JP2002164325A - Method for suppressing adhesion of particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method wherein the number of particles to be stuck to the surface of a sample, electrostatically attracted to an electrostatic chuck, is reduced easily and their adhesion can be suppressed. SOLUTION: In a plasma treatment apparatus, the sample S is placed on the electrostatic chuck 8, a switch 10 is turned on; a DC voltage is applied to the electrostatic chuck 8 by a DC power supply 9, in a state such that the sample S is attracted to the electrostatic chuck 8 by electrostatic force; a gas such as C4F8, SF6 or the like is introduced into a reaction chamber 2a via a gas inlet pipe 6 at a prescribed pressure (6 mTorr or higher) and for a prescribed time (30 s or longer); and many particles which are stuck to the surface of the sample S are removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus for performing plasma processing on a sample adsorbed on an electrostatic chuck, and suppresses particles (dust, dust, processing residues, etc.) from adhering to the sample. On how to do it.

[0002]

2. Description of the Related Art A plasma generated in a reactor is used to etch a sample such as a semiconductor substrate or a glass substrate.
Performing a plasma treatment such as ashing is widely performed in a semiconductor device manufacturing process. In an apparatus for performing such a plasma processing, an electrostatic chuck is provided to hold a sample to be processed in a reactor. This electrostatic chuck uses an electrostatic chuck method.
A plate-shaped conductor whose outer surface is covered with a thin-film insulator is fixed in the reactor, the sample is brought into close contact with the insulator surface, and a predetermined DC voltage is applied between the conductor and the sample. Then, an electrostatic force is generated between the two, and the sample is attracted and held on the electrostatic chuck by the electrostatic force.

[0003] With the sample thus adsorbed to the electrostatic chuck, a reaction gas is introduced into the reactor, the introduced reaction gas is excited to generate plasma, and the generated plasma is used. The sample is subjected to plasma processing such as etching and ashing.

[0004]

In such a method of electrostatically attracting a sample to an electrostatic chuck by such an electrostatic chucking method, a sample is placed on the electrostatic chuck and then placed on the electrostatic chuck. When a voltage is applied, the surface of the sample is charged, and there is a problem that particles such as dust, dust, and residues from the plasma treatment easily adhere to the surface. When such particles adhere to the sample, the sample after the plasma processing cannot obtain desired physical properties and a desired processing shape.
There is a demand for a method for suppressing the adhesion of particles to a sample.

[0005] The present invention has been made in view of such circumstances, and by applying a gas after applying a voltage to an electrostatic chuck, the number of particles adhering to the surface of a sample can be easily reduced. It is another object of the present invention to provide a method for suppressing particle adhesion that can suppress particle adhesion.

[0006]

According to a first aspect of the present invention, there is provided a plasma processing apparatus for performing plasma processing on a sample adsorbed on an electrostatic chuck in a reactor. In the method for suppressing the adhesion to the sample surface, the method further comprises introducing a gas into the reactor after adsorbing the sample on the electrostatic chuck, and removing particles adhering to the sample surface. I do.

In the method for suppressing particle adhesion according to the first invention, a gas is introduced into the reactor after applying a voltage to an electrostatic chuck in the reactor on which the sample is placed, and the gas adheres to the surface of the sample. Remove the particles that are

According to a second aspect of the present invention, in the first aspect of the present invention, the plasma used in the plasma processing is generated by exciting a reaction gas, and is introduced to suppress the adhesion of the reaction gas and the particles. The gas is of the same type.

In the particle adhesion suppressing method according to the second aspect of the present invention, a reaction gas used for plasma generation is used as such a gas introduced for suppressing the particle adhesion to the sample surface. Therefore, it is not necessary to specially prepare a gas for suppressing particle adhesion.

[0010] A particle adhesion suppressing method according to a third invention is characterized in that, in the first or second invention, the introduction time of the gas introduced for suppressing the particle adhesion is 30 seconds or more.

According to the third aspect of the present invention, the gas is introduced for a period of 30 seconds or more.
Therefore, the effect of gas introduction is sufficiently exhibited, and the adhesion of particles can be suppressed efficiently.

In a fourth aspect of the present invention, in the first or second aspect, the pressure of the gas introduced to suppress the adhesion of the particles is 6 mTorr or more.

In the particle adhesion suppressing method according to the fourth invention, the gas is introduced at a pressure of 6 mTorr or more.
Therefore, the effect of gas introduction is sufficiently exhibited, and the adhesion of particles can be suppressed efficiently.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a configuration diagram of a plasma processing apparatus for performing the particle adhesion suppressing method according to the present invention. In FIG. 1, reference numeral 1 denotes a reactor, which is a reaction chamber 2a in which a sample is provided and plasma processing is performed.
And a plasma generation chamber 2b for generating plasma above the plasma generation chamber 2b
And

The plasma generation chamber 2b has the shape of a hollow cylinder, and one end of a waveguide 4 is connected to the center of the upper wall through a microwave introduction window 3. The microwave introduction window 3 is formed by molding a dielectric such as quartz glass into a plate shape, and seals the plasma generation chamber 2b from the outside in an airtight state. A microwave oscillator (not shown) is connected to the other end of the waveguide 4, and the microwave oscillated by the microwave oscillator is guided to the microwave introduction window 3 by the waveguide 4, and the microwave introduction window 3 The light is transmitted and incident into the plasma generation chamber 2b. Around the plasma generation chamber 2b, the plasma generation chamber 2b and one end of the waveguide 4 are surrounded by the plasma generation chamber 2b.
Excitation coil 5 is arranged concentrically with b.

A gas introduction pipe 6 for introducing gas into the reaction chamber 2a and the plasma generation chamber 2b is provided near the upper end of the reaction chamber 2a.
Are connected so as to penetrate the peripheral surface of the reaction chamber 2a. An exhaust port 7 to which an exhaust device (not shown) is connected is opened in a lower wall of the reaction chamber 2a.

At the bottom of the reaction chamber 2a, an electrostatic chuck 8 is provided at a position facing the microwave introduction window 3.
The electrostatic chuck 8 is composed of a conductor and an insulating film covering the surface of the conductor, on which a sample S such as a silicon wafer is placed. Electrostatic chuck 8
Is connected to a DC power supply 9 via a switch 10, and by applying a DC voltage to the electrostatic chuck 8,
The sample S is held by suction on the electrostatic chuck 8.

In the case where the sample S is subjected to, for example, an etching process by using the plasma processing apparatus having such a configuration, the following is performed. First, the sample S to be processed is placed on the electrostatic chuck 8.
Is placed, the switch 10 is turned on, a predetermined DC voltage is applied to the electrostatic chuck 8, and the sample S is attracted and held on the electrostatic chuck 8 by electrostatic force. Thereafter, the pressure in the reaction chamber 2a and the plasma generation chamber 2b is reduced to a predetermined pressure by exhausting air from the exhaust port 7, and then the reaction chamber 2
Reaction gas such as C ₄ F ₈ gas and SF ₆ gas is introduced into the plasma generation chamber 2a at a predetermined flow rate. Then, the plasma generating chamber 2 is formed while forming a magnetic field by the exciting coil 5.
b. A microwave is supplied into b and the introduced reaction gas is subjected to ECR.
The sample S that is attracted to the electrostatic chuck 8 is excited by a divergent magnetic field generated by the exciting coil 5 and having a magnetic flux density decreasing toward the reaction chamber 2a.
The plasma is drawn out, and the sample S
Is etched.

Next, a specific example of a method for suppressing adhesion of particles, which is a feature of the present invention, which is performed on a plasma processing apparatus having such a configuration and operation will be described.

In the plasma processing apparatus having the above-described configuration, a gas is introduced after a DC voltage is applied to the electrostatic chuck 8. That is, after the sample S is placed on the electrostatic chuck 8, the switch 10 is turned on, a DC voltage is applied to the electrostatic chuck 8 by the DC power supply 9, and the sample S is attracted to the electrostatic chuck 8 by electrostatic force. In this state, a predetermined type of gas is introduced into the reaction chamber 2a through the gas introduction pipe 6 at a predetermined pressure and a predetermined flow rate for a predetermined time. An example of gas introduction at this time is as follows. The gas used is of the same type as the gas introduced in the etching process. Gas type: C ₄ F ₈ , SF ₆ Gas flow rate: C ₄ F ₈ 85 sccm, SF ₆ 130 s
ccm Gas pressure: 12 mTorr Introduction time: 60 seconds

When the gas is introduced while the sample S is adsorbed on the electrostatic chuck 8 as described above, the electric charges existing on the surface of the sample S are linked to the molecules of the introduced gas, and the electric charges are transferred to the reaction chamber 2a. It is considered that as a result, the amount of charge on the surface of the sample S is reduced, and a large number of particles adhering thereto are removed. At this time, it is needless to say that the charge amount on the surface of the sample S is not reduced to the extent that the suction effect on the electrostatic chuck 8 is lost.

Next, the measurement result of the number of particles on the surface of the sample S in such a case will be described. A silicon wafer having a diameter of 5 inches was used as the sample S, and the silicon wafer was sucked and held by the electrostatic chuck 8, and then gas was introduced under the above-described conditions. Thereafter, the sample S was taken out and the particles adhering to the surface were removed. The number was measured. The measurement results of the four examples were compared with those having a size of 0.3 to 0.5 μm and 0.5
It is shown in Table 1 below, divided into those having a size of μm or more.

[0023]

[Table 1]

Further, as a comparative example of the present invention, a similar silicon wafer having a diameter of 5 inches was used as a sample S, which was adsorbed and held on the electrostatic chuck 8, and then left as it was without introducing gas. After leaving for a second, the number of particles attached to the surface was measured. The measurement results of the four cases are 0.3-
Table 2 below shows those having a size of 0.5 μm and those having a size of 0.5 μm or more.

[0025]

[Table 2]

As is clear from the comparison between Tables 1 and 2, it can be seen that the number of particles adhering to the sample S can be significantly reduced by introducing the gas.

Next, the optimal range of the conditions (time and pressure) for gas introduction for suppressing such particle adhesion will be described.

(Optimal range of gas introduction time) Under the following conditions (only the gas introduction time is variable and other conditions are constant), the sample S is adsorbed on the electrostatic chuck 8 and then the gas is introduced. The number of particles adhering to was measured. FIG. 2 shows the measurement results in this case. In FIG. 2, the horizontal axis represents the gas introduction time, and the vertical axis represents the number of particles attached. Sample S: 5 inch diameter silicon wafer Gas type: C ₄ F ₈ , SF ₆ Gas flow rate: 85 sccm for C ₄ F ₈ and 130 s for SF ₆
ccm Gas pressure: 12 mTorr Introducing time: 0 second (comparative example), 15 seconds, 30 seconds, and 60 seconds

From the results shown in FIG. 2, when the gas introduction time is set to 30 seconds or more, the number of adhered particles becomes extremely small, and the effect of suppressing the particle adhesion accompanying the gas introduction can be efficiently exhibited. You can see that. Therefore, the time for introducing the gas is preferably 30 seconds or more.

Under the following conditions (the optimum range of the pressure of the introduced gas) (only the gas pressure is variable and other conditions are constant), the sample S
Is adsorbed to the electrostatic chuck 8 and then gas is introduced to the sample S.
The number of particles adhering to was measured. The measurement result in this case is shown in FIG. In FIG. 3, the horizontal axis represents the pressure of the introduced gas, and the vertical axis represents the number of particles attached. Sample S: 5 inch diameter silicon wafer Gas type: C ₄ F ₈ , SF ₆ Gas flow rate: 85 sccm for C ₄ F ₈ and 130 s for SF ₆
ccm Introduction time: 60 seconds Gas pressure: 0 mTorr (Comparative Example), 6 mTorr, 1
0mTorr, 12mTorr, 15Tmor, 18
6 cases of Tmorr

From the results shown in FIG. 3, the pressure of the introduced gas was set to 6
When mTorr or more, the number of attached particles is extremely small, and it can be seen that the effect of suppressing the attachment of particles due to gas introduction can be efficiently exhibited. Therefore, the pressure of the gas to be introduced is preferably set to 6 mTorr or more.

In the above-described example, the case where the present invention is applied to a plasma processing apparatus that generates plasma by microwaves has been described. However, the present invention is applicable to a plasma processing apparatus that generates plasma by high-frequency discharge. Needless to say.

[0033]

As described above in detail, in the method for suppressing the adhesion of particles according to the present invention, the gas is introduced after applying a voltage to the electrostatic chuck on which the sample is placed, so that the particles adhering to the surface of the sample are reduced. Can be easily reduced. As a result, in the plasma processing apparatus, it is possible to obtain a sample after the plasma processing having desired physical properties and a desired shape.

In addition, since a reaction gas used for plasma generation is used as a gas introduced to suppress the adhesion of particles to the sample surface, a gas for suppressing the adhesion of particles is specially prepared. It is not necessary to keep it, and the adhesion of particles can be suppressed easily at low cost.

Further, the introduction time and pressure of the gas introduced for suppressing the adhesion of particles are each set to 30 seconds or more, and
Since the pressure is set to mTorr or more, the adhesion of particles can be suppressed efficiently.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a plasma processing apparatus for performing a particle adhesion suppressing method according to the present invention.

FIG. 2 is a graph showing a change in the number of particles adhering to a sample when the introduction time of a gas to be introduced is changed.

FIG. 3 is a graph showing a change in the number of particles attached to a sample when the pressure of a gas to be introduced is changed.

[Explanation of symbols]

 Reference Signs List 1 reactor 2a reaction chamber 2b plasma generation chamber 3 microwave introduction window 4 waveguide 5 excitation coil 6 gas introduction pipe 7 exhaust port 8 electrostatic chuck 9 DC power supply 10 switch S sample

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toshihiko Ochi 1-10 Fuso-cho, Amagasaki-shi, Hyogo F-term in Sumitomo Precision Industries, Ltd. (Reference) 4G075 AA24 AA30 AA52 BC01 BC06 BD14 CA26 CA42 CA47 CA65 DA02 EA01 EB01 EB31 EC06 EC25 FC04 5F004 AA14 BA16 BB07 BB14 BB22 CA02 CA09 DA00 DA18

Claims (4)

[Claims] A plasma processing apparatus for performing plasma processing on a sample adsorbed on an electrostatic chuck in a reactor, wherein the method comprises suppressing adhesion of particles in the reactor to a surface of the sample. After adsorbing the sample on an electric chuck, a gas is introduced into the reactor to remove particles adhering to the sample surface. 2. The plasma used in the plasma processing is generated by exciting a reactive gas, and the reactive gas and the gas introduced for suppressing the adhesion of particles are of the same type. Item 4. The method for suppressing particle adhesion according to Item 1. 3. The method according to claim 1, wherein an introduction time of the gas introduced for suppressing particle adhesion is set to 30 seconds or more. 4. The method according to claim 1, wherein the pressure of the gas introduced for suppressing particle adhesion is set to 6 mTorr or more.