JP2882254B2 - 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 plasma processing method, and more particularly to a plasma processing method suitable for performing a plasma processing while controlling the temperature of a wafer.

[0002]

2. Description of the Related Art As a first prior art, for example, JP-B-56-53853 and JP-B-57-44747.
It is known that a wafer is electrostatically attracted onto a sample stage and processed by plasma, as described in Japanese Patent Application Laid-Open Publication No. H10-163,036. As a second conventional technique, as described in Japanese Patent Publication No. 2-27778 and Japanese Patent Laid-Open Publication No. 2-30128, a wafer is placed on a sample table and mechanically supported by a clamp. It is known that a He gas is introduced into the back surface of a wafer to perform processing while cooling the wafer by utilizing heat conduction, free convection or forced convection of the gas. Further, as a third prior art, as described in JP-A-58-32410 and JP-A-60-115226, after a wafer is electrostatically adsorbed on a sample table, He gas is applied to the back surface of the wafer. It is known to process the wafer while cooling the wafer by utilizing heat conduction, free convection or forced convection of the gas.

[0003]

When a wafer is continuously processed using the above-described conventional technology, for example, when an etching process is performed, there are the following problems to be solved. In the first prior art, since the heat transfer between the wafer and the sample stage is only a solid-solid contact, it is difficult to sufficiently cool the wafer being processed. In the second prior art, the cooling characteristic of the wafer is superior to that in the first prior art. However, as a new problem, since the outer periphery of the wafer is mechanically supported by the clamp, foreign matters due to chipping and the Foreign matter is easily generated by the adhesion of the deposit, and there is a problem in reducing dust. In the third related art, dust reduction can be achieved as compared with the second related art. However, in the method of performing the plasma processing while introducing the cooling gas to the back surface of the wafer as in the second and third conventional techniques, the flow rate and the exhaust amount of the cooling gas are finely changed alternately in order to control the wafer temperature during the processing. It is necessary to control the back surface pressure by adjusting, and there is a problem that the control becomes complicated. Further, it is necessary to provide a means for introducing a cooling gas to the sample stage, and the structure becomes complicated.

An object of the present invention is to provide a plasma processing method capable of easily controlling the temperature of a wafer during processing and simplifying the structure.

[0005]

In order to achieve the above object, a gas having a pressure higher than the processing pressure is introduced into the processing chamber .
After placing the wafer on the sample table in an atmosphere controlled to a pressure higher than the processing pressure, the wafer is electrostatically attracted and fixed on the sample table, and the gas is sealed in the gap between the sample table and the back of the wafer.
I can put it in . Thereafter, the pressure in the processing chamber is controlled to a predetermined processing pressure, and plasma processing of the wafer is performed.

[0006]

By placing a wafer in an atmosphere controlled at a pressure higher than the plasma processing pressure and electrostatically adsorbing the gas, a gas having a pressure higher than the processing pressure is also contained in the gap between the wafer and the sample stage. Thereafter, the pressure in the processing chamber is controlled to the plasma processing pressure. During the plasma processing, the gas sealed between the wafer and the sample stage leaks into the processing chamber through a gap due to the surface roughness between the wafer and the sample stage, and the pressure of the sealed gas gradually decreases. By adjusting the containment pressure or the electrostatic attraction force before placing the wafer, it is possible to maintain a gas pressure sufficient to cool the wafer during plasma processing.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. In this case, an etching process using a magnetic field microwave etching apparatus will be described as an example of the plasma process.

First, an overview of the magnetic field microwave etching apparatus will be described with reference to FIGS. 1 and 4. FIG.
The flow of wafer processing will be described with reference to FIG. Wafer 1
It is taken out of the load cassette 3 by the straight arm 2 and
It is carried into the load lock chamber 4. Then, the wafer 1 carried into the load lock chamber 4 is carried by the turning arm 7 toward the etching chamber 6 in the buffer chamber 5 which is a vacuum atmosphere, and is carried into the etching chamber 6.
Then, it is etched by a method to be described later, taken out into the atmosphere via the buffer chamber 5 and the unload lock chamber 8, and stored in the unload cassette 9.

Next, the structure of the etching chamber 6 will be described with reference to FIG. The etching of the wafer 1 is performed by the discharge tube 1
The process gas 11 introduced at a predetermined flow rate into 0 is turned into plasma 14 by the interaction of the microwave 12 and the magnetic field generated by the solenoid coil 13, and the high-frequency power is applied from the high-frequency power supply 16 to the lower electrode 15 which is a sample stage. The temperature control is performed while controlling the energy of ions incident on the wafer 1 and further circulating the coolant 18 from the circulator 17 through the lower electrode 15. On the lower electrode 15, an electrostatic chucking electrode 21 formed by spraying Al ₂ O ₃ on an Al electrode 19 in a reduced-pressure atmosphere to form an insulating film 20 is fixed.
Is connected to a DC power supply 24 via a low-pass filter 22 and a switch 23. In order to support the wafer 1 for performing the etching process, the lower electrode 15 is raised to support the outer periphery of the wafer 1 by the wafer presser 25, and then the plasma 14 is generated in the etching chamber 6 by the above-described method. Is turned on, a DC voltage is applied to both ends of the insulating film 20, and the insulating film 20 is supported by the generated electrostatic attraction force.

Next, the detailed configurations of the lower electrode 15 and the electrostatic attraction electrode 21 will be described with reference to FIGS. The lower electrode 15 and the electrostatic chucking electrode 21 are provided with wafer push-up pins 26 for lifting the wafer 1 from the electrostatic chucking electrode 21 for transferring the wafer 1 to the center of the mounting surface of the wafer 1. It is provided through a hole 27 provided in the electro-adsorption electrode 21. On the mounting surface of the electrostatic chucking electrode 21 on which the wafer 1 is mounted, a plurality of grooves 28 extending radially from the hole 27 and an annular groove 29 connecting the grooves 28 to each other are formed. These grooves 28 and 29 have a depth of 0.05 to 0.1.
mm and a width of 0.5 to 1 mm, which are processed by ultrasonic processing. One end of the wafer lifting pin 26 is supported by the slide bearing 30, and the other end is hermetically sealed by an O-ring 31. A plurality of gaps 32 are provided on the outer periphery of the slide bearing 30. Thereby, when the wafer 1 is not on the electrostatic attraction electrode 21, the grooves 28, 29 on the electrostatic attraction electrode 21
From the space between the wafer push-up pin 26 and the hole 27 is in communication with the etching chamber 6. The lower electrode 15 is provided with an exhaust hole 33 penetrating to the space between the wafer push-up pin 26 and the hole 27. Exhaust hole 3
When the valve 34 connected to the valve 3 is opened, the gas can be exhausted by a vacuum pump 36 for exhausting the etching chamber 6 through the valve 35 shown in FIG.

Next, an etching method using the above-configured apparatus will be described with reference to FIG. First, the pressure is adjusted to, for example, about 10 Torr by evacuating while introducing the process gas 11 into the etching processing chamber 6 at a predetermined flow rate. As a result, the grooves 28, 2 on the electrostatic chucking electrode 21 in communication with the etching chamber 6 are formed.
The pressure in the space from 9 to the gap between the wafer push-up pin 26 and the hole 27 is also about 10 Torr.

In this state, the wafer 1 is conveyed to the etching chamber 6 by the swivel arm 7 and the wafer push-up pins 2
After the wafer 1 is lifted by raising the rotating arm 6, the rotating arm 7
Is turned to the load lock chamber 4 side, and the wafer lifting pins 26 are lowered again. Thereby, the wafer 1 is placed on the electrostatic chucking electrode 21.

Then, with the lower electrode 15 raised and the outer periphery of the wafer 1 supported by the wafer retainer 25, the microwave 12 and the solenoid coil 13 are turned on to generate the plasma 14. Thereafter, the switch 23 is turned on to electrostatically attract the wafer 1 onto the electrostatic attracting electrode 21. Thus, the process gas 11 having a gas pressure of about 10 Torr is sealed in the space extending from the grooves 28 and 29 on the electrostatic chucking electrode 21 to the gap between the wafer push-up pin 26 and the hole 27, and the pressure on the back surface of the wafer 1 is reduced to about It becomes 10 Torr.

Next, once the microwave 14 and the solenoid coil 13 are turned off to extinguish the plasma 14, and the switch 23 is turned off to release the power supply for electrostatic attraction.
The evacuation of the process gas 11 from the inside of the etching processing chamber 6 is increased, and adjusted to an etching processing pressure lower than the initial pressure. During this time, the wafer 1 remains supported by the residual suction force. Groove 2 on electrostatic attraction electrode 21
The process gas 11 existing in the space extending from the gaps 8 and 29 to the gap between the wafer push-up pins 26 and the holes 27 causes the pressure drop in the etching chamber 6 to lower the outer peripheral surface of the wafer 1 and the outer peripheral surface of the electrostatic chucking electrode 21. Leaks into the etching processing chamber 6 through a gap having a surface roughness of about. The process gas 11 excluding the leakage is sealed on the back side of the wafer 1.

In addition, in addition to the above, the electrostatic chucking electrode 21 may be of a bipolar type and the wafer 1 may be electrostatically chucked during this time.

Next, the microwave 12 and the solenoid 1
3 is turned on again to generate the plasma 14, and the switch 23
Turn on. Thus, the wafer 1 is given an electrostatic attraction force, and is etched while being supported on the electrostatic attraction electrode 21. During the etching process of the wafer 1, the wafer push-up pins 26 are moved from the grooves 28 and 29 on the electrostatic attraction electrode 21.
The process gas 11 sealed in the space reaching the gap between the hole 27 and the gas leaks into the etching chamber 6 due to a pressure difference between the pressure in the etching chamber 6 and the pressure gradually decreases.
However, there is no problem because the wafer 1 is initially kept at a higher pressure so that the pressure required to maintain the temperature of the wafer 1 at a predetermined temperature is maintained during the etching process.

Thereafter, when the etching process is completed, the valve 34 is opened, and the vacuum pump 36 opens the electrostatic attraction electrode 2.
1. Wafer lifting pins 26 and holes 2 from grooves 28 and 29 on
After exhausting the process gas 11 in the space up to the gap 7, the microwave 12 and the solenoid coil 13 are turned off to extinguish the plasma 14, and the switch 23 is turned off to release the electrostatic attraction of the wafer 1. And the lower electrode 15
To release the support of the wafer 1 by the wafer presser 25.

Next, Table 1 shows the results of an experimental study on the temperature change of the wafer 1 during the etching process in the present etching method.

[0019]

[Table 1]

From this result, it is found that the amount of warpage of the wafer 1 is about 5 μm.
When the applied voltage to the electrostatic chucking electrode 21 is -300 V or more, the temperature change of the wafer 1 during the etching process is within about 1 ° C., and a good result is obtained. When the warpage of the wafer 1 is as large as about 30 μm, when the applied voltage is −300 V, the temperature change of the wafer 1 during the etching process is as large as about 2.7 ° C.
By increasing the applied voltage to -600V to increase the attraction force, the temperature change can be suppressed within 1 ° C,
Good results were obtained. The amount of heat input to the wafer 1 at this time was about 120 W / 6 inches.

The processing temperature of the wafer 1 can be set by changing the pressure on the back surface of the wafer 1 when the wafer 1 is placed and electrostatically attracted, or by changing the pressure on the back surface of the wafer 1 at the start of the etching process. The reproducibility of the temperature for each wafer during continuous processing can be obtained by providing a pressure gauge between the exhaust hole 33 and the valve 34 and controlling the pressure at the start of etching to a constant value.

The grooves 28 and 29 on the electrostatic attraction electrode 21
In addition to the process gas 11, a gas other than the process gas such as He gas may be used as a gas to be sealed in the space from the wafer push-up pin 26 to the gap between the holes 27. In this case, He gas or the like is introduced into the etching processing chamber 6 before the wafer 1 is placed, and when the wafer is placed and the electrostatic adsorption is completed, the process gas 11 is replaced with a containment gas such as He gas. It is introduced into the etching processing chamber 6, and the etching processing is performed by controlling the processing pressure to a predetermined value.

As described above, according to the present embodiment, a gas is introduced into the processing chamber, and the wafer is placed on the sample table in an atmosphere controlled to a pressure higher than the etching processing pressure. Then, the wafer in plasma processing is cooled between the wafer and the sample stage by controlling the pressure in the processing chamber to the processing pressure and performing plasma processing on the wafer. It is possible to maintain a gas with sufficient pressure to easily control the temperature of the wafer during processing and to provide a conventional mechanism for supplying a cooling gas between the wafer and the sample stage. Therefore, the structure of the apparatus can be simplified.

[0024]

According to the present invention, the temperature of the wafer can be easily controlled and the structure can be simplified.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of an etching processing chamber of an apparatus for performing a plasma processing method of the present invention.

FIG. 2 is a longitudinal sectional view showing details of a wafer arrangement part of an etching processing chamber part of FIG. 1;

FIG. 3 is a partial sectional view showing details of FIG. 2;

FIG. 4 is a plan view showing an overall configuration of an etching apparatus which is one embodiment of a plasma processing apparatus for performing the plasma processing method of the present invention.

FIG. 5 is a time chart showing an etching method as an embodiment of the plasma processing method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wafer, 11 ... Process gas, 15 ... Lower electrode, 1
6 ... High frequency power supply, 20 ... Insulating film, 21 ... Electrostatic attraction electrode,
22: low-pass filter, 23: switch, 24: DC power supply, 25: wafer holder, 26: wafer lifting pin,
27 ... hole, 28, 29 ... groove, 30 ... slide bearing, 31
... O-ring, 33 ... exhaust hole, 34 ... valve, 36 ... vacuum pump.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-32410 (JP, A) JP-A-60-115226 (JP, A) JP-A-4-150937 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) H01L 21/3065

Claims (1)

(57) [Claims] A step of mounting a wafer on a sample table in a processing chamber system in which a gas pressure is higher than a processing pressure; and a step of electrostatically adsorbing the wafer on the sample table and the sample table and the wafer.
A plasma processing method, comprising: a step of controlling the inside of the processing chamber to a predetermined pressure after sealing a gas in a gap between the back surface and the substrate; and a step of performing a plasma processing on the wafer at the predetermined pressure.