JP2001176958A - Plasma processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma processing method and a plasma processing system employing an electrostatic suction unit in which adhesion of particles to a semiconductor substrate is reduced. SOLUTION: In the plasma processing system employing an electrostatic suction unit 1, a semiconductor substrate 4 is charged negatively by applying a minus voltage to a suction electrode 2 which has been applied with a plus voltage before a plasma 5 disappears and then the plasma is extinguished.

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 provided with an electrostatic chuck for holding a semiconductor substrate.

[0002]

2. Description of the Related Art At the present time, with the increasing integration of various semiconductor devices such as memories and microcomputer chips, miniaturization of integrated circuits is rapidly advancing. For example, at present, semiconductor devices having integrated circuits of the 0.25 μm rule to the 0.18 μm rule are mass-produced, and the importance of measures for preventing particle contamination on the surface of a semiconductor substrate such as a semiconductor wafer is increasing.

Conventionally, plasma C using reactive plasma has been used for processing a semiconductor substrate in a semiconductor device manufacturing process.
A VD (Chemical Vapor Deposition) apparatus, a plasma etching apparatus and the like are used. In these plasma processing apparatuses, an electrostatic suction apparatus is widely used. Hereinafter, the electrostatic attraction device will be described with reference to FIG. Electrostatic suction device 1
Are the adsorption electrodes 2 and 2 'and the adsorption electrodes 2 and 2'
And a predetermined DC voltage is applied between the attraction electrode 2 and the semiconductor substrate 4 to generate an electrostatic force between the two. It is adsorbed and held on

[0004] The electrostatic attraction device 1 has a single-polarity type having a single voltage applied by one attraction electrode 2 and a single attraction voltage.
Are two or more, and the polarity of the applied voltage is two. The conventional example shown in FIG. 4 is a bipolar electrostatic attraction device 1 in which an attraction electrode 2 is divided into two, an outer peripheral side and an inner peripheral side. In the case of the monopolar type, since the ground is taken to the reaction chamber wall via the plasma 5, the attracting force does not occur unless the plasma 5 is generated on the semiconductor substrate 4. Further, even after the application of the voltage to the attraction electrode 2 is stopped, the residual attraction force is large, and it is necessary to generate the plasma 5 to peel off the semiconductor substrate 4 from the electrostatic attraction device 1, which causes a decrease in throughput. Cause. Further, if the semiconductor substrate 4 is to be peeled off from the surface of the electrostatic attraction device 1 in a state where the residual attraction force is large, the semiconductor substrate 4 is displaced or broken, which causes a transport trouble.

On the other hand, in the bipolar type, the semiconductor substrate 4 can be applied without generating plasma by applying positive and negative voltages to the adsorption electrodes 2 and 2 ', respectively.
There is an advantage that can be adsorbed. Further, the residual attraction force after the application of the voltage to the attraction electrodes 2 and 2 'is stopped is small, which is advantageous from the viewpoint of throughput. For this reason, the bipolar type has recently become mainstream in place of the monopolar type.

[0006] Unlike the mechanical suction device such as the clamp type, the electrostatic suction device 1 has almost no particles due to sliding dust generation because there is no portion directly in contact with the surface of the semiconductor substrate 4. However, the use of the electrostatic attraction device 1 causes a problem that particles attached to the semiconductor substrate 4 due to another cause increase. This means that the surface of the semiconductor substrate 4 is charged by using the electrostatic attraction device 1 to cause particles to adhere. Here, the behavior of particles during plasma processing will be described.

While the high frequency is applied and the plasma 5 is maintained, the generated particles are trapped and floated on the interface between the plasma region and the sheath region on both the high frequency electrode side and the ground electrode side. This is because in the state where the plasma 5 is being generated, the high-frequency electrode and the ground electrode are negatively charged due to the bias voltage, and are repelled by the similarly negatively charged particles and Coulomb force.

When the application of the high frequency is stopped and the plasma 5 is extinguished, the particles trapped at the boundary between the plasma region and the sheath region move and adhere to the surface of the semiconductor substrate 4. As measures to prevent this, Japanese Patent Application Laid-Open No. 3-153885 discloses that a semiconductor substrate 4 is carried into a reaction chamber while plasma is generated, and the semiconductor substrate 4 is generated while plasma 5 is generated.
Is disclosed from the reaction chamber. This is to generate and maintain the plasma 5 so that particles are trapped at the interface between the plasma region and the sheath region, thereby preventing the particles from adhering to the surface of the semiconductor substrate 4. In the present invention, when the semiconductor substrate 4 is carried into the reaction chamber, the region of the plasma density is changed from a low region to a high region, and when the semiconductor substrate 4 is carried out of the reaction room, the region of the semiconductor substrate is changed from a high region to a low region. The movement of the semiconductor substrate 4 may cause a bias in the in-plane potential of the semiconductor substrate 4 and may cause device damage. For this reason, there is a problem that the yield of semiconductor device manufacturing is reduced. Incidentally, Japanese Patent Application Laid-Open No. 3-153885 can be mentioned as this kind of technology.

[0009]

In the above-mentioned prior art, it is desirable to extinguish the plasma when the semiconductor substrate 4 is carried into and out of the reaction chamber. There is a problem that particles trapped on the boundary surface with the region adhere to the surface of the semiconductor substrate 4 immediately after performing the plasma processing.

An object of the present invention is to provide a plasma processing method and a plasma processing apparatus in which particles are less attached to the surface of the semiconductor substrate 4 while preventing device damage. It is to be.

[0011]

According to the present invention, a negative voltage is applied to all the attracting electrodes 2 of the electrostatic attracting apparatus 1 before the application of the high frequency is stopped and the plasma is extinguished.
The semiconductor substrate 4 is negatively charged, and the negatively charged particles are repelled by electrostatic force to prevent the particles from adhering to the surface of the semiconductor substrate 4. At this time, during the plasma processing on the semiconductor substrate 4, positive and negative voltages are applied to the attraction electrodes 2 and 2 'in the electrostatic attraction device 1 to attract the semiconductor substrate 4, and the positive voltage is applied immediately before the plasma processing is completed. A negative voltage is applied to the suction electrode 2 to which the above voltage was applied.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS.

FIG. 1 shows a parallel plate type plasma etching apparatus to which an embodiment of the present invention is applied. In this apparatus, an upper electrode 7 and an electrostatic chuck 1 are installed in a reaction chamber 6 held in a vacuum. In this embodiment, the electrostatic chuck 1
A high-frequency electrode 8 for applying a high-frequency of 500 W is built in as a lower electrode. The upper electrode 7 is grounded. A semiconductor substrate 4 is provided in the electrostatic chuck 1.
The electrodes 2 and 2 ′ for adsorbing the semiconductor substrate are built in. The semiconductor substrate 4 is adsorbed on the electrostatic adsorption device 1 to perform plasma processing.

The processing gas 9 is SF ₆ (sulfur hexafluoride)
Is introduced into the reaction chamber 6 through the upper electrode 7 at 300 sccm and BCl ₃ (boron trichloride) at 80 sccm, and the plasma 5 is generated by the high frequency applied to the high frequency electrode 8 built in the electrostatic adsorption device 1. A process (here, an etching process) is performed by exposing the semiconductor substrate 4 to the plasma 5. The processing gas 9 and the reaction products are exhausted from an exhaust port 10.

FIG. 2 is a side sectional view of the electrostatic chuck 1 of the embodiment, and shows an enlarged view when the semiconductor substrate 4 is sucked. Electrostatic electrodes 2 and 2 ′ are provided inside the electrostatic adsorption device 1. A DC power supply 11 for applying a positive voltage, a DC power supply 11 ″ for applying a negative voltage, and switches 12 and 12 for turning on and off the application of voltages of respective polarities to the attracting electrode 2. ″. The other attracting electrode 2 'is provided with a DC power supply 11' for applying a negative voltage and a switch 12 'for turning ON / OFF the voltage application. By supplying power to these suction electrodes 2 and 2 ′, the semiconductor substrate 4 is suctioned and held on the upper surface of the electrostatic suction device 1.

Since the semiconductor substrate 4 is heated by the plasma 5, it is often necessary to cool the semiconductor substrate 4 to maintain an appropriate temperature. Since normal plasma processing is performed under a low pressure of about several Pa, the heat transfer efficiency between the semiconductor substrate 4 and the upper surface of the electrostatic chuck 1 is low, and the cooling efficiency of the semiconductor substrate 4 is low. Therefore, while adsorbing the semiconductor substrate 4 on the upper surface of the electrostatic attraction device 1, a heat transfer gas such as helium (He) having a high thermal conductivity is supplied between the two at the upper surface of the electrostatic attraction device 1. To increase the thermal conductance between the two and promote heat transfer. By controlling the pressure of the heat transfer gas, the thermal conductance between the semiconductor substrate 4 and the upper surface of the electrostatic chuck 1 is adjusted. Although not shown here, the surface shape of the upper surface of the electrostatic attraction device 1 is uneven, so that the pressure of the heat transfer gas is made uniform at the center and the periphery of the semiconductor substrate 4.

A refrigerant flow path 14 is formed inside the electrostatic attraction device 1, and a refrigerant supply port 1 is formed by a cooling device connected to the outside.
5, the refrigerant is supplied through the refrigerant passage 14 and discharged from the refrigerant outlet 16 to cool the electrostatic adsorption device 1. Heat received by the semiconductor substrate 4 during the plasma processing is released to the refrigerant flowing inside the refrigerant flow path 14 via the electrostatic adsorption device 1. The cover 17 is provided on the electrostatic chuck 1
To protect the semiconductor from plasma.

High frequency electrode 8 built in electrostatic chuck 1
Is provided with a high frequency power supply 18 for applying a high frequency and a switch 12 '''for turning on / off the application. Although not shown, the switches 12, 12 ',
A controller is connected to each of the switches 12 ″ and 12 ′ ″, and the timing of switching each switch can be precisely performed.

The electrostatic chuck 1 has a pusher pin 1.
9 is provided, and serves to transfer the semiconductor substrate 4 carried into the reaction chamber 6 to the electrostatic suction device 1 using a transfer arm (not shown).

Next, a procedure for performing a plasma etching process on a silicon wafer of φ200 (8 inches) as the semiconductor substrate 4 using the semiconductor processing apparatus of the embodiment will be described. Further, main functions and effects of the present invention will be described according to this processing procedure with reference to FIG. FIG. 3 shows the density of the plasma 5, the potential of the suction electrode 2, the potential of the suction electrode 2 ′, and the pressure of the heat transfer gas flowing between the electrostatic suction device 1 and the semiconductor substrate 4. It is a figure showing an example of a time change. The horizontal axis of each graph represents time, and the same time on the horizontal axis indicates the same time.

(1) From t1 to t2, the semiconductor substrate 4 is carried into the reaction chamber 6 and received by the pusher pin 19;
It is installed on the upper surface of the electrostatic suction device 1.

(2) At t3, the positive electrode 400 is added to the suction electrode 2.
V, a voltage of minus 400 V is applied to the adsorption electrode 2 ′,
The semiconductor substrate 4 is attracted to the electrostatic attraction device 1.

(3) At t4, a heat transfer gas flows between the electrostatic attraction device 1 and the semiconductor substrate 4 to increase the thermal conductance between the two, so that the semiconductor substrate 4 is cooled well.

(4) At t5, a processing gas is introduced into the reaction chamber 6, and a plasma 5 is generated to etch the semiconductor substrate 4.

(5) Before the plasma etching of the semiconductor substrate 4 is completed (t6), the switches 17 'and 1
By switching 7 ″, the power supply to the suction electrode 2 is switched from +400 V to −150 V. At the same time, the voltage applied to the suction electrode 2 ′ to which the voltage of −400 V has been applied is reduced to −150 V. Accordingly, the residual suction force of the electrostatic suction device 1 after the plasma 5 has disappeared can be reduced, and a decrease in throughput can be prevented.

(6) At t7, the application of the high frequency is stopped to end the plasma processing. At this time, the negatively charged particles trapped at the boundary surface between the plasma region and the sheath region try to move to the surface of the semiconductor substrate 4,
Since the semiconductor substrate 4 is negatively charged, adhesion to the surface of the semiconductor substrate 4 can be prevented by Coulomb force.

At the same time, the supply of the heat transfer gas flowing between the electrostatic chuck 1 and the semiconductor substrate 4 is stopped.

(7) Particles trapped at the interface between the plasma region and the sheath region when the plasma 5 is generated are adsorbed at (t8) after being carried away from the reaction chamber by the fluid force of the processing gas. The voltage application to the electrodes 2 and 2 'is stopped.

(8) The semiconductor substrate 4 is carried out of the reaction chamber 6.

By repeating the procedures (1) to (8) described above, the semiconductor substrate 4 can be continuously processed.

It is important in this embodiment that the negative voltage applied to the attraction electrode 2 to reduce the residual attraction force of the electrostatic attraction device 1 after the power supply to the attraction electrodes 2 and 2 'is stopped. Lowering the voltage and the high-frequency electrode 1
This means that the semiconductor substrate 4 is negatively charged when the application of the high frequency to 5 is stopped and the plasma is extinguished. Since the semiconductor substrate 4 is negatively charged when the plasma is extinguished, it is possible to prevent the negatively charged particles trapped in the plasma sheath region from adhering to the wafer due to Coulomb force.

The high-frequency applied power, the type and flow rate of the processing gas, and the voltage applied to the electrode for adsorption shown in this embodiment are merely examples, and are not limited thereto. In addition, although the processing method has been described here by taking the plasma etching apparatus as an example, it is needless to say that the processing method is not limited to the plasma etching apparatus and can be used in a semiconductor manufacturing apparatus using plasma, such as plasma CVD. Further, in the embodiment, a high frequency is used as a means for generating plasma, but it is apparent that the present invention is also effective for plasma generated by other means such as microwaves.

[0033]

As described above, according to the present invention, it is possible to provide a plasma processing method using an electrostatic attraction device in which particles are less attached to a semiconductor substrate.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a plasma processing apparatus showing an embodiment of the present invention.

FIG. 2 is an enlarged side sectional view of an electrostatic chuck used in a plasma processing apparatus according to an embodiment of the present invention.

FIG. 3 is a sequence diagram illustrating a plasma processing method according to an embodiment of the present invention.

FIG. 4 is a side sectional view showing a conventional example of an electrostatic suction device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electrostatic suction device, 2 ... Suction electrode, 3 ... Insulation material, 4 ...
Semiconductor substrate, 5: plasma, 6: reaction chamber, 7: upper electrode, 8: high-frequency electrode, 9: processing gas, 10: exhaust port, 1
DESCRIPTION OF SYMBOLS 1 ... DC power supply, 12 ... Switch, 13 ... Heat transfer gas supply pipe, 14 ... Refrigerant flow path, 15 ... Refrigerant supply port, 16 ... Refrigerant discharge port, 17 ... Cover, 18 ... High frequency power supply, 19 ... Pusher pin.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayuki Hachiya 1-1-1, Kokubuncho, Hitachi City, Ibaraki Prefecture Inside Kokubu Works, Hitachi, Ltd. (72) Katsumi Oyama 1-1-1, Kokubuncho, Hitachi City, Ibaraki Prefecture No. 1 F-term in Kokubu Office of Hitachi, Ltd. (reference) 4K030 FA03 GA02 LA15 5F004 AA16 BA04 BB22 BB25 BD04 DA11 DA18 DB01 5F031 CA02 HA16 HA19 HA35 HA37 HA38 HA40 MA28 MA32 PA26 5F045 AA08 BB15 EM05

Claims (1)

[Claims] In a plasma processing apparatus provided with an electrostatic suction device having two or more suction electrodes, (1) a positive voltage is applied to at least one of the suction electrodes, and a negative voltage is applied to at least one of the suction electrodes. And (2) generating plasma and performing processing on the semiconductor substrate, and (3) changing the polarity of the voltage applied to the attraction electrode from minus to plus. The process of changing,
(4) A plasma processing method comprising a step of extinguishing the plasma while a negative voltage is applied to the adsorption electrode.