JP3315197B2 - Plasma processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing an object to be processed.

[0002]

2. Description of the Related Art When a conventional object to be processed, for example, a semiconductor wafer is separated from a semiconductor wafer holding portion of an electrostatic chuck for attracting and holding the wafer by electrostatic force, plasma is generated. The plasma is stopped, and the semiconductor wafer holding portion of the electrostatic chuck is brought into contact with electrically grounded conductive pins on the back surface of the semiconductor wafer in order to remove residual charges charged on the semiconductor wafer itself. A method for removing the residual charge charged on the surface and removing the residual charge charged on the semiconductor wafer holding portion of the electrostatic chuck through the semiconductor wafer, thereby separating the workpiece from the workpiece holding portion of the electrostatic chuck. It has been known.

[0003]

However, in the means for bringing the electrically grounded conductive pins into contact with the back surface of the semiconductor wafer after stopping the plasma, the pins are brought into point contact with the back surface of the semiconductor wafer. However, a single contact of the pins cannot completely eliminate the residual charges charged on the semiconductor wafer itself and the residual charges charged on the semiconductor wafer holding portion of the electrostatic chuck. It is necessary to contact the pins several times, and there has been a problem that the contact of the pins may damage the back surface of the semiconductor wafer. Further, if the residual charge charged on the semiconductor wafer itself and the residual charge charged on the semiconductor wafer holding portion of the electrostatic chuck are not completely removed, the semiconductor wafer is separated from the semiconductor wafer holding portion of the electrostatic chuck by pins. When the pins for lifting the semiconductor wafer from the back surface rise above the semiconductor wafer holding portion of the electrostatic chuck, portions where the pins are not in contact, for example, the peripheral portion of the back surface of the semiconductor wafer remain adsorbed by residual charges,
When the semiconductor wafer itself warps, and the pins are further raised, the periphery of the semiconductor wafer is detached from the semiconductor wafer holding portion of the electrostatic chuck, and at this moment, the semiconductor wafer jumps due to the recoil of the warp and hits the wall of the processing chamber, etc. There is a problem that the wafer itself is damaged. Further, when an insulating film, for example, an oxide film such as a natural oxide film is formed on the surface of the semiconductor wafer, residual charges charged on the surface of the insulating film are:
Even when a conductive pin that is electrically grounded contacts, the part that does not contact the pin is electrically blocked by the insulating film, so that the residual charge on the surface of the insulating film can be removed over the entire surface. There was a problem that it was not possible.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method in which an object to be processed is attracted and held by an electrostatic force from an object holding portion of an electrostatic chuck while maintaining a horizontal state with the object holding portion of the electrostatic chuck.
It is an object of the present invention to provide a method for detaching an object to be detached.

[0005]

According to the present invention, the electrostatic chuck is provided by applying a voltage to an electrostatic chuck provided in a processing chamber.
In a plasma processing method in which an object to be processed is attracted and held on a holding surface of a chuck, and a processing gas introduced into a processing chamber is turned into plasma by high-frequency power to perform plasma processing on the object, the high-frequency power A step of stopping the voltage applied to the electrostatic chuck, and a pin that penetrates the electrostatic chuck in a state where the high-frequency power is applied. Lifting the workpiece from the holding surface of the electrostatic chuck , and holding the workpiece and the electrostatic chuck .
It removes the residual charge on the holding surface .

[0006]

According to the present invention, the object to be processed is detached from the object holding portion of the electrostatic chuck during the generation of the plasma, so that ions or electrons in the plasma are transferred between the object and the object holding portion of the electrostatic chuck. And if the residual charge is negative,
If the residual charge is neutralized by the ions and the residual charge is positive, the neutralized charge is neutralized by the electrons and the residual charge charged on the workpiece holding portion or the workpiece of the electrostatic chuck is more reliably and quickly eliminated. Can be.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a plasma etching apparatus to which an object to be processed according to an embodiment of the present invention is applied will be described with reference to the drawings. First, the configuration of the plasma etching apparatus will be described with reference to FIGS.

In this plasma etching apparatus, as shown in FIG. 1, an airtight processing chamber 1, an upper electrode 2 and a lower electrode 3 for generating plasma in the processing chamber 1, It comprises an exhaust system 4 for reducing the pressure, and a loading / unloading system 6 for loading / unloading an object to be processed, for example, a semiconductor wafer 5 into / from the processing chamber 1.

In the processing chamber 1, at least the inner wall surface is formed of a conductor, for example, Al, and the surface of the inner wall surface is subjected to an alumite oxide treatment. A heating means (not shown) for preventing a product from adhering to the inner wall surface, for example, a heater is built in, and a heating temperature, for example, 50 ° C. to 100 ° C.
It can be set to an appropriate temperature within the range.

The upper electrode 2 is disposed in the upper part of the processing chamber 1, and one end of the upper electrode 2 passes through the upper part of the processing chamber 1 in an airtight manner, and a processing gas such as CHF ₃ , a gas supply pipe 7 for supplying a processing gas such as CF ₄ or CO or an inert gas such as N ₂ gas, and the other end is supplied from the gas supply pipe 7 in the direction of the semiconductor wafer 5. A plurality of gas discharge ports 8 for discharging the processed processing gas are formed radially, and the upper electrode 2 is electrically grounded by a wiring 9.

The lower electrode 3 is provided at a position facing the upper electrode 2 and has an electrostatic chuck 10 for attracting and holding the semiconductor wafer 5 by electrostatic force. An electrostatic chuck sheet 11 of the electrostatic chuck 10 as a holding portion for sucking and holding the semiconductor wafer 5 is made of an electrolytic foil copper 12 made of a conductive material on both sides of an insulating film, for example, a polyimide film 13 made of a polyimide resin. Each is glued with an adhesive to form a sandwich structure. Further, a power supply rod 14 for supplying a high voltage, for example, a voltage of 200 V to 3 KV to the electrolytic foil copper 12 is connected to the electrolytic foil copper 12, and the power supply rod 14 is provided on the bottom surface of the processing chamber 1. It penetrates in an airtight and insulated state, and is connected to a high-voltage power supply 15 via switching means, for example, an electromagnetic switch 16. The electromagnetic switch 16 is configured to be turned on or off by a control signal of a control unit 17.

Further, a susceptor 1 made of a conductive material, for example, Al is provided below the electrostatic chuck sheet 11.
The susceptor 18 is provided with a blocking
RF via the capacitor 19, for example 13.56MH
It is connected to a high frequency power supply 21 of z, 40 MHz or the like.
A susceptor support 22 is provided below the susceptor 18.
The temperature of the semiconductor wafer 5 is set to, for example, −30 ° C. to −150 ° C. inside the susceptor support 22.
A refrigerant reservoir 20 containing a refrigerant, for example, liquid nitrogen, is provided in order to bring the temperature to ° C. refrigerant discharge pipe 24 for discharging the N ₂ is connected.

The susceptor 18, the susceptor support 22, and the electrostatic chuck sheet 11 have a heat transfer function of transferring the temperature of the coolant reservoir 20 to the semiconductor wafer 5 via the electrostatic chuck sheet 11. Heat transfer medium supply passage 25 for supplying a medium, for example, He gas as an inert gas.
Are drilled.

Further, as shown in FIG.
The susceptor 18 of the lower electrode 3, the susceptor support 22, the electrostatic chuck sheet 11 provided on the upper surface of the susceptor 18, and a plurality of through holes 26 penetrating the bottom surface of the processing chamber 1. For example, three holes are provided. Inside the through hole 26, a pin 28 formed of a conductive member and electrically grounded via an inductance 27 is provided. Further, the pin 28 is connected to a pin support 30 via an insulating member such as a ceramic 29.
The bellows 5 is provided on the periphery of the pin support 30 and on the bottom surface of the processing chamber 1 so that the space between the processing chamber 1 and the pin support 30 is airtight and expandable.
0 is provided, and the pin support 30 is connected to up / down means such as an air cylinder 31 for vertically moving the pin 28 by moving the pin support 30 up and down. The pin 28 is moved up and down by the up and down driving of the 31, and the detaching means 5 is placed so that the semiconductor wafer 5 is placed on the holding surface 32 of the electrostatic chuck sheet 11 or is detached from the holding surface 32.
1 is configured.

As shown in FIG. 1, the exhaust system 4 has a gas outlet 33 at the bottom of the processing chamber 1 for reducing the pressure in the processing chamber 1. It is connected to a vacuum exhaust device 35, for example, a turbo molecular pump, via an exhaust gas pipe 34, and is configured.

The loading / unloading system 6 is provided with a loading / unloading port 36 for loading or unloading the semiconductor wafer 5 on a side wall of the processing chamber 1.
7, the gate valve 3
A load lock chamber 38 is provided at a position opposed to the processing chamber 1 across the load chamber 7, and a loading / unloading arm for loading / unloading the semiconductor wafer 5 into / from the processing chamber 1 is provided in the load lock chamber 38. 39 are provided and configured.
The plasma etching apparatus has been described.

The operation of the plasma etching apparatus having the above-described structure for detaching the semiconductor wafer 5 from the electrostatic chuck sheet 11 which holds the semiconductor wafer 5 by electrostatic force will be described.

The gate valve 37 is opened, the semiconductor wafer 5 held by the carry-in / out arm 39 is moved above the electrostatic chuck sheet 11 in the processing chamber 1, and the semiconductor wafer 5 is delivered to the pins 28. The loading / unloading arm 39 returns to the load lock chamber 38, closes the gate valve 37,
The pins 28 are lowered by the air cylinder 31, and the semiconductor wafer 5 is placed on the holding surface 32 of the electrostatic chuck sheet 11.

The holding surface 32 of the electrostatic chuck sheet 11
When the semiconductor wafer 5 is placed on the semiconductor wafer 5, the switch 16 is closed in advance, and a high voltage is supplied to the electrolytic foil copper 12 of the electrostatic chuck sheet 11, so that the surface of the semiconductor wafer 5 is as shown in FIG. As described above, the negative charge 40 is charged, the positive charge 41 is charged on the holding surface 32 of the electrostatic chuck sheet 11, and the positive charge 40 and the negative charge 41 generate an electrostatic attraction force. The semiconductor wafer 5 is suction-held by the holding surface 32 of the electrostatic chuck sheet 11 by the electrostatic suction force.

Next, a processing gas is supplied from a gas supply pipe 7, and the processing gas is introduced into the processing chamber 1 from a gas discharge port 8.
The pressure in the processing chamber 1 is set to a set value, for example, 10 mTorr to 10 mTorr.
The gas is stabilized at Torr, and He gas is supplied from the heat transfer medium supply path 25 to the entire back surface of the semiconductor wafer 5. Next, a processing power, for example, 500 to 2 KW is applied from the high-frequency power supply 21 to generate plasma between the upper electrode 2 and the semiconductor wafer 5, and the semiconductor wafer 5 is etched by the plasma. No, semiconductor
Since the wafer 5 is quasi-grounded, the suction force of the semiconductor wafer 5 attracted to the holding surface 32 of the electrostatic chuck sheet 11 increases. Next, a process of detaching the semiconductor wafer 5 from the holding surface 32 of the electrostatic chuck sheet 11 will be described. After the applied power of the high-frequency power supply 21 is reduced to an applied power at which the semiconductor wafer 5 is hardly etched, for example, 80 W or less,
The He gas supplied from the heat transfer medium supply passage 25 to the entire back surface of the semiconductor wafer 5 is stopped, and the electrostatic chuck sheet 11 is stopped.
The high voltage application to the electrolytic foil copper 12 is cut off by opening the switch 16.

Further, as shown in FIG. 3, ions in the plasma generated by the applied power which does not proceed with the etching of the semiconductor wafer 5 described above, for example, when the processing gas is CO, CO
+ Or electrons enter between the semiconductor wafer 5 and the holding surface 32 of the electrostatic chuck sheet 11, and the negative residual charges 40 charged from the periphery of the semiconductor wafer 5 to the surface of the semiconductor wafer 5 are formed by ions, The positive residual charges 41 charged on the holding surface 32 of the electrostatic chuck sheet 11 are neutralized (discharged) toward the center of the semiconductor wafer 5 by the electrons. With the progress of the neutralization, the pins 28 are raised by the air cylinder 31, the semiconductor wafer 5 is raised, and ions or electrons in the plasma are generated between the semiconductor wafer 5 and the holding surface 32 of the electrostatic chuck sheet 11. The neutralization (removal of charge) of the residual charge remaining on the surface of the semiconductor wafer 5 and the holding surface 32 of the electrostatic chuck sheet 11 is accelerated, and the semiconductor wafer 5 is separated from the holding surface 32 of the electrostatic chuck sheet 11. .

The effect of the embodiment constructed as described above will be described. Residual charges charged on the semiconductor wafer 5 and the semiconductor wafer holding surface 32 of the electrostatic chuck sheet 11
Is neutralized by ions or electrons in the plasma from the periphery of the semiconductor wafer 5 toward the center of the semiconductor wafer 5, and the semiconductor wafer 5 is separated from the holding surface 32 of the electrostatic chuck sheet 11 by the pins 28. Therefore, even if the pins 28 for lifting the semiconductor wafer 5 from the back surface rise above the holding surface 32 of the electrostatic chuck sheet 11, the semiconductor wafer 5 itself is not adsorbed by the peripheral edge of the back surface of the semiconductor wafer 5 due to residual charges. The semiconductor wafer 5 can be detached from the holding surface 32 of the electrostatic chuck sheet 11 while keeping a horizontal state without warping. Also,
The residual charge charged on the semiconductor wafer 5 and the residual charge charged on the semiconductor wafer holding surface 32 of the electrostatic chuck sheet 11 can be uniformly removed over the entire surface. Further, when the residual charge of the object to be processed is separated from the object to be processed during generation of the plasma, it can escape to the upper electrode or the like through the plasma and remove more residual charge.

Although the embodiment has been described with reference to the plasma etching apparatus, the present invention is not limited to the plasma etching apparatus, but may be applied to an apparatus for processing an object to be processed by plasma, such as CVD or LCD.

[0024]

According to the present invention, the object to be processed is held on the object holding portion of the electrostatic chuck because the residual charge charged on the object to be processed or the object to be processed is more reliably removed. The object can be detached from the portion while maintaining a more horizontal state, and the object to be processed can be detached more safely because the object does not bounce due to warpage.

[0025]

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a plasma etching apparatus to which a first embodiment according to the present invention is applied.

FIG. 2 is a schematic cross-sectional view showing an operation of detaching the object to be processed of FIG. 1 from an electrostatic chuck.

FIG. 3 is a partial cross-sectional view showing an operation of neutralizing a residual charge remaining on an object to be processed and an electrostatic chuck in FIG. 1;

[Description of sign]

 DESCRIPTION OF SYMBOLS 1 Processing chamber 2 Upper electrode 3 Lower electrode 4 Exhaust system 5 Workpiece (semiconductor wafer) 6 Loading / unloading system 10 Electrostatic chuck 11 Electrostatic chuck sheet (workpiece holding part) 28 Pin 32 Holding surface 51 Release means

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/68 B23Q 3/15 H01L 21/3065

Claims (1)

(57) [Claims] A voltage is applied to an electrostatic chuck provided in a processing chamber.
A plasma processing method for adsorbing and holding an object to be processed on the holding surface of the electrostatic chuck and converting the processing gas introduced into the processing chamber into plasma with high-frequency power to perform plasma processing on the object to be processed. After the completion of the step, a step of stopping the voltage applied to the electrostatic chuck by applying the high-frequency power to such an extent that the plasma is generated but the object to be processed is not subjected to the plasma processing; and Removing the object from the holding surface of the electrostatic chuck by raising a pin that penetrates the electric chuck,
A plasma processing method, comprising: removing charges remaining on the object to be processed and the holding surface of the electrostatic chuck.