JPH06177081A - Plasma processor - Google Patents

Abstract

PURPOSE:To adsorb and hold a material to be processed and to uniformly process it irrespective of presence/absence of a plasma. CONSTITUTION:A first electrode 6 and a second electrode 7 disposed on a concentrical circle are interposed to be held between two polymer films 5A and 5B to constitute an electrostatic chuck sheet 5 to cover a susceptor 4. The electrode 6 is connected to a positive electrode side of a DC power source 63, and the electrode 7 is connected to a negative electrode side of a DC power source 73 and a positive electrode side of the power source 63 through a switch. The switch is so constituted that, the electrode 7 is switched to the negative electrode side of the power source 73 when a plasma is not generated and the electrode 7 is switched to the positive electrode side of the power source 63 when the plasma is generated. Thus, even if the plasma is not generated, a material to be processed is adsorbed, and since the plasma is generated, the electrodes 6, 7 are set to the same potential, etching is executed uniformly.

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 plasma processing an object to be processed such as a semiconductor wafer.

[0002]

2. Description of the Related Art In a semiconductor wafer processing step, an etching process is performed by a plasma etching process apparatus for forming a contact hole, for example.
In this plasma etching processing apparatus, the conventional method shown in FIG.
As shown in FIG. 1, a susceptor 10 made of a conductive material is provided on a susceptor support 11 in a reaction container (not shown). The susceptor 10 is connected to a high frequency power source (not shown) and also serves as an electrode (lower electrode), and the susceptor support 11 and the susceptor 10 are provided with He or the like on the back surface of the wafer W mounted on the upper surface of the susceptor 10. A backside gas supply path (not shown) for supplying the backside gas is formed.

On the upper surface of the susceptor 10, an electrostatic chuck sheet 12 made of an insulating material whose surface serves as a wafer mounting surface.
The electrostatic chuck sheet 12 is provided with a unipolar electrode (electrode for electrostatic chuck) 15 connected to a DC power source 14 via a switch unit 13 inside the electrostatic chuck sheet 12. A gas introducing portion (not shown) which also serves as an electrode (upper electrode) is arranged above the susceptor 10, and the upper electrode is grounded.

In such a plasma etching apparatus, first, the wafer W is placed on the electrostatic chuck sheet 12 and a high frequency is applied between the upper and lower electrodes.
A process gas is supplied to the gas inlet to generate plasma, and the reactive ions generated by this plasma are transferred to the wafer W.
A predetermined etching process is performed by being incident on the surface of the. By the way, in this etching process, in order to stabilize the processing temperature of the wafer W and process the wafer W uniformly,
Although the backside gas is supplied to the back surface of the wafer W via the above-mentioned backside gas supply passage, if the backside is supplied without adsorbing the wafer W on the electrostatic chuck sheet 10, this backside gas is generated. The pressure W causes the wafer W to be displaced on the susceptor 10. Therefore, after plasma is generated, a voltage is applied to the unipolar counter electrode 15, a conductive path is formed through this plasma, and the wafer W is attracted to the electrostatic chuck sheet 12 by electrostatic force, and then the backside gas is flowed. I have to.

[0005]

However, in the above-described plasma etching apparatus, the wafer W can be adsorbed only during plasma generation, and therefore the backside gas can be supplied only after plasma generation. There wasn't. For this reason, it takes some time for the temperature of the wafer W to stabilize after the backside gas starts to flow, but the plasma etching process is performed within the unstable time until the temperature stabilizes.
The in-plane distribution uniformity of is worse. In particular, when the total plasma etching processing time is short, the ratio of the unstable time is large, which adversely affects the etching processing process, the degree of non-uniformity of the in-plane distribution is large, and the yield is low.

On the other hand, Japanese Patent Application Laid-Open No. 57-196211 discloses a technique of arranging a pair of electrodes inside an insulator and applying positive and negative voltages to the electrodes. For example, the backside gas can be flown because the wafer W can be adsorbed and held even when plasma is not generated, but the in-plane uniformity in the etching process is deteriorated because the in-plane potential of the wafer W is different. is there.

The present invention has been made under these circumstances, and an object thereof is to adsorb and hold an object to be processed regardless of whether plasma is generated or not, and to evenly dispose the object to be processed. Another object of the present invention is to provide a plasma processing apparatus capable of performing the above processing.

[0008]

According to the present invention, a voltage is applied to an electrode provided on a surface of a susceptor to hold an object to be processed by electrostatic attraction on a mounting surface of the susceptor, and the object is processed by plasma. In the plasma processing apparatus described above, the electrode is divided into a first electrode and a second electrode, and a switch section for switching the potentials of these electrodes is provided, and the switch section is provided with the first electrode during plasma generation. The electrodes and the second electrode are switched to have the same potential different from the potential of the object to be processed, and when the plasma is not generated, the first electrode and the second electrode have different potentials from each other. It is characterized by being switched.

[0009]

By electrically connecting the first electrode and the second electrode to direct current power supplies having mutually different potentials, a loop of the first electrode → the object to be processed → the second electrode is formed, so that the object to be processed is formed. The body is attracted to the electrostatic chuck sheet. However, one DC power supply may not be provided. After that, the backside gas is allowed to flow therethrough to stabilize the object to be processed at a predetermined processing temperature.

Then, a predetermined plasma etching process is performed by applying a voltage to the high frequency power source and supplying a process gas into the reaction vessel to generate plasma. In this case, when plasma is generated,
Since the changeover switch unit is changed over and the potentials of the first electrode and the second electrode are connected to the same DC power source, both electrodes have the same potential. Therefore, regardless of whether or not plasma is generated, the object to be processed can be adsorbed and held, and the object to be processed can be uniformly processed.

[0011]

FIG. 1 is a vertical sectional view of a plasma etching apparatus according to this embodiment. In FIG. 1, 2 is a reaction container,
Gate valves G1 and G2 are provided on the left and right side walls of the reaction vessel 2, respectively, and the reaction vessel 2 is connected to a load lock chamber (not shown) via each of the gate valves G1 and G2. An exhaust pipe 21 connected to a vacuum pump via a valve (not shown) is provided near the bottom surface of the left side wall of the reaction vessel 2.

A cylindrical susceptor support 3 made of a conductive metal such as aluminum is disposed in the center of the bottom surface of the reaction vessel 2. A cooling jacket 31 is formed inside the susceptor support 3, and a liquid supply pipe 32 and a drain pipe 33 are connected to the cooling jacket 31 so as to penetrate the floor wall of the reaction vessel 2.

A disk-shaped susceptor 4 made of a conductive metal such as aluminum is provided on the upper surface of the susceptor support 3.
Are attached by bolts or the like not shown. The susceptor 4 is electrically connected to a high frequency power source 42 via a capacitor 41 to form an electrode (lower electrode), and the high frequency power source 42 is grounded via a switch 42a.

Then, a heat transfer medium, for example, a backside gas such as He is supplied to the back surface of the wafer W on the susceptor support 3 and the susceptor 4 through a backside gas supply hole formed in an electrostatic chuck sheet described later. A backside gas supply pipe 43 for supplying the gas to the susceptor support 3 and the susceptor 4 is provided from the bottom surface side of the reaction vessel 2 and the three pressure pins 45 ( In FIG. 1, only two are shown.) Are provided through three through holes 46 formed in the susceptor support 3 and the susceptor 4, respectively.

On the surface of the susceptor 4, the susceptor 4 is
The electrostatic chuck sheet 5 formed in a circular shape in conformity with the surface shape of is attached. As shown in FIG. 2, the electrostatic chuck sheet 5 is composed of two polymer films 5A and 5B made of a dielectric material such as polyimide, and a plurality of (constantly arranged) concentric circles. In the embodiment, the two planar shapes are composed of a ring-shaped first conductive sheet 6 and a second conductive sheet 7.
The edges of the polymer films 5A and 5B are fused. Each of the conductive sheets 6 and 7 is made of a conductor such as copper and constitutes an electrode (electrode for an electrostatic chuck). Further, the electrostatic chuck sheet 5 is formed with a large number of air supply holes 51 through which the backside gas from the backside gas supply pipe 43 flows.

The first counter electrode 6 is provided with a conductive wire covered with an insulating cable 61 built in the susceptor 4 and a power supply rod 62 passed through a through hole 34 formed in the susceptor support 3. , Which is electrically connected to the positive electrode side of a DC power source 63 having a voltage of 2000 volts, for example. The second counter electrode 7 is electrically connected to the switch portion 8 via a conductive wire covered with an insulating cable 71 and a power supply rod 72 passed through the through hole 35. The switch section 8
Is, for example, a relay switch, which electrically connects the electrode 7 to the negative electrode side of the DC power source 73 having a voltage of 2000 V when plasma is not generated, and which is indicated by a dotted line in FIG. 1 during plasma generation. The second counter electrode 7
Is electrically connected to the positive electrode side of the power source 63 to which the first counter electrode 5 is connected.

The negative side of the power source 63 and the power source 73
Of the positive electrode side of the switch section 63a and the switch section 73, respectively.
It is grounded via a. Further, in this embodiment, a control unit 80 for controlling the switch unit 42a for turning on / off the high frequency power source 42, the valve 43a for shutting off and flowing the gas in the backside gas supply pipe 43, and the like are provided. The switch unit 8 is configured to be switched by an instruction output based on a predetermined program in the unit 80.

An upper electrode 9 also serving as a gas introduction chamber is arranged above the susceptor 3 so as to face the susceptor 4, and the upper electrode 9 is grounded. And
A process gas supply pipe 91 for supplying a processing gas, for example, an etching gas such as CF ₄ is connected to the upper electrode 9, and a process is performed on the electrode surface of the upper electrode 9 (gas injection plate of the gas introduction chamber). In order to eject the etching gas supplied from the gas supply pipe 91 downward,
A large number of small holes 92 are formed.

Next, the operation of the above embodiment will be described. First, the wafer W is transferred into the reaction container 2 by a transfer arm (not shown) via the gate valve G2, and the elevating mechanism 44 is raised to transfer the wafer W to the pressure pin 45, and then the elevating mechanism 44 is lowered. The wafer W is placed on the electrostatic chuck sheet 5. On the other hand, the inside of the reaction vessel 2 is made into a vacuum atmosphere through the exhaust pipe 23 by a vacuum pump (not shown), and the cooling liquid is supplied through the liquid supply pipe 32 and drained through the drain pipe 33. Flow through the cooling jacket 31.

By switching the switch section 8 to the power source 73 side based on a predetermined sequence in the control section 80, the polyimide layer between the electrode 6 and the wafer W and between the electrode 7 and the wafer W is removed. Since a capacitor is formed and the lateral portion of the wafer W can be regarded as a resistance, a closed loop of power supply 63 → capacitor → resistance → capacitor → power supply 73 is formed, and as a result, as shown in FIG. Therefore, the wafer W is attracted to the electrostatic chuck sheet 5 by the electrostatic force.

Next, the valve 43a is opened in response to a control signal from the controller 80, and a backside gas such as He is supplied to the back surface of the wafer W through the backside gas supply pipe 43 and the supply holes 51 of the electrostatic chuck sheet 5. To stabilize the temperature of the wafer W at a predetermined processing temperature. After that, the switch unit 42 is controlled by a control signal from the controller 80.
a is closed and the high-frequency power source 42 supplies, for example, 380 KHz,
By applying a high frequency voltage of 1.5 Kw between the susceptor 4 and the upper electrode 9 and supplying an etching gas such as CF ₄ from the process gas supply pipe 91 into the reaction vessel 2 through the small holes 92. Plasma is generated, and the reactive ions generated by the plasma are incident on the surface of the wafer W to cause a chemical reaction with a substance to be processed on the surface of the wafer W, and a predetermined plasma etching process is performed.

During plasma generation, the changeover switch section 8 is changed over to the power source 63 side to electrically connect the electrodes 6 and 7 to the same power source 63 as shown by the broken line in FIG. A voltage of +2000 volts is applied to electrodes 6 and 7 by 63. Therefore, although the above-mentioned closed loop is released, the lower electrode 4 is connected through the plasma.
Since a conductive path is formed between the upper electrode 9 and the upper electrode 9, the wafer W is maintained at a negative potential through the plasma, so that the wafer W is continuously attracted to the electrostatic chuck sheet 5.

When the predetermined etching process of the wafer W is completed, the switch unit 8 is switched to the power source 73 side by the control signal from the control unit 80 and the switch unit 42a is turned off to stop the plasma generation. The valve 43a is closed to shut off the backside gas supply. Next, the wafer W is lifted by the elevating mechanism 44 and held by the pressure pin 45, then transferred to a transfer arm (not shown) and transferred to a load lock chamber (not shown) via the gate valve G1.

According to the above-mentioned embodiment, when plasma is not generated, the electrode for the electrostatic chuck is made into a bipolar electrode to attract the wafer W to the electrostatic chuck sheet 5, and when plasma is generated. Since the electrode for the electrostatic chuck is made into a single electrode to attract the wafer W, the wafer W can be attracted and held regardless of the presence or absence of plasma. Therefore, the backside gas is allowed to flow before the plasma is generated and the wafer W
The temperature of can be stabilized at a predetermined temperature,
Since the potential of the wafer W can be maintained uniform during plasma generation, the wafer W can be processed uniformly.
Yield improves.

In the above, the electrodes 6 and 7 are not limited to the ring-shaped ones shown in FIG.
It may have a half-moon shape or a comb tooth shape as shown in (a) and (b), respectively, and the number is not limited to one, but is composed of a plurality of electrodes. Good. Since the wafer W has a negative potential due to the properties of plasma, the electrodes 6 and 7 may be set to the ground level potential during plasma generation depending on the magnitude of the potential.

The present invention is not limited to the plasma etching apparatus, but may be applied to an apparatus for performing film formation or ashing with plasma, and the object to be processed is not the semiconductor wafer W. It may be.

[0027]

According to the present invention, the object to be processed can be adsorbed and held regardless of the generation of plasma, and the object to be processed can be stabilized at a predetermined processing temperature before the plasma is generated. Since the potential of the object to be processed can be made uniform, the object to be processed can be uniformly processed.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a plasma processing apparatus according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of an electrostatic chuck sheet.

FIG. 3 is an explanatory view of the operation of the embodiment of the present invention.

FIG. 4 is a plan view showing another example of an electrode for an electrostatic chuck.

FIG. 5 is a cross-sectional view for explaining a conventional plasma processing apparatus.

[Explanation of symbols]

 2 reaction vessel 3 susceptor support 4 susceptor (lower electrode) 42 high frequency power supply 43 backside gas air supply pipe 5 electrostatic chuck sheet 6 first electrode 7 second electrode 63, 73 DC power supply 8 changeover switch unit 80 control unit 9 Upper electrode

Claims (1)

[Claims] 1. A voltage is applied to an electrode for an electrostatic chuck provided on the surface of a susceptor in a reaction vessel to attract and hold an object to be processed by electrostatic force on a mounting surface of the susceptor, and plasma is applied to the object to be processed. In the plasma processing apparatus for processing, the electrode for the electrostatic chuck is divided into a first electrode and a second electrode, and a switch unit for switching the potentials of these electrodes is provided. Is switched so that the first electrode and the second electrode have the same potential different from the potential of the object to be processed, and when the plasma is not generated, the first electrode and the second electrode are switched to each other. A plasma processing apparatus, wherein the plasma processing apparatus is switched to have different potentials.