JPH09120988A - Plasma processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent attraction failures of an electrostatic chuck without deteriorating the electrostatic chuck and decreasing the throughput and strengthen its attraction force. SOLUTION: With the aid of an electrostatic attraction generated by applying a positive DC voltage to an electrostatic chuck 11, a wafer W is attracted to the chuck 11, and a processing gas is supplied to a processing chamber 2 to generate a plasma, thereby processing the wafer W with the plasma. In this case, after the processed wafer W is released from the chuck 11, a nitrogen gas introduced to the chamber 2 prior to attracting the following wafer W to the chuck 11, and a negative DC voltage is applied to the chuck 11 for DC discharging. Thus, the charges in a gas is attracted to the surface of the chuck 11, so that the residual charge is removed therefrom.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing method for subjecting an object to be processed to various types of plasma processing including etching processing.

[0002]

2. Description of the Related Art For example, when an etching process in a semiconductor manufacturing process is taken as an example, when a contact hole is formed by etching an insulating film on the surface of a semiconductor wafer (hereinafter referred to as "wafer"), plasma is conventionally used. The etching equipment used is used. Among them, a so-called parallel plate type etching apparatus in which electrodes are arranged to face each other in the upper and lower parts of the processing chamber is particularly used because it is suitable for processing a wafer having a relatively large diameter.

By the way, since it is necessary to hold the wafer at a predetermined position on the electrode during the etching process, in the conventional etching apparatus described above, for example, JP-A-4-51542 is used.
An electrostatic chuck, such as that disclosed in U.S. Pat. This electrostatic chuck has a structure in which an electrode is provided inside an insulator, and an electrostatic force (Coulomb force) generated when a DC voltage is applied to this electrode is used to attract and hold a wafer. There is.

In this case, when the number of times the object to be processed is attracted increases, charges having a polarity opposite to the DC voltage applied when the object to be processed is attracted to the insulator surface of the electrostatic chuck gradually. As a result, the wafer may remain, and as a result, the wafer may not be surely attracted even if a DC voltage is applied. Therefore, conventionally, a method of preventing such a suction failure of the electrostatic chuck has been proposed. For example, Japanese Patent Publication Sho-63-36
In No. 138, a method of preventing the adsorption failure of the electrostatic chuck by introducing a gas having a discharge pressure into the processing chamber after removing the wafer and performing high frequency discharge at the electrodes in the processing chamber (hereinafter,
"Plasma neutralization") has been proposed, and Japanese Patent Application Laid-Open No. 4-51542 discloses that an inert gas is introduced at that time to cause electric discharge.

[0005]

However, in all of the above-mentioned conventional methods, the charge is removed in the same discharge state as the original etching process, so that the reaction product is deposited on the surface of the electrostatic chuck. There is a problem in that the surface of the electrostatic chuck is sputtered (so-called “depot” is attached). Further, in each of the related arts described above, a plasma discharge is generated after the etching-processed wafer is completely unloaded from the processing chamber to remove charges, and after the removal of the charges is completed, the next wafer is processed in the processing chamber. I have to carry it in. For this reason, in each of the above-mentioned conventional techniques, it is not possible to simultaneously carry out the carry-out of the wafer from the process chamber and the carry-in of the wafer into the process chamber and the step of preventing the suction failure, and there is a problem in throughput.

Further, conventionally, there was another problem because a DC voltage was already applied to the electrostatic chuck before the wafer was placed on the electrostatic chuck. That is, in this type of etching apparatus or the like, a wafer carried in by a carrier means such as a carrier arm is placed on the electrostatic chuck, or a processed wafer is separated from the electrostatic chuck. A supporting member such as a lifter pin, which is provided in the mounting table and whose tip can freely project from the electrostatic chuck, is used as a mechanism for delivering to the conveying means.

Therefore, when a direct current voltage is applied to the electrostatic chuck in this manner before the wafer is placed on the electrostatic chuck, the supporting member is grounded via a resistor, and thus the supporting member is grounded. When the voltage rises, a DC discharge is generated between this support member and the electrostatic chuck. For example, if a positive DC voltage is applied, a negative charge will accumulate on the surface of the electrostatic chuck, which will cause adsorption failure. There was a problem that occurs.

The present invention has been made in view of the above problems, and an object of the present invention is to prevent defective adsorption of an object to be processed to the electrostatic chuck without deteriorating the electrostatic chuck and reducing the throughput. It is an object of the present invention to provide a plasma processing method capable of further increasing the adsorption force with respect to an object to be processed, thereby solving the above problem.

[0009]

In order to achieve the above object, the plasma processing method according to claim 1 uses an electrostatic force generated by applying a DC voltage to an electrostatic chuck in a processing chamber to be processed. Is adsorbed on the electrostatic chuck, and while supplying a predetermined processing gas into the processing chamber, plasma is generated in the processing chamber by supplying high-frequency power, and a predetermined amount is applied to the object to be processed on the electrostatic chuck. In the method of performing plasma treatment, after the predetermined plasma treatment is completed, the supply of the processing gas and the supply of high-frequency power are stopped, and then the object to be plasma-treated is separated from the electrostatic chuck. Then, before the next object to be processed is adsorbed on the electrostatic chuck, the electrostatic chuck is applied when the object is adsorbed with the gas introduced into the processing chamber. The DC voltage applied to the opposite polarity of the DC voltage, it is characterized in that applied to the electrostatic chuck.

In this case, as described in claim 2, the process of applying a DC voltage to the electrostatic chuck when adsorbing the object to be processed and the DC voltage having a polarity opposite to the DC voltage are applied to the electrostatic chuck. It is preferable to add a process of grounding the electrode of the electrostatic chuck to the process of applying the voltage to the electrode.

Further, as described in claim 3, it is preferable that the gas pressure of the gas to be introduced is set to at least a gas pressure at which direct current discharge is generated. In this case, when the applied DC voltage is relatively high, the gas pressure is low, and when the applied DC voltage is relatively low, the gas pressure is high.

Further, as described in claim 4, the object to be processed is placed on or separated from the electrostatic chuck by a supporting member such as a lifter pin which is projectable from the electrostatic chuck. The DC voltage of the opposite polarity may be applied during operation.

Further, as described in claim 5, the object to be processed is carried in and out of the processing chamber by a carrying means such as a carrying arm, and the DC voltage of the reverse polarity is applied during the operation of the carrying means. You may make it apply.

Further, as described in claim 6, a gate valve for loading and unloading the object to be processed is provided in the processing chamber, and
The DC voltage of the opposite polarity may be applied while the gate valve is open.

According to a seventh aspect of the present invention, an object to be processed is attracted onto the electrostatic chuck by utilizing an electrostatic force generated by applying a DC voltage to the electrostatic chuck inside the processing chamber,
While supplying a predetermined processing gas into the processing chamber, plasma is generated in the processing chamber by supplying high-frequency power,
In the method of subjecting an object to be processed on the electrostatic chuck to a predetermined plasma treatment, the object to be processed is placed on the electrostatic chuck, a processing gas is introduced into the processing chamber, and DC discharge is generated in the processing chamber. First step of setting the gas pressure to be performed, a second step of applying a DC voltage to the electrostatic chuck after the first step, and a plasma processing of the pressure in the processing chamber after the second step. The third step of setting the pressure at the time, and the third step
And a fourth step of supplying high-frequency power after the step of (1), the plasma processing method is provided.

In this case, as described in claim 8, the step of supplying the heat transfer gas to the back surface (surface on the electrostatic chuck side) of the object to be processed between the second step and the fourth step. May be added for processing. For example, before or after the third step of setting the pressure in the processing chamber to the pressure during plasma processing,
The heat transfer gas is supplied.

In the inventions of claims 1 to 8, the "electrostatic chuck" has a structure in which, for example, a conductive thin film is sandwiched from above and below by an insulating material such as a polyimide resin. And, "to apply a direct current voltage to the electrostatic chuck" means to apply a predetermined direct current voltage to the thin film, that is, the electrode in the electrostatic chuck thus configured. When a Coulomb force is generated by applying a predetermined DC voltage to the thin film in the electrostatic chuck,
This Coulomb force makes it possible to attract and hold the object to be processed on the upper surface of the electrostatic chuck.

According to the first aspect of the present invention, for example, if a positive DC voltage is applied to the electrostatic chuck when adsorbing the object to be processed, the object to be processed after the plasma processing is removed from the electrostatic chuck by, for example, a lifter pin. After being separated by the support member, a negative DC voltage is applied to the electrostatic chuck in a state where gas is introduced into the processing chamber before the next object to be processed is adsorbed on the electrostatic chuck.

Here, the gas introduced into the processing chamber is not particularly limited, but for example, an inert gas such as Ar (argon) gas, and other N ₂ (nitrogen) gas can also be preferably used. . In this manner, a DC voltage having a polarity opposite to that of the DC voltage applied to the electrostatic chuck when adsorbing the object to be processed is applied to the electrostatic chuck with a proper gas introduced into the processing chamber. A direct current discharge can be generated by this to attract the electric charge in the gas to the surface of the electrostatic chuck. This makes it possible to charge the surface of the electrostatic chuck to the opposite polarity to the residual charge, eliminate the adsorption failure, and further increase the attraction force of the object to be processed to the electrostatic chuck. Theoretically, the above effect should not be obtained unless the DC discharge is generated, but the above effect may be obtained even when the DC discharge is not generated. This is probably because a small amount of charged particles in the gas were attracted to the surface of the electrostatic chuck.

In the above-mentioned conventional plasma neutralization,
Although about 50 W of electric power was required, 1 W or less is sufficient as the electric power required for DC discharge as in the present invention. Therefore, it is unlikely that the depot will adhere to the surface of the electrostatic chuck,
Also, the surface of the electrostatic chuck is not sputtered. Regarding the gas pressure as well, it is sufficient if it is equal to or higher than the pressure at which direct current discharge is generated, so that the restriction of the gas pressure is looser than that of plasma static elimination.

When the electrode of the electrostatic chuck is once grounded between the application of the DC voltage at the time of adsorption and the application of the DC voltage of the opposite polarity as in claim 2, the electrode of the lifter pin, etc. When the support member rises and comes into contact with the wafer, part of the charges remaining on the wafer and the thin film of the electrostatic chuck flow to the ground, and the wafer can be easily separated from the electrostatic chuck.

Further, by setting the gas pressure of the gas to be introduced to be the gas pressure at which the DC discharge is generated, the DC discharge can be generated more reliably and the reliability of the process can be improved.

Further, by applying the DC voltage of the opposite polarity during the operation of the support member, the operation of the transfer means, and the opening of the gate valve, the electrostatic chuck adsorption is performed in parallel with these operations. The process of preventing defects and enhancing the suction power is performed, and the influence on the throughput can be suppressed.

According to a seventh aspect of the present invention, the object to be processed is placed on the electrostatic chuck, the processing gas is introduced into the processing chamber, and the processing chamber is set to a gas pressure at which DC discharge is generated. If a DC voltage is applied to the chuck, DC discharge will not occur between the support member such as lifter pins and the electrostatic chuck as in the conventional case. Then, as a result of the processing gas being DC-discharged, the processing space becomes conductive, negative charges are supplied to the wafer, and the wafer is firmly attracted to the electrostatic chuck by the Coulomb force. After that, the pressure in the processing chamber may be set to the pressure during plasma processing, and high-frequency power may be supplied from a high-frequency power source or the like to perform normal etching processing.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present invention will be described based on an example applied to an etching method. FIG.
FIG. 3 schematically shows a cross section of the etching apparatus 1 used in the embodiment of the present invention. The processing chamber 2 in this etching apparatus 1 is formed in a cylindrical processing container 3 made of aluminum or the like which has been airtightly closed and can be treated with oxidized alumite, and the processing container 3 itself is grounded via a ground wire 4. There is. An insulating support plate 5 made of ceramic or the like is provided at the bottom of the processing chamber 2.
A substantially columnar susceptor 6 which constitutes a lower electrode for mounting an object to be processed, for example, a semiconductor wafer (hereinafter, referred to as “wafer”) W having a diameter of 8 inches, is accommodated in an upper and lower part of the substrate so as to be vertically movable. .

The susceptor 6 is supported by an elevating shaft 7 which loosely penetrates the insulating support plate 5 and the bottom of the processing container 3, and the elevating shaft 7 is a drive motor 8 installed outside the processing container 3. It can move up and down freely. Therefore, by the operation of the drive motor 8, the susceptor 6 is
Can move up and down as shown by the reciprocating arrow in FIG. In order to ensure the airtightness of the processing chamber 2, a stretchable airtight member such as a bellows 9 is provided between the susceptor 6 and the insulating support plate 5 so as to surround the outside of the elevating shaft 7. There is.

The susceptor 6 is made of aluminum whose surface is subjected to oxidation treatment.
Heating means such as a ceramic heater (not shown)
Also, a coolant circulation path (not shown) for circulating a coolant with an external coolant source (not shown) is provided, and the wafer W on the susceptor 6 can be maintained at a predetermined temperature. It is configured like this. The temperature is automatically controlled by a temperature sensor (not shown) and a temperature control mechanism (not shown).

An electrostatic chuck 11 for attracting and holding the wafer W is provided on the susceptor 6. As shown in FIG. 2, the electrostatic chuck 11 has a structure in which a conductive thin film 12 is sandwiched between polyimide resins 13 from above and below. When the switch 14 is connected to the plus terminal 15, the plus voltage from the high voltage DC plus power source 16 installed outside the processing container 3
For example, a positive voltage of +1.5 kV to +2 kV is applied to the thin film 12
The wafer W is attracted and held on the upper surface of the electrostatic chuck 11 by the Coulomb force generated at that time. When the switch 14 is connected to the negative terminal 17, a negative voltage from a high voltage DC negative power source 18 installed outside the processing container 3, for example, a negative voltage of −1.5 to −2 kV is applied to the thin film 12. Is applied to. In addition, the switch 14 is the ground terminal 1
The thin film 12 is designed to be grounded when the connection operation is made to 9.

A flow path (not shown) for heat transfer gas such as He (helium) gas is formed in the susceptor 6, and is provided on the back surface of the wafer W attracted and held on the electrostatic chuck 11. On the other hand, by supplying this heat transfer gas, the heat transfer between the wafer W and the electrostatic chuck is made uniform and the transfer efficiency is improved.

As shown in FIG. 2, a plurality of lifter pins 20 are provided inside the susceptor 6 so as to move up and down in the susceptor 6 to lift up the wafer W from the electrostatic chuck 11. There is. The lifter pin 20 constitutes the support member according to the present invention. 20 lifter pins
The other end of is connected to ground via a high impedance body, for example, a 3 megohm resistor.

On the periphery of the susceptor 6, an inner focus ring 21 having a substantially plane plane is provided so as to surround the electrostatic chuck 11. The inner focus ring 21 is made of conductive single crystal silicon, and has a function of effectively injecting ions in plasma to the wafer W.

On the outer circumference of the inner focus ring 21, there is further provided an outer focus ring 22 having a substantially flat plane. The outer focus ring 22 is made of quartz having an insulating property, and the upper edge of the outer periphery thereof is formed in a curved shape having an outward convex shape so that gas is smoothly discharged without settling. This outer focus ring 22
Has a function of suppressing diffusion of plasma generated between the susceptor 6 and an upper electrode 51 described later, together with a shield ring 53 described later.

The baffle plate 2 is provided around the front susceptor 6.
3, the inner peripheral portion of the baffle plate 23 is fixed to the susceptor 6 by means of bolts or the like via a quartz support or the like. Therefore, the baffle plate 23 also moves up and down as the susceptor 6 moves up and down. A large number of through holes 23a are formed in the baffle plate 23 and has a function of uniformly discharging gas.

An insulating support 31 made of alumina and a cooling member 32 made of aluminum are provided above the processing chamber 2.
A diffusion member 33 for introducing an etching gas or another gas into the processing chamber 2 via the above is provided. Further, a cooling medium circulation path 34 is formed above the cooling member 32, and has a function of cooling the upper electrode 51 described later to a predetermined temperature by circulating a chiller (cooling medium) supplied from the outside. doing.

As shown in FIG. 2, the diffusing member 33 has a hollow structure having upper and lower two-stage baffle plates 35, and further, these upper and lower two-stage baffle plates 3 are provided.
A large number of diffusion holes 35a are formed in each of the Nos. 5 at different positions. A gas introducing port 36 is provided at the center of the diffusing member 33, and a gas introducing pipe 38 is connected via a valve 37. The gas introduction pipe 38 is provided with valves 39 and 40 and a corresponding mass flow controller 41 for adjusting the flow rate.
A processing gas supply source 43 and a purge gas supply source 44 are connected via 42. In the embodiment of the present invention,
CF ₄ gas is supplied from the processing gas supply source 43, and N ₂ (nitrogen) gas is supplied from the purge gas supply source 44.

The gas from the processing gas supply source 43 and the purge gas supply source 44 is introduced into the processing chamber 2 from the gas introduction pipe 38 through the introduction port 36 and the diffusion hole 35a of the diffusion member 33. ing. As shown in FIG. 2, the cooling member 32 is also provided with a large number of discharge ports 32a, so that the gas in the baffle space S formed between the baffle plate 35 of the diffusion member 33 and the cooling member 32 is discharged. It is designed to discharge downward.

Below the diffusing member 33, an upper electrode 51 is fixed to the lower surface of the cooling member 32 so as to face the susceptor 6. The upper electrode 51 is made of conductive single crystal silicon, is fixed to the peripheral portion of the lower surface of the cooling member 32 by a fixing bolt (not shown), and is electrically connected to the cooling member 32. The upper electrode 51 also has a large number of ejection openings 51a, which are connected to the ejection openings 32a of the cooling member 32. Therefore, the gas in the baffle space S is discharged from the discharge port 32a,
Through 51a, the wafer W on the electrostatic chuck 11 is uniformly discharged.

A shield ring 53 is arranged around the lower end of the upper electrode 51 so as to cover the above-mentioned fixing bolt. The shield ring 53 is made of quartz, and has a function of forming a gap narrower than the gap between the electrostatic chuck 11 and the upper electrode 51 together with the outer focus ring 22 and suppressing diffusion of plasma. ing. The upper end of the shield ring 53 and the processing container 3
An insulating ring 54 made of fluorine-based synthetic resin is provided between the insulating ring 54 and the ceiling wall.

An exhaust pipe 62 communicating with a vacuuming means 61 such as a vacuum pump is connected to the lower portion of the processing container 3, and the above-mentioned baffle plate 23 disposed around the susceptor 6 is connected.
The inside of the processing chamber 2 can be evacuated to an arbitrary degree of vacuum up to several mTorr.

Next, the high frequency power supply system of the etching apparatus 1 will be described. First, for the susceptor 6 serving as the lower electrode, the frequency is about several hundred kHz, for example, 80.
The power from the high frequency power source 63 that outputs the high frequency power of 0 kHz is supplied through the matching device 64. On the other hand, to the upper electrode 51, the power from the high frequency power source 66 that outputs the high frequency power of a frequency of 1 MHz or higher, for example, 27.12 MHz, which is higher than that of the high frequency power source 63, via the matching unit 65, is used. It is configured to be supplied through the cooling plate 32.

A load lock chamber 72 is adjacent to a side portion of the processing container 3 via a gate valve 71. In the load lock chamber 72, a transfer unit 73 such as a transfer arm is provided for transferring the wafer W, which is the object to be processed, to and from the processing chamber 2 in the processing container 3.

Next, the control system of the etching apparatus 1 will be described. A drive motor 8 for moving the susceptor 6 up and down, a plus terminal 15 and a minus terminal 1 of a switch 14.
7, connection operation to the ground terminal 19, high-voltage DC positive power supply 16, high-voltage DC negative power supply 18, lifter pin 20 in the susceptor 6, valves 39 and 40, mass flow controllers 41 and 42, evacuation means 61, high-frequency power supply 6
3, 66 are controlled by the controller 74.

The main part of the etching apparatus 1 according to the embodiment of the present invention is configured as described above, and under the control of the controller 74, for example, the oxide film (SiO ₂ ) of the silicon wafer W is etched. Explaining the operation and the like in the case of processing, first, the gate valve 71
After the wafer is opened, the wafer W is carried into the processing chamber 2 by the transfer means 73. At this time, due to the operation of the drive motor 8, the susceptor 6 descends, the lifter pin 20 projects onto the electrostatic chuck 11, and is in a standby state for receiving the stack W. Then, the wafer W carried into the processing chamber 2 by the carrying means 73 is transferred onto the lifter pin 20 protruding above the electrostatic chuck 11, as shown in FIG. After transferring the wafer W onto the lifter pin 20 in this manner, the transfer means 73 is retracted and the gate valve 71 is closed.

On the other hand, when the transfer of the wafer W onto the lifter pins 20 is completed, the drive motor 8 is operated to move the susceptor 6 to a predetermined processing position, for example, the gap between the upper electrode 51 and the susceptor 6 becomes 10 mm to 20 mm. The lifter pins 20 supporting the wafer W are lowered into the susceptor 6 at the same time. Thus, as shown in FIG. 2, the wafer W is placed on the electrostatic chuck 11.

Next, the inside of the processing chamber 2 is evacuated by the evacuation means 61, and after a predetermined degree of vacuum is reached,
Predetermined processing gas (C ₄ F ₈ gas) from the processing gas supply source 43
Is supplied at a predetermined flow rate, and the pressure in the processing chamber 2 is, for example, 7
The pressure is reduced to 0 mTorr to 80 mTorr (P1 in FIG. 4), and DC discharge easily occurs. here,
The switch 14 is connected to the plus terminal 15 and is grounded until now. However, a predetermined plus voltage from the high voltage DC plus power source 16, for example, a positive voltage of 1.5 kV to 2 kV is conductive in the electrostatic chuck 11. Applied to the thin film 12 of. As a result, the wafer W is attracted. Then, the heat transfer gas starts to be supplied to the back surface of the wafer W, and CF _{4 is} further added.
The pressure in the processing chamber 2 due to the gas introduction is further reduced to the pressure during the etching process, for example, to 20 mTorr (P2 in FIG. 4).

After the pressure in the processing chamber 2 reaches the pressure during the etching process, for example, 20 mTorr as described above, the high frequency power source 66 supplies a high frequency power of 27.12 MHz to the upper electrode 51. When electric power is supplied, plasma is generated between the upper electrode 51 and the susceptor 6. At the same time, high frequency power having a frequency of 800 kHz and a power of, for example, 1 kW is supplied from the high frequency power supply 64 to the susceptor 6. In this way, stable plasma is immediately generated by supplying high-frequency power to the top and bottom simultaneously.

The processing chamber 2 is generated by the generated plasma.
The process gas inside is dissociated, and the etchant ions generated at that time are incident on the silicon oxide film (SiO ₂ ) on the surface of the wafer W while the incident speed of the etchant ions is controlled by the high frequency of a relatively low frequency supplied to the susceptor 6. Will be etched.

In this case, the susceptor 6 is provided with an outer focus ring 22 on the outer periphery of an inner focus ring 21 arranged so as to surround the wafer W, and above the outer focus ring 22 around the upper electrode 51. Since the arranged shield ring 53 is located and constitutes a gap shorter than that between the upper surface of the electrostatic chuck 11 and the lower surface of the upper electrode 51, as described above, the susceptor 6 is provided.
The diffusion of the plasma generated between the upper electrode 51 and the upper electrode 51 is suppressed, and the density of the plasma is high. Of course, even if the pressure inside the processing chamber 2 is as high as 20 mTorr, the diffusion of plasma can be effectively suppressed.

Moreover, since the inner focus ring 21 is arranged around the wafer W, the fluorine radicals are uniformly incident on the wafer W, and the etching rate of the silicon oxide film (SiO ₂ ) on the surface of the wafer W is It is uniform and high.

When the predetermined etching is completed in this way, as shown in the timing chart of FIG. 4, the supply of the high frequency power to the upper electrode 51 and the susceptor 6 is stopped, and the processing into the processing chamber 2 is performed. The gas supply is stopped. Then the supply of heat transfer gas to the backside of the wafer is stopped,
When the switch 14 is connected to the ground terminal 19, the application of the plus voltage from the high voltage DC plus power source 16 to the conductive thin film 12 of the electrostatic chuck 11 is stopped,
The conductive thin film 12 is grounded.

Next, nitrogen gas is supplied into the processing chamber 2 from the purge gas supply source 44, and the residual processing gas is purged from the processing chamber 2. By supplying this nitrogen gas, the pressure in the processing chamber 2 is, for example, 70 mTorr to 80 mTorr.
The degree of vacuum is about r. Next, the gate valve 71 is opened, the susceptor 6 is lowered, and at the same time the lifter pin 20 is raised, so that the wafer W after the etching process is lifted up from the electrostatic chuck 11 to be in the state shown in FIG.

Here, in the electrostatic chuck 11 using the highly insulating resin 13 such as polyimide, when the wafer W is attracted, the conductive thin film 12 of the electrostatic chuck 11 is used.
Since a predetermined positive voltage is applied to the electrostatic chuck 1, the voltage application to the thin film 12 is stopped, the lifter pins 20 are raised, and the wafer W is lifted up.
A charge (negative charge) having a polarity opposite to the adsorption voltage (for example, a positive voltage of 1.5 kV to 2 kV) remains on the surface of 1.
The surface of the electrostatic chuck 11 is in a negatively charged state.

If the negatively charged state is left, the conductive thin film 1 in the electrostatic chuck 11 is trying to adsorb the wafer W for the next etching process.
When a predetermined positive voltage from the high voltage DC positive power source 16 is applied again to 2, the positive voltage applied by the negative residual charge on the surface of the electrostatic chuck 11 is canceled and a sufficient voltage is applied to the wafer W. Can not be.
As a result, the attraction force decreases, and there is a possibility that the wafer W cannot be reliably attracted onto the electrostatic chuck 11 even if a predetermined plus voltage is applied from the high voltage DC plus power source 16.

Therefore, in the present embodiment, the lifter pin 20 is relatively raised with respect to the susceptor 6, and as shown in FIG.
When the wafer W which has been subjected to the etching process is separated from the electrostatic chuck 11 as shown in FIG. 5, the switch 14 is connected to the minus terminal 17, and a predetermined minus voltage from the high voltage DC minus power source 18 is applied to the inside of the electrostatic chuck 11. The conductive thin film 12 is applied for a predetermined time, for example, about 1.0 sec. In the present embodiment, the negative voltage applied from the high voltage DC negative power source 18 is a voltage at which DC discharge is generated with respect to the nitrogen gas, for example, a negative voltage of about -1.0 to -2 kV. good.

As described above, a DC voltage (minus voltage) having a polarity opposite to the DC voltage (plus voltage) applied when the wafer W is attracted is applied to the conductive thin film 12 in the electrostatic chuck 11. Then, direct-current discharge is performed in the nitrogen gas supplied into the processing chamber 2, and positive charges are attracted to the surface of the electrostatic chuck 11 at that time, and the surface of the electrostatic chuck 11 can be positively charged. .

In this way, the negative voltage from the high voltage DC negative power source 18 is applied to the conductive thin film 12 in the electrostatic chuck 11 for a predetermined time, and the switch 14 is again connected to the ground terminal 19 to operate the electrostatic chuck 11. The conductive thin film 12 is again grounded. For example, in the present embodiment in which the electrostatic chuck 11 is formed by using the polyimide resin 13, the application time of the negative voltage is set to about 1.0 sec.
It is possible to charge the surface of No. 1 with a polarity opposite to that of the residual charge, that is, the surface of the electrostatic chuck 11 in the present embodiment is positively charged. By charging the surface of the electrostatic chuck 11 with a positive charge in this manner, it is possible to prevent a suction failure and further increase the suction force.

On the other hand, after the gate valve 71 is opened as described above, the lifter pin 20 is relatively raised with respect to the susceptor 6, and the wafer W which has been subjected to the etching process is shown in FIG.
When the electrostatic chuck 11 is separated from the electrostatic chuck 11 as shown in FIG. In this way, the transfer means 73 advanced into the processing chamber 2 enters the lower surface of the wafer W, and then the lifter pin 20 descends to transfer the wafer W supported on the lifter pin 20 to the transfer means 73. After that, the transfer means 73 retracts into the load lock chamber 72, so that the wafer W after the etching process is processed in the process chamber 2
It is carried out from inside.

The etching-processed wafer W carried out from the processing chamber 2 in this manner is carried by the carrying means 73 to a processing apparatus for carrying out the next processing step as appropriate. Then, the transfer means 73 transfers the wafer W that has been subjected to the etching process to the next processing apparatus, receives the next new wafer W to be subjected to the etching process, and loads the unprocessed wafer W into the processing chamber 2. . Then, the unprocessed wafer W loaded into the processing chamber 2 by the transfer means 73 is transferred onto the lifter pins 20 protruding above the electrostatic chuck 11, and then the transfer means 73 is retracted from the inside of the process chamber 2. Then, the gate valve 71 is closed.

Then, as described above, the unprocessed wafer W
When the hand-over of the lifter pins 20 onto the lifter pins 20 is completed, the susceptor 6 moves up and at the same time the lifter pins 20 move down,
As shown in FIG. 2, the wafer W is placed on the electrostatic chuck 11.

Then, a CF ₄ gas, which is an etching gas, is supplied from the processing gas supply source 43 into the processing chamber 2, and the pressure in the processing chamber 2 is, for example, 70 mTorr to 80 mTorr.
The pressure is reduced to (P1 in FIG. 4), and DC discharge easily occurs. Then, the switch 14 is the positive terminal 15
A predetermined positive voltage from the high-voltage DC positive power source 16, for example, a positive voltage of 1.5 kV to 2 kV is applied to the conductive thin film 12 in the electrostatic chuck 11. As a result, DC discharge is generated and the wafer W is adsorbed.

Next, heat transfer gas starts to be supplied to the back surface of the wafer W, and the pressure in the processing chamber 2 due to the introduction of CF ₄ gas is, for example, 20 mT which is the pressure during etching processing.
The pressure is further reduced to orr (P2 in FIG. 4). When high frequency power is applied to the upper electrode 51 and the susceptor 6, plasma is generated in the processing chamber 2, the CF ₄ gas is dissociated to start the etching process, and thereafter, the same process is repeated. , The etching process on the wafer W is continuously performed.

During the etching process, the electrostatic chuck 1
A positive voltage is applied to the conductive thin film 12 in 1 but the residual charge (negative charge) on the surface of the electrostatic chuck 11 has been removed in advance as described above.
The wafer W can be favorably adsorbed and held on the electrostatic chuck 11 by the Coulomb force without causing the adsorption failure.

In the embodiment of the invention described above, the lifter pin 20 is relatively raised with respect to the susceptor 6 to separate the wafer W from the electrostatic chuck 11, and at the same time, the conductivity in the electrostatic chuck 11 is reduced. Although the negative voltage is applied to the thin film 12 having a conductive property, the lifter pin 20 is relatively raised with respect to the electrostatic chuck 11 to apply the negative voltage to the thin film 12 when the wafer W is electrostatic chucked. It may be any time after the wafer 11 is separated from above 11 and before the next wafer W is attracted onto the electrostatic chuck 11. Further, the timing of opening the gate valve 71 may be before or after applying the negative voltage as long as it is after introducing the purge gas.

The reverse polarity DC voltage applied to the conductive thin film 12 in the electrostatic chuck 11 is not necessarily a negative voltage, but a negative DC voltage for attracting the wafer W is applied. It is necessary to apply a positive DC voltage as a reverse polarity voltage. Further, although the example in which the nitrogen gas is supplied as the purge gas into the processing chamber 2 after the etching process is completed, the gas supplied into the processing chamber 2 is not limited to the nitrogen gas, and for example, Ar (argon) may be used. Inert gas such as gas can also be preferably used.

Further, although the embodiment has been shown for the structure in which the high frequency power is applied to the upper electrode and the lower electrode, the present invention is not limited to such a structure. In addition, although the above-described embodiment of the invention is a process of etching a silicon oxide film (SiO ₂ ) on the surface of a silicon semiconductor wafer, the present invention is not limited to this, and the method of the present invention is not limited to other plasma
For example, the ashing process, the sputtering process, the CVD process and the like can be performed. Further, the object to be processed is not limited to the wafer but may be an LCD substrate.

The following experiment was conducted in order to further confirm the operation and effect of this embodiment described above. (Experiment) 1. Purpose As described above, when the wafer is placed as it is without removing the static electricity from the surface of the electrostatic chuck, the adsorption failure occurs due to the surface of the electrostatic chuck being negatively charged. Therefore, in this experiment, by applying a reverse voltage (negative voltage) to the electrostatic chuck with the gas introduced into the processing chamber before placing the wafer, the surface of the electrostatic chuck is positively charged. Check if suction failure is prevented.

In this experiment, the reverse voltage was applied in the processing chamber 2 in the N ₂ purge gas atmosphere. The reverse voltage application sequence at that time is shown in FIG. In FIG. 5, “H.
"V" is the high DC voltage applied to the electrostatic chuck, "BP"
Is a back pressure gas as a heat transfer gas supplied to the back surface of the wafer, “N ₂ ” is a nitrogen gas as a purge gas to be introduced into the processing chamber, and “LP” is a lifter pin that supports the wafer and moves up and down. Is represented.

As a comparative example, a plasma neutralization method for neutralizing the surface of the electrostatic chuck by using plasma generated by high frequency discharge was taken up, and the experimental example of the present invention was compared with the adsorption force. The discharge condition of the comparative example is that plasma is generated in an N ₂ gas atmosphere, and the pressure in the processing chamber at that time is 3
High frequency power of 50 W was applied to the upper electrode only for 3 seconds at 00 mTorr.

2. Experimental Method Measurement of Adsorption Force The relationship between the high DC voltage applied to the electrostatic chuck and the adsorption force was investigated. The attraction force is that the helium gas is supplied to the back surface (lower surface) of the wafer through the hole in which the lifter pin of the electrostatic chuck on which the wafer is mounted moves up and down, and the helium gas supply pressure (Back Press) when the wafer floats up. ) Defined in. First, in order to check the adsorption force, a Bare wafer and an Ox wafer (S under the thickness of 1 μm on the bottom surface of the Bare wafer were used).
Each of the wafers on which the iO ₂ film was formed) was measured using the applied DC voltage and the applied time as parameters.

3. Experimental Results FIG. 6 shows the attraction force on the surface of the electrostatic chuck according to the present invention and the comparative example. According to this, when the same high DC voltage is applied, it is apparent that the experimental example of the present invention has a stronger adsorption force than the comparative example. It should be noted that, in the experimental example of the present invention, even if the voltage of the reverse voltage and the application time are changed, the fluctuation of the adsorption force is small. Therefore, even if the pressure of the helium gas is increased, the wafer will not float up.
The heat transfer between the wafer W and the susceptor 6 is improved, and the temperature of the wafer W is made uniform.

[0071]

According to the present invention, it is possible to further increase the attraction force by reducing the throughput without lowering the throughput and charging the surface of the electrostatic chuck to the opposite polarity to the residual charge.
Further, the electrostatic chuck is not deteriorated by sputtering or the like as compared with the conventional method of removing the residual charges by using plasma. Further, the effect can be obtained with a smaller electric power than in the case of the conventional plasma neutralization.

Particularly, in the case of claim 2, it is possible to prevent the adsorption failure and further enhance the adsorption force, and in claim 3, if the pressure is equal to or higher than the pressure at which DC discharge is generated, no special pressure adjustment is required. Is. According to the plasma processing method of claims 4 to 6, it is possible to carry out in parallel while carrying out the carry-in / carry-out of the object to be processed such as a wafer and the operation of other mechanisms and devices associated therewith, so that rapid processing is possible. The throughput is also good.

According to the seventh and eighth aspects, since DC discharge does not occur between the supporting member such as the lifter pin and the electrostatic chuck as in the conventional case, the charge is not accumulated on the surface of the electrostatic chuck. Therefore, the suction failure is prevented. Moreover, this can be performed as a series of continuous processing in sequence, and the throughput is also good. The invention of claim 1 and the invention of claim 8 do not necessarily have to be implemented in combination, and have individual effects.

[Brief description of the drawings]

FIG. 1 is a cross-sectional explanatory diagram of an etching apparatus used in an embodiment of the present invention.

FIG. 2 is an enlarged explanatory view of a main part near an upper electrode and a lower electrode in the etching apparatus of FIG. 1, showing a state where a wafer is attracted to an electrostatic chuck.

FIG. 3 is an enlarged explanatory view of a main part near an upper electrode and a lower electrode in the etching apparatus of FIG. 1, showing a state in which a wafer is lifted up from an electrostatic chuck.

FIG. 4 is an explanatory diagram showing a timing chart according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a reverse voltage application sequence in an experiment.

6 is a graph showing a relationship between an applied voltage value of a DC high voltage applied to an electrostatic chuck and an attraction force in a method based on the experimental example of FIG. 5 and a conventional plasma static elimination method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Etching apparatus 2 Processing chamber 3 Processing container 6 Susceptor 11 Electrostatic chuck 12 Thin film 13 Resin 16 High voltage DC positive power supply 18 High voltage DC negative power supply 19 Ground terminal 20 Lifter pin 43 Processing gas supply source 44 Purge gas supply source 51 Upper electrode 61 Vacuum drawing Means 63, 66 High frequency power source 71 Gate valve 72 Load lock chamber 73 Transfer means W Wafer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location C23F 4/00 C23F 4/00 A H01L 21/3065 H02N 13/00 D H02N 13/00 H05H 1 / 46 B H05H 1/46 H01L 21/31 C // H01L 21/31 21/302 CF

Claims (8)

[Claims] 1. An object to be processed is adsorbed on the electrostatic chuck by using an electrostatic force generated by applying a DC voltage to the electrostatic chuck inside the processing chamber, and a predetermined processing gas is supplied into the processing chamber. Meanwhile, in the method of generating plasma in the processing chamber by supplying high-frequency power and performing predetermined plasma processing on the object to be processed on the electrostatic chuck, in the processing gas after the predetermined plasma processing is completed. And the supply of high-frequency power are stopped, and the object to be processed which has been subjected to plasma processing is separated from the electrostatic chuck, and then the object to be processed next is adsorbed on the electrostatic chuck. Before, while a gas was introduced into the processing chamber, a DC voltage having a reverse polarity to a DC voltage applied to the electrostatic chuck when adsorbing the object to be processed was applied to the electrostatic chuck. A characteristic is a plasma processing method. 2. Between the process of applying a direct current voltage to the electrostatic chuck when adsorbing the object to be processed and the process of applying a direct current voltage of the opposite polarity to the direct current voltage to the electrostatic chuck. The plasma processing method according to claim 1, wherein the electrode of the electric chuck is grounded. 3. The plasma processing method according to claim 1, wherein the gas pressure of the introduced gas is at least a gas pressure at which direct current discharge is generated. 4. Mounting of an object to be processed on the electrostatic chuck
The separation is performed by a support member that is capable of protruding from the electrostatic chuck, and a DC voltage of opposite polarity is applied during the operation of the support member.
The plasma processing method according to claim 1. 5. An object to be processed is carried in and out of a processing chamber by a transfer means, and a DC voltage having a reverse polarity is applied during the operation of the transfer means. The plasma processing method according to claim 1. 6. The process chamber is provided with a gate valve for loading and unloading the object to be processed, and a DC voltage of reverse polarity is applied while the gate valve is open. The plasma processing method according to claim 1. 7. An object to be processed is attracted onto the electrostatic chuck by using an electrostatic force generated by applying a DC voltage to the electrostatic chuck inside the processing chamber, and a predetermined processing gas is supplied into the processing chamber. While, while generating plasma in the processing chamber by the supply of high-frequency power, in a method of performing a predetermined plasma processing on the object to be processed on the electrostatic chuck, the object to be processed is placed on the electrostatic chuck, A first step of introducing a processing gas into the processing chamber and setting the gas pressure in the processing chamber to generate a DC discharge; and, after the first step,
A second step of applying a DC voltage to the electrostatic chuck, a third step of setting the pressure in the processing chamber to a pressure during plasma processing after the second step, and a step of And a fourth step of supplying high-frequency power. 8. Between the second step and the fourth step,
The plasma processing method according to claim 7, further comprising a step of supplying a heat transfer gas to the back surface of the object to be processed.