JP2002164329A - Plasma treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma treatment apparatus, in which the distribution of a plasma is uniform, whose degradation due to an aged deterioration is small and which can perform micromachining operations. SOLUTION: In the plasma treatment apparatus 1 which executes a plasma treatment to a substrate W to be treated, an upper electrode 21 which faces a susceptor 5 as a lower electrode is provided with an electrode support 22 and an electrode plate 23, and a cavity 62 whose dimensions are decided, in such a way that resonance is generated at the frequency of supplied high-frequency electric power and that an electric field at right angles with respect to the electrode plate 23 is generated is installed, in the central part on the side of the electrode support 23 at the boundary part between both. A shielding ring which surrounds the electrode plate 23 has a shape, whose rear surface is flush with the electrode plate 23, and it is formed of a blank which is hardly eroded by the plasma.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a plasma processing apparatus for performing plasma processing on a substrate such as a semiconductor substrate, and an electrode and a shield ring used therein.

Conventionally, for example, in a semiconductor manufacturing process, a plasma device has been used as a device for etching an insulating film on a surface of a semiconductor wafer or the like to form a contact hole, for example.

[0003] Above all, a parallel plate type plasma apparatus in which electrodes are arranged above and below the processing chamber has excellent uniformity, can process a large-diameter wafer, and has a relatively simple apparatus configuration. It has become.

In a conventional parallel plate type etching apparatus, for example, as disclosed in Japanese Patent Application No. 2000-116304, electrodes are provided on the upper and lower sides of a processing chamber so as to face each other. Is mounted on the lower electrode, an etching gas is introduced into the processing chamber, and high-frequency power is supplied to the lower electrode to generate plasma between the upper and lower electrodes, and an etchant component generated by dissociation of the etching gas causes It is configured to etch an insulating film of a semiconductor wafer.

FIG. 3 is a diagram schematically showing an upper electrode and a shield ring in Japanese Patent Application No. 2000-116304. As shown in FIG. 3, the upper electrode 121 has an electrode plate 123, an electrode support 122 located above the electrode plate 123, and a cavity 162 provided at a boundary between the two.

Further, the periphery of the upper electrode 121 is fixed to the upper part of the processing chamber of the plasma apparatus by an insulating material 125, and a shield ring 155 is arranged below the insulating material 125.

As described above, in order to meet the demands for finer processing, improved processing speed, and uniform processing, the upper electrode 12
1, a shield ring 155 protruding from the upper electrode surface to the lower electrode side is provided to confine the plasma, and further, a cavity 162 is provided at the boundary between the electrode plate 123 and the electrode support 122 to homogenize the plasma. Is being planned.

[0008]

[Problems to be solved by the invention]
000-116304, the technique disclosed in
It has been found that the projection of the shield ring protruding toward the lower electrode, which plays a role of confining the plasma, is abraded due to aging and the plasma distribution changes.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the conventional plasma apparatus, and an object of the present invention is to provide a uniform plasma distribution, a small deterioration due to aging, and a fine processing. , To provide a new and improved plasma device.

[0010]

According to the present invention, there is provided a processing chamber, a first electrode on which an object to be processed can be placed in the processing chamber, and a first electrode in the processing chamber. A second electrode disposed in opposition, a processing gas supply system capable of introducing a processing gas into the processing chamber, an exhaust system capable of evacuating the processing chamber, and supplying high-frequency power to at least one of the first and second electrodes. In a plasma processing apparatus having a high-frequency power supply system for applying a predetermined plasma process to an object to be processed into plasma by applying a process gas to plasma, the second electrode is a conductive material provided to face the first electrode. An electrode plate made of a body or a semiconductor, a conductive support provided on the surface of the electrode plate opposite to the processing chamber to support the electrode plate, and a cavity provided at the center of the support And the second electrode The enclosed plasma processing apparatus characterized by shield ring having an electrode plate in the same plane into the processing chamber side are arranged is provided.

A structure in which a hollow portion is not provided at the center of the support for supporting the electrode plate may be used. Further, it is preferable that the resistance value of the shield ring is made of a material lower than the resistance value of the electrode plate or the same material. For example, silicon or SiC can be applied to those materials.

The resistance value of the shield ring is 1 to 10Ωc.
m, the resistance value of the electrode plate can be 65-85 Ωcm. Further, the outer diameter of the electrode plate may be larger than the outer diameter of the first electrode.

According to such a configuration, the distribution of the plasma is made uniform by suppressing the electric field at the central portion from becoming strong, and the use of a shield ring flush with the electrode surface minimizes deterioration due to aging and enables fine processing. A new and improved plasma device can be provided.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
A preferred embodiment of the plasma device according to the present invention will be described in detail. In this specification and drawings,
For components having substantially the same functional configuration,
Repetitive description will be omitted by giving the same reference numerals.

(First Embodiment) FIG. 1 is a sectional view showing a configuration of a plasma apparatus 1 according to a first embodiment of the present invention. The processing chamber 2 in the plasma apparatus 1 is formed as a cylindrical processing container made of, for example, aluminum that has been subjected to anodized aluminum and is grounded.

An insulating support plate 3 made of ceramic or the like is provided at the bottom of the processing chamber 2, and a substrate to be processed, for example, a semiconductor wafer W having a diameter of 8 inches, is provided on the insulating support plate 3.
A susceptor support 4 having a substantially cylindrical shape for mounting the susceptor is provided. A susceptor 5 constituting a lower electrode is provided on the susceptor support 4, and a high-pass filter (HPF) 6 is connected to the susceptor 5.

A heat exchange chamber 7 is provided inside the susceptor support 4, and a heat exchange medium circulates from outside through a heat exchange medium introduction pipe 8 and a heat exchange medium discharge pipe 9, and the semiconductor is exchanged through the susceptor 5. The wafer W is configured to be maintained at a predetermined temperature. The temperature is automatically controlled by a temperature sensor (not shown) and a temperature control mechanism (not shown).

On the susceptor 5, an electrostatic chuck 11 for holding the semiconductor wafer W by suction is provided. The electrostatic chuck 11 has a configuration in which, for example, a conductive thin-film electrode 12 is sandwiched from above and below by a polyimide resin, and a DC power source 1 installed outside the processing chamber 2.
When a voltage of, for example, 1.5 to 1.5 kV is applied to the electrode 12, the Coulomb force causes the wafer W to be suction-held on the upper surface of the electrostatic chuck 11. Needless to say, a configuration in which the wafer W is held on the susceptor 5 by pressing the peripheral portion of the wafer W by a mechanical clamp without depending on such an electrostatic chuck may be employed.

Further, the insulating plate 3, the susceptor support 4, the susceptor 5, and the electrostatic chuck 11 are formed with a gas passage 14 for supplying, for example, He gas to the back surface of the semiconductor wafer W. The semiconductor wafer W is maintained at a predetermined temperature via a heat transfer medium such as He gas.

At the periphery on the susceptor 5, the electrostatic chuck 1
A substantially annular focus ring 15 is provided so as to surround the focus ring 1. The focus ring 15 is made of, for example, conductive silicon and has a function of effectively causing ions in the plasma to enter the semiconductor wafer W.

An upper electrode 21 is supported above the processing chamber 2 via an insulating member 25 and a shield ring 55. The upper electrode 21 includes, for example, an electrode support 22 made of aluminum whose surface is anodized, and
It has an electrode plate 23 facing in parallel with the susceptor 5 and having a large number of discharge holes 24. The susceptor 5 and the upper electrode 21 are separated, for example, by about 10 to 60 mm. Detailed configurations of the upper electrode 21 and the shield ring 55 will be described later.

The electrode support 22 is provided with a gas inlet 26 and is connected to a gas supply pipe 27. Further, it is connected to a processing gas supply source 30 via a valve 28 and a mass flow controller 29, and an etching gas and other processing gases are introduced into the processing chamber 2.

Examples of the processing gas include fluorocarbon gas (C _x F _y ) and hydrofluorocarbon gas (C
_p H _q F _r), such as, it is possible to use a gas containing a halogen element.

An exhaust pipe 31 leading to an exhaust device 35 such as a vacuum pump is connected to a lower portion of the processing chamber 2. The exhaust device 35 is provided with a vacuum pump such as a turbo molecular pump, and the inside of the processing chamber 2 is, for example, 10 mTorr to 100 mTorr.
It is possible to evacuate to an arbitrary degree of reduced pressure of 0 mTorr.

A gate valve 32 is provided on the side wall of the processing chamber 2 so that the semiconductor wafer W can be transferred between an adjacent load lock chamber (not shown) with the gate valve 32 opened. Has become.

Next, a high-frequency power supply system of the plasma apparatus 1 will be described. First, for the upper electrode 21,
Power is supplied from a first high-frequency power supply 40 that outputs high-frequency power having a frequency of, for example, 27 to 150 MHz via a matching unit 41 and a power supply rod 33. Further, a low-pass filter (LPF) 42 is connected to the upper electrode 21.

By applying such a high frequency, a high-density plasma can be formed in the processing chamber 2 in a preferable dissociated state, and plasma processing under low-pressure conditions becomes possible. In the present embodiment, as the high-frequency power supply 40, 60
MHz.

On the other hand, the susceptor 5 serving as the lower electrode is supplied with power from a high frequency power supply 50 that outputs high frequency power having a frequency of, for example, about 800 KHz to 4 MHz via a matching unit 51. . By applying a frequency in such a range, an appropriate ion action can be given without damaging the semiconductor wafer W.

Next, the configuration of the upper electrode 21 and the shield ring 55 will be described in detail. FIG. 2 is a sectional view schematically showing the upper electrode 21 and the shield ring 55.

As shown in FIG. 2, a cavity 62 is provided at the center of the electrode support base 22 provided above the electrode plate 23 so as to be in contact with the electrode plate 23. This cavity 62
The resonance occurs at the frequency of the high-frequency power supplied to the upper electrode 21 and an electric field orthogonal to the electrode plate 23 is generated therein, that is, the electrode plate of the electrode plate 23 to which the high-frequency power is supplied. The thickness from the surface is
The dimensions are determined so as to be larger than the electrode plate 23.

When resonance occurs in the cavity 62 and an electric field orthogonal to the electrode plate 23 is generated, the cavity 62
The electric field of the electrode plate 23 and the electric field of the electrode plate 23 are combined, and the electric field of the electrode plate 23 can be controlled by the electric field of the electrode plate 23 just below the cavity 62 in the electrode plate 23. Therefore, a more uniform plasma distribution can be realized.

As shown in FIG. 3, the conventional shield ring 155 is on the semiconductor wafer side in order to form a gap shorter than the distance between the upper electrode and the semiconductor wafer to obtain the effect of confining plasma. It was configured to protrude downward. In addition, it is usually made of quartz, and because it protrudes downward, it is easily cut by plasma.

For this reason, as shown in FIG. 2, the shield ring 55 according to the present embodiment has the lower portion flush with the electrode plate 23. The resistance value may be set lower than the resistance value of the electrode plate 23, and may be made of the same material as the electrode plate 23. As a material used for the electrode plate 23 and the shield ring 55, silicon can be used.

In consideration of the electric field distribution between the lower electrode and the upper electrode, the shield ring 55 and the electrode plate 23
Are 1 to 10 Ωcm and 65 to 85 Ωc, respectively.
m is appropriate.

FIG. 4 is an etching rate in a plasma apparatus using the conventional shield ring 155, and FIG.
FIG. 4 is a diagram showing an etching rate in a plasma device using the shield ring 55 according to the present embodiment.

FIGS. 4 and 5 show the average (nm / min.) Of the etching rates when processing is performed under the same conditions and for the same time except for the material and structure of the shield ring.
Are measured in two directions (X and Y directions) orthogonal to the distance (mm) from the center of the semiconductor wafer. Here, the shield ring 155 is made of quartz, and the shield ring 55 is made of silicon having a resistance value of about 2Ω.

As shown in FIGS. 4 and 5, when the conventional shield ring 155 is used, the distance from the center is 100 m.
In the range exceeding m, the etching rate clearly decreases. On the other hand, the high-frequency current flowing through the low-resistance shield ring 55 is reduced by the higher-resistance shield ring 15.
5, the plasma density in that portion is increased, and the uniformity of the plasma over the entire surface of the semiconductor wafer can be improved.

Further, according to the material and configuration of the conventional shield ring 155, it is considered that the protruding portion is constantly exposed to the plasma, is shaved, changes with time, and does not exhibit the original plasma confinement effect. It is obvious that this tendency becomes more remarkable when the processing is repeated a plurality of times.

In the present embodiment, the electrode 23
The electric field can be controlled by the upper cavity 62, and the distribution of the plasma can be kept sufficiently uniform. Therefore, by employing the shield ring 55 together, a more reliable plasma device 1 can be realized.

Conversely, by employing the shield ring 55, the plasma distribution can be kept sufficiently uniform.
A similar effect can be obtained even with a structure in which the cavity 62 is not provided in the upper part of the third embodiment. In order to further uniform the plasma distribution, the electrode plate 2
It is also useful to make the diameter of 3 larger than the diameter of the susceptor 5 as the lower electrode.

(Second Embodiment) Next, a shield ring according to a second embodiment will be described. FIG.
FIG. 7 is a schematic sectional view showing the periphery of the shield ring 255 according to the present embodiment, FIG. 7 is an enlarged view of a portion A in FIG.
Is a schematic cross-sectional view showing the periphery of the conventional shield ring 155, and FIG. 9 is an enlarged view of a portion B in FIG.

As shown in FIGS. 8 and 9, when the distance between the wafer W and the electrode plate 23 of the upper electrode is, for example, 20 mm, the conventional shield ring 155 protrudes downward, for example, by about 7 mm, and a step is formed. The distance from the surface was reduced to 13 mm.

However, when there is such a step,
As the time of exposure to the plasma increases, the surface of the shield ring 155 is consumed, and the gas pressure on the wafer W decreases. For this reason, the etching rate decreases, and the removability of the contact hole changes. As shown in FIGS. 6 and 7, the shield ring 255 is formed flush with the electrode plate 23 in order to alleviate this temporal change.

FIG. 10 is a diagram showing the rate of decrease in the etch rate due to a change with time, and FIG. 11 is a diagram showing a comparison of the amount of change in the etch rate within the wafer surface. These are the results of performing plasma processing by supplying 27,12 MHz power from the high frequency power supply for upper electrode 40 and 800 KHz from the high frequency power supply 50 for the lower electrode in the plasma processing apparatus 1 according to the first embodiment. is there.

The electrode plate 23 is made of single crystal silicon, the resistance is 1 to 10 Ω · cm, and the shield ring 155 (conventional type) and the shield ring 255 (improved type) are both made of quartz.
Insulating (-1016 Ω · cm). Other processing conditions were optimized for each shield ring.

That is, for the conventional shield ring 155, the pressure is 40 mTorr, the power supplied to the upper electrode / the power supplied to the lower electrode = 2000/1400 W, the distance between the electrode plate 23 and the wafer W is 17 mm, and the processing gas flow rate is C ₄ F _8. / A
r / O ₂ = 21/510/11 sccm, wafer center backside cooling gas pressure / wafer edge backside cooling gas pressure =
10/35 Torr, lower electrode temperature / upper electrode temperature / processing chamber side wall temperature = −20 / 30/50 ° C.

For the improved shield ring 255,
Pressure 50 mTorr, upper electrode supply power / lower electrode supply power = 2000/1400 W, interval between electrode plate 23 and wafer W = 17 mm, processing gas flow rate C ₄ F ₈ / Ar / O ₂ =
21/450/10 sccm, wafer center backside cooling gas pressure / wafer edge backside cooling gas pressure = 12/25
Torr, lower electrode temperature / upper electrode temperature / processing chamber side wall temperature = 0/30/50 ° C.

In FIG. 10, the horizontal axis represents the plasma processing time, and the vertical axis represents the rate of change of the etching rate. The decrease in the etching rate after 100 hours of the plasma processing time is as follows.
In contrast to the conventional step-type shield ring 155, which was about 8%, the use of the improved flat shield ring 255 in which the step with the electrode plate 23 was eliminated could be reduced to about 4%.

In FIG. 11, the center on the wafer W surface,
The vertical axis represents the rate of change of the etching rate in the middle part and the peripheral part after 100 hours of the plasma processing. As described above, in the improved shield ring 255, the amount of change at the central portion and the intermediate portion of the wafer is almost zero, and at the peripheral portion,
Approximately 1000 Å / min.
What changed was about 500 ° / min. And reduced.

Next, the reason why the etching rate change rate is reduced as described above will be described with reference to FIG. FIG.
FIG. 2 is a diagram showing a temporal change in pressure on a wafer. FIG.
2 (a) and (b) respectively show a conventional shield ring 1
(C) and (d) show the initial state using the improved shield ring 255 and after the plasma processing for 100 hours, respectively. The horizontal axis represents the set pressure, and the vertical axis represents the difference between the pressure measured at each position (right, top, notch, center) on the wafer and the set pressure.

The consumption of the shield ring was about 2 mm / 100 hours for both the conventional type and the improved type. However, in the conventional shield ring 155, the difference between the set pressure and the measured pressure changes before and after the processing. Also, the absolute value of the pressure difference is larger than that of the improved type.

It is considered that this is because the step of the shield ring 155 causes a pressure fluctuation. If the pressure difference differs depending on the location on the wafer, the removability of the contact hole will not be uniform, and there is a risk that the yield will deteriorate. Further, it can be seen that the change with time in the pressure causes a decrease in the etch rate and a change in the removability of the processed hole.

As described in detail above, according to the shield ring of the second embodiment, the gas pressure on the wafer is made uniform, and the gas pressure on the wafer is reduced due to the consumption of the shield ring after the plasma processing. Reduces aging and reduces the decrease in etching rate due to aging.
By improving the removability of a processing hole and its uniformity in a wafer, a high-performance film forming apparatus capable of performing finer processing can be provided.

Although the preferred embodiment of the plasma apparatus according to the present invention has been described with reference to the accompanying drawings, the present invention is not limited to this example. It is clear that a person skilled in the art can conceive various changes or modifications within the scope of the technical idea described in the claims, and those modifications naturally fall within the technical scope of the present invention. It is understood to belong.

For example, the shape of the shield ring is not limited to the example described in the present embodiment, but may be any other shape as long as the upper electrode and the lower surface are flush with each other. Although the case where a semiconductor wafer is used as a substrate to be processed and the substrate is etched is shown, the target to be processed may be another substrate such as a liquid crystal display device substrate. Other processing may be used.

[0056]

As described above, according to the present invention,
It is possible to provide a new and improved plasma apparatus in which plasma distribution is uniform, deterioration due to aging is small, and fine processing is possible.

[Brief description of the drawings]

FIG. 1 shows a plasma apparatus 1 according to an embodiment of the present invention.
It is sectional drawing which shows a structure of.

FIG. 2 is a cross-sectional view schematically showing an upper electrode 21 and a shield ring 55.

FIG. 3 is a diagram schematically showing an upper electrode and a shield ring in a conventional plasma device.

FIG. 4 is a diagram showing an etching rate in a plasma device using a conventional shield ring 155.

FIG. 5 is a diagram showing an etching rate in a plasma device using the shield ring 55 according to the present embodiment.

FIG. 6 is a schematic sectional view showing the periphery of a shield ring 255 according to the present embodiment.

FIG. 7 is an enlarged view of a portion A in FIG. 6;

FIG. 8 is a schematic sectional view showing the periphery of a conventional shield ring 155.

FIG. 9 is an enlarged view of a portion B in FIG. 8;

FIG. 10 is a diagram showing an etch rate decrease rate due to a change with time.

FIG. 11 is a diagram showing a comparison of a change amount of an etch rate in a wafer surface.

FIG. 12 is a diagram showing a change over time in pressure on a wafer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Upper electrode 22 Electrode support 23 Electrode plate 33 Power supply rod 55 Shield ring 62 Cavity

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazuya Kato FBS term in Tokyo Electron Co., Ltd. 5-3-6 Akasaka, Minato-ku, Tokyo 4G075 AA30 AA42 AA61 BC02 BC04 BC06 BD14 CA25 CA47 CA65 DA02 EA05 EB01 EB41 EC13 EC21 FB04 FB06 FC11 FC15 FC20 5F004 AA16 BA06 BB11 BB29 DA00 DA23 DA26

Claims (13)

[Claims] A processing chamber; a first electrode on which an object to be processed can be placed in the processing chamber; a second electrode opposed to the first electrode in the processing chamber; and a processing gas in the processing chamber. A processing gas supply system capable of introducing a gas; an exhaust system capable of evacuating the processing chamber; and applying a high-frequency power to at least one of the first and second electrodes to convert the processing gas into plasma to form the processing target. A high-frequency power supply system for performing predetermined plasma processing on the body; and a plasma processing apparatus having the same: the second electrode is made of a conductor or a semiconductor provided so as to face the first electrode. An electrode plate, a conductive support provided on the surface of the electrode plate opposite to the processing chamber to support the electrode plate,
A cavity provided in the center of the support; a shield ring having the same surface as the electrode plate is disposed around the second electrode in the processing chamber. A plasma processing apparatus. 2. The plasma processing apparatus according to claim 1, wherein a resistance value of the shield ring is lower than a resistance value of the electrode plate. 3. The shield ring and the electrode plate,
3. The plasma processing apparatus according to claim 2, wherein the plasma processing apparatus is made of the same material. 4. The shield ring and the electrode plate,
The plasma processing apparatus according to claim 3, wherein the plasma processing apparatus is made of silicon. 5. The resistance value of said shield ring is 1 to 1
3. The plasma processing apparatus according to claim 2, wherein the value is 0 Ωcm. 6. The electrode plate has a resistance value of 65 to 85 Ωc.
3. The plasma processing apparatus according to claim 2, wherein m is m. 7. The method of claim 1, wherein an outer diameter of the electrode plate is larger than an outer diameter of the first electrode.
7. The plasma processing apparatus according to any one of 4, 5, and 6. 8. A processing chamber; a first electrode on which an object to be processed can be placed in the processing chamber; a second electrode disposed opposite to the first electrode in the processing chamber; and a processing gas in the processing chamber. A processing gas supply system capable of introducing a gas; an exhaust system capable of evacuating the processing chamber; and applying a high-frequency power to at least one of the first and second electrodes to convert the processing gas into plasma to form the processing target. A high-frequency power supply system for performing predetermined plasma processing on the body; and a plasma processing apparatus having the same: the second electrode is made of a conductor or a semiconductor provided so as to face the first electrode. An electrode plate and a conductive support provided on the surface of the electrode plate opposite to the processing chamber to support the electrode plate; Same surface as the electrode plate A plasma processing apparatus, comprising: a shield ring having a resistance value, wherein a resistance value of the shield ring is lower than a resistance value of the electrode plate. 9. The shield ring and the electrode plate,
The plasma processing apparatus according to claim 8, wherein the plasma processing apparatus is made of the same material. 10. The plasma processing apparatus according to claim 9, wherein the shield ring and the electrode plate are made of silicon. 11. The resistance value of the shield ring is 1 to
9. The plasma processing apparatus according to claim 8, wherein the pressure is 10 Ωcm. 12. A resistance value of said electrode plate is 65-85Ω.
The plasma processing apparatus according to claim 1, wherein the diameter is cm. 13. The device according to claim 8, wherein an outer diameter of the electrode plate is larger than an outer diameter of the first electrode.
13. The plasma processing apparatus according to any one of 0, 11 and 12.