JPH01181544A - Electrostatic chuck - Google Patents

Abstract

PURPOSE:To make a quick separation of a material to be chucked without damaging the material, by applying DC voltage between the material to be chucked and an electric conductor in the reverse direction to the one applied at chucking as well as to add the specified power by a separation power application equipment in the direction of separation. CONSTITUTION:DC voltage is applied between an electric conductor 1 coated outside with an insulating material 2 and a material 3 to be chucked which is contacting the surface of the insulating material 2, to produce an electrostatic power between the two chucking the material 3 to be chucked. At the separation of the material 3 to be chucked, DC voltage is applied between the material 3 to be chucked and the electric conductor 1 in the reverse direction to one applied at chucking. Also, at operation of a reverse voltage application equipment 7, the specified power is given to the material 3 to be chucked by separation power application equipment 5, 4 and 4a in the direction of separation from the electric conductor 1. By this method, the material to be chucked can be separated rapidly without being damaged.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is used, for example, in a semiconductor integrated circuit manufacturing apparatus, and is used to process a sample whose surface is subjected to various treatments such as film formation or etching. This invention relates to an electrostatic chuck that attracts and holds by electrostatic force.

[Prior art]

For example, electron cyclotron resonance (E 1 ectron resonance)
A CV port (Che+m1) is used to form a thin film of a desired material on a semiconductor substrate using IECR plasma generated using
calVaporDeposition) device,
Semiconductor integrated circuit manufacturing equipment, such as dry etching equipment that forms fine circuit patterns on semiconductor substrates, extracts ECR plasma generated in a plasma generation chamber by the action of a divergent magnetic field, and connects it to the plasma generation chamber. The semiconductor substrate held in the sample chamber is irradiated with light to form a thin film on the substrate. In these devices, electrostatic adsorption is used to hold the semiconductor substrate in the sample chamber. Electrostatic chucks that utilize this action are used.

As this electrostatic chuck, a flat conductor whose outer surface is covered with a thin film insulator is fixed in the sample chamber, and the semiconductor substrate to be attracted is brought into close contact with the surface of the insulator. By applying a predetermined DC voltage between the body and the semiconductor substrate,
There is a monopolar electrostatic chuck that generates an electrostatic force between the two and uses this electrostatic force to attract and hold a semiconductor substrate on a conductor.

[Problem that the invention seeks to solve]

Now, in such an electrostatic chuck, when removing an object that is in the attracted state, the procedure is to interrupt the application of the DC voltage, eliminate the electrostatic force, and then detach the object. . However, even after the above-mentioned interruption, a charge remains in the insulator covering the conductor and electrostatic force remains for a while, so a long waiting time is required before the object to be attracted can be removed. There are difficulties, and
In order to force the adsorbed object to detach against the remaining electrostatic force,
When a large detachment force is applied to this, there is a risk that the detachment force may destroy the attractable object, especially when the attractable object is a fragile object such as a semiconductor substrate.

FIG. 4 is a graph showing the adsorption force generated when a DC voltage is applied and the residual adsorption force immediately after the application is interrupted when a silicon semiconductor substrate is adsorbed by a conventional electrostatic chuck. The Q mark indicates the former, and the * mark indicates the latter. As shown in this figure, in the conventional electrostatic chuck, the residual adsorption force increases as the adsorption time increases, and when the application of DC voltage is interrupted after adsorption for 20 minutes, the It is clear that a suction force having a magnitude of approximately 50% of the suction force remains immediately after the interruption.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an electrostatic chuck that can quickly remove an object to be attracted without being destroyed.

[p means to solve the problem]

The electrostatic chuck according to the first invention of the present application applies a DC voltage between a conductor whose outer surface is covered with an insulator and an object to be attracted that is in contact with the surface of the insulator. In an electrostatic chuck that attracts and holds an object by an electrostatic force generated in the electrostatic chuck, when the object is released, a direct current is generated between the object and the conductor in the opposite direction to that during attraction. The electrostatic chuck according to the second invention of the present application is characterized in that the electrostatic chuck is equipped with a reverse voltage applying means for applying a voltage, and the electrostatic chuck according to the second invention of the present application has the reverse voltage applying means, and when the means operates, a
It is characterized by comprising a detachment force applying means for applying a predetermined force in a direction of detachment from the conductor.

[Effect]

In the first invention of the present application, prior to detaching the object to be attracted, the reverse voltage applying means applies a DC voltage between the object to be attracted and the conductor in the opposite direction to that during attraction, and between the two. After reducing the generated electrostatic force, the object to be attracted is released. Further, in the second invention of the present application, the detachment force applying means is operated together with the operation of the reverse voltage applying means,
When the electrostatic force between the attraction object and the conductor is reduced and becomes smaller than the detachment force applied to the attraction object by the detachment force applying means, the attraction object is detached by this detachment force.

〔Example〕

The present invention will be described in detail below based on drawings showing embodiments thereof. FIG. 1 is a schematic cross-sectional view showing the structure of an electrostatic chuck according to the present invention.

In the figure, reference numeral 1 denotes a disk-shaped conductor, and the outer surface of the conductor 1 is covered with an insulator 2 over its entire surface. In a semiconductor manufacturing device using ECR plasma, a ceramic (Alt O+) with excellent heat resistance is used as the insulator 2, and the insulator 2 is integrally molded with the conductor 1 during firing. Alternatively, it can be deposited in a thin film form on the surface of the conductor 1 by thermal spraying on the surface of the conductor 1.

The conductor 1 is connected to the positive side of a first DC power supply 5 whose negative side is connected to ground via a power supply changeover switch 7, and the negative side of a second DC power supply 6 whose positive side is connected to ground. When the power selector switch 7 is in the switching position shown in FIG. When it is in the position, it is connected to the second DC power source 6 and is negatively charged.

An electromagnetic cylinder 4 is disposed on one side of the conductor 1 and moves the plunger forward or backward in response to whether or not an excitation current is supplied to the solenoid S. The plunger of the electromagnetic cylinder 4 penetrates the center of the electric conductor l in the thickness direction from the negative side thereof, and has a disc-shaped pressing member at its tip on the other side of the electric conductor l. 4a is fixed. When an excitation current is applied to the solenoid S, the electromagnetic cylinder 4 generates an electromagnetic force corresponding to the excitation current, advances the plunger by the electromagnetic force, and presses the pressing member 4a against the insulator 2.
The electromagnetic cylinder 4 operates to protrude from the surface, and when the solenoid S is not energized with excitation current and the plunger is in its retracted position, one surface of the pressing member 4a is in contact with the conductor l. It is set so as to form a road surface with the surface of the insulator 2 on the other side. Therefore, the force generated by the electromagnetic cylinder 4 in response to the excitation of the solenoid S is applied to the object 3 that is attracted and held on the surface of the insulator 2 on the opposite side to the position where the electromagnetic cylinder 4 is disposed, as will be described later. , acts as a detachment force from the surface of the insulator 2 via the pressing member 4a.

Reference numeral 9 in the figure is a control section that controls the operation of the electrostatic chuck according to the present invention, and its output signal is given to the solenoid S of the electromagnetic cylinder 4 and the power changeover switch 7. When the output signal from the control unit 9 is applied to the solenoid S, an excitation current is applied to the solenoid S, and the electromagnetic cylinder 4 generates the detachment force. 9, the switch 7 is switched from one switching position to the other switching position shown in FIG. The second
It is designed to switch to a state where it is connected to a DC power source 6.

Now, when attracting and holding the object 3 with the electrostatic chuck configured as above, first, the object 3 is placed on the surface of the insulator 2 on the opposite side to the position where the electromagnetic cylinder 4 is placed.
It is placed approximately concentrically with the conductor l. At this time, the control unit 9 is not giving an output signal to the solenoid S, and since the electromagnetic cylinder 4 is in the retracted state while plunging, the object 3 is placed closely on the surface of the insulator 2. be placed.

Further, the control unit 9 does not issue an output signal to the power supply changeover switch 7, and the conductor 1 is connected to the first DC power supply 5 and is in a positively charged state. Now, when a part of the object 3 placed in this way is connected to the ground via the ground switch 8 and the ground switch 8 is turned on, a gap between the conductor 1 and the object 3 is created. Electrostatic force is generated, and the object to be attracted 3 is attracted to the conductor 1 via the insulator 2 due to this electrostatic force, and is held on the surface of the insulator 2. When the electrostatic chuck according to the present invention is used in a semiconductor manufacturing device using ECR plasma, the object 3 to be attracted is grounded through the plasma irradiated to it, so the object 3 to be attracted is grounded. There is no need to provide a circuit as shown in FIG. 1 for connection, and the object 3 to be attracted is attracted and held on the surface of the insulator 2 at the same time as the plasma irradiation to the surface of the object 3 starts.

When a predetermined process such as a film forming process by plasma irradiation or an etching process is completed on the target object 3 that has been attracted and held, and the target target 3 is removed, the end of the process is detected by an appropriate means. The control unit 9 issues a switching signal to the power selector switch 7, and also issues an excitation signal to the solenoid S of the electromagnetic cylinder 4. As a result,
The conductor l is connected to the second DC power supply 6, and changes from a positively charged state to a negatively charged state, and a DC voltage in the opposite direction to that at the time of attraction is generated between the electric conductor l and the object to be attracted 3. is applied, and the object to be attracted 3 is pressed in the direction of separation from the surface of the insulator 2 by a separation force generated by the electromagnetic cylinder 4 and acting on the central portion of the object through the pressing member 4a.

FIG. 2 is a graph showing how the attraction force between the conductor 1 and the object 3 changes over time after a DC voltage in the opposite direction to that during attraction is applied between the two. As shown in this figure, the adsorption force, which was about 0.7 kg immediately after the application of the reverse voltage started, was reduced to less than 0.1 kg by applying the reverse voltage for 20 to 30 seconds, and at this point, the adsorption force was reduced to less than 0.1 kg. By separating the adsorbed object 3, the adsorbed object 3
can be easily removed from the M with a small amount of force.

Further, FIG. 3 shows the detachment force when the magnitude of the reverse voltage is variously changed and the electromagnetic cylinder 4 is operated together with the application of the reverse voltage to apply a detachment force of 300 g to the object 3. 3 is a graph showing the time required until the adsorbed object 3 is separated by the following steps. As shown in this figure (the time required for the detachment of the adsorbed object 3 is short, for example, 600
When a reverse voltage of V is applied, it is possible to detach the attracted object 3 in about 5 seconds after application, and when the reverse voltage is 2
Even when the voltage is as low as 00V, it is possible to detach the object 3 in a short time of 20 seconds or less, and the electrostatic chuck according to the present invention can quickly remove the object 3. It is clear that it can be withdrawn.

. Since the electromagnetic force generated by the electromagnetic cylinder 4 corresponds to the magnitude of the excitation current to the solenoid S, the excitation current is changed depending on the degree of breakability of the object 3 to be attracted.
By adjusting the detachment force applied to the object 3, it is possible to reliably detach the object 3 without destroying it.

Note that FIGS. 2 and 3 show the case where a silicon semiconductor substrate is used as the object 3 to be attracted.

In this embodiment, the electromagnetic cylinder 4 is used as a means for applying a detachment force to the object 3 to be attracted, but a structure in which the detachment force is applied to the object 3 to be attracted may be adopted by other means.

Further, in this embodiment, when the object to be attracted 3 is attracted, the conductor l is connected to the first DC power source 5, and the object to be attracted 3 is connected to the first DC power source 5.
Although the configuration is such that it is connected to the second DC power supply 6 when disconnected, it goes without saying that this connection state may be reversed.

Furthermore, in this embodiment, the application of a reverse voltage and the application of detachment force when the object 3 to be attracted is detached are automatically performed by the operation of the control section 9. The application may be performed by manually switching the power supply selector switch 7, and the application of the detachment force to the object to be attracted may also be performed manually by providing a manual switch in the excitation circuit of the solenoid S and operating the switch. Good too.

〔effect〕

As detailed above, in the electrostatic chuck according to the present invention, when detaching an object to be attracted, a DC voltage is applied between the object and the conductor in the opposite direction to that during attraction, and a voltage is generated between the two. Since the electrostatic force caused by the adsorption is quickly reduced, the time required for the adsorbed object to become detachable is greatly shortened, and it is possible to quickly remove the adsorbed object. Since the detachment force applying means applies a predetermined force in the detachment direction to the object to be attracted, the present invention has excellent effects such as being able to reliably separate the object without destroying the object. play.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a schematic cross-sectional view showing the structure of an electrostatic chuck according to the present invention, and FIG. 2 shows temporal changes in adsorption force after application of a reverse voltage. Figure 3 is a graph showing the time required for the object to be attracted to detach when the detachment force imparting means is operated, and Figure 4 is a graph showing the magnitude of the attraction force and residual attraction force in a conventional electrostatic chuck. This is a graph showing. 1... Conductor 2... Insulator 3... Object to be attracted 4... Electromagnetic cylinder 5... First DC power supply 6
...Second DC power supply 7...Power supply selector switch patent Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Noboru Kono Figure 1 Figure 4 Figure 2 Figure 3

Claims (1)

[Claims] 1. A DC voltage is applied between a conductor whose outer surface is covered with an insulator and an object to be attracted that is in contact with the surface of the insulator, and the electrostatic force generated between the two , adsorbing the object to be adsorbed;
The electrostatic chuck for holding the electrostatic chuck may include a reverse voltage applying means for applying a DC voltage in a direction opposite to that during attraction between the attraction object and the conductor when the attraction object is released. Features an electrostatic chuck. 2. A DC voltage is applied between a conductor whose outside is covered with an insulator and an object to be attracted that is in close contact with the surface of the insulator, and the electrostatic force generated between the two causes the object to be attracted. adsorption,
In the electrostatic chuck for holding, a reverse voltage applying means applies a DC voltage in a direction opposite to that during attraction between the attracted object and the conductor when the attracted object is released; and the reverse voltage An electrostatic chuck characterized by comprising a detachment force applying means for applying a predetermined force to the object to be attracted in a direction of detaching from the conductor when the applying means operates.