas usually used in this field, such as an Ar gas or a He gas, can be used. Can be. Such a processing gas reaches the gas diffusion space 17 above the shower head 16 from the processing gas supply system 15 via the gas supply pipe 15a and the gas introduction part 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 a 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 the vacuum pump provided in the exhaust system 20, the pressure inside the vacuum chamber 1 can be reduced to a predetermined degree of vacuum. Further, a gate valve 24 for opening and closing the loading / unloading port of the semiconductor wafer W is provided on the upper side wall of the lower portion 1b 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 outer periphery of the upper portion 1a of the vacuum chamber 1, and a processing space between the support table 2 and the shower head 16 is provided. A magnetic field is formed around the object. The whole of the magnetic field forming mechanism 21 can be rotated around the vacuum chamber 1 at a predetermined rotation speed, preferably 10 to 20 rpm, by a rotation mechanism 25.
[0022]
As shown in FIG. 2, the magnetic field forming mechanism 21 has a plurality of magnet segments 22 (16 in 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 are S, N, S, N,. The outer periphery of the segment magnet 22 is preferably surrounded by a ring 23 of a magnetic material (for example, iron) in order to increase magnetic efficiency.
[0023]
That is, in the magnetic field forming mechanism 21, in the state shown in FIG. 2, the magnets of the adjacent magnet segments 22 are arranged so that the directions of the magnets are opposite to each other in the radial direction. Accordingly, magnetic field lines are formed between adjacent magnet segments 22 in the chamber 1 as shown in the figure, and for example, 0.02 to 0.2 T (200 to 2000 G) in the peripheral portion of the processing space, that is, near the inner wall of the vacuum chamber 1. Preferably, a magnetic field of 0.03 to 0.045 T (300 to 450 G) is formed, and the multipole magnetic field is weakly formed at the center of the semiconductor wafer W.
[0024]
The reason why the magnetic field strength range is defined in this way is that if the magnetic field strength is too strong, it may cause magnetic flux leakage, and if the magnetic field strength 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 device, and is not necessarily limited to this numerical range.
[0025]
The fact that the magnetic field at the center of the semiconductor wafer W described above is weak is preferably originally zero T (tesla). However, a magnetic field that affects the etching process is not formed in the portion where the semiconductor wafer W is disposed. Any value may be used as long as the value does not affect the wafer processing. In the state shown in FIG. 2, a magnetic field having a magnetic flux density of, for example, 420 μT (4.2 G) or less is applied to the peripheral portion of the wafer, thereby exerting a 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 rotated by a rotating mechanism 27 to a predetermined position. It can rotate at a rotation speed (preferably 30 to 300 rpm). Here, the rotation speed 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 interlinking the conductor ring 26 to prevent the magnetic flux from passing through the inside of the conductor ring. The magnetic field strength inside the ring 26 is reduced according to the rotation speed of the conductor ring 26.
[0028]
That is, the magnetic field intensity 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 in the chamber 1 when the conductor ring 26 is not rotating is 0.033T ( From 330 G) to a state where the number of revolutions of the conductor ring 26 is increased to 200 rpm to 0.017 T (170 G).
[0029]
As described above, in the present embodiment, the state in which a multipole magnetic field is formed around the semiconductor wafer W in the vacuum chamber 1 by controlling the rotation speed of the conductor ring 26 and the state in which the semiconductor The configuration is such that the multipole magnetic field around the wafer W can be substantially set to a very weak state (preferably about half).
[0030]
Therefore, for example, when etching the above-described silicon oxide film or the like, a multi-pole magnetic field is formed around the semiconductor wafer W in the vacuum chamber 1 to perform the etching. Can be improved. On the other hand, when etching the above-described organic low dielectric constant film (Low-K) or the like, etching is performed without substantially forming (weakening) a multipole magnetic field around the semiconductor wafer W in the vacuum chamber 1. By doing so, the uniformity of the etching rate in the plane 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, with the vertical axis representing the etching rate (etching rate) and the horizontal axis representing the distance from the center of the semiconductor wafer. In each of FIGS. 4 to 6, curve A indicates a case where a multipole magnetic field of 0.03 T (300 G) is formed in the vacuum chamber 1, and curve B indicates a multipole magnetic field of 0.08 T (800 G) in the vacuum chamber 1. This is shown when a magnetic field is formed.
[0032]
FIG. 4 shows a case where a silicon oxide film is etched with a C ₄ F ₈ gas, FIG. 5 shows a case where a silicon oxide film is etched with a CF ₄ gas, and FIG. 6 shows an organic low dielectric constant with a mixed gas containing N ₂ and H _2. This shows a case where the film (Low-K) is etched. As shown in FIGS. 4 and 5, when etching a silicon oxide film with a gas containing C and F such as C ₄ F ₈ or CF ₄ gas, the etching is performed in a vacuum chamber 1 with a multipole magnetic field weak. It can be seen that performing the method can improve the in-plane uniformity of the etching rate. Further, as shown in FIG. 6, when the organic low dielectric constant film (Low-K) is etched with a mixed gas containing N ₂ and H ₂ , the etching is performed in a vacuum chamber 1 in a state where the multipole magnetic field is weak. It can be seen that performing the method can improve the in-plane uniformity of the etching rate.
[0033]
As described above, in the present embodiment, the state of the multi-pole magnetic field in the vacuum chamber 1 can be easily controlled by rotating the conductor ring 26, and the optimum multi-pole magnetic field In this state, good processing can be performed.
[0034]
The material of the conductor ring 26 is not limited to aluminum, but may be a non-magnetic material having good conductivity, for example, copper or brass. The thickness of the ring is such a size that sufficient eddy current is generated and mechanical strength is sufficiently obtained, and 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 at a predetermined position. Is placed on the support table 2 which has been lowered. Next, when a predetermined voltage is applied to the electrode 6a of the electrostatic chuck 6 from the DC power supply 13, the semiconductor wafer W is attracted to the support table 2 by Coulomb force.
[0037]
Thereafter, after the transport 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 is evacuated.
[0038]
After the inside of the vacuum chamber 1 has 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, the pressure is maintained at about 1.33 to 133 Pa (10 to 1000 mTorr), preferably about 2.67 to 26.7 Pa (20 to 200 mTorr).
[0039]
In this state, high frequency power having a frequency of 13.56 to 150 MHz, for example, 100 MHz, and 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 the high-frequency power to the support table 2 as the lower electrode as described above, the high-frequency electric field is applied to the processing space between the shower head 16 as the upper electrode and the support table 2 as the lower electrode. Is formed, whereby 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 of a predetermined intensity in the vacuum chamber 1 or substantially. First, the multipole magnetic field is set in the vacuum chamber 1 in a state where the magnetic field is almost halved.
[0041]
When a multipole magnetic field is formed, a portion (for example, a portion indicated by P in FIG. 2) corresponding to the magnetic pole of the side wall portion (deposit shield) of the vacuum chamber 1 may be locally cut. On the other hand, the magnetic pole is moved relative to the wall of the vacuum chamber 1 by rotating the magnetic field forming mechanism 21 around the vacuum chamber 1 by the rotation mechanism 25 having a drive source such as a motor. It is possible to prevent the wall of the chamber 1 from being cut off locally.
[0042]
When the predetermined etching process is performed, the supply of the high-frequency power from the high-frequency power supply 10 is stopped, the etching process is stopped, and then the semiconductor wafer W is carried out of the vacuum chamber 1 to the outside in a procedure reverse to the above-described procedure.
[0043]
In the above embodiment, the case where the present invention is applied to an etching apparatus for etching a semiconductor wafer has been described, but the present invention is not limited to such a case. For example, the present invention is applicable to an apparatus for processing a substrate other than a semiconductor wafer, and is also applicable to plasma processing other than etching, for example, a film forming apparatus such as CVD.
[0044]
【The invention's effect】
As described above, according to the present invention, an appropriate multipole magnetic field state can be easily controlled and set according to the type of the plasma processing process, and excellent plasma processing can be easily performed.
[Brief description of the drawings]
FIG. 1 is a view schematically showing 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 a relationship between rotation of a conductor ring shown in FIGS. 1 and 2 and a magnetic field intensity in a chamber.
FIG. 4 is a diagram showing an example of a relationship between an in-plane distribution of an etching rate of a semiconductor wafer and a magnetic field according to the embodiment of the present invention.
FIG. 5 is a diagram showing an example of a relationship between an in-plane distribution of an etching rate of a semiconductor wafer and a magnetic field according to the embodiment of the present invention.
FIG. 6 is a diagram showing an example of a relationship between an in-plane distribution of an etching rate of a semiconductor wafer and a magnetic field according to an embodiment of the present invention.
[Sharp sign]
DESCRIPTION OF SYMBOLS 1 ... Vacuum chamber, 2 ... Support table, 3 ... Insulating plate, 4 ... Support base, 5 ... Focus ring, 6 ... Electrostatic chuck, 7 ... Ball screw, 8 ... Bellows, 9 ... Bellows cover, 10 ... High frequency power supply , 11: Matching box, 12: Power supply line, 13: DC power supply, 14: Baffle plate, 15: Processing 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 for accommodating the substrate to be processed, a mechanism provided in the processing chamber to generate plasma for performing a predetermined plasma process on the substrate to be processed, and a plurality of magnet segments composed of permanent magnets are arranged; A magnetic field forming mechanism that is provided outside the processing chamber and forms a predetermined multi-pole 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 around a central axis of the ring. 2. The plasma processing apparatus according to claim 1, wherein the number of rotations of said conductor ring is controllable. 3. 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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