(12) United States Patent
`Hirose
`
`I IIIII IIIIIIII Ill lllll lllll lllll lllll lllll lllll lllll lllll 111111111111111111
`
`US006485602B2
`US 6,485,602 B2
`Nov. 26, 2002
`
`(10) Patent No.:
`(45) Date of Patent:
`
`(54) PIASMA PROCESSING APPARATUS
`
`FOREIGN PArENT DOCUMENTS
`
`(75)
`
`Inventor: Eiji Hirose, Nirasaki (JP)
`
`JP
`
`2001-7086
`
`1/2001
`
`(73) As.5ignee: Tokyo Electron Limited, Tokyo (JP)
`
`• cited by examiner
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by O days.
`
`Primary Examiner-Thi Dang
`(74) Altorney, Agenl, or Firm-Obion, Spivak, McClelland,
`Maier & Neustadt, P.C.
`
`(21) Appl. No.: 09/906,731
`Jul. 18, 2001
`Prior Publication Data
`
`(22) Filed:
`
`(65)
`
`US 2002/0007915 Al Jan. 24, 2002
`Foreign Application Priority Data
`
`(30)
`
`(JP) ....................................... 2000-219783
`Jul. 19, 2000
`HOlL 21/(H)
`(51) Int. Cl.7
`.... .... .... .... ... .. ................
`(52) U.S. Cl . ............................ 156/345.44; 156/345.47;
`118/ 723 E
`(58) Field of Search ....................... 156/345.44, 345.43,
`156/345.47; 118/723 E; 204/298.08, 298.34
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`(57)
`
`ABSTRACT
`
`The present invention concerns a plasma processing appa(cid:173)
`ratus for processing a proces.5ing object by applying two
`type.s of bigb-frequeocy power witb differeot frequeocies to
`generate plasma. A first high-frequency line is provided with
`a first filter circuit for attenuating a high-frequency current
`from a second bigb-frequency power supply. A second
`high-frequency line is provided with a second filter circuit
`for attenuating a high.frequency current from a first high(cid:173)
`frequency power supply. Tbe first filter circuit is provided
`with a variable capacitor for changing a circuit constant. For
`changing the circuit constant, the variable capacitor is varied
`so that a resonance point becomes greater than an optimum
`resonance point most attenuating a high frequency in the
`second high.frequency power supply. Doing so decreases a
`sputter rate of the generated plasma affected on a wall
`surface of the processing chamber.
`
`5,900,103 A
`
`• 5/ 1999 Tomoyasu et al. .... ... 118/723 E
`
`7 Claims, 7 Drawing Sheets
`
`10
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`\
`
`20
`
`w
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`21
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`14
`
`F.irst. matching
`cucutt
`
`17
`
`16
`
`A
`
`11
`
`12
`
`33
`
`18
`
`Second matching
`circuit
`
`19
`
`15
`
`Page 1 of 13
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`APPLIED MATERIALS EXHIBIT 1006
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`

`

`U.S. Patent
`
`Nov. 26, 2002
`
`Sheet 1 of 7
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`US 6,485,602 B2
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`20
`
`20b
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`20a
`
`w
`
`21
`
`10
`
`\
`
`14
`
`First matching
`circuit
`
`17
`
`A
`
`16
`
`p
`
`11
`
`12
`
`33
`
`18
`
`Second matching
`circuit
`
`19
`
`15
`
`FIG. 1
`
`Page 2 of 13
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`

`

`U.S. Patent
`
`Nov. 26, 2002
`
`Sheet 2 of 7
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`US 6,485,602 B2
`
`Voltage
`
`Voltage
`
`FIG. 2
`
`Time
`
`FIG. 3
`
`Time
`
`Page 3 of 13
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`

`

`U.S. Patent
`
`Nov. 26, 2002
`
`Sheet 3 of 7
`
`US 6,485,602 B2
`
`Voltage
`
`FIG. 4
`
`Maximum Average
`C4Fa,'Ar/02: 773
`722
`: 520
`501
`1200 Ar/02
`c 1000
`·e 800
`<
`'";' 600
`~ 400
`.....
`FIG. SA ~ 200
`:::,
`0..
`0
`en
`-200
`0
`
`10
`
`20
`
`Maximum
`C4FafAr/02: 782
`378
`1200 Ar/02
`c 1000
`·e 800 ~
`600
`<1>
`~ 400
`.....
`==
`<1> 20
`:::,
`0..
`0
`FIG. 58 en
`-200
`0
`
`10
`
`20
`
`nme
`--+-C4Fa,'Ar/02
`--o-Ar/02
`
`40
`
`50
`Distance
`
`--+-C4FafAr/02
`--o-Ar/02
`
`30
`
`Average
`730
`360
`
`30
`
`40
`
`50
`Distance
`
`Page 4 of 13
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`

`

`U.S. Patent
`
`Nov. 26, 2002
`
`Sheet 4 of 7
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`US 6,485,602 B2
`
`IZI
`
`Optimum i
`resonancei
`point
`· Resonance
`point
`
`40
`
`FIG. 6
`
`10
`
`\
`
`First matching
`curcutt
`
`37
`
`36
`
`31
`
`41
`
`FIG. 7
`
`38
`
`Second matching
`curcuit
`
`39
`
`35
`
`Page 5 of 13
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`

`

`U.S. Patent
`
`Nov. 26, 2002
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`Sheet 5 of 7
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`US 6,485,602 B2
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`51
`
`51b
`
`51a
`
`21
`
`50
`
`\
`
`14
`
`First .matching
`curcu1t
`
`17
`
`16
`
`p
`
`11
`
`12
`
`33
`
`18
`
`Seco~d matching
`curcuit
`
`19
`
`15
`
`FIG. 8
`
`Page 6 of 13
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`

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`U.S. Patent
`
`Nov. 26, 2002
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`Sheet 6 of 7
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`US 6,485,602 B2
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`60
`
`\
`
`40
`
`34
`
`First matching
`curcuit
`
`37
`
`36
`
`31
`
`42
`
`42a
`
`41
`
`38
`
`Second matching
`curcuit
`
`39
`
`35
`
`FIG. 9
`
`Page 7 of 13
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`

`

`U.S. Patent
`
`Nov. 26, 2002
`
`Sheet 7 of 7
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`US 6,485,602 B2
`
`6a
`
`First filter
`curcuit
`
`6b
`
`Second filter
`curcuit
`
`3a
`
`First .matching
`curcu1t
`
`Sa
`
`4a
`
`4b
`
`2a
`
`2b
`
`Seco~d matching
`curcu1t
`
`Sb
`
`3b
`
`F I G. 10 PRIOR ART
`
`Page 8 of 13
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`

`

`US 6,485,602 B2
`
`1
`PLASMA PROCESSING APPARATUS
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`This application is based upon and claims the benefit of
`priority from the prior Japanese Patent Application No.
`2000-219783, filed Jul. 19, 2000, the entire contents of
`which are incorporated herein by reference.
`
`BACKGROUND OF THE INVENTION
`
`5
`
`2
`In this technology, however, a potential difference occurs
`between the plasma potential and the wall surface of the
`processing chamber 1. Sputtering due to an ion component
`in the plasma erodes the wall surface. Simultaneously apply-
`ing two types of high-frequency power decreases an effec(cid:173)
`tive ground area for one electrode compared to the case
`where a single frequency is applied. A sputter rate increases
`for the decreased ground area, causing more damages of the
`wall surface. This has been a cause of the shortening of the
`10 processing chamber life (usable period).
`The problem of shortening the processing chamber life
`becomes more serious when the processing object such as a
`semiconductor wafer has an increased area, throughput is
`increased, or the high-frequency power is increased to
`15 further increase the sputter rate, and the like.
`Conventionally, countermeasures have been taken to sup(cid:173)
`press damages to the wall surface. For example, the pro(cid:173)
`cessing chamber is enlarged to increase the ground area and
`decrease the sputter rate. Alternatively, a resin coating is
`20 applied to the wall surface to prevent wear to the wall
`surface. In any case, substantial countermeasures is
`unavailable, causing a problem of increasing costs for addi(cid:173)
`tional processing.
`
`1. Field of the Invention
`The present invention relates to a plasma processing
`apparatus capable of suppressing a damage due to sputtering
`to a wall surface of a processing chamber during plasma
`occurrence.
`2. Description of the Related Art
`Conventionally, there are two types of plasma processing
`apparatuses. One type generates plasma by applying high(cid:173)
`frequency power with a single type of frequency. The other
`type generates plasma by applying high-frequency power
`with two types of frequency. Especially, the latter type of
`plasma processing apparatus is configured to generate high(cid:173)
`density plasma using high-frequency power with a high 25
`frequency, and generate a bias potential using high(cid:173)
`frequency power with a low frequency. In recent years, there
`is often used a plasma processing apparatus which alternates
`the two types of frequencies according to necessity.
`As shown in FIG. 10, this plasma processing apparatus
`comprises upper and lower electrodes 2a and 2b, and first
`and second high-frequency power supplies 3a and 3b. The
`upper and lower electrodes 2a and 2b are arranged parallel
`facing each other in a processing chamber 1. The first and
`second high-frequency power supplies 3a and 3b supply 35
`these upper and lower electrodes 2a and 2b with first and
`second high-frequency powers having different frequencies.
`A matching circuit Sa is provided in the middle of a first
`power supply line 4a connecting the first high-frequency
`power 3a and the upper electrode 2a. A matching circuit Sb
`is provided on a second power supply line 4b connecting the
`second high-frequency power 3b and the lower electrode 2b.
`Further, the first power supply line 4a connects with a first
`filter circuit 6a as a return circuit. This filter circuit 6a has 45
`a fixed circuit constant and attenuates a second high(cid:173)
`frequency component. The second power supply line 4b
`connects with a second filter circuit 6b as a return circuit.
`This filter circuit 6b has a fixed circuit constant and attenu(cid:173)
`ates a first high-frequency component. In the first and second
`filter circuits 6a and 6b, each circuit constant is set to a value
`resonating with a high frequency to be filtered.
`When plasma processing is applied to a processing object
`such as a semiconductor wafer, the processing object is
`mounted on the lower electrode 2b, for example. The first 55
`and second high-frequency power supplies 3a and 3b supply
`corresponding high-frequency powers to the upper and
`lower electrodes 2a and 2b, respectively, to generate plasma
`P therebetween. Further, a bias voltage is applied to the
`lower electrode 2b to perform specified plasma processing 60
`for the semiconductor wafer on the lower electrode 2b.
`The plasma processing apparatus attenuates high(cid:173)
`frequency power with a different frequency on the first and
`second power supply lines 4a and 4b. The first and second
`high-frequency power supplies 3a and 3b supply respective
`high-frequency powers to the upper and lower electrodes 2a
`and 2b under an optimum condition.
`
`BRIEF SUMMARY OF THE INVENTION
`
`It is an object of the present invention to provide a plasma
`processing apparatus capable of decreasing a sputter rate
`damaging a processing chamber wall surface during plasma
`30 generation and extending the usable life of the processing
`chamber.
`In order to achieve the above-mentioned objects, a plasma
`processing apparatus according to the present invention for
`applying a specified plasma processing to a processing
`object comprises first and second electrodes arranged in
`parallel in a processing chamber so that they face to each
`other; a first high-frequency power supply for applying a
`first high-frequency power to the first and second electrodes
`via a first power supply line; a second high-frequency power
`40 supply for applying a second high-frequency power to the
`second electrode via a second power supply line; a first filter
`circuit for attenuating the second high-frequency power
`flowing through the first power supply line; and a second
`filter circuit for attenuating the first high-frequency power
`flowing through the second power supply line, wherein the
`first filter circuit includes a variable capacitor for varying a
`circuit constant in order to increase a resonance point from
`an optimum resonance point most attenuating the second
`high-frequency power and for decreasing a sputter rate for a
`50 wall surface of the processing chamber during plasma
`occurrence.
`Additional objects and advantages of the invention will be
`set forth in the description which follows, and in part will be
`obvious from the description, or may be learned by practice
`of the invention. The objects and advantages of the invention
`may be realized and obtained by means of the instrumen(cid:173)
`talities and combinations particularly pointed out hereinaf(cid:173)
`ter.
`
`BRIEF DESCRIPTION OF THE SEVERAL
`VIEWS OF THE DRAWING
`The accompanying drawings, which are incorporated in
`and constitute a part of the specification, illustrate presently
`embodiments of the invention, and together with the general
`65 description given above and the detailed description of the
`embodiments given below, serve to explain the principles of
`the invention.
`
`Page 9 of 13
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`

`

`US 6,485,602 B2
`
`5
`
`3
`FIG. 1 is a configuration chart showing a first embodiment
`of a plasma processing apparatus according to the present
`invention;
`FIG. 2 shows a voltage characteristic from a second
`high-frequency power supply on a power supply line a when
`a first filter circuit shown in FIG. 1 is omitted;
`FIG. 3 shows a voltage characteristic from the second
`high-frequency power supply on the power supply line a
`when a capacitor capacity of the first filter circuit in FIG. 1
`is set to 2,500 pF;
`FIG. 4 shows a voltage characteristic from the second
`high-frequency power supply on the power supply line a
`when a capacitor capacity of the first filter circuit in FIG. 1
`is set to 2,000 pF;
`FIG. SA shows the relationship between a sputter rate for
`the processing chamber wall surface and a capacitor capac(cid:173)
`ity for the filter circuit when the capacitor capacity is 2,500
`pF;
`FIG. SB shows the relationship between a sputter rate for
`the processing chamber wall surface and a capacitor capac(cid:173)
`ity for the filter circuit when the capacitor capacity is 2,200
`pF;
`FIG. 6 shows a decrease in the sputter rate;
`FIG. 7 is a configuration chart showing a second embodi- 25
`ment of the plasma processing apparatus according to the
`present invention;
`FIG. 8 is a configuration chart showing a third embodi(cid:173)
`ment of the plasma processing apparatus according to the 30
`present invention;
`FIG. 9 is a configuration chart showing a fourth embodi(cid:173)
`ment of the plasma processing apparatus according to the
`present invention; and
`FIG. 10 is a configuration chart exemplifying a conven(cid:173)
`tional plasma processing apparatus.
`
`4
`surface of a semiconductor wafer W for performing, say,
`reactive ion etching (RIE).
`Since the first matching circuit 17 is provided, it is
`possible to supply the maximum power to the upper elec-
`trade 12 from the first high-frequency power supply 14.
`Since the second matching circuit 19 is provided, it is
`possible to supply the maximum power to the lower elec(cid:173)
`trode 13 from the second high-frequency power supply 15.
`The first power supply line 16 is provided with a first filter
`10 circuit 20. The second power supply line 18 is provided with
`a second filter circuit 21. The first filter circuit 20 includes
`an LC series resonant circuit with varying the circuit con(cid:173)
`stant. The LC series resonant circuit selectively filters a
`high-frequency current output from the second high-
`15 frequency power supply 15 for preventing the current from
`reaching the first high-frequency power supply 14. The
`second filter circuit 21 includes an LC series resonant circuit
`with a fixed circuit constant. This LC series resonant circuit
`prevents a high-frequency current from the first high-
`20 frequency power supply 14 from reaching the second high(cid:173)
`frequency power supply 15.
`The circuit constant for the first filter circuit 20 is changed
`by using a variable capacitor 20a and changing the capaci(cid:173)
`tance. The sputter rate according to the plasma P is
`decreased by changing the capacity of the variable capacitor
`20a.
`In the plasma processing apparatus according to the
`present invention, the first filter circuit 20 is not limited to
`the function as a return circuit. Since the circuit constant is
`variable, the first filter circuit also allows the capacitor
`capacitance to be varied in accordance with the sputter rate,
`varying with the plasma potential and decreasing the sputter
`rate to such a degree that the product throughput is only
`35 slightly affected. Since the sputter rate can be decreased, it
`is possible to suppress damage to the wall surface of the
`processing chamber 11 and extend the processing chamber
`life (usable period).
`The following describes how to set the circuit constant of
`40 the first filter circuit 20. First, the optimum resonance point
`is to be found.
`The first high-frequency power supply 14 (60 MHz) and
`the second high-frequency power supply 15 (2 MHz) apply
`high-frequency power to the upper electrode 12 and the
`45 lower electrode 13, respectively. The capacitor capacity of
`the first filter circuit 20 is varied by measuring a voltage
`waveform, say, at point A on the first power supply line 16.
`When a coil 20b of the first filter circuit 20 is set to an
`inductance of 2.5 µH, for example, the capacitor capacity
`resonant with the 2-MHz high frequency is up to approxi(cid:173)
`mately 2,500 pF. When two frequencies (60 MHz and 2
`MHz) are applied, the capacitor capacitance is divided into
`three types, namely, no filter circuit provided, the capacitor
`capacity set to 2,500 pF, and the capacitor capacity set to
`2,000 pF. The voltage waveform in each case is measured at
`point A on the first power supply line 16. As measurement
`results, FIG. 2 shows a voltage characteristic with no filter
`circuit provided. FIG. 3 shows a voltage characteristic with
`the capacitor capacity set to 2,500 pF. FIG. 4 shows a
`voltage characteristic with the capacitor capacity set to 2,000
`pF.
`As clearly seen in these figures, when the coil inductance
`L is fixed to 2.5 µH, the capacitor capacity is 2,500 pF,
`allowing the voltage waveform to most optimally resonate
`65 with the sine wave. When the capacitor capacity is set to
`2,000 pF, the sine wave is slightly deformed in comparison
`with that of 2,500 pF.
`
`DETAILED DESCRIPTION OF IBE
`INVENTION
`
`Embodiments of the present invention will be described in
`further detail with reference to the accompanying drawings.
`The following describes the first embodiment of the
`present invention with reference to FIGS. 1 to 6.
`FIG. 1 schematically shows a plasma processing appara(cid:173)
`tus 10 for etching as the first embodiment. This plasma
`processing apparatus 10 includes a processing chamber
`(processing area) 11 formed of a conductive material such as
`aluminum. In this processing chamber 11, an upper electrode
`12 and a lower electrode 13 are arranged in parallel with a 50
`specified interval so that they face each other. The upper
`electrode 12 is connected to a first high-frequency power
`supply 14 via a first power supply line 16 and a first
`matching circuit 17. The lower electrode 13 is connected to
`a second high-frequency power supply 15 via a second 55
`matching circuit 19. This lower electrode 13 also functions
`as a chuck top for mounting a processing object such as a
`semiconductor wafer, for example.
`The first high-frequency power supply 14 applies, say,
`60-MHz high-frequency power to the upper electrode 12. 60
`Plasma P is generated in an atmosphere of process gas
`supplied between the upper electrode 12 and the lower
`electrode 13.
`The second high-frequency power supply 15 applies
`2-MHz high-frequency power to the lower electrode 13 to
`generate a bias potential corresponding to the plasma poten(cid:173)
`tial. An ion component in the plasma is introduced to the
`
`Page 10 of 13
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`

`

`US 6,485,602 B2
`
`10
`
`20
`
`Frequency=60
`
`5
`Accordingly, when the first filter circuit 20 is used only as
`a return circuit, setting the capacitor capacity to 2,500 pF
`provides an optimum resonance point. According to this
`embodiment, however, the first filter circuit 20 is requested
`to have the function of decreasing the sputter rate in addition 5
`to the function as a return circuit.
`For this purpose, the above-mentioned optimum reso(cid:173)
`nance point just needs to be shifted so that frequency f [ =Yin
`v'(L-C)] becomes large, where C is capacitance and L is
`inductance (coil).
`Specifically, the relationship between the sputter rate and
`the capacitor capacity is examined. For this purpose, the
`plasma processing apparatus is operated under the following
`conditions. Given that the coil inductance is fixed to 2.5 µH
`and the capacitor capacity is set to 2,500 pF in the first filter 15
`circuit 20, the sputter rate is measured under the following
`process conditions 1 and 2. The measurement results in the
`relation shown in FIG. SA. Likewise, when the capacitor
`capacity is set to 2,000 pF, measuring the sputter rate results
`in the relationship shown in FIG. SB.
`1. Process condition for C4F8/Ar/0 2 gas
`Wafer: 300 mm
`Film to be etched: Silicon oxide film
`Processing: Contact
`Power applied to the upper electrode:
`MHz, Power=3,300 W
`Power applied to the lower electrode: High frequency=2
`MHz, Power=3,800 W
`Gap between electrodes: 35 mm
`Process pressure: 20 mTorr
`Process gas: C4 F8 =20 seem
`Ar=400 seem
`0 2=15 seem
`2. Process condition for Ar/0 2 gas
`Film to be etched: Silicon oxide film
`Processing: Contact
`Power applied to the upper electrode: Frequency=60 40
`MHz, Power=3,300 W
`Power applied to the lower electrode: High frequency=2
`MHz, Power=3,800 W
`Gap between electrodes: 35 mm
`Process pressure: 20 mTorr
`Process gas: Ar=400 seem
`0 2=400 seem
`According to the results in FIGS. SA and SB, it is clear
`that the filter circuit set at 2.5 µH and 2,000 pF greatly
`decreases the sputter rate for the Ar/0 2 gas compared to the
`filter circuit set at 2.5 µH and 2,500 pF. Further, it is clear
`that the C4F8/Ar/0 2 gas causes little change in the sputter
`rate for both filter circuits. Basically, the C4F8/Ar/0 2 gas is
`a chemical sputter involving a chemical reaction. The Ar/0 2
`gas is physical sputter. This means that the plasma potential
`varies with the circuit constants.
`Accordingly, it is found that the filter circuit with 2.5 µH
`and 2,000 pF is superior to the optimally resonant filter
`circuit with 2.5 µH and 2,500 pF, which decreases the sputter
`rate. Actually, however, the former is slightly inferior to the
`latter with respect to the resonance phenomenon.
`According to this embodiment as mentioned above, the
`first high-frequency line 16 is provided with the first filter
`circuit 20 for attenuating a high-frequency current from the
`second high-frequency power supply 15. The second high(cid:173)
`frequency line 18 is provided with the second filter circuit 21
`
`6
`for attenuating a high-frequency current from the first high(cid:173)
`frequency power supply 14. The variable capacitor 20a is
`provided as means for changing the circuit constant of the
`first filter circuit 20.
`When the first filter circuit 20 optimally resonates with a
`high frequency of the first high-frequency power supply 14,
`the filter circuit may not provide a circuit constant for
`increasing the sputter rate on the wall surface of the pro(cid:173)
`cessing chamber 11. In this case, the variable capacitor 20a
`of the first filter circuit 20 is adjusted to have a capacitor
`capacity so that the resonance point becomes lower than the
`optimum resonance point. This can decrease the sputter rate
`on the wall surface of the processing chamber 11, suppress
`damage thereto, and extend the usable life of the processing
`chamber 11.
`The first embodiment has been explained as an example
`of the plasma processing apparatus capable of varying the
`circuit constant by providing the variable capacitor 20a in
`the first filter circuit 20 installed on the power supply line 16
`for generating high-density plasma. It is also possible to
`provide a similar effect by replacing the capacitor in the first
`filter circuit 20 with a fixed capacitor and replacing the
`capacitor in the second filter circuit 21 provided on the
`power supply line 18 with a variable capacitor.
`FIG. 7 shows a schematic configuration of a plasma
`25 processing apparatus according to the second embodiment.
`A plasma processing apparatus 30 includes a processing
`chamber 31 formed of a conductive material such as alu(cid:173)
`minum. In this processing chamber 31, an upper electrode
`32 and a lower electrode 33 are arranged in parallel with a
`30 specified interval so that they face each other. The upper
`electrode 32 is connected to a first high-frequency power
`supply 34 via a first power supply line 36 and a first
`matching circuit 37. The lower electrode 33 is connected to
`a second high-frequency power supply 35 via a second
`35 matching circuit 39. This lower electrode 33 also functions
`as a chuck top for mounting a processing object such as a
`semiconductor wafer, for example.
`The first high-frequency power supply 34 applies, say,
`60-MHz high-frequency power to the upper electrode 32.
`Plasma P is generated in an atmosphere of process gas
`supplied between the upper electrode 32 and the lower
`electrode 33.
`The second high-frequency power supply 35 applies
`2-MHz high-frequency power to the lower electrode 33 to
`45 generate a bias potential corresponding to the plasma poten(cid:173)
`tial. An ion component in the plasma is introduced to the
`surface of a semiconductor wafer W for performing, say,
`reactive ion etching (RIE).
`The first power supply line 36 is provided with a third
`50 filter circuit 40 for attenuating the second frequency power
`from the second high-frequency power supply 35. A first
`filter circuit 42 capable of varying the circuit constants is
`provided between the third filter circuit 40 on the first power
`supply line 36 and the processing chamber 31. The second
`55 power supply line 38 is provided with a second filter circuit
`41 for attenuating the first high-frequency power. The LC
`series resonant circuits with fixed circuit constants, respec(cid:173)
`tively.
`The first filter circuit 42 includes a variable capacitor 42a.
`60 This variable capacitor 42a is used to decrease the sputter
`rate by slightly adjusting the circuit constants of 2.5 µH and
`2,500 pF for optimum resonance down to the circuit con(cid:173)
`stants of 2.5 µH and 2,000 pF for less effective resonance.
`On the first power supply line 36, the third filter circuit 40
`65 is exclusively used for attenuating high frequency from the
`second high-frequency power supply 35. The first filter
`circuit 42 is exclusively used for decreasing the sputter rate.
`
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`US 6,485,602 B2
`
`8
`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.
`5 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 equiva(cid:173)
`lents.
`What is claimed is:
`1. A plasma processing apparatus for applying specified
`plasma processing to a processing object, comprising:
`
`7
`Accordingly, this second embodiment can provide effects
`similar to those for the above-mentioned first embodiment.
`The second embodiment has been explained as an
`example of the plasma processing apparatus capable of
`varying the circuit constant by providing the variable capaci(cid:173)
`tor 42a in the first filter circuit 42 installed on the power
`supply line 36 for generating high-density plasma. It is also
`possible to provide a similar effect by substituting a variable
`capacitor for the capacitor in the second filter circuit 41
`installed on the power supply line 38, for generating a bias 10
`potential.
`FIG. 8 shows a schematic configuration of a plasma
`processing apparatus according to the third embodiment.
`The mutually corresponding parts in FIGS. 8 and 1 for the 15
`first embodiment are designated by the same reference
`numerals and a detailed description is omitted for simplicity.
`This plasma processing apparatus 50 substitutes a fixed
`capacitor for a variable capacitor (C) in a first filter circuit
`51 connected to the first power supply line 16. The fixed coil 20
`is replaced by a variable coil for configuring variable
`inductance.
`This is because the similar effects are available by making
`frequency f greater than the optimum resonance point and
`shifting the resonance point to the negative side. Instead of 25
`the capacitor capacity, the inductance is varied so that the
`resonance point becomes greater. Accordingly, it is possible
`to increase the sputter rate of the plasma P by varying the
`inductance of the variable coil 51b.
`FIG. 9 shows a schematic configuration of a plasma 30
`processing apparatus according to the fourth embodiment.
`The mutually corresponding parts in FIGS. 9 and 7 for the
`second embodiment are designated by the same reference
`numerals and a detailed description is omitted for simplicity.
`A plasma processing apparatus 60 according to this
`embodiment is configured to provide a selection switch 43
`between the first filter circuit 40 and the third filter circuit 42
`according to the above-mentioned second embodiment.
`This configuration example makes processing chamber 40
`protection and throughput selectable so as to comply with
`the process conditions for various processing objects.
`Namely, a process may have little effect on the processing
`chamber in such a case that the high-frequency power
`supply generates little high-frequency power or the process- 45
`ing object is processed in a short time. In this case, the
`plasma processing apparatus selects the conventional third
`filter circuit 40 with the fixed circuit constant to give
`preference to the productivity for improved throughput. By
`contrast, a process may have a large effect on the processing 50
`chamber in such a case that the high-frequency power
`supply generates a large high-frequency power or the pro(cid:173)
`cessing object is processed in a long time. In this case, the
`plasma processing apparatus selects the first filter circuit 42
`to give preference to processing chamber protection.
`Always protecting the processing chamber's inner wall
`degrades throughput in some degree. Since the selection
`switch is provided, it is possible to determine whether to
`prioritize protection of the processing chamber's inner wall
`or improvement of the throughput.
`As in the third embodiment, the fourth embodiment can
`also provide similar effects by using the variable coil instead
`of the variable capacitor.
`Each of the above-mentioned embodiments can decrease
`the sputter rate on the wall surface of the processing 65
`chamber, suppress damage thereto, and extend the usable
`life of the processing chamber.
`
`55
`
`first and second electrodes arranged in parallel in a
`processing chamber;
`a first high-frequency power supply for applying first
`high-frequency power to said first electrode via a first
`power supply line;
`a second high-frequency power supply for applying sec(cid:173)
`ond high-frequency power to said second electrode via
`a second power supply line;
`a first filter circuit for attenuating said second high(cid:173)
`frequency power flowing through said first power sup(cid:173)
`ply line; and
`a second filter circuit for attenuating said first high(cid:173)
`frequency power flowing through said second power
`supply line,
`wherein said first filter circuit includes a variable capaci(cid:173)
`tor for varying a circuit constant in order to increase a
`resonance point from an optimum resonance point most
`attenuating said second high-frequency power and for
`decreasing a sputter rate for a wall surface of said
`processing chamber during plasma occurrence.
`2. The first filter circuit according to claim 1, wherein a
`35 resonance point most attenuating high-frequency power
`depends on frequency f[ ='hitv'(L-C)] according to a capacitor
`( capacitor capacity C) and a coil (inductance L) constituting
`a filter circuit.
`3. The second filter circuit instead of said first filter circuit
`according to claim 1, wherein there is provided a variable
`capacitor for varying a circuit constant and decreasing a
`sputter rate for a wall surface of said processing chamber
`during plasma occurrence so that a resonance point becomes
`greater than an optimum resonance point most attenuating
`said first high-frequency power.
`4. Means for varying said circuit constant according to
`claim 1, wherein a variable coil is provided instead of said
`variable capacitor to change said circuit constant by varying
`an inductance.
`5. A plasma processing apparatus for applying specified
`plasma processing to a processing object, comprising:
`first and second electrodes arranged in parallel in a
`processing chamber so that they face each other;
`a first high-frequency power supply for applying first
`high-frequency power to said first electrode via a first
`power supply line;
`a second high-frequency power supply for applying sec(cid:173)
`ond high-frequency power to said second electrode via
`a second power supply line;
`a first filter circuit for decreasing a sputter rate for a wall
`surface of said processing chamber during plasma
`occurrence by having a variable capacitor for varying a
`circuit constant so that a resonance point becomes
`greater than an optimum resonance point most attenu(cid:173)
`ating said second high-frequency power flowing
`through the first power supply line;
`
`60
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`US 6,485,602 B2
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`9
`a second filter circuit for attenuating said first high(cid:173)
`frequency power flowing through said second power
`supply line; and
`a third filter circuit for attenuating a second high(cid:173)
`frequency power flowing through said first power sup-
`ply line, wherein said third filter circuit is provided
`adjacent to said first filter circuit.
`6. The second filter circuit instead of said first filter circuit
`according to claim 5, wherein there is provided a variable
`capacitor for varying a