JPH06291174A - Electrostatic chuck, and method for adhering and holding semiconductor wafer to electrostatic chuck - Google Patents

Abstract

PURPOSE:To provide a structure of an electrostatic chuck whereby the yield of non-defective can be improved in the case of the etching of the surface of a semiconductor wafer or the processing for forming its film, and to provide a method for adhering and holding semiconductor wafer to electrostatic chuck using the structure. CONSTITUTION:A power supply 4 of an electrostatic chuck 1 whereby an electrostatic force is applied to a semiconductor wafer 5 via an insulator 2 is formed as a variable voltage power supply. When the semiconductor wafer 5 is attracted by the electrostatic chuck 1, the voltage of the power supply 4 is lowered, and the number of particles which are stuck on the semiconductor wafer 5 from the surroundings thereof is reduced. When the semiconductor wafer 5 is processed after chucked, the voltage of the power supply 4 is increased to enhance the cooling of the electrostatic chuck 1 to be improved and the processing of the semiconductor wafer 4 which is performed at a suitable temperature is made easy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an electrostatic chuck used in a manufacturing apparatus of a semiconductor integrated circuit, particularly a DRAM by fine processing of LSI and the like, and a method of adsorbing and holding a semiconductor wafer on the electrostatic chuck having the structure. Regarding

[0002]

2. Description of the Related Art As is well known, in an electrostatic chuck used in a semiconductor manufacturing apparatus, an electrostatic force is applied to a semiconductor wafer via an insulator so that the semiconductor wafer is attracted to the surface of the insulator. It is held in a high-temperature gas or a gas that has been turned into plasma for surface treatment such as thin film formation or etching on the treated surface. The structure is usually two or two sets of foil-shaped or film-shaped electrodes embedded side by side in the same plane in the disk-shaped insulator made of heat-resistant ceramics such as Al ₂ O ₃ for DC power supply. By applying a DC voltage between the two electrodes or two sets of electrodes and bringing a semiconductor wafer having a diameter close to that of the insulator into close contact with the surface of the insulator. An electrostatic force is applied between one or two sets of electrodes and the semiconductor wafer to hold the semiconductor wafer in an attracted state so that the semiconductor wafer is attracted to the surface of the insulator and the wafer is not separated.

In addition, the electrostatic chuck constructed in this manner attracts the semiconductor wafer to the surface of the insulator in a state of being in close contact with the entire surface of the insulator.
Since it is held, it is used as a cooling means for keeping the wafer at an appropriate temperature during the surface treatment in the vacuum pressure range of 0.1 mTorr to several Torr. Therefore, the electrostatic chuck can flow the heat medium. It is used by fixing it to the heat transfer surface of the electrostatic chuck holder formed on.

[0004]

Conventionally, in order to utilize the cooling action of this type of electrostatic chuck as a semiconductor substrate table on which a semiconductor wafer is mounted or mounted, cooling is performed in a vacuum pressure and a vacuum state is applied. Since the heat transfer effect of the gas is extremely small, it is necessary to increase the heat transfer area by increasing the actual contact area between the electrostatic chuck insulator surface whose surface is microscopically uneven and the semiconductor wafer. Contact pressure is 10
An adsorption voltage of about g / cm ² or more was required.

However, when such a high voltage is applied between the electrodes in the insulator when the wafer is attracted, many particles are often attracted to the wafer processing surface at the same time when the wafer is attracted. When particles adhere to the wafer processing surface, the following problems occur. (1) When the wafer surface is treated by etching: When particles adhere to a portion other than the resist, the etching rate around the contact point between the particles and the wafer becomes slower, and when this portion is etched, the etching is performed in a predetermined manner. Etching of other portions becomes excessive, resulting in non-uniform etching, which causes a problem that the yield rate decreases due to an increase in over-etched portions.

(2) When the wafer surface treatment is a film formation process by CVD: After the treatment, the particle portion becomes a large protrusion, or the particle portion is not uniformly formed, so that a defect partially occurs, and thus it is a non-defective product. The yield rate decreases. An object of the present invention is to reduce the number of particles adhering to a wafer processing surface when a semiconductor wafer is attracted to an insulator surface of an electrostatic chuck, thereby improving the yield rate of non-defective products. And a method for attracting and holding a semiconductor wafer by an electrostatic chuck having this configuration.

[0007]

In order to solve the above problems, in the present invention, the power source of the electrostatic chuck for generating an electrostatic force for attracting and holding the semiconductor wafer on the surface of the insulator is constituted as a variable voltage power source. . Then, the attraction and holding of the semiconductor wafer by the electrostatic chuck provided with the variable voltage power source is performed by using the power source voltage for attracting the semiconductor wafer and the power source voltage for holding the attracted semiconductor wafer in the attraction state during the processing step. To lower the power supply voltage during adsorption,
It is assumed that the power supply voltage during the treatment process is increased.

When the semiconductor wafer is brought to the insulator surface of the electrostatic chuck by the wafer transfer means, the voltage rise from the power supply voltage at the time of attracting the semiconductor wafer to the power supply voltage for holding the semiconductor wafer in the attraction state during the processing step. For this purpose, it is preferable that after the semiconductor wafer is adsorbed, the wafer transfer means is moved to a position where the electrostatic force by the electrostatic chuck power supply is substantially not applied.

Further, the wafer transfer means for bringing the semiconductor wafer to the surface of the insulator of the electrostatic chuck transfers the wafer processing surface vertically downward and insulates the electrostatic chuck while keeping the wafer processing surface vertically downward. In the case of the transfer means for adsorbing and holding onto the body surface, it is preferable to raise the power supply voltage after the semiconductor wafer is adsorbed after the wafer transfer means is no longer directly below the area range of the semiconductor wafer.

[0010]

When the electrostatic chuck power supply is configured as a variable voltage power supply as described above, the voltage for adsorbing the semiconductor wafer on the insulator surface of the electrostatic chuck and the adsorption state of the semiconductor wafer during the processing are held. It is possible to easily obtain a voltage that can most effectively achieve the purpose of each step, such as the voltage.

Therefore, as a method of adsorbing and holding a semiconductor wafer on an electrostatic chuck equipped with a variable voltage power supply, the power supply voltage is lowered at the time of adsorption, and more specifically, the weight of the wafer is 1 or less.
Since it is g / cm ² , the voltage necessary and sufficient for adsorption is set to, for example, 600 V, so that the electric force that passes through the semiconductor wafer from the electrode of one or the other set of the electrostatic chuck connected to the power source is passed. The amount of lines leaking to the outside of the wafer is reduced, and the number of particles sucked from around the wafer to the wafer processing surface is reduced.

On the other hand, when the insulator of the electrostatic chuck is used as a heat transfer medium after the semiconductor wafer is attracted, the power supply voltage is increased, and specifically, the heat flow resistance from the semiconductor wafer to the insulator is effective. Since the contact pressure between the semiconductor wafer and the insulator surface needs to be about 10 g / cm ^{2 in} order to reduce the power consumption to a low level, the power supply voltage is set to, for example, 1000 to 1500 V to effectively cool the semiconductor wafer to an appropriate temperature. Easy to keep.

When the electrostatic chuck is used as a wafer cooling means, a sufficient cooling action can be obtained even if the semiconductor wafer is held until just before entering the processing step, for example, about 10 seconds before. In the case where it is brought to the insulator surface of the electrostatic chuck by the transfer means, it is necessary to raise the power supply voltage after the wafer transfer means is moved to a position where the electrostatic force by the power supply of the electrostatic chuck does not substantially reach. , Even if an electric line of force that cannot fit into the semiconductor wafer occurs, since there is no transfer means having particles in the vicinity of the wafer, the number of particles adhering to the wafer is only the number attracted at the time of adsorption by the low voltage, The problem of yield reduction of non-defective products due to particle adhesion does not occur.

Further, the wafer transfer means for bringing the semiconductor wafer to the insulator surface of the electrostatic chuck transfers the wafer processing surface vertically downward and insulates the electrostatic chuck with the wafer processing surface vertically downward. In the case of a transfer means for adsorbing to and holding on the body surface, if the power supply voltage is raised after the semiconductor wafer is adsorbed after the wafer transfer means does not exist immediately below the area range of the semiconductor wafer, the power supply is increased. Due to the increase in voltage, the semiconductor wafer cannot be completely filled,
There are no particles that are captured by the lines of electric force that pass through the surface of the semiconductor wafer and pass through the lower surface of the semiconductor wafer, and there are no particles that pass through the surface of the semiconductor wafer and that are captured by lines of electric force that pass outside the area of the semiconductor wafer. Since the particles are sucked up along the lines of electric force while resisting gravity, they do not reach the wafer processing surface. Therefore, the power supply voltage can be increased without moving the wafer transfer means to the maximum extent each time prior to the wafer processing, and the degree of freedom in operating the semiconductor manufacturing apparatus is improved.

[0015]

FIG. 1 shows an embodiment of the present invention. In this embodiment, the electrostatic chuck 1 comprises a disc-shaped insulator ₂ made of Al ₂ O ₃ and foil-shaped planar electrodes 3A, 3B embedded side by side in the same plane in the insulator 2. And a DC power source 4 to which electrodes 3A and 3B are connected to both electrodes. Although not shown here, the DC power supply 4 is configured by using a transformer whose primary side is connected to a low-voltage AC power supply and a rectifier that rectifies the AC high voltage on the secondary side of the transformer.
By adjusting the input voltage to the primary side of the transformer, the magnitude of the DC voltage applied between the electrodes 3A and 3B can be changed.

Reference numeral 5 in the drawing denotes a semiconductor wafer, which is transferred from a standby position (not shown) to a position shown in the drawing by a hand 6 as a wafer transfer means. In this embodiment, the hand 6 is configured as a face-down transfer means for transferring with the wafer processing surface facing downward in the vertical direction, and is formed into a disk shape, and a table 6A having guide holes 6C formed at its peripheral edge at equal intervals in the circumferential direction. An arm 6B having a pedestal 6A at its tip, a guide pin 8 for guiding the movement in the vertical direction by a guide hole 6C and positioning the wafer 5 coaxially with the pedestal 6A, and a spring 7 for elastically supporting the wafer 5. It is constructed using and. Further, reference numeral 9 in the drawing is an electrostatic chuck holder for holding the electrostatic chuck 1 in the semiconductor manufacturing apparatus main body,
The contact surface with the electrostatic chuck 1 is cooled by the heat medium circulating inside.

Adsorption and holding of the wafer 5 by the electrostatic chuck 1 are performed as follows. First, the hand 6 which holds the wafer 5 on the spring 7 and brings it directly below the electrostatic chuck 1.
Or the electrostatic chuck holder 9 is lowered by a driving mechanism (not shown) to push the guide pin 8 into the guide hole 6C and bring the upper surface of the wafer 5 and the lower surface of the insulator 2 of the electrostatic chuck 1 into contact with each other. After the contact, the electrostatic chuck holder 9 and the hand 6 still continue to relatively move in the vertical direction to ensure the entire contact between the upper surface of the wafer 5 and the lower surface of the insulator 2. After that, the voltage supplied to the primary side of the transformer constituting the DC power supply 4 is adjusted so that the output voltage of the rectifier connected to the secondary side of the transformer becomes about 600V. As a result, the wafer 5 is attracted to the lower surface of the insulator 2 and the power supply voltage is as low as 600 V.
The amount of electric force lines leaking toward the lower surface of the wafer is extremely small, and the number of particles sucked from the hand 6 does not need to be large.

After adsorbing the wafer 5, the hand 6 is lowered or the electrostatic chuck holder 9 is raised according to the operation sequence of the semiconductor manufacturing apparatus, and then the hand 6 is directed to the standby position of the next wafer to be processed. In this moving step, the voltage of the DC power supply 4 is set to 1 after the time when the hand 6 moves to a position that does not exist directly below the area range of the wafer 5 in this moving process.
Increase to 200V. The specific time when the voltage rises may be immediately after the hand 6 moves out of the area under the wafer 5 or when the electrostatic chuck holder 9 further moves in the vertical direction to reach the wafer processing position. .

By the above adsorption and holding method,
Although the number of particles on the hand 6 increases with the number of wafers processed, it was confirmed that the number of particles attracted to the wafer processing surface did not increase, and that less than half of the particles adhered to the wafer were adhered to the wafer.

[0020]

According to the present invention, since the structure of the electrostatic chuck and the method for attracting and holding the semiconductor wafer to the electrostatic chuck are as described above, the following effects can be obtained. According to the configuration of claim 1, the most effective power supply voltage can be selected in order to improve the yield rate of non-defective products at each stage of adsorption of a semiconductor wafer and holding for processing.

According to the method of claim 2, the number of particles adhering to the wafer processing surface is reduced, the cooling effect of the electrostatic chuck is improved, and it becomes easy to maintain the wafer at an appropriate temperature during processing. And the productivity of the semiconductor manufacturing apparatus is improved. According to the third aspect of the present invention, since the power supply voltage after the wafer is attracted by the low power supply voltage is increased after the wafer transfer means is moved to a position where the electrostatic force in the electrostatic chuck does not reach, the wafer transfer means is processed together with the number of processed wafers. Even if the number of particles above increases, there are no particles attracted to the wafer during the power supply voltage rise stage,
The number of adhered particles remains low and the yield rate of non-defective products does not decrease even if the treatment is repeated continuously.

According to the method of claim 4, since the power supply voltage can be increased from the time when the wafer transfer means deviates just below the area range of the wafer, the degree of freedom in operating the semiconductor manufacturing apparatus is increased and the productivity of the apparatus is improved. To do.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining a configuration of an electrostatic chuck according to the present invention and a method for adsorbing and holding a semiconductor wafer on the electrostatic chuck according to the configuration.

[Explanation of symbols]

 1 Electrostatic Chuck 2 Insulator 4 DC Power Supply (Variable Voltage Power Supply) 5 Wafer (Semiconductor Wafer) 6 Hand (Wafer Transfer Means)

Claims (4)

[Claims] 1. In an electrostatic chuck for attracting and holding a semiconductor wafer on the surface of an insulator by applying an electrostatic force to the semiconductor wafer through the insulator, the power source for applying the electrostatic force to the semiconductor wafer is variable. An electrostatic chuck that is configured as a voltage power supply. 2. A semiconductor wafer is attracted onto the surface of an insulator of the electrostatic chuck by using the electrostatic chuck according to claim 1.
A method for holding the semiconductor wafer, wherein the power supply voltage for adsorbing the semiconductor wafer and the power supply voltage for holding the adsorbed semiconductor wafer in an adsorbed state during the processing step are made different, and the power supply voltage at the time of adsorption is lowered. A method for adsorbing and holding a semiconductor wafer on an electrostatic chuck, characterized by increasing a power supply voltage during a process. 3. The adsorption / holding method according to claim 2, wherein the semiconductor wafer is a wafer when the voltage rises from the power supply voltage at the time of adsorption of the semiconductor wafer to the power supply voltage for holding the semiconductor wafer in the adsorption state during the processing step. When the carrier is brought to the insulator surface of the electrostatic chuck, after the semiconductor wafer is attracted, the wafer carrier is moved to a position where the electrostatic chuck power does not substantially exert the electrostatic force. A method of attracting and holding a semiconductor wafer to an electrostatic chuck, which is characterized in that 4. A method for adsorbing and holding a wafer according to claim 3, wherein the wafer transfer means for bringing the semiconductor wafer to the insulator surface of the electrostatic chuck transfers the processing surface of the wafer vertically downward and the wafer. In the case of a transfer means for adsorbing and holding on the insulator surface of the electrostatic chuck with the processing surface facing vertically downward, the wafer transfer means controls the increase of the power supply voltage after the semiconductor wafer is adsorbed within the area range of the semiconductor wafer. A method for adsorbing and holding a semiconductor wafer on an electrostatic chuck, which is performed after it no longer exists directly below.