JPH04122046A - Electrostatic attraction device - Google Patents

Abstract

PURPOSE:To control potential of a substrate surface while making a large current flow through the substrate and to attract the substrate by static electricity by burying a second electrode which provides potential to the substrate in an insulating material and by bringing it into a surface contact with the substrate. CONSTITUTION:An insulating part 62 is formed to a film thickness of 30mum by alumina flame-spraying on an Mo electrode 61 of a first electrode, and a second electrode 63 of Mo is formed in a groove of a depth of 50mum and a width of 40mum and flattened. The second electrode 63 is led out from a side of an electrostatic attracting device. Thereby, it is possible to set potential of a substrate 64 at a positive side not less than a self-bias of plasma, to realize normal attraction function even while a large current is flowing to the second electrode 63 when a large area substrate is used and to control potential of the substrate freely.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an electrostatic adsorption device for holding or fixing various objects in a predetermined position by electrostatic adsorption.
In particular, it is attached to an electrostatic chuck device suitable for holding a substrate to be processed in a vacuum device such as a dry etching device, a sputtering device, or a plasma CVD device.

[Prior Art 1] Conventionally, as devices for holding and fixing objects, there are mechanical chucks and vacuum chucks using mechanical methods, and electrostatic chucks using electrostatic force. However, when holding a substrate in normal semiconductor manufacturing equipment, especially manufacturing equipment that uses plasma, mechanical chucks: 1. Because a part of the mechanical chuck covers the surface of the substrate, the desired treatment is applied to that part of the substrate. impossible to do.

2. Since a part of the mechanical chuck is exposed on the substrate surface, it is exposed to plasma and becomes a cause of impurity contamination.
This makes the spatial distribution of plasma non-uniform.

3. Stress occurs because the chucking force is applied unevenly to a portion of the base. On the other hand, chuck the substrate uniformly.
It is not possible to correct the warpage.

On the other hand, vacuum chucks have the major problem that they cannot be used in vacuum equipment. In contrast to these chuck devices, electrostatic chucks can not only be used in a vacuum, but also can grip the entire surface of a substrate with uniform force and expose the entire surface of the substrate to uniform plasma, making it ideal for semiconductor manufacturing. It is very advantageous as a means for holding the substrate of the device.

The principle of electrostatic chuck will be briefly explained. As shown in FIG. 3, a base body 33 is placed on a planar electrode 31 via an insulator 32 having a dielectric constant ε and a film thickness d, and a voltage V is applied between the electrode 31 and the base body 33. The base 33 is attracted by electrostatic force. The adsorption force F at this time is expressed as F=1/2·ε·S·(V/d). Here, S is the electrode area, and ■ is the applied voltage.1 For example, an electrode with a diameter of 2 inches is used, alumina with a dielectric constant of 10 and a film thickness of 100 gm is used as an insulator, and V
= 1 kV, the value of F is ideally around 8.
The force is quite strong at 7N, and for example, a Si wafer can be adsorbed without any problem.

In this electrostatic adsorption device, the electrodes that apply the substrate potential are generally as follows.

One method is to apply a potential to the substrate 42 using a bottle electrode 41 as shown in FIG. 4, and a voltage is applied between the base electrode 43 and the base electrode 43 via an insulator to attract the substrate. In this case, the substrate potential may be grounded, or a DC potential may be applied to the substrate 42 by using a circuit configuration as shown in FIG. A method has also been proposed in which electrostatic adhesion is performed by utilizing the electrical conductivity of plasma and using a potential difference between a substrate set to a self-bias value due to the plasma and a base electrode via an insulator. (Unexamined Japanese Patent Publication No. 55-90228) [Problem 1 to be solved by the invention! However, there are still many problems with the above electrostatic chuck. First, when a bottle electrode is used: 1. Since the base and the electrode are in point contact, poor contact is likely to occur.

2. Since the bottle requires parallelism with the electrostatic chuck,
Although it is common to use a spring, the springiness changes due to temperature changes and the balance with the force of the electrostatic chuck is lost.

3. Because the contact area between the substrate and the electrode is small, the bottle electrode melts due to Joule heat when a large current flows from the substrate to the electrode. This happens when the bottle is lifted up or when a large area substrate is used, causing a large amount of current to flow through this bottle electrode.

There are other problems.

In addition, with the method of setting the potential of the substrate to a self-bias value by the plasma and not actively applying a DC potential, 1. It is very difficult to control the potential of the substrate, and in order to control the potential, it is necessary to Pressure inside the device,
The plasma state must be set to a desired state by changing the high frequency power, high frequency frequency, gas type, etc.

2. Because the adsorption force does not work in the absence of plasma,
A base cannot be placed on a horizontally facing electrode or a downwardly facing electrode.

There were such problems that it was difficult to put it into practical use.

[Means for Solving the Problems (and Effects) J According to the present invention, a base body having a conductive material or a semiconductor material is placed on the first electrode via an insulator, and the first electrode and the In an electrostatic adsorption device that applies a voltage between substrates and holds the substrate on the first electrode by electrostatic adsorption force, a second electrode that applies a potential to the substrate is embedded in the insulator, and By making surface contact with the substrate, the potential of the substrate can be set to the positive side beyond the self-bias of the plasma, and when a large-area substrate is used, the adsorption function can be maintained normally even when a large amount of current flows through the second electrode. The purpose of the present invention is to provide an electrostatic adsorption device that can freely control the potential of the substrate.

“Embodiment” Implementation of the present invention! ! ! 6. FIG. 1 is a schematic sectional view of an electrostatic adsorption device showing an embodiment of the present invention, and FIG. 2 is a schematic plan view. An insulating material 12 is formed on the first electrode 11 . A groove with a depth t is formed on the surface of the insulator 12, and a second electrode 13 is embedded inside the groove. In this figure, the extraction electrode of the second electrode is taken out at one place in the center of the electrostatic adsorption device, but the extraction position does not have to be particularly limited, and it may be taken out from multiple places. Although the shape is not particularly limited, it is desirable to have a configuration in which the current path has a large cross-sectional area so that the current density flowing through the second electrode is small, and the current does not concentrate in one place.

The dielectric constant of the insulating material 12 is C2, the film thickness is d, and the area of the first electrode is 51. If S2 is the area of the second electrode, W is the weight of the base 14, and V is the voltage applied between the first electrode and the base, then the attraction force F is
The conditions that should be satisfied by the dielectric strength voltage E of the insulating material 12 are expressed by the following equation.

F = 1/2・E ・(Sl-Szl' (V/d
ν) W −1llE, >V7 (d-t)
-121 1f again! The minimum cross-sectional area of two electrodes is 31. ,
The upper limit of the current density flowing through the second electrode is j, 1. Then,
The maximum current I flowing in the substrate area S is I '' J as y x S, , , The value of aJsam is not a clear value, but in the case of A1 it is about I x 10'A/cm'', and No. , 11, etc., the value is even higher. When the contact point between the substrate and the second electrode is close to point contact, the current density at the contact point is high even if the current flowing through the substrate is small, and the current cannot flow to the second electrode. In the case of a surface contact where the contact point between the substrate and the second electrode has a large area, as in the case of mounting, the current is not determined by the current density at the contact point, and the wiring width of the second electrode and the multiplication of t are The maximum value of the current value is defined by the current density flowing through the cross-sectional area S°. The electrode material is not particularly limited as long as it satisfies the above conditions, and may be A1.11.1io, P
Metals such as T, metal silicides, and semiconductor materials such as low-resistance Si may also be used. On the other hand, insulating materials should also satisfy the above conditions (in addition to alumina, etc., 5iOt,
5iJ4. There are no particular problems with polyimide-based polymer materials.

[Example] Example III of the present invention will be described below. A schematic cross-sectional view and a schematic plan view of the electrostatic adsorption device are shown in FIGS. 6 and 7, respectively. The first electrode 61 having a base diameter of 3 inches is a Mo electrode. Absolutely perfect with alumina spraying! A group 62 is formed to have a film thickness of 300 μm, and a second electrode 63 is formed in a groove having a depth of 50 μm and a radius of 40 μm and is flattened. The second electrode was drawn out from the side of the electrostatic chuck device. The dielectric breakdown voltage of this alumina insulating film is approximately I x 10'
V/c■, and 2500V/250μm, so when a 4-inch wafer was attracted by applying 100V (IV) in the atmosphere, it was attracted with a force of 0.2 N/cm or more.This electrostatic adsorption device The RF-DC coupling bias sputtering equipment (T-Ohmi, T, Ic
Hikawa et al.

J, Appi, phys, 66, pp-475
6-476611989)) was used for the substrate and target sides.

81 is a vacuum chamber, 82 is a 5-inch Si target,
83 is a permanent magnet, 84 is a 4 inch Si board, 85.86
is an electrostatic adsorption device according to the present invention, 87 is a 100 MHz high frequency power supply, 88 is a matching circuit, 89.90 is a DC power supply that determines the potential of the target and the substrate, 91.92 is a low-pass filter, and 93 is an electrode shield. The experimental conditions are shown below.

Input gas = Ar Gas pressure...8 Torr Target DC potential - -200V Input high frequency electric car 400W Substrate DC potential - +5V Substrate temperature -300°C In this case, when measuring the current flowing into the board, it is 1.8A However, there were no problems such as heat generation or disconnection of the electrode material, and high-quality Si single crystals were grown on the substrate that was attracted by the electrostatic attraction device. - When a similar experiment was conducted using an electrostatic chuck device in which the second electrode of the force cylinder was an Inconel bottle electrode, the Inconel bottle was heated and melted due to the large current, and the substrate was removed from the electrostatic chuck device. I slipped. Furthermore, when using an electrostatic adsorption device without a second electrode, the self-bias of the substrate was approximately 15 V and the substrate was adsorbed by electrostatic adsorption, but the ion energy irradiated to the substrate was too high and the substrate Damage occurred, and the crystal grown on the substrate was amorphous Si with poor crystallinity.

A second embodiment of the present invention will be described below. A schematic cross-sectional view and a schematic plan view of the formed electrostatic adsorption device are shown in FIG. 9 and 1.
The first electrode 101 shown in FIG. 0 and having a base diameter of 3 inches is a W electrode. Insulating part 102 is formed with a film thickness of 300 μm by alumina spraying, with a diameter of 2 cm and a depth of 50 μm in the center.
A second electrode 103 of W is formed in the groove and is planarized. The second electrode was drawn out from the back side of the electrostatic adsorption device. The dielectric breakdown voltage of this alumina insulating part 102 is approximately 1xlO'V/cm, which is 2500V/250V/cm.
cm, so when a 6-inch wafer was adsorbed by applying 100 OV in the air, it was completely adsorbed. This electrostatic adsorption device was used on the substrate side and target side of the RF-DC coupled bias sputtering device shown in Fig. 8, the target and substrate sizes were set to 6 inches, and the high frequency input power was set at 900.
When the same experiment as in Example 1 was conducted except that W was used, the t flow flowing into the substrate was 4. With OA, heat generation from electrode materials, etc.
No problems such as wire breakage occurred, and a high-quality Si single crystal similar to that in Example 1 grew on the substrate adsorbed by the electrostatic adsorption device.

A third embodiment of the present invention will be described below. A schematic cross-sectional view and a schematic plan view of the formed electrostatic chuck device are shown in FIG. 1I and FIG. be. Absolute J
The i part 112 is 5102 with a film thickness of 50 um, and has an insulation [1
o, oot in the groove of 112 depth 20gm and width 40um
Ω・cm poly-3i second electrode 113 is embedded,
Flattened. The second electrode was drawn out from a line 115 at a depth of 20c1 and a radius of 1 on the side surface of the electrostatic adsorption device. The dielectric breakdown voltage of this S10□ insulating film is approximately 6X10
'V/cm and 18000v/30μm.

In the atmosphere, 100O with i5 and 1×10Torr depressurization
When V was applied and a 4-inch wafer was adsorbed, it was completely adsorbed. Example 1 An experiment similar to Example 1 was conducted using this electrostatic adsorption device on the substrate side and target side of the RF-DC coupled bias sputtering device shown in FIG.
Similarly, although the current flowing into the substrate was 1.8 A, no problems such as heat generation or disconnection occurred, and a high-quality Si single crystal grew on the substrate that was attracted by the electrostatic attraction device.

[Effects of the Invention] As explained above, a base having a conductive material or a semiconductor material is placed on a first electrode via an insulator, and a voltage is applied between the first electrode and the base, In an electrostatic adsorption device that holds the substrate on the first electrode by electrostatic adsorption force, a second electrode that applies a potential to the substrate is embedded in the insulator and brought into surface contact with the substrate. By controlling the potential of the substrate surface while passing a large current through it, it became possible to attract the substrate using electrostatic force. This is particularly effective when controlling the potential from the self-bias caused by plasma to the positive side or when using a large-area substrate.

[Brief explanation of the drawing]

FIG. 111 is a vertical cross-sectional view showing the concept of the electrostatic chuck device of the present invention, FIG. 2 is a plan view thereof, and FIGS. 3 to 5 are explanatory diagrams for explaining the principle of a general electrostatic chuck. FIG. 6 is a schematic cross-sectional view of the electrostatic chuck device according to the first embodiment of the present invention, FIG. 7 is a plan view thereof, and FIG. 8 is a biased electrostatic chuck device shown in FIGS. 9 is a schematic sectional view of an electrostatic chuck device according to a second embodiment of the present invention, FIG. 10 is a plan view thereof, and FIG. 11 is a schematic sectional view of an electrostatic chuck device according to a second embodiment of the present invention FIG. 12 is a schematic cross-sectional view of the electrostatic adsorption device according to the third embodiment, and a plan view thereof. 11.31.43. ] ]01.1ll --- First electrode 1
232.44.62.102.112--Insulator 13
．． 63,103.113.115 =-second electrode 14,
42.64.104.114・-Substance Attorney Patent Attorney Yamashita Tank Taira Figure Figure Figure Figure Figure Figure Figure Figure

Claims (1)

[Claims] (1) A base body having a conductive material or a semiconductor material is disposed on the first electrode via an insulator, and a voltage is applied between the first electrode and the base body. In an electrostatic adsorption device configured to hold the substrate on an electrode by electrostatic adsorption force, a second electrode for applying a predetermined potential to the substrate is embedded in the insulator, and a second electrode for applying a predetermined potential to the substrate; An electrostatic adsorption device characterized in that a second electrode is in surface contact with the base.