JPH05190655A - Electrostatic attraction device - Google Patents

Abstract

PURPOSE:To control electric potential of a substrate freely while showing normal attraction function by providing a substrate of a conductor or a semiconductor substance on a first electrode with an insulator between and by burying a second electrode which provides it with an electric potential in the insulator. CONSTITUTION:An Mo-made first electrode 61 has an outer diameter and an inner diameter of a large circle of 9cm and 6cm, respectively and a diameter of a small circle of 3cm and a space part of an Mo-made second electrode 63 which provides an electric potential to a substrate 64 is about 1mm. An insulator 62 is formed of 250mum-thick alumina, separated from the second electrode 63 and a periphery is enclosed. When 1kV is applied in air and a 4 inch wafer is attracted, it is attracted completely by a force of 0.2N/cm or more. It becomes possible to control an electric potential of a substrate surface while making a large current flow through a substrate and to attract the substrate by electrostatic force. It is also resistant to thermal stress and is useful when controlling an electric potential at a positive side from self-bias by plasma and when a substrate of a large area is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chucking device for holding or fixing various objects at a predetermined position by electrostatic chucking, and more particularly to a dry etching device, a sputtering device, a plasma CVD device and the like. The present invention relates to an electrostatic adsorption device suitable for holding a substrate to be processed in a vacuum device.

[0002]

2. Description of the Related Art Conventional methods for holding and fixing objects include mechanical chucks and vacuum chucks by mechanical methods, and electrostatic chucks based on the principle of electrostatic force. However, in the case of holding a substrate in an ordinary semiconductor manufacturing apparatus, particularly in a manufacturing apparatus using plasma, the mechanical chuck is 1. Due to the fact that a part of the mechanical chuck covers the surface of the substrate, that part of the substrate cannot be subjected to the desired treatment. 2. Since a part of the mechanical chuck is exposed on the surface of the substrate, the mechanical chuck is exposed to the plasma, which causes contamination of impurities, and also makes the spatial distribution of the plasma uneven. 3. Since the chucking force is unevenly applied to a part of the substrate, stress is generated. On the other hand, chuck the substrate evenly,
The warp cannot be corrected.

However, the vacuum chuck has the following problems.
The major problem is that it cannot be used in a vacuum device.
In contrast to these chuck methods, the electrostatic chuck can be used not only in a vacuum but also can adsorb the entire surface of the substrate with a uniform force and expose the entire surface of the substrate to a uniform plasma. It is very advantageous as a substrate holding method.

The principle of the electrostatic chuck will be briefly described. As shown in FIG. 8, a substrate 33 is placed on an electrode 31 on a plane via an insulator 32 having a dielectric constant ε film thickness d, a voltage V is applied between the plane electrode 31 and the substrate 33, and the substrate is moved by electrostatic force. Adsorb. The attracting force F at this time is represented by F = 1/2 · ε · S · (V / d) ² . Here, S represents an electrode area, and V represents an applied voltage. For example, if an electrode having a diameter of 2 inches is used as S, and an insulator having a relative dielectric constant of 10 and a film thickness of 100 μm is used and V = 1 kV, the value is ideally about 8.
It has a considerably strong force of 7 N and, for example, a Si wafer or the like can be adsorbed without any problem.

In this electrostatic attraction device, the following method is generally used for the electrodes that apply the substrate potential. 1
One is a method of applying a potential of the base 42 by the pin electrode 41 as shown in FIG. 9, and a voltage is applied between the base electrode 43 and an insulating material to adsorb the base. In this case, the substrate potential can be grounded, or a direct current potential can be applied to the substrate 42 by the circuit configuration shown in FIG. Further, a method has also been proposed in which the electrostatic conductivity is utilized by utilizing the electric conductivity of plasma and by the potential difference between a base body set to a self-bias value by plasma and a base electrode via an insulator. (JP-A-55-90228)

[0006]

However, there are still many problems with the above electrostatic chuck.
First, the problem when using a pin electrode is shown. 1. Since the base and the electrode are in point contact with each other, poor contact is likely to occur. 2. Since the pin must be parallel to the electrostatic chuck,
It is common to use a spring, but the spring property changes due to temperature changes, and the balance with the force of the electrostatic chuck is lost. 3. Since the contact area between the base and the electrode is small, the Joule heat causes the pin electrode to melt when a large current flows from the base to the electrode. This happens especially when the DC potential of the substrate is raised to the positive side of the self-bias with respect to the plasma or when a large-area substrate is used, and a large amount of electron current flows through this pin electrode. There are problems such as.

Further, in the method in which the potential of the substrate is set to the value of the self-bias due to plasma and the DC potential is not positively applied, It is very difficult to control the electric potential of the substrate.
The plasma state must be set to a desired state by changing the high frequency power, the high frequency frequency, the gas type, and the like. 2. When plasma is not present, the adsorption force does not work, so that the substrate cannot be placed on the lateral electrodes or the downward electrodes. However, there were some problems, and it was difficult to put them into practical use.

[0008]

According to the present invention, a substrate having a conductive substance or a semiconductor substance is placed on an insulating material on the first electrode, and the first electrode and In an electrostatic attraction device that applies a voltage between the bases and holds the base on the first electrode by an electrostatic attraction force,
A second electrode for applying a potential to the substrate is embedded in the insulator and is brought into surface contact with the substrate to set the potential of the substrate on the positive side above the self-bias of plasma,
The present invention provides an electrostatic adsorption device that exhibits a normal adsorption function even when a large amount of current flows to the second electrode when a large-area substrate is used and that can control the potential of the substrate freely. The principle of the present invention will be described in detail with reference to the drawings. FIG. 6 is a schematic sectional view for explaining the principle of the electrostatic attraction device of the present invention, and FIG. 7 is a schematic plan view thereof. An insulating material 12 is formed in a donut shape on the first electrode indicated by 11. The second electrode for applying an electric potential to the substrate is the insulating material 1
It is surrounded by 2 and is spatially separated. In this figure, one second electrode is shown as a cylinder, but the shape and number are not particularly limited. The cross-sectional area of the current path is large so that the density of the current flowing through the second electrode is small, so that the current is not concentrated at one location.

The dielectric constant of the insulating material 12 is ε, the film thickness is d,
Assuming that the area of the first electrode is S ₁ , the weight of the substrate 14 is W, and the voltage applied between the first electrode and the substrate is V, the adsorbing force F and the withstand voltage E _B of the insulating material 12 must satisfy the following conditions. It can be expressed by a formula.

[0010] F = 1/2 · ε · S 1 · (V / d) 2> W ... (1) E B> V / d ... (2) The minimum cross-sectional area of the second electrode S _min, second When the upper limit of the current density flowing through the electrodes is J _max , the maximum current I flowing through the substrate area S is I = j _max XS _min . Although the value of j _max is not clear, in the case of Al, it is 1 × 10 ⁵ A / cm ²
However, the value is even higher in the case of refractory metals such as Mo and W. When the contact between the base and the second electrode is close to point contact, even if the current flowing through the base is small, the current density at the contact point is high and current cannot flow, but like the electrostatic attraction device according to the present invention, When the contact of the second electrode is a surface contact having a large area, the current is not defined by the current density at the contact point, and the current density is the current density flowing in the cross-sectional area obtained by multiplying the wiring width L of the second electrode by t. The maximum value will be specified. Further, since the second electrode is spatially separated from the insulator, it is not necessary to worry about the difference in the coefficient of thermal expansion between the insulator and the second electrode even when the temperature of the base is increased. Further, according to this structure, the second electrode is not exposed to the plasma space, which has advantages such as influence on the plasma and suppression of impurity contamination.

The electrode material is not particularly limited as long as the above conditions are satisfied, and metals such as Al, W, Mo and Pt, metal silicides, and semiconductor materials such as low resistance Si may be used. On the other hand, the insulating material may similarly satisfy the above-mentioned conditions, and in addition to alumina or the like, SiO ₂ , Si ₃ N ₄ , or a polyimide-based polymer material does not pose any particular problem.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view of an electrostatic chucking device according to a first embodiment of the present invention, and FIG. 2 is a plan view thereof. In the figure, reference numeral 61 is a first electrode, 62 is an insulator, 63 is a second electrode, and 64 is a base.

The first electrode is a Mo electrode, and the diameter of the great circle is 9 cm and 6 cm at the outer and inner circumferences, and the diameter of the small circle at the center is 3 cm. On the other hand, the second electrode 63 is also Mo, and the space portion is about 1 mm. The insulator 62 is made of alumina having a film thickness of 250 μm and is separated from the second electrode 61 and surrounds the periphery thereof. The breakdown voltage of this alumina insulating film is approximately 1 × 10 ⁵ V / cm.
Since it is 2500 V / 250 μm, 1000 V was applied in the atmosphere to adsorb a 4-inch wafer, and it was adsorbed completely with a force of 0.2 N / cm ² or more. This electrostatic adsorption device is an rf-dc coupled bias sputtering device (T. Ohmi, T. Ichikawa, et.
al, J .; Appl. Phys. 66, pp. 4756
An experiment was carried out using -4766 (1989) on the substrate side and the target side. 81 is a vacuum chamber, 82 is 5
Inch Si target, 83 permanent magnet, 84 a 4-inch Si substrate, 85, 86 electrostatic chuck according to the present invention, 87 is 100 MHz _Z frequency power source, 88 is a matching circuit, 89 and 90 of the target and the potential of the substrate A DC power supply to be determined, 91 and 92 are low-pass filters, and 93 is an electrode shield. The experimental conditions are shown below.

Input gas: Ar gas pressure: 8 mTorr Target DC potential: -200 V Input high frequency power: 400 W Substrate DC potential: +5 V Substrate temperature: 300 ° C. In this case, the current flowing into the substrate is 1.8 A, but the electrode material is However, problems such as heat generation and wire breakage did not occur, and a good-quality Si single crystal grew on the substrate attracted by the electrostatic attraction device. On the other hand, when a similar experiment was conducted using an electrostatic adsorption device in which the second electrode was an Inconel pin electrode, the Inconel pin generated heat due to a large current and melted, and the substrate slipped off the electrostatic adsorption device. Oops. Further, when the electrostatic adsorption device without the second electrode was used, the self-bias of the substrate was about −5 V, and the substrate was adsorbed by electrostatic adsorption, but the ion energy applied to the substrate was too high and the Damage has occurred. The crystal grown on the substrate was amorphous Si with poor crystallinity.

[Other Embodiments] FIG. 4 is a schematic sectional view of an electrostatic chucking device according to a second embodiment of the present invention, and FIG. 5 is a plan view thereof. In the figure, reference numeral 101 is a first electrode, 102
Is an insulator, 103 is a second electrode, and 104 is a base.

The first electrode 101 and the second electrode 103 are Mo electrodes, and alumina is used as the insulator 102. The diameter of each of the insulator 102 and the second electrode 103 shown in the plan view is 10 cm, 7
cm, 5 cm, 2 cm. Moreover, each space was about 1 mm. The thickness of this alumina insulating film is 25
Since the dielectric breakdown voltage is 0 μm and the dielectric breakdown voltage is about 1 × 10 ⁵ V / cm and 2500 V / 250 μm, 1000 V was first applied in the atmosphere to adsorb a 6-inch wafer, and it was completely adsorbed. This electrostatic adsorption device is shown in FIG.
An experiment similar to that of the first embodiment was conducted except that the target and the substrate size were set to 6 inches and the high-frequency input power was set to 900 W by using on the substrate side and the target side of the -dc coupled bias sputtering apparatus. The flowing current was 4.0 A, but problems such as heat generation and disconnection did not occur, and a high-quality Si single crystal similar to that of Example 1 was grown on the substrate attracted by the electrostatic chuck.

[0018]

As described above, a substrate having a conductive substance or a semiconductor substance is placed on the first electrode via an insulator, and a voltage is applied between the first electrode and the substrate, In an electrostatic chucking device for holding the substrate on the first electrode by electrostatic chucking force, a second electrode for applying a potential to the substrate is used.
By spatially separating the electrode of the substrate from the insulator and making surface contact with the substrate, it is possible to control the potential of the substrate surface while flowing a large current through the substrate and to attract the substrate by electrostatic force. It was Strong against thermal stress,
In particular, it is effective when the potential of the substrate is controlled to the positive side from the self-bias by plasma while raising the substrate temperature, or when a large area substrate is used.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an electrostatic attraction device according to a first embodiment of the present invention.

FIG. 2 is a plan view of the electrostatic attraction device according to the first embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view showing a case where the electrostatic attraction device shown in FIGS. 1 and 1 is applied to a bias sputtering device.

FIG. 4 is a schematic cross-sectional view of an electrostatic attraction device according to a second embodiment of the present invention.

FIG. 5 is a plan view of an electrostatic attraction device according to a second embodiment of the present invention.

FIG. 6 is an explanatory diagram for explaining the principle of the electrostatic chuck of the present invention.

FIG. 7 is an explanatory diagram for explaining the principle of the electrostatic chuck of the present invention.

FIG. 8 is a schematic sectional view of a conventional electrostatic attraction device.

FIG. 9 is a schematic sectional view of a conventional electrostatic attraction device.

FIG. 10 is a schematic cross-sectional view of a conventional electrostatic attraction device.

[Explanation of symbols]

 61,101 first electrode 62,102 insulator 63,103 second electrode 64,104 substrate

Claims (3)

[Claims] 1. A substrate having a conductive material or a semiconductor material with an insulator interposed therebetween is disposed on the first electrode, and the first electrode is provided.
In the electrostatic attraction device configured to hold the substrate on the first electrode by the electrostatic attraction force by applying a voltage between the electrode and the substrate, a predetermined potential is applied to the substrate. An electrostatic chucking device, wherein a second electrode for applying is spatially separated from the insulator, and the second electrode is in surface contact with the substrate. 2. The electrostatic adsorption device according to claim 1, wherein a surface of the second electrode and the insulator, which is in contact with the base, is surrounded by the insulator. 3. The electrostatic attraction device according to claim 1, wherein a side surface of the second electrode is surrounded by an insulator with a space interposed therebetween.