JP2003059910A - Plasma processing equipment - Google Patents

Abstract

(57) Abstract: An object of the present invention is to provide a plasma processing apparatus having an electrostatic chuck in which the etching rate does not decrease even if the resistance of an insulating member decreases. The electrostatic chuck includes a vacuum chamber (2), means for generating plasma, an electrostatic chuck (40) for attracting an object to be processed (W), and a DC voltage power supply (60). Has a pair of electrodes (48A, 48B) for applying a DC voltage to adsorb the object to be processed, and isolates the DC voltage power supply from the ground potential when the object to be processed is subjected to the plasma processing. In this state, the plasma processing apparatus is connected to the pair of electrodes, and connects the ground potential (S1, S2) to each of the pair of electrodes when the object is detached.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus, and more particularly to a plasma processing apparatus for performing processing such as etching using plasma on an object to be processed which is fixed by an electrostatic chuck method in a vacuum chamber.

[0002]

2. Description of the Related Art Dry etching using plasma,
Plasma treatments such as ashing, thin film deposition, plasma doping, and surface modification are widely used in various industrial fields including semiconductor manufacturing devices and liquid crystal display manufacturing devices.

For example, when a conductor film or an insulating film is formed on a semiconductor silicon wafer or a glass substrate of a liquid crystal display, and these are etched,
It is necessary to fix these objects to be processed to the mounting part in the vacuum chamber. An "electrostatic chuck" is often used as the fixing means.

FIG. 8 is a schematic view illustrating the structure of a mounting portion having such an electrostatic chuck.

The mounting portion shown in the figure has a mounting table 130 and an electrostatic chuck 140 provided thereon, and is appropriately arranged in a vacuum chamber (not shown) in the plasma processing apparatus. The electrostatic chuck 140 illustrated in the figure has a so-called “bipolar type” structure. An insulating member 146 made of ceramic or an organic material is fixed by a fixing means 144 on a support base 142 made of aluminum (Al) or the like. As the fixing means 144, for example, an adhesive, indium (In) solder, brazing, or the like can be used.

Inside the insulating member 146, a pair of electrodes 148A and 148B are embedded. These electrodes 1
48A and 148B are connected to a DC high-voltage power supply 160 via a power supply unit 152. In addition, the power supply unit 152
Are mounted on the mounting table 130 and the support table 142 by the insulator 150.
Insulated from. Further, a high frequency cut filter 165 or the like is appropriately provided between the high voltage power supply 160 and the electrodes 148A and 148B.

An object to be processed W such as a semiconductor wafer or a glass substrate is placed on the insulating member 146 and fixed by applying a voltage from the high voltage power source 160 to the electrodes 148A and 148B.

FIG. 9 is a schematic diagram showing the distribution of electric charges when a voltage is applied to the electrostatic chuck. That is, although the figure illustrates only one of the bipolar electrodes, for example, when a positive DC voltage is applied to the electrode 148A, the interface between the electrode 148A and the insulating member 146, the insulating member 146, and the object to be treated. Negative, positive, and negative charges are induced between the object W and the object W, respectively. As a result,
"Coulomb force" between the workpiece W and the insulating member 146
Alternatively, an attractive force called “Johnson-Rahbek force” is generated, and the workpiece W is attracted to the insulating member 146.
Even when an insulator is used as the insulating member 146, the same effect can be obtained although the suction force is reduced.

By providing such an electrostatic chuck 140 in the plasma processing apparatus, a mechanical chucking mechanism is not required, and the object W to be processed can be easily fixed even if it is detached.

In this way, with the workpiece W fixed, plasma processing can be carried out by introducing a predetermined process gas into the vacuum chamber to generate plasma. For example, plasma treatment such as dry etching or ashing can be performed by generating active species by plasma of process gas and supplying the activated species to the surface of the object W to be treated. As a process gas for forming such plasma, for example, when etching a thin film on the surface of an object to be processed, oxygen gas (O ₂ ), fluorine-based gas such as CF ₄ , NF ₃ or Cl _A gas to which a halogen-based gas such as ₂ is added can be used.

[0011]

By the way, in the plasma processing, the workpiece W is thus treated by the electrostatic chuck 1.
In many cases, high frequency power is applied to the workpiece W side while being fixed by 40. For example, in the case of the mounting portion illustrated in FIG. 8, a high frequency power supply 180 is connected to the mounting table 130 so that high frequency power can be applied. Then, by introducing a process gas into the vacuum chamber and applying high-frequency power to the mounting table 130, plasma is generated in the vacuum chamber or a high-frequency bias is applied to the object W to promote etching. You can

However, the present inventor has found that in such a high frequency bias application type plasma processing apparatus, the etching rate varies depending on the electric resistance of the insulating member 146 of the electrostatic chuck 140.

FIG. 10 is a graph illustrating the relationship between the resistivity of the insulating member 146 and the etching rate of the object W to be processed. That is, the horizontal axis of the figure represents the volume resistivity (Ωcm) of the ceramic used as the insulating member 146 in logarithm, and the vertical axis represents the etching rate of the silicon oxide film formed on the object W to be processed. .

From the figure, it can be seen that the etching rate decreases as the volume resistivity of the insulating member 146 (ceramic) decreases. That is, when the volume resistivity is less than ^{10 1 4} [Omega] cm, the etching rate begins to fall.

A similar phenomenon was observed when the thickness of the insulating member 146 above the electrodes 148A and 148B was reduced and the resistance component was reduced. Furthermore, a similar phenomenon
It has been found that the object to be processed is plasma-processed by using plasma generated by microwaves or the like, and particularly when the high-frequency bias is applied to the object W to be processed, it has been found to occur remarkably.

Insulating member 146 used for electrostatic chuck
Is desirable to have a small thickness in order to increase the adsorption force of the object to be processed W and to enhance the heat conduction to the object to be processed W. On the other hand, a material that can withstand plasma processing such as etching is used. At the same time, it is desirable that it be inexpensive and easily manufactured.

However, if the etching rate is lowered as illustrated in FIG. 10, there is a problem in that the design selection range such as the material and thickness of the insulating member 146 is narrowed.

The present invention has been made based on the recognition of the above problems, and an object thereof is a plasma processing apparatus having an electrostatic chuck which does not cause a decrease in etching rate even if the resistance of an insulating member decreases. To provide.

[0019]

In order to achieve the above object, a plasma processing apparatus of the present invention comprises a vacuum chamber capable of maintaining an atmosphere depressurized with respect to the atmosphere, and means for generating plasma in the vacuum chamber. An electrostatic chuck provided in the vacuum chamber for adsorbing an object to be plasma-processed, and a DC voltage power supply, wherein the electrostatic chuck applies a DC voltage to adsorb the object to be processed. Having a pair of electrodes to apply, when performing the plasma treatment of the object to be processed, the DC voltage power supply is in a state of being isolated from the ground potential, one of the pair of electrodes of the DC voltage power supply A positive electrode is connected, a negative electrode of the DC voltage power source is connected to the other of the pair of electrodes, and a ground potential is connected to each of the pair of electrodes when the workpiece is attached or detached. To.

According to the above construction, even when the resistance of the insulating member of the electrostatic chuck is low, it is possible to prevent the plasma power from leaking to the ground and solve the problem such as a decrease in etching rate.

Here, the means for generating the plasma is
A “microwave excitation type” including a waveguide for guiding the microwave and a transmission window for introducing the microwave into the vacuum chamber can be used.

Alternatively, the means for generating the plasma is
An “inductively coupled type” including a high-frequency power source that generates high-frequency power, a conductor antenna that propagates the high-frequency power, and a transparent window that introduces the high-frequency power from the conductor antenna into the vacuum chamber may be used. it can.

Alternatively, the means for generating the plasma is
A high-frequency power source for applying high-frequency power may be included in the mounting table on which the object to be processed is mounted.

Further, the electrostatic chuck further has an insulating member provided between the pair of electrodes and the object to be processed, and the volume resistivity of the insulating member is 10 ¹⁴ Ωc.
Even in the case of m or less, according to the present invention, it is possible to prevent the plasma power from leaking to the ground and solve the problem such as a decrease in etching rate.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to specific examples.

FIG. 1 is a schematic diagram showing a cross-sectional structure of a main part of a plasma processing apparatus according to an embodiment of the present invention.

FIG. 3 is a sectional view showing the structure of the mounting portion in more detail.

First, the overall structure will be described.
The plasma processing apparatus of the present invention is a so-called “microwave excitation type” apparatus, and has a vacuum chamber 2 in which a plasma processing chamber 10 and a plasma generation chamber 20 are provided. The vacuum chamber 2 has a gas supply port 22 for introducing a process gas, and is evacuated in the direction of arrow E by a vacuum pump (not shown). Further, in order to regulate the flow of the process gas, an exhaust rectifying plate 12 having a predetermined conductance opening is appropriately provided.

The plasma processing chamber 10 is a space for subjecting the object W to plasma processing such as etching and ashing, and an electrostatic chuck 40 is provided on the mounting table 30. The workpiece W is placed and fixed on the electrostatic chuck 40. Then, in order to cool the workpiece W during the plasma processing, a cooling medium 14 such as a fluorine-based insulating fluid is appropriately circulated.

On the other hand, in the plasma generation chamber 20, the microwave M is supplied through the waveguide 28 and the slot 2
It is introduced into the vacuum chamber 2 from the dielectric window 24 via 6. The dielectric window 24 is made of, for example, quartz, Al ₂ O ₃ , A
It is formed of a dielectric such as 1N and has a role of introducing the microwave M while maintaining the airtightness of the vacuum chamber 2.

The microwave introduced in this way is
Plasma of the process gas supplied from the gas supply port 22 is generated. Further, the generated plasma is generated by the permanent magnet 2
It is confined within a predetermined range by the magnetic field of 5. On the other hand, the high frequency power supply 80 is connected to the mounting table 30 and 100 kH
By supplying a high frequency power of about 100 MHz from z, plasma can be generated even in the vicinity of the object to be processed W, or etching by plasma can be promoted by the bias effect.

FIG. 2 is a schematic diagram showing another specific example of the plasma processing apparatus according to the embodiment of the present invention.
In this figure, elements similar to those described above with reference to FIG. 1 are marked with the same reference numerals and not described in detail.

The apparatus illustrated in FIG. 2 is of a type called a so-called "induction coupling plasma (ICP) apparatus", and an ICP antenna 27 made of a conductor is connected to the dielectric window 24. Has been done. One end of the antenna 27 is grounded, and the other end is connected to the high frequency power supply 84 via the matching unit 29.

The high frequency power having a frequency of about 2 MHz to 100 MHz supplied from the high frequency power supply 84 to the antenna 27 is introduced into the chamber 2 through the dielectric window 24,
A plasma of the process gas introduced through the gas supply port 22 is generated.

Next, the structure of the electrostatic chuck 40 provided in the plasma processing apparatus illustrated in FIGS. 1 and 2 will be described in detail with reference to FIG. The electrostatic chuck is provided on the mounting table 30 and has a “bipolar type” structure. Then, the insulating member 4 made of ceramic or an organic material is placed on the support base 42 made of aluminum (Al) or the like.
6 is fixed by the fixing means 44. Fixing means 4
For example, an adhesive, indium (In) solder, brazing, or the like can be used as 4.

Inside the insulating member 46, a pair of electrodes 4
8A and 48B are buried. These electrodes 48A,
48B is connected to the DC high-voltage power supply 60 via the power supply unit 52. The power supply unit 52 is insulated from the mounting table 30 and the support table 42 by the insulator 50. Furthermore, between the high voltage power supply 60 and the electrodes 48A, 48B,
A high frequency cut filter 65 and the like are appropriately provided.

An object to be processed W such as a semiconductor wafer or a glass substrate is placed on the insulating member 46, and the high voltage power source 6
It is fixed by applying a voltage from 0 to the electrodes 48A and 48B.

FIG. 4 is a plan perspective view of the insulating member 46 as viewed from above. That is, the power feeding portion 52 insulated by the insulator 50 is provided in the center. A pair of electrodes 48A and 48B connected to the power feeding portion 52 are provided so as to face each other, and the insulating member 46 surrounds the electrodes. In addition, such an insulating member 46 has
A hole 47 through which a lift pin penetrates to facilitate lifting and carrying and placing is provided.

The planar shape of the electrodes 48A and 48B is
The shape is not limited to that illustrated in FIG. 4, and various shapes in which a plurality of electrodes having different polarities are arranged alternately or alternately can be adopted.

In the configuration described above, the high voltage power source 60 includes the high voltage generator 60A, the switch 60B, and
60C and. The high voltage generator 60A is isolated from the ground potential. That is, the voltage can be applied in the “floating” state.

On the other hand, the switches 60B and 60C have electrodes 4
8A and 48B can be switched between the high voltage generation unit 60A and the ground potential. That is, the switch 60B connects the connection end T1 of the electrode 48A to the ground potential S1 and one pole (positive electrode or negative electrode) S2 of the high voltage generation unit 60A.
Switch between and. In addition, the switch 60C includes the electrode 4
The connection terminal T2 of 8B is switched between the other pole (negative electrode or positive electrode) S3 of the high voltage generation unit 60A and the ground potential S4.

The operation will be described. First, the object W to be processed is introduced into the vacuum chamber 2 and placed on the electrostatic chuck 40 prior to the plasma processing. Specifically, for example, the object W to be processed is transferred and placed on the electrostatic chuck 40 by a transfer unit (not shown). At this time, as illustrated in FIG. 5, the electrodes 48A and 48B are connected to the ground potentials S1 and S4, respectively.

Next, the switches 60B and 60C are switched to connect the electrodes 48A and 48B to both ends of the high voltage generator 60A, as illustrated in FIG. In this state, high voltages having opposite polarities are applied to the electrodes 48A and 48B, and the object W to be processed is adsorbed and fixed on the surface of the insulating member 46.

Thereafter, plasma is generated and a predetermined plasma treatment such as etching and ashing is performed. At this time, by applying high-frequency power from the high-frequency power source 80 to the mounting table 30, plasma is generated around the object W to be processed, or plasma processing such as etching and ashing is promoted by utilizing the high-frequency bias effect. be able to.

When the predetermined plasma treatment is completed, the plasma is stopped and the switches 60B and 60C are switched to connect the electrodes 48A and 48B to the ground potentials S1 and S4, respectively, as shown in FIG. In this state, the electric charge that attracts the object W to be processed disappears, and the adsorption action of the electrostatic chuck is eliminated.

Thereafter, the object W to be processed is taken out from the mounting table by a transporting means (not shown) or the like.

As described above, in the present invention,
Electrodes 48A and 48B of the electrostatic chuck during plasma processing
, A high voltage isolated from the ground potential is applied. In this way, by applying a high voltage to the electrodes 48A and 48B in a floating state, it is possible to prevent the etching rate from decreasing even when the resistance of the insulating member 46 is small.

FIG. 7 is a graph illustrating the relationship between the resistivity of the insulating member 46 and the etching rate of the workpiece W in the present invention. That is, the horizontal axis of the figure shows the volume resistivity (Ωcm) of the ceramic used as the insulating member 46.
Is expressed in logarithm, and the vertical axis represents the etching rate of the silicon oxide film formed on the object W to be processed. Also, in the figure,
The relationship of the etching rate in the conventional plasma processing apparatus shown in FIG. 10 is also shown.

From FIG. 7, it is understood that in the plasma processing apparatus of the present invention, the etching rate does not decrease even if the volume resistivity of the insulating member 46 (ceramic) decreases. Specifically, the volume resistivity of the insulating member 46 is 10
Even if it is less than ¹⁴ Ωcm, the etching rate does not decrease.

In the plasma processing apparatus of the present invention, the etching rate does not decrease because the power supply of the electrostatic chuck 40 is isolated from the ground potential during etching. That is, as a result of the study by the present inventor, it was found that the decrease in the etching rate as illustrated in FIG. 10 is caused by the electric power for generating the plasma leaking to the ground potential through the insulating member 46. did. That is, in the case of the conventional electrostatic chuck as illustrated in FIGS. 8 and 9, since one end of the high voltage power supply 160 is connected to the ground potential, when the resistance of the insulating member 146 becomes small, the high frequency power supply 180 High frequency power supplied is insulating member 1
It will leak to the ground level via 46. As a result, high frequency power is lost and the etching rate is reduced.

On the other hand, according to the present invention, since the object W to be processed is placed in a floating state and a high voltage is applied,
Circuits that leak high frequency power to ground are not formed. Therefore, even if the resistance of the insulating member 46 becomes small, it is possible to prevent the etching rate from decreasing.

According to the present invention, in the plasma processing apparatus as illustrated in FIG. 1 or FIG. 2, even when plasma is generated by the microwave M, the electric power for plasma generation supplied by the microwave is grounded. Leakage can be prevented. As a result, it is possible to effectively prevent a decrease in the etching rate.

Particularly, when the area of the dielectric window 24 as shown in FIG. 1 or 2 becomes large, the area of the ground is not sufficiently large with respect to the cathode in the vacuum chamber 2, so that the electrostatic chuck 40 has It is recognized that the leakage with respect to the ground potential tends to be remarkable. According to the present invention, even in such a case, by making the high-voltage power supply 60 in a floating state, it is possible to reliably prevent a leak to the ground potential.

Furthermore, from the high frequency power source 80 to the mounting table 3
Even when the high frequency power is supplied to 0, since the leak circuit of the high frequency power to the ground is not formed, the etching rate does not decrease. The present invention is particularly advantageous in that in such a case, the high frequency power supplied from the high frequency power supply 80 can be reliably prevented from leaking to the ground.

Further, according to the present invention, as the material of the insulating member 46 of the electrostatic chuck, one having a small specific resistance can be used. Furthermore, it is possible to reduce the thickness of the insulating member 46 above the electrodes 48A and 48B. As a result, the range of selection of the material of the insulating member 46 is expanded, the suction force for adsorbing the object W to be processed can be further increased, and the heat conduction to the object W to be processed can be improved.

In the case of etching using plasma, it may be desirable to provide a protective layer of fluorine resin or the like on the surface of the insulating member 46 in order to prevent damage due to etching. According to the present invention, even in such a case, it is advantageous in that the thickness of the insulating member 46 can be reduced and a sufficient suction force can be secured.

In particular, as shown in FIGS. 1 to 3, when high frequency power is applied to the mounting table 30 from the high frequency power supply 80, the radical component of the plasma is strongly attacked by the insulating member 46. It is easily damaged. Even in such a case, according to the present invention, it is advantageous in that the attraction force of the object to be processed W can be secured by applying the coating of the fluorine resin and forming the insulating member 46 thin. Is.

The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples.

For example, in the present invention, the positional relationship between the plasma generating chamber and the plasma processing chamber, and the specific structures of the plasma generating chamber and the plasma processing chamber, can be changed by those skilled in the art as long as those skilled in the art can obtain the function and effect of the present invention. Included in the range.

More specifically, for example, a microwave waveguide for transmitting microwaves and an ICP antenna are
It does not necessarily have to be provided above the vacuum chamber 2, and a configuration provided on the side surface or below the vacuum chamber 2 is also included in the scope of the present invention.

Further, regarding the arrangement relationship, shape, or size relationship of each element such as the vacuum chamber 2, the microwave waveguide 28, the antenna 27, and the gas supply port 22,
A configuration in which those skilled in the art can appropriately change and obtain the operation and effect of the present invention is included in the scope of the present invention.

Furthermore, in the specific example described above,
Although only the main configuration of the vacuum chamber has been described, the present invention can be applied to all plasma processing apparatuses having such a vacuum chamber, for example, an etching apparatus, an ashing apparatus, a thin film deposition apparatus, a surface processing apparatus, a plasma. Any plasma processing apparatus realized as a doping apparatus or the like is included in the scope of the present invention.

[0063]

As described in detail above, according to the present invention,
When the object to be processed is treated with plasma, the resistance of the insulating member of the electrostatic chuck is low by keeping the DC voltage power supply isolated from the ground potential and connecting it to the electrode of the electrostatic chuck. Also in this case, plasma power can be prevented from leaking to the ground, and problems such as a decrease in etching rate can be solved.

As a result, the range of selection of the material for the insulating member is expanded, and the thickness can be reduced to enhance the suction force.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of a main part of a plasma processing apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing another specific example of the plasma processing apparatus according to the embodiment of the present invention.

3 is a cross-sectional view showing the structure of a mounting portion of the plasma processing apparatus of FIG. 1 in more detail.

FIG. 4 is a plan perspective view of an insulating member 46 viewed from above.

FIG. 5 shows electrodes 48A and 48B connected to ground potential S1 and
It is a schematic diagram showing the state connected to S4.

FIG. 6 shows electrodes 48A and 48B connected to a high voltage generator 6 respectively.
It is a schematic diagram showing the state connected with both ends of 0A.

FIG. 7 is a graph illustrating the relationship between the resistivity of the insulating member 46 and the etching rate of the workpiece W according to the present invention.

FIG. 8 is a schematic view illustrating the structure of a mounting portion having an electrostatic chuck in a conventional plasma processing apparatus.

FIG. 9 is a schematic diagram showing the distribution of charges when a voltage is applied to the electrostatic chuck.

10 is a graph illustrating the relationship between the resistivity of the insulating member 146 and the etching rate of the object to be processed W. FIG.

[Explanation of symbols]

2 vacuum chamber 10 Plasma processing chamber 12 Exhaust straightening plate 14 Cooling medium 20 Plasma generation chamber 22 Gas supply port 24 Dielectric window 25 permanent magnets 26 slots 27 antenna 28 microwave waveguide 29 Matching device 30, 130 Placement table 40, 140 electrostatic chuck 42, 142 support 44, 144 fixing means 46,146 Insulating member 48A, 48B, 148A, 148B electrodes 50, 150 insulator 52, 152 power supply unit 60,160 High voltage power supply 60A high voltage generator 60B, 60C switch 65 high frequency cut filter 80, 84 high frequency power supply M microwave W to be processed

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05H 1/46 C23C 16/458 // C23C 16/458 H01L 21/302 BF term (reference) 4G075 AA24 AA30 BC01 BC06 CA25 CA26 CA42 CA65 DA02 EB01 EC21 EC30 FB02 FB04 FB06 FC15 4K030 CA04 CA06 DA04 FA01 FA04 GA02 5F004 BA20 BB07 BB11 BB14 BB22 BD01 DA01 DA04 DA17 DA26 5F031 HA19 MA28 MA32

Claims (5)

[Claims] 1. A vacuum chamber capable of maintaining an atmosphere decompressed with respect to the atmosphere, means for generating plasma in the vacuum chamber, and an object to be processed which is provided in the vacuum chamber and to be plasma-processed. An electrostatic chuck and a DC voltage power supply are provided, wherein the electrostatic chuck has a pair of electrodes for applying a DC voltage to attract the object to be processed, and when the object to be processed is plasma-treated. The DC voltage power supply is isolated from the ground potential, the positive electrode of the DC voltage power supply is connected to any one of the pair of electrodes, and the DC voltage power supply is connected to the other of the pair of electrodes. A plasma processing apparatus, wherein a negative electrode is connected, and a ground potential is connected to each of the pair of electrodes when the object to be processed is attached or detached. 2. The means for generating plasma includes a waveguide for guiding microwaves and a transmission window for introducing the microwaves into the vacuum chamber. Plasma processing equipment. 3. The high-frequency power source for generating high-frequency power, the conductor antenna for propagating the high-frequency power, and the transparent window for introducing the high-frequency power from the conductor antenna into the vacuum chamber. The plasma processing apparatus according to claim 1, further comprising: 4. The plasma processing apparatus according to claim 1, further comprising a high frequency power source for applying high frequency power to a mounting table on which the object to be processed is mounted. 5. The electrostatic chuck further has an insulating member provided between the pair of electrodes and the object to be processed, and the volume resistivity of the insulating member is 10 ¹⁴ Ωcm or less. It exists, The plasma processing apparatus of any one of Claims 1-4 characterized by the above-mentioned.