JP2004047511A - Method for releasing, method for processing, electrostatic attracting device, and treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for releasing which can rapidly and stably release a material to be attracted to be attracted by an electrostatic chuck, and to provide a method for processing, an electrostatic attracting device and a treatment apparatus. <P>SOLUTION: When residual charge of a wafer, attracted to the electrostatic chuck, is removed by using a plasma of an inert gas, a destaticizing voltage V<SB>plasma</SB>is applied to a chuck electrode. The V<SB>plasma</SB>corresponds to a self-bias potential V<SB>dc</SB>of the wafer at plasma application time. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
1. Field of the Invention The present invention relates to a method for removing a workpiece to be held by electrostatic force, a processing method, an electrostatic suction apparatus, and a processing apparatus.
[0002]
[Prior art]
2. Description of the Related Art In a manufacturing process of a semiconductor device, a liquid crystal display device and the like, an electrostatic chuck is used as a structure for holding a substrate to be processed such as a semiconductor wafer at a predetermined position. The electrostatic chuck sucks and holds the substrate using electrostatic force (Coulomb force). Since the electrostatic chuck can be used even in a vacuum, it is suitably used for plasma processing such as plasma etching.
[0003]
The electrostatic chuck includes a dielectric and an electrode. The dielectric is made of an insulating material such as ceramic or resin. The substrate is mounted on a mounting surface formed on a dielectric, and is attracted by electrostatic force as described later. Further, the electrode is embedded inside the dielectric. The electrodes are formed, for example, in a plate shape, and are respectively arranged so as to face the substrate via a dielectric.
[0004]
Usually, a negative DC voltage is applied to the electrodes. Due to the application of the DC voltage, charges having a polarity opposite to the polarity of the applied voltage are induced on the surface of the dielectric material overlapping the electrodes. Due to the charge induced on the dielectric surface, a charge of the opposite polarity is induced on the back surface of the substrate. As a result, an electrostatic force is generated between the back surface of the substrate and the mounting surface of the dielectric, and the substrate is suction-held on the dielectric surface.
[0005]
[Problems to be solved by the invention]
The method and apparatus for separating a substrate using the electrostatic chuck have the following problems.
(1) Attraction to the electrostatic chuck is released by stopping the application of the voltage to the electrode. However, even after the application of the voltage is stopped, electric charges remain on the surfaces of the substrate and the dielectric. Such a residual charge forms a so-called residual attraction force between the substrate and the electrostatic chuck. The detachment of the substrate from the electrostatic chuck is performed, for example, by raising a lift pin that penetrates the electrostatic chuck. If the residual suction force is greater than the lifting pressure of the lift pins, the substrate may be spattered, warped, or failed in detachment at the time of detachment.
[0006]
For this reason, it is necessary to remove the residual charge (discharge) immediately after stopping the application of the DC voltage. As such a static elimination method, there is a method of exposing a dielectric and a substrate to plasma of an inert gas such as an argon gas to release residual charges through the plasma. In such a plasma static elimination method, the substrate is detached from the dielectric by raising the lift pins at a timing at which the residual charge is reduced to a predetermined degree due to the exposure to the plasma, or at a timing expected to decrease.
[0007]
FIG. 14 schematically shows how the residual attraction force changes during plasma static elimination. As shown in FIG. 14, the chuck voltage V _esc Is applied, the substrate has a force f ₀ Is adsorbed on the dielectric. Thereafter, the generation of plasma is stopped, and at the same time, the timing t _off Chuck voltage V _esc Is stopped. At this time, a plasma of a neutralizing gas such as an inert gas is generated. Charges charged on the substrate are removed by ions or the like in the plasma. The residual charge is reduced, and the attracting force f is a force f capable of stably releasing the substrate. _safe Timing t when ₀ Then, the generation of the static elimination plasma is stopped, and the substrate is separated.
[0008]
Since the substrate is exposed to the plasma during the neutralization period, the substrate is charged by electrons and the like in the plasma, and as a result, the negative self-bias voltage V _dc Occurs. For this reason, in the state where the plasma is applied, the substrate always has the self-bias voltage V _dc Force f based on ₁ Works. From this, as shown in the figure, at the time of plasma static elimination, the adsorption force f becomes f ₁ Decrease asymptotically to
[0009]
If the self-bias voltage V _dc Adsorption force f based on ₁ If the static elimination proceeds at the same speed as that of the plasma static elimination, the attraction force f decreases so as to gradually approach f = 0. At this time, the suction force f is f _safe Timing t ₀ 'Is t ₀ Substantially faster than. As described above, in static elimination using plasma, the self-bias voltage V _dc As a result, the static elimination speed is reduced. For this reason, the substrate may be exposed to the plasma for a long time, which may have an undesirable effect on the elements of the substrate. Further, since it takes a long time to remove static electricity, the throughput is reduced.
[0010]
As described above, according to the conventional method for removing static electricity from the electrostatically chucked substrate, a sufficiently high static removal rate cannot be obtained due to the self-bias voltage generated on the substrate by the plasma, and the rapid removal of the substrate is not sufficient. It was not what was planned.
[0011]
(2) Also, as shown in FIG. _esc ) Is applied to the ground potential at once. In this case, since the potential difference between the substrate and the electrode fluctuates instantaneously, there is a possibility that an element formed on the substrate has an undesirable effect. As described above, in the conventional method of detaching the substrate, in which the electrode is dropped from the chuck potential to the ground potential at once, there is a possibility that the device of the substrate may be damaged when the application of the chuck voltage is stopped.
[0012]
(3) The lift pins for lifting the substrate are usually made of a plasma-resistant insulator such as alumina. When the lift pins are made of a conductive material and, for example, one end thereof is grounded, the charge remaining on the back surface of the substrate can be removed, and the charge removal speed can be improved.
[0013]
However, if the lift pins are made of a conductive material, for example, aluminum, they cannot be used under high temperature process conditions. In addition, the SUS system is liable to generate metal contamination by contact with fluorine radicals suitably used as a dry cleaning gas. As described above, the conventional lift pins cannot improve the static elimination speed without deteriorating the processing reliability.
[0014]
In view of the above circumstances, an object of the present invention is to provide a separation method, a processing method, an electrostatic suction apparatus, and a processing apparatus capable of quickly and stably releasing an object to be suctioned onto an electrostatic chuck. .
Another object of the present invention is to provide a separation method, a processing method, and a processing apparatus capable of separating an object to be suctioned onto an electrostatic chuck without damaging the object.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, a detachment method according to a first aspect of the present invention includes:
A method for detaching an object to be adsorbed, which is placed on a dielectric containing an electrode and is applied to the electrode by application of a DC voltage having a predetermined polarity and is electrostatically adsorbed to the dielectric by an electrostatic force, is separated from the dielectric. ,
Stopping the application of the DC voltage to the electrode,
Exposing the object to be adsorbed to plasma for static elimination,
A voltage application step of applying a DC voltage having the same polarity as a self-bias voltage generated on the object to be adsorbed to the electrode by exposure to the plasma,
It is characterized by having.
[0016]
In the above method, it is preferable that the magnitude of the DC voltage is substantially equal to or smaller than the self-bias voltage.
[0017]
In the above method, for example, the plasma is formed by applying a high-frequency voltage to a pair of plate electrodes,
The DC voltage is set to, for example, substantially the same amplitude as the high-frequency voltage.
[0018]
The method may further include a self-bias voltage measuring step of measuring the self-bias voltage,
In the voltage applying step, the DC voltage corresponding to the self-bias voltage measured in the self-bias voltage measuring step may be applied to the electrode.
[0019]
In the above method, the voltage applying step may further include a step of superimposing and applying an attenuated alternating voltage to the DC voltage.
[0020]
To achieve the above object, a processing method according to a second aspect of the present invention includes:
A step of placing the object to be processed on a dielectric material containing the electrodes,
A step of applying a DC voltage to the electrode to cause the object to be processed to be attracted to the dielectric by electrostatic force;
Performing a predetermined process on the object to be processed;
After the end of the process, stopping the application of the DC voltage to the electrode,
Exposing the object to be treated to plasma for static elimination,
A voltage application step of applying a DC voltage having the same polarity as a self-bias voltage generated in the object to be processed by exposure to the plasma to the electrode,
A step of separating the object to be processed, which has been neutralized by exposure to the plasma, from the dielectric,
It is characterized by having.
[0021]
In the above method, it is preferable that the magnitude of the DC voltage is substantially equal to or smaller than the self-bias voltage.
[0022]
In the above method, the plasma is formed, for example, by applying a high-frequency voltage to a pair of plate electrodes,
The DC voltage is set to, for example, substantially the same magnitude as the amplitude of the high-frequency voltage.
[0023]
The method may further include a self-bias voltage measuring step of measuring the self-bias voltage,
In the voltage applying step, for example, the DC voltage corresponding to the self-bias voltage measured in the self-bias voltage measuring step is applied to the electrode.
[0024]
The method may further include the step of superimposing and applying an attenuated alternating voltage to the DC voltage.
[0025]
In order to achieve the above object, the detachment method according to the third aspect of the present invention comprises:
A detachment method in which an object to be adsorbed, which is placed on a dielectric containing an electrode and is adhered to the dielectric by electrostatic force by application of a predetermined DC voltage to the electrode, is detached from the dielectric,
Stopping the application of the predetermined DC voltage to the electrode;
A step of applying a DC voltage of the same polarity, which is smaller than the predetermined DC voltage, to the electrode,
A step of setting the electrode to a reference potential after applying the DC voltage of the same polarity, which is smaller than the predetermined DC voltage, to the electrode,
After setting the electrode to the reference potential, a step of releasing the object to be adsorbed,
It is characterized by having.
[0026]
To achieve the above object, a processing method according to a fourth aspect of the present invention includes:
A step of placing the object to be processed on a dielectric material containing the electrodes,
A step of applying a first DC voltage to the electrode to cause the object to be processed to be attracted to the dielectric by electrostatic force;
Performing a predetermined process on the object to be processed on the dielectric,
Applying a second DC voltage having the same polarity, which is smaller than the first DC voltage, to the electrode after the end of the processing;
After stopping the application of the second DC voltage, setting the electrode to a reference potential;
After setting the electrode to the reference potential, a step of releasing the object to be adsorbed,
It is characterized by having.
[0027]
To achieve the above object, a processing apparatus according to a fifth aspect of the present invention includes:
A chamber in which predetermined processing is performed on the object to be processed,
A dielectric provided in the chamber, including an electrode, and applying a direct current voltage for adsorption to the electrode, the dielectric to which the object to be processed is adsorbed;
Gas supply means for supplying a gas for static elimination into the chamber;
Plasma generation means for generating a plasma of the gas in the chamber;
Voltage switching for switching a voltage applied to the electrode between the DC voltage for adsorption and a DC voltage for static elimination having the same polarity as a self-bias voltage generated in the object to be processed by exposure to the plasma. Means,
A control unit for exposing the object to be processed to the plasma generated by the plasma generation unit, and applying the DC voltage for static elimination to the electrode by the voltage switching unit,
It is characterized by having.
[0028]
In the above configuration, it is desirable that the magnitude of the DC voltage is substantially equal to or smaller than the self-bias voltage.
[0029]
To achieve the above object, a processing apparatus according to a sixth aspect of the present invention includes:
A chamber in which predetermined processing is performed on the object to be processed,
A dielectric provided in the chamber, including an electrode, and a target to be processed is attracted by electrostatic force by application of a first DC voltage to the electrode;
Voltage switching means for switching a voltage applied to the electrode between the first DC voltage, a second DC voltage having the same polarity, which is smaller than the first DC voltage, and a reference voltage;
After switching the voltage applied to the electrode from the first DC voltage to the second DC voltage by the voltage switching means, the voltage is switched to a reference voltage, and the workpiece is separated from the dielectric. Means,
It is characterized by having.
[0030]
In order to achieve the above object, an electrostatic suction device according to a seventh aspect of the present invention includes:
A dielectric which comprises an electrode therein and which applies a DC voltage to the electrode to adsorb the object to be adsorbed on one surface by electrostatic force;
The dielectric is provided so as to go up and down through the one surface, and separates the adsorbed object from the one surface in a state of being in contact with the adsorbed object. At least the surface is made of a material containing nickel. Separation means;
It is characterized by having.
[0031]
In the above configuration, it is preferable that the separation unit is set to a reference potential.
[0032]
To achieve the above object, a processing apparatus according to an eighth aspect of the present invention includes:
A chamber in which predetermined processing is performed on the object to be processed,
Provided in the chamber, provided with an electrode inside, by applying a DC voltage to the electrode, the dielectric to attract the object to be processed on one surface by electrostatic force,
The dielectric is provided so as to go up and down through the one surface, and separates the processing object from the one surface in a state of being in contact with the processing object. At least the surface is formed of a material including nickel. Separation means;
It is characterized by having.
[0033]
In the above configuration, it is preferable that the separation unit is set to a reference potential.
[0034]
The processing apparatus further includes a gas supply unit configured to supply a processing gas into the chamber.
Plasma generating means for generating a plasma of the gas in the chamber;
May be provided.
[0035]
BEST MODE FOR CARRYING OUT THE INVENTION
(First Embodiment)
Hereinafter, a plasma processing apparatus according to a first embodiment of the present invention will be described with reference to the drawings. The first embodiment is an example in which the present invention is applied to a plasma etching apparatus for performing plasma etching on a semiconductor wafer (hereinafter, wafer W) as a processing target.
[0036]
FIG. 1 shows a configuration of a plasma processing apparatus 11 according to the first embodiment. A series of operations performed by the plasma processing apparatus 11 shown in FIG.
[0037]
As shown in FIG. 1, the plasma processing apparatus 11 according to the first embodiment includes a substantially cylindrical chamber 12. The chamber 12 is made of anodized aluminum or the like. The chamber 12 is grounded.
[0038]
An exhaust pipe 13 is connected to a lower part of the chamber 12. The exhaust pipe 13 is connected to a pump that can be evacuated, such as a turbo molecular pump, and the pressure in the chamber 12 can be reduced to about several Pa.
[0039]
At the bottom of the chamber 12, a support plate 14 made of an insulator such as ceramic is provided. A substantially cylindrical susceptor 15 is provided on the support plate 14. The susceptor 15 functions as a mounting table for the wafer W and as a lower electrode for plasma generation, as described later.
[0040]
The susceptor 15 is made of aluminum or the like whose surface is anodized. FIG. 2 is an enlarged view of the susceptor 15 and its peripheral portion. As shown in FIG. 2, the susceptor 15 is formed in a substantially cylindrical shape. The upper surface of the susceptor 15 main body is formed flat.
[0041]
A coolant channel 16 is formed inside the susceptor 15. A chiller (refrigerant) can flow through the refrigerant flow path 16, and adjusts the susceptor 15 and its vicinity to a predetermined temperature. Further, a through hole 17 penetrating vertically through the susceptor 15 is provided substantially in the center of the susceptor 15.
[0042]
On the susceptor 15, a heater layer 18 is provided. The heater layer 18 is composed of, for example, a flat insulator layer in which a resistor is embedded. The insulator layer is made of, for example, a ceramic such as aluminum oxide and aluminum nitride. The wafer W placed on the susceptor 15 is heated to a predetermined temperature by the heater layer 18.
[0043]
A flat plate-shaped electrostatic chuck 19 is provided on the heater layer 18. The upper surface of the electrostatic chuck 19 forms a mounting surface of the wafer W. Further, as described later, the electrostatic chuck 19 attracts and holds the placed wafer W by electrostatic force.
[0044]
In the susceptor 15 and the heater layer 18, for example, a flow path (not shown) of a heat transfer gas such as helium gas is formed. By supplying the heat transfer gas to the back surface of the wafer W held on the electrostatic chuck 19, a gas film is formed between the back surface of the wafer W and the upper surface of the electrostatic chuck 19. Thereby, heat transfer between the wafer W and the electrostatic chuck 19 becomes uniform, and heat conduction efficiency is improved.
[0045]
The heater layer 18 and the electrostatic chuck 19 are formed smaller in diameter than the susceptor 15. An annular focus ring surrounding the heater layer 18 and the electrostatic chuck 19 is provided on the periphery of the upper surface of the susceptor 15. The focus ring includes an inner focus ring 20a and an outer focus ring 20b.
[0046]
The inner focus ring 20a is made of a conductive material such as single crystal silicon. The inner focus ring 20a has substantially the same inner diameter as the outer diameter of the electrostatic chuck 19 and surrounds the outer periphery thereof. The inner focus ring 20a has a function of effectively causing ions in the plasma to be incident on the wafer W.
[0047]
The outer focus ring 20b is made of an insulating material such as quartz. The outer focus ring 20b has substantially the same inner diameter as the outer diameter of the inner focus ring 20a, and surrounds the outer circumference. The outer focus ring 20b suppresses the diffusion of the plasma above the susceptor 15.
[0048]
Further, the susceptor 15, the heater layer 18, and the electrostatic chuck 19 are provided with lift pin holes 21 penetrating therethrough. For example, three lift pin holes 21 are provided, and a lift pin 22 can advance and retreat inside each of them.
[0049]
The lift pins 22 are made of a plasma-resistant insulating material such as alumina and nickel. The plurality of lift pins 22 are fixed by a ring-shaped pointing member 23, and are configured to be integrally lifted and lowered by a cylinder 24. The lift pins 22 are driven to protrude from the electrostatic chuck 19 and to be buried. By the lifting and lowering operation of the lift pins 22, the wafer W is placed on the electrostatic chuck 19 and detached from the placement surface, as shown in FIG.
[0050]
Here, the electrostatic chuck 19 will be described in detail with reference to FIG. The electrostatic chuck 19 includes a dielectric 25 and electrodes 26a and 26b.
[0051]
The dielectric 25 is made of a ceramic such as aluminum oxide or aluminum nitride, or a resin such as polyimide. The dielectric 25 is formed, for example, in a disk shape with a thickness of about 4 mm. One surface (lower surface) of the dielectric 25 is joined to the upper surface of the heater layer 18. The other surface (upper surface) of the dielectric 25 forms a mounting surface of the wafer W.
[0052]
The pair of electrodes 26 a and 26 b are buried inside the dielectric 25. The electrodes 26a and 26b are made of, for example, a thin plate of a refractory metal such as tungsten. The electrodes 26a and 26b are each formed in a substantially semicircular shape, for example, as shown in FIG. Returning to FIG. 2, the pair of electrodes 26 a and 26 b are connected to one ends of power supply lines 27 a and 27 b passing through the through hole 17, respectively. The other ends of the power supply lines 27a and 27b are drawn out through the through holes 17 and are connected to a power supply unit 28.
[0053]
The power supply unit 28 includes first and second DC power supplies 29a and 29b, a third DC power supply 30, a power supply switch 31, and a polarity switch 32. The power supply unit 28 is connected to the control device 100.
[0054]
The first and second DC power supplies 29a and 29b supply a chuck voltage (± V) for electrostatically attracting the wafer W to the electrostatic chuck 19, as described later. _esc ) Is applied to the electrodes 26a and 26b. The first and second DC power supplies 29a and 29b respectively supply positive or negative DC power, for example, DC power of 1 kV to 2 kV in magnitude.
[0055]
In addition, the third DC power supply 30 supplies a self-bias voltage (V _dc ) (V) _plasma ) Is applied to the electrodes 26a and 26b. Here, the static elimination voltage V _plasma Is the chuck voltage V _esc Smaller than | V _esc |> | V _plasma |). Also, the static elimination voltage V _plasma Is the self-bias voltage V _dc Approximately equal to (V _dc ≒ V _plasma ) Is desirable, but the self-bias voltage V _dc Voltage may be smaller than (| V _dc |> | V _plasma |).
[0056]
The power supply switch 31 applies 1) the output voltage of the first and second DC power supplies 29a and 29b, 2) the output voltage of the third applied power supply 30, or 3) the application of the ground voltage to the power supply lines 27a and 27b. Switch.
[0057]
When the power supply switch 31 is connected to the first and second DC power supplies 29a and 29b, both of the pair of electrodes 26a and 26b have the same DC voltage (chuck voltage V _esc ) Is applied. When a DC voltage is applied to the pair of electrodes 26a and 26b, positive and negative charges are induced on the surface of the dielectric 25 near the electrodes 26a and 26b, respectively. These charges induce charges of opposite polarities on the mounting surface of the wafer W mounted on the dielectric 25, respectively. Thereby, an electrostatic force (Coulomb force) is formed between the front surface of the dielectric 25 and the back surface of the wafer W, and the wafer W is electrostatically attracted to the surface of the dielectric 25.
[0058]
When the power supply switch 31 connects the power supply lines 27a and 27b to the third DC power supply 30, the electrodes 26a and 26b apply a neutralization voltage (V) to be described later. _plasma ) Is applied. In other cases, the power supply switch 31 grounds the electrodes 26a and 26b by, for example, a frame ground.
[0059]
The polarity switching switch 32 switches the connection between the power supply switches 31 and the power supply lines 27a and 27b connected to the pair of electrodes 26a and 26b, respectively. This switches the connection between the electrodes 26a, 26b and the first and second DC power supplies 29a, 29b, and simultaneously switches the polarity of the DC voltage applied to the pair of electrodes 26a, 26b. The polarity switch 32 switches the polarity of the voltage applied to the electrodes 26a and 26b, for example, every time one wafer W is processed. Thereby, the accumulation of the residual charges in the dielectric 25 is reduced.
[0060]
Returning to FIG. 1, an upper electrode 33 is provided on the upper part of the chamber 12. The upper electrode 33 is supported in the chamber 12 by an insulating support 34 made of an insulating material. The upper electrode 33 includes an electrode support 35, a diffusion member 36, and an electrode plate 37.
[0061]
The electrode support 35 is made of a conductor such as aluminum. A coolant passage 16 (not shown) is formed inside the electrode support 35 as temperature control means, and the electrode support 35 and its surroundings are maintained at a predetermined temperature.
[0062]
The diffusion member 36 is configured to form a hollow inside the electrode support 35. The diffusion member 36 is connected to the gas supply pipe 38, and the processing gas supplied from the gas supply pipe 38 is diffused by the diffusion member 36. As the processing gas, an etching gas and other gases, for example, carbon tetrafluoride and nitrogen are used. Note that a configuration in which various gases are mixed from a plurality of gas supply pipes or supplied alone may be employed.
[0063]
The electrode plate 37 is formed of a disk-shaped member made of silicon, silicon carbide, or the like. The electrode plate 37 constitutes the lower surface of the upper electrode 33 and is arranged so as to face the wafer W mounted on the susceptor 15 (electrostatic chuck 19). The electrode plate 37 is locked at its peripheral edge to the electrode support 35 by a screw (not shown). This screwed portion is covered with an annular shield ring 39 made of an insulating material such as ceramic or fluororesin.
[0064]
A large number of gas holes 40 are provided in the electrode plate 37. The gas hole 40 communicates with a hollow portion formed by the diffusion member 36. The processing gas diffused by the diffusion member 36 is uniformly discharged from the many gas holes 40 into a space in the chamber 12, particularly, a space above the wafer W.
[0065]
The electrode plate 37 is connected to a high-frequency power supply 42 via a matching unit 41. A high frequency power of 1 MHz or higher, for example, 27.12 MHz, is applied to the electrode plate 37 of the upper electrode 33.
[0066]
On the other hand, a high frequency power supply 44 is connected to the susceptor 15 constituting the lower electrode via a matching unit 43. The susceptor 15 is applied with high-frequency power having a frequency of about several hundred kHz or more, for example, 800 kHz.
[0067]
By applying high-frequency power to the upper electrode 33 and the lower electrode, a high-frequency electric field is formed between them. In the plasma space thus formed, the processing gas discharged from the gas holes 40 of the electrode plate 37 is in a plasma state. The surface of the wafer W is etched by the etching active species (such as ions) generated in the plasma.
[0068]
A load lock chamber 46 is provided on the side of the chamber 12 via a gate valve 45. The load lock chamber 46 functions as a transfer port for loading the wafer W into and out of the chamber 12. A transfer mechanism 47 such as a transfer arm for transferring the wafer W between the chamber 12 and the load lock chamber 46 is provided in the load lock chamber 46.
[0069]
Hereinafter, the etching operation of the plasma processing apparatus 11 having the above configuration will be described. Here, a case where a silicon oxide film formed on a silicon wafer W is etched will be described. FIG. 5 shows an example of a timing chart of the etching process. The operation described below is an example, and any operation may be used as long as a similar result is obtained.
[0070]
First, the gate valve 45 is opened, and the wafer W is carried into the chamber 12 from the load lock chamber 46 by the transfer mechanism 47. At this time, the lift pins 22 are at the raised position and protrude from the surface of the electrostatic chuck 19. The transfer mechanism 47 places the wafer W on the lift pins 22. Thereafter, the transport mechanism 47 is retracted outside the chamber 12, and the gate valve 45 is closed.
[0071]
The control device 100 drives the cylinder 24 to lower the lift pins 22. When the lift pins 22 are buried in the electrostatic chuck 19, the wafer W is placed on the surface of the electrostatic chuck 19.
[0072]
Further, the control device 100 operates the vacuum pump to set the inside of the chamber 12 to a predetermined degree of vacuum, for example, a pressure of about 0.001 Pa (0.1 mTorr).
[0073]
At this time, the control device 100 uses the power supply switch 31 to connect the power supply lines 27a and 27b to the first and second DC power supplies 29a and 29b. As a result, a pair of electrodes 26a and 26b of the electrostatic chuck 19 have a DC voltage (chuck voltage V) having different polarities, for example, a magnitude of 1 kV to 2 kV, respectively. _esc ) Is applied. Thus, the wafer W is attracted to the surface of the electrostatic chuck 19 by the electrostatic force as described above.
[0074]
The control device 100 sets the CF from the gas supply pipe 38 into the chamber 12. ₄ A gas is introduced, and the inside of the chamber 12 is set to an etching pressure, for example, 2 Pa (20 mTorr). Thereafter, a high frequency power of, for example, a frequency of 27.12 MHz and a power of 2 kW is supplied to the upper electrode 33. The susceptor 15 as a lower electrode is supplied with high-frequency power having a frequency of 800 kHz and a power of 1 kW, for example.
[0075]
By the supply of the high-frequency power, a plasma of the above gas is generated between the upper electrode 33 and the susceptor 15. The etching active species in the gas plasma impinges on the surface of the wafer W placed on the susceptor 15 (electrostatic chuck 19), and etches the silicon oxide film on the surface of the wafer W. After a predetermined time, the control device 100 stops supplying the etching gas and stops applying the high-frequency voltage to the upper electrode 33 and the susceptor 15. At this time, the etching process ends.
[0076]
In this state, electric charges remain on the wafer W and the dielectric 25, and the control device 100 subsequently performs a charge removal process. First, the control device 100 connects the power supply lines 27 a and 27 b to the third DC power supply 30 by the power supply switch 31. As a result, the electrodes 26a and 26b are connected to the neutralization voltage V _plasma Is applied.
[0077]
After the etching process, the control device 100 starts supply of an inert gas, for example, oxygen, into the chamber 12 and raises the pressure in the chamber 12 to a pressure suitable for static elimination, for example, 9 Pa to 10 Pa (70 mTorr to 70 Pa). 80 mTorr).
[0078]
Next, the control device 100 applies a high-frequency voltage for static elimination to the upper electrode 33. At this time, the minimum required high-frequency power capable of generating plasma is applied to the upper electrode 33.
[0079]
By supplying the high-frequency power, a plasma of an inert gas (static plasma) is generated in the chamber 12. The electric charge charged on the wafer W is gradually removed by the ions in the plasma of the inert gas. At this time, the self-bias voltage V is applied to the wafer W exposed to the plasma. _dc Has occurred.
[0080]
During the charge removal processing, the electrodes 26a and 26b are supplied with the self-bias voltage V. _dc , And a neutralization voltage of substantially the same polarity (V _plasma ) Is applied. This static elimination voltage V _plasma Is the self-bias voltage V of the wafer W during plasma exposure. _dc Is obtained by an experiment or the like, and is a preset value. Also, for example, V _plasma Is determined so as to correlate with the high-frequency voltage applied at the time of static elimination (at the time of plasma generation), and is, for example, a half value (substantially the amplitude) of the difference between the minimum value and the maximum value.
[0081]
After a predetermined time, the control device 100 grounds the power supply lines 27a and 27b (as a reference voltage) by the power supply switch 31, and applies the voltage V to the electrodes 26a and 26b. _plasma Is stopped, the application of the high-frequency voltage to the upper electrode 33 is stopped, and the charge elimination is terminated. V _plasma After the stop of the application of the control signal, the control device 100 raises the lift pins 22 to release the wafer W from the electrostatic chuck 19.
[0082]
Here, the end timing of the charge elimination is set to a timing at which the attraction force acting on the wafer W decreases to a predetermined level and the wafer W can be stably detached. The separation timing is determined by experiments and the like. Note that the suction state of the wafer W to the electrostatic chuck 19 may be determined in real time, and the release timing may be determined.
[0083]
After the end of the charge removal, the control device 100 opens the gate valve 45. The wafer W on the lift pins 22 at the raised position is carried out of the chamber 12 to the load lock chamber 46 by the transfer mechanism 47. Thus, the process of processing the wafer W is completed.
[0084]
In the processing steps described above, during the neutralization using plasma, the neutralizing voltage V is applied to the electrodes 26a and 26b. _plasma Is applied. Self bias voltage V _dc Static elimination voltage V corresponding to _plasma Is applied, the charge elimination speed is increased, and the time required for the suction force to decrease to a force at which the wafer W can be separated can be substantially reduced.
[0085]
FIG. 6 shows a change in the suction force f acting on the wafer W at the time of static elimination. As shown in FIG. 6, the chuck voltage V is applied to the electrodes 26a and 26b. _esc Is applied, the wafer W has a substantially constant suction force f. ₀ Is adsorbed on the dielectric 25.
[0086]
When the etching process is completed, V _esc Is stopped, and then an inert gas is introduced into the chamber 12 to generate the plasma. At this time, the self-bias voltage V _dc V corresponding to _plasma Is applied to the electrodes 26a and 26b, the potential difference between the electrodes 26a and 26b and the wafer W is reduced, and ideally, the potentials are substantially the same.
[0087]
When the electrodes 26a, 26b and the wafer W are at substantially the same potential, as shown in FIG. 6, the attraction force f acting on the wafer W approaches zero (f = 0) as the charge elimination progresses. Decrease.
[0088]
The charge removal end timing, that is, the detachment timing of the wafer W, is determined by the residual adsorption force f, which is a force f capable of stably detaching the wafer W. _safe Time t to reach ₁ Set later. For example, f _safe Is smaller than the lifting force of the lift pin 22.
[0089]
Here, the voltage V _plasma Time t when applying ₁ Is the voltage V applied to the electrodes 26a and 26b as shown below. _plasma Time t when no voltage is applied ₀ Is substantially shorter than.
[0090]
That is, the voltage V is applied to the electrodes 26a and 26b. _plasma Is not applied, the self-bias voltage V of the wafer W is applied between the wafer W and the dielectric 25. _dc Electrostatic attraction force f based on ₁ Works. For this reason, as shown by the dotted line in FIG. _plasma Is not applied, the suction force f is f ₁ Decrease asymptotically to At this time, the suction force is f _safe Withdrawal time t which decreases to ₀ Is the voltage V _plasma Time t when applying ₁ Substantially slower than.
[0091]
Accordingly, the self-bias voltage V generated on the wafer W during plasma static elimination _dc V corresponding to _plasma By applying, the charge can be removed in a substantially short time. Also, by setting the wafer W and the electrodes 26a and 26b at substantially the same potential, the minimum value of the suction force f can be ideally set to zero, and more stable separation of the wafer W can be achieved. It becomes possible.
[0092]
As described above, according to the first embodiment of the present invention, the self-bias voltage V of the wafer W is applied to the electrodes 26a and 26b during static elimination using plasma. _dc V corresponding to _plasma Is applied. As a result, the wafer W and the electrodes 26a and 26b have substantially the same potential, and the self-bias voltage V _dc Is almost zero.
[0093]
As a result, the suction force f decreases so as to approach zero, and the rate of decrease (the static elimination speed) of the suction force f is substantially increased. Therefore, the wafer W can be more quickly and stably detached, and the throughput can be improved.
[0094]
In the first embodiment, the voltage V _plasma Is set to, for example, half of the difference between the minimum value and the maximum value of the high-frequency voltage applied to the electrode 33. But V _plasma Is not limited to this, and V _dc And a voltage that can substantially eliminate the potential difference between the wafer W and the electrodes 26a and 26b. In addition, even if they are not the same value, any value may be used as long as the residual adsorption force f can be made smaller than the conventional value, for example, the same polarity and the same or smaller value.
[0095]
Also, the voltage V applied to the electrodes 26a and 26b _plasma Is not limited to a constant voltage as shown in FIG. V _plasma May have any waveform, for example, a rectangular wave, a triangular wave, a sine wave, or the like.
[0096]
FIG. _plasma Is applied as a square wave attenuated alternating voltage. The waveform shown in FIG. _dc The magnitude gradually decreases around the voltage level corresponding to and the polarity changes at predetermined intervals. Such a wave is obtained by superimposing a high-frequency voltage of a predetermined frequency on a DC voltage corresponding to a self-bias voltage. The frequency at this time is preferably a relatively low frequency of several tens to several kHz, for example.
[0097]
Further, the self-bias voltage V of the wafer W during static elimination _dc May be measured directly or indirectly from the voltage near the wafer W in real time. In this case, for example, a lead wire is connected to a power supply line of the susceptor 15 as disclosed in Japanese Patent Application Laid-Open No. Hei 6-232820, and V is correlated with the voltage based on a high-frequency voltage detected via the lead wire. _dc Can be used. Further, as disclosed in JP-A-8-33556, a lead made of silicon is provided in the vicinity of a wafer W and electrically connected to a susceptor, and the lead is pulled out from a power supply rod connected to the susceptor. From the line, V _dc With a certain correlation with _dc A method of monitoring the level may be used.
[0098]
(Second embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. The plasma processing apparatus according to the second embodiment has the same configuration as that shown in FIGS.
[0099]
In the second embodiment, the chuck voltage (V) applied to the electrodes 26a and 26b is _esc FIG. 8 shows a timing chart of the application of ()). As shown in FIG. 8, in the second embodiment, the chuck voltage V applied to the electrodes 26a and 26b _esc From the high voltage (-600 V in the figure) _esc Lower voltage V _esc After resetting to ', the reference potential (preferably, ground potential) is set.
[0100]
In the second embodiment, the third DC power supply 30 applies the voltage V to the electrodes 26a and 26b. _esc Apply '. The control device 100 switches (re-sets) the chuck voltage applied to the electrodes 26a and 26b by the power supply switch 31.
[0101]
FIG. 9 shows an equivalent circuit diagram in a state where the wafer W is attracted to the electrostatic chuck 19. Note that the symbol i in the figure indicates the current flowing in the circuit. The symbol ΔV indicates a potential difference between the wafer W and the electrodes 26a and 26b, and ΔV = V _esc -V _dc Can be expressed as In the equivalent circuit shown in FIG. 9, the chuck voltage V applied to the electrodes 26a and 26b _esc Is stopped, that is, when the power supply switch 31 _esc FIG. 10 shows a change in the potential difference ΔV when switching from the ground to the ground.
[0102]
As shown in FIG. 10, when the electrodes 26a and 26b are set to the reference potential at once, the potential difference ΔV applied to the wafer W is V _esc -V _dc From zero to zero. At this time, a large current i instantaneously flows through the circuit including the wafer W. Such a steep and large change in potential and current may cause destruction of elements formed on the wafer W and the like.
[0103]
FIG. 11 shows a high voltage chuck voltage V _esc From the low voltage V _esc The state of the change in the potential difference ΔV when the reference potential is set after resetting to 'is shown. As shown in FIG. 11, the potential difference ΔV applied to the wafer W is _esc '-V _dc It becomes zero after decreasing to. Therefore, the potential change of the wafer W when the electrodes 26a and 26b are grounded is relatively small, and the current i flowing through the circuit including the wafer W has a small peak value and a relatively small magnitude. As described above, by reducing the amount of current flowing through the wafer W and the change in voltage of the wafer W when the chuck voltage is released, damage to elements formed on the wafer W can be suppressed.
[0104]
In the second embodiment, the reset voltage is the high chuck voltage V _esc It is only necessary that the voltage is smaller than the voltage of the same polarity, and the magnitude may be any value. Further, the time for applying the reset voltage may be any time. Also, V _esc May be changed once so as to gradually decrease in multiple stages as shown in FIG. In addition, as shown in FIG. 13, it may be changed linearly.
[0105]
In the first and second embodiments, the lift pins 22 are entirely made of a plasma-resistant insulating material such as alumina or nickel. However, at least the surface of the lift pin 22 may be made of nickel or a material having a high nickel content.
[0106]
By forming the lift pins 22 from a conductive nickel material and setting them at the reference potential or the reference potential, the charge on the back surface of the wafer W, which is difficult to be neutralized, can be quickly removed, and the static elimination speed can be improved. Nickel has plasma resistance, and particularly has high resistance to fluorine radicals used for dry cleaning of an apparatus. For this reason, generation of contamination due to contact with plasma is prevented. Furthermore, nickel has heat resistance and does not have the possibility of softening or deformation even when used under high temperature conditions.
[0107]
In the above embodiment, the bipolar electrostatic chuck 19 using the pair of electrodes 26a and 26b is used. However, the present invention is also applicable to a monopolar type or a structure including three or more electrodes.
[0108]
In the above embodiment, a plasma etching apparatus for etching a silicon oxide film on the surface of a silicon semiconductor wafer using fluorine gas has been described as an example. However, the type of film to be etched, the type of etching gas, and the like are not limited to those described above. As the inert gas used for static elimination, hydrogen, nitrogen, helium, argon, neon, xenon, or the like may be used in addition to oxygen.
[0109]
In the above example, a so-called parallel plate type plasma processing apparatus is used. However, any other plasma processing apparatus such as an inductive coupling type, a microwave type, and an ECR type may be used. Further, the present invention is not limited to plasma etching, and can be applied to an apparatus for performing other plasma processing such as ashing, sputtering, and CVD. Further, it is needless to say that the present invention can be used not only in a plasma processing apparatus but also in a processing apparatus such as a heat treatment apparatus, a CVD apparatus, and a sputtering apparatus that performs processing without using plasma. That is, the present invention can be applied to any processing apparatus that performs a single-wafer processing in a state where the object to be processed is attracted by the electrostatic attraction structure.
[0110]
Further, the object to be processed is not limited to a semiconductor wafer, and can be applied to a liquid crystal display device substrate. Further, any object can be used as long as it can be electrostatically attracted and is subjected to a predetermined process. Is also good.
[0111]
【The invention's effect】
According to the present invention, there is provided a separation method, a processing method, an electrostatic suction apparatus, and a processing apparatus capable of quickly and stably releasing an object to be suctioned onto an electrostatic chuck.
Further, according to the present invention, there is provided a detachment method, a treatment method, and a treatment apparatus capable of detaching an object to be attracted adsorbed on an electrostatic chuck without damaging the object.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of a processing apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating a configuration around a susceptor of the processing apparatus illustrated in FIG. 1;
FIG. 3 is a diagram illustrating a lifted state of a lift pin.
FIG. 4 is a diagram showing a configuration of an electrode.
FIG. 5 is a diagram showing an example of a timing chart.
FIG. 6 is a diagram showing a change in applied voltage at the time of charge elimination and a change in attraction force.
FIG. 7 shows another method of applying an applied voltage at the time of static elimination.
FIG. 8 is a diagram illustrating a method of applying a voltage when the chuck voltage is released.
FIG. 9 shows an equivalent circuit diagram of a wafer and an electrostatic chuck.
FIG. 10 is a diagram showing a change in a potential difference ΔV when a charge elimination voltage is not applied.
FIG. 11 is a diagram showing a change in a potential difference ΔV when a static elimination voltage is applied.
FIG. 12 is a diagram showing a change in a potential difference ΔV according to another embodiment of the present invention.
FIG. 13 is a diagram showing a change in a potential difference ΔV according to another embodiment of the present invention.
FIG. 14 is a diagram showing a change in an attraction force during static elimination in a conventional method.
[Explanation of symbols]
11 Plasma processing equipment
12 chambers
15 Susceptor
19 Electrostatic chuck
22 lift pins
24 cylinders
25 Dielectric
26a, 26b electrodes
27a, 27b feeder
28 Feeder
29a, 29b, 30 DC power supply
31 Power supply switch
32 Polarity switch
33 upper electrode
45 Gate valve
46 Load lock chamber
47 Transport mechanism
100 control device

Claims (20)

A method for detaching an object to be adsorbed, which is placed on a dielectric containing an electrode and is applied to the electrode by application of a DC voltage having a predetermined polarity and is electrostatically adsorbed to the dielectric by an electrostatic force, is separated from the dielectric. ,
Stopping the application of the DC voltage to the electrode,
Exposing the object to be adsorbed to plasma for static elimination,
A voltage application step of applying a DC voltage having the same polarity as a self-bias voltage generated on the object to be adsorbed to the electrode by exposure to the plasma,
A detachment method, comprising: The detachment method according to claim 1, wherein the magnitude of the DC voltage is substantially equal to or smaller than the self-bias voltage. The plasma is formed by applying a high-frequency voltage to a pair of plate electrodes,
3. The detaching method according to claim 1, wherein the DC voltage is set to be substantially equal to an amplitude of the high-frequency voltage. Further, a self-bias voltage measuring step of measuring the self-bias voltage is provided,
In the voltage applying step, the DC voltage corresponding to the self-bias voltage measured in the self-bias voltage measuring step is applied to the electrode,
The detaching method according to claim 1 or 2, wherein: The detachment method according to any one of claims 1 to 4, wherein the voltage applying step further includes a step of applying an attenuated alternating voltage to the DC voltage in a superimposed manner. A step of placing the object to be processed on a dielectric material containing the electrodes,
A step of applying a DC voltage to the electrode to cause the object to be processed to be attracted to the dielectric by electrostatic force;
Performing a predetermined process on the object to be processed;
After the end of the process, stopping the application of the DC voltage to the electrode,
Exposing the object to be treated to plasma for static elimination,
A voltage application step of applying a DC voltage having the same polarity as a self-bias voltage generated in the object to be processed by exposure to the plasma to the electrode,
A step of separating the object to be processed, which has been neutralized by exposure to the plasma, from the dielectric,
A processing method comprising: 7. The processing method according to claim 6, wherein the magnitude of the DC voltage is substantially equal to or smaller than the self-bias voltage. The plasma is formed by applying a high-frequency voltage to a pair of plate electrodes,
8. The processing method according to claim 6, wherein the DC voltage is set to be substantially the same as the amplitude of the high-frequency voltage. Further, a self-bias voltage measuring step of measuring the self-bias voltage is provided,
In the voltage applying step, the DC voltage corresponding to the self-bias voltage measured in the self-bias voltage measuring step is applied to the electrode,
The processing method according to claim 6 or 7, wherein: The processing method according to any one of claims 6 to 9, further comprising a step of superimposing and applying an attenuated alternating voltage to the DC voltage. A detachment method in which an object to be adsorbed, which is placed on a dielectric containing an electrode and is adhered to the dielectric by electrostatic force by application of a predetermined DC voltage to the electrode, is detached from the dielectric,
Stopping the application of the predetermined DC voltage to the electrode;
A step of applying a DC voltage of the same polarity, which is smaller than the predetermined DC voltage, to the electrode,
A step of setting the electrode to a reference potential after applying the DC voltage of the same polarity, which is smaller than the predetermined DC voltage, to the electrode,
After setting the electrode to the reference potential, a step of releasing the object to be adsorbed,
A detachment method, comprising: A step of placing the object to be processed on a dielectric material containing the electrodes,
A step of applying a first DC voltage to the electrode to cause the object to be processed to be attracted to the dielectric by electrostatic force;
Performing a predetermined process on the object to be processed on the dielectric,
Applying a second DC voltage having the same polarity, which is smaller than the first DC voltage, to the electrode after the end of the processing;
After stopping the application of the second DC voltage, setting the electrode to a reference potential;
After setting the electrode to the reference potential, a step of releasing the object to be adsorbed,
A processing method comprising: A chamber in which predetermined processing is performed on the object to be processed,
A dielectric provided in the chamber, including an electrode, and applying a direct current voltage for adsorption to the electrode, the dielectric to which the object to be processed is adsorbed;
Gas supply means for supplying a gas for static elimination into the chamber;
Plasma generation means for generating a plasma of the gas in the chamber;
Voltage switching for switching a voltage applied to the electrode between the DC voltage for adsorption and a DC voltage for static elimination having the same polarity as a self-bias voltage generated in the object to be processed by exposure to the plasma. Means,
A control unit for exposing the object to be processed to the plasma generated by the plasma generation unit, and applying the DC voltage for static elimination to the electrode by the voltage switching unit,
A processing device comprising: 14. The processing apparatus according to claim 13, wherein the magnitude of the DC voltage is substantially equal to or smaller than the self-bias voltage. A chamber in which predetermined processing is performed on the object to be processed,
A dielectric provided in the chamber, including an electrode, and a target to be processed is attracted by electrostatic force by application of a first DC voltage to the electrode;
Voltage switching means for switching a voltage applied to the electrode between the first DC voltage, a second DC voltage having the same polarity, which is smaller than the first DC voltage, and a reference voltage;
After switching the voltage applied to the electrode from the first DC voltage to the second DC voltage by the voltage switching means, the voltage is switched to a reference voltage, and the workpiece is separated from the dielectric. Means,
A processing device comprising: A dielectric which comprises an electrode therein and which applies a DC voltage to the electrode to adsorb the object to be adsorbed on one surface by electrostatic force;
The dielectric is provided so as to go up and down through the one surface, and separates the adsorbed object from the one surface in a state of being in contact with the adsorbed object. At least the surface is made of a material containing nickel. Separation means;
An electrostatic attraction device comprising: 17. The electrostatic attraction device according to claim 16, wherein the separation unit is set to a reference potential. A chamber in which predetermined processing is performed on the object to be processed,
Provided in the chamber, provided with an electrode inside, by applying a DC voltage to the electrode, the dielectric to attract the object to be processed on one surface by electrostatic force,
The dielectric is provided so as to go up and down through the one surface, and separates the processing object from the one surface in a state of being in contact with the processing object. At least the surface is formed of a material including nickel. Separation means;
A processing device comprising: 19. The processing apparatus according to claim 18, wherein the separation unit is set to a reference potential. Further, gas supply means for supplying a processing gas into the chamber,
Plasma generating means for generating a plasma of the gas in the chamber;
The processing apparatus according to claim 18, further comprising:

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