JPH0722498A - Method and device for releasing electrostatic chuck from semiconductor wafer - Google Patents

Abstract

PURPOSE:To provide a method and device for releasing an electrostatic chuck from a semiconductor wafer without damaging the semiconductor element formed on the surface of the wafer by eliminating the electrostatic attraction by using a means which removes the charges accumulated on the surface of the wafer when the wafer is electrostatically chucked. CONSTITUTION:A method for releasing an electrostatic chuck from a wafer is provided for a plasma treatment device which has an electrostatic chuck which permits a semiconductor wafer 22, which is to be treated by plasma by being placed on a bottom electrode 12, to adhere to the bottom electrode 12 by electrostatic attraction. Positive potential is applied to a top electrode which faces the semiconductor wafer 22 and the top electrode is brought closer to the semiconductor wafer 22. The negative charges induced to the surface of the semiconductor wafer being treated by plasma are neutralized and the electrostatic chuck is released.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer electrostatic chuck releasing method and an electrostatic chuck releasing method for releasing electrostatic chucking force in a semiconductor wafer plasma processing apparatus for holding and cooling a semiconductor wafer by electrostatic chuck means. It is a thing.

[0002]

2. Description of the Related Art It is known that when a semiconductor wafer (hereinafter also referred to as a "timely wafer") is subjected to plasma processing such as dry etching or CVD, the temperature of the wafer during processing affects plasma processing characteristics. Generally, a wafer undergoing plasma processing is brought into a high temperature state due to radiant heat from plasma or conversion of kinetic energy of ions / electrons incident on the wafer into thermal energy. Therefore, conventionally, in the plasma processing apparatus, a device for keeping the temperature of the wafer at a predetermined temperature has been made, and, for example, various cooling means for the wafer have been taken.

One of them is an electrostatic chucking method called electrostatic chuck which utilizes electrostatic chucking force (electrostatic attraction). A plasma processing apparatus using this method is shown in the schematic sectional view of FIG. The present apparatus has a basic configuration in which a lower electrode 12 and an upper electrode 13, both of which face to each other are planar, are disposed so as to be correctly opposed to each other inside a processing chamber 11 formed of a container having a vacuum exhaust port 18. . A reaction gas according to a processing purpose is fed into the processing chamber 11 from a process gas inlet 23, and a discharge generated when a high frequency voltage supplied from a high frequency power supply 17 is applied between these electrodes. Thus, plasma is generated in the space between both electrodes. Reference numeral 16 is a matching box for adjusting the output of the high frequency power supply 17 described above. Then, the wafer 22 is placed on the plate-like dielectric material 14 which is provided on the entire upper surface of the lower electrode 12, and is brought into contact with the above-mentioned plasma to be subjected to plasma treatment in a predetermined process. .
The lower electrode 12 is provided therein with a constant temperature water circulation passage 15 for circulating constant temperature water.

In this plasma processing apparatus, the electrostatic attraction force generated by the principle as shown in the schematic view of FIG.
The wafer 22 is the lower electrode 1 whose temperature is adjusted by constant temperature water.
It is stuck on top of 2. In FIG. 4, the surface of the wafer 22 in the plasma 25 is connected to ground through the plasma (since plasma may be considered as a resistive conductor). In this state, if a negative DC voltage from the DC bias power supply 21 is applied to the lower electrode 12, the lower electrode 12
Current is not flowed because it is covered with the dielectric 14, but + (positive) charge is induced on the wafer 22 side and − (negative) charge is generated on the lower electrode 12 side across the dielectric 14. On the other hand, during plasma processing, negative charges are accumulated on the surface of the wafer 22. Therefore, due to the electrostatic attraction force that these charges attract each other,
The wafer 22 is brought into close contact with the lower electrode 12 side via the dielectric 14. In this way, the wafer 22 is brought into close contact with the temperature-adjusted lower electrode 12 side, so that the thermal conductivity between the wafer 22 and the lower electrode 12 is dramatically increased, and the wafer 22 is kept at the electrode temperature during the plasma processing. It is cooled to near temperature. In this case, it is more effective to use an insulator having excellent heat conduction characteristics, such as boron nitride, for the dielectric 14.

For example, as shown in the schematic view of FIG. 5, a plasma 25 is generated by a method of peeling off the wafer 22 adhered to the lower electrode 12 side by electrostatic attraction after plasma processing such as etching is completed. In such a state, a method of applying a reverse bias voltage 24 (a positive bias voltage opposite to that at the time of electrostatic attraction) in which the polarity of the DC bias power supply 21 is reversed to the lower electrode 12 is generally adopted. By this operation,
This is because the charge separation that has been induced in the dielectric 14 is canceled and the electrostatic attraction force between the wafer 22 and the lower electrode 12 disappears.

[0006]

In the conventional wafer electrostatic chuck release method and apparatus of the plasma processing apparatus as described above, plasma must be generated at the time of electrostatic chuck release in the same manner as during plasma processing. Of course, during the generation of plasma, the wafer surface is naturally exposed to the charged particles in the plasma, so that the semiconductor element formed on the wafer surface is damaged. In this case, even if the plasma processing of the wafer is performed with the minimum damage, the damage due to the plasma at the time of releasing the electrostatic chuck is added, and considering that the plasma processing with lower damage is required thereafter, The electrostatic chuck releasing method and the apparatus therefor have a problem that they are not satisfactory in terms of technology and processes.

The present invention has been made to solve the above-mentioned problems, and the electrostatic attraction force is eliminated by a means for removing charges accumulated on the wafer surface at the time of electrostatic chucking to form on the wafer surface. It is an object of the present invention to provide a method for releasing an electrostatic chuck of a semiconductor wafer of a plasma processing apparatus and an apparatus therefor, which does not cause damage to a semiconductor element that is already installed.

[0008]

According to a method of releasing an electrostatic chuck of a semiconductor wafer according to the present invention, a semiconductor wafer placed on one electrode and subjected to plasma treatment is brought into close contact with one electrode by electrostatic attraction. A method of releasing electrostatic chuck of a semiconductor wafer in a plasma processing apparatus having electrostatic chuck means, wherein a positive potential is applied to the other electrode facing the semiconductor wafer to bring the electrode closer to the semiconductor wafer.
The electrostatic chuck is released by neutralizing the negative charges induced on the surface of the semiconductor wafer during plasma processing.

The semiconductor wafer electrostatic chuck releasing device according to the present invention is also equipped with an electrode of the plasma processing apparatus, the other electrode being placed so as to face the semiconductor wafer placed via the insulator plate. A DC power source connected to apply a positive bias to the other electrode, and a gap adjusting device having a mechanism capable of moving the other electrode in parallel to the vicinity of the semiconductor wafer in a plasma processing apparatus for semiconductor wafers. It is equipped.

[0010]

In the present invention, as the electrostatic chuck releasing means for the semiconductor wafer, the other electrode is installed so as to face the semiconductor wafer placed on one electrode of the plasma processing apparatus via the insulator plate. By applying a positive bias from the DC power source to this other electrode and making it possible to move the other electrode in parallel to the vicinity of the semiconductor wafer by means of the gap adjusting device, the distance between the other electrode and the wafer surface is minimized, for example. By approaching up to 1 mm, charge separation due to the negative charges accumulated on the wafer surface during plasma processing in the state of the electrostatic chuck is eliminated, so that the electrostatic attraction force between the wafer and one of the electrodes disappears and the electrostatic attraction is eliminated. The chuck is released.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the electrostatic chuck releasing method according to the present invention will be described with reference to the schematic principle diagram of FIG. In the figure,
Reference numerals 11 to 24 indicate the same or corresponding parts as the partial reference numerals described with reference to the conventional example diagrams of FIGS. First, FIG. 1A shows the wafer 22 and the dielectric 14 immediately after the plasma treatment.
This shows the state of charge separation on the surface (both upper and lower sides), and the wafer 22 passes through the dielectric 14 and the lower electrode through the dielectric 14 due to the electrostatic attraction by the − charge of the wafer 22 and the + charge of the upper surface of the dielectric 14. It is in close contact with (one electrode) 12. A high frequency voltage for plasma discharge is applied between the lower electrode 12 and an upper electrode (not shown), but the lower electrode 12 is maintained at a ground potential in terms of direct current.

Next, as shown in FIG. 1B, the later-described positive potential electrode (the other electrode) 1 that directly faces the wafer 22 is brought close to the wafer 22, and the positive bias from the DC bias power source 20 is instantaneously applied. Application. As a result, the negative electric charge (negative electric charge) on the surface of the wafer 22 is neutralized and removed, and the electrostatic attraction force between the wafer 22 and the dielectric 14 and thus the lower electrode 12 is lost. Therefore, the wafer 22 is usually taken out from the plasma processing apparatus in this state.

Thereafter, as shown in FIG. 1 (c),
DC bias power source 2 is applied to lower electrode 12 while plasma is being generated.
By momentarily applying a reverse bias of positive potential from 1, the ± charges on both surfaces of the dielectric 14 are removed. That is, as is clear from the above description, the wafer 22 is not exposed to plasma and damaged when the electrostatic chuck is released.

FIG. 2 is a schematic explanatory view showing an embodiment of an apparatus configuration for realizing the electrostatic chuck releasing method according to the present invention. FIG. 2 shows a conventional device of FIG. 3 to which specific devices for carrying out the electrostatic chuck releasing method of FIG. 1 are added. That is, the upper electrode (other electrode) 1
In order to give 3 the function of the positive potential electrode 1 (see FIG. 1b) used when releasing the electrostatic chuck, the upper electrode 13 is made to approach the upper surface of the lower electrode 12 by a minimum of 1 mm. A gap adjuster 19 is provided. Further, a DC bias power source 20 for applying a positive voltage to the upper electrode 13 is additionally provided. The operation of this device is the same as that of the phenomenon described with reference to FIG.

In the configuration example of this embodiment, the upper electrode 1
Although the gap adjuster 19 is provided so as to move 3 up and down, the gap adjuster may be provided so as to move the lower electrode 12. Also, one DC bias power supply 20 and one DC bias power supply 21 for applying a bias voltage to the upper electrode 13 and the lower electrode 12, respectively, are provided, but this is not necessary. For example, a relay is used for each electrode. Alternatively, it may be possible to switch and apply the voltage. Further, in the present embodiment, the case where the upper electrode 13 is provided with the function of a positive potential electrode for releasing the electrostatic chuck has been described. However, an electrode different from the upper electrode 13 is added and a dedicated positive potential electrode is provided. May be provided.

In addition to the above, the present invention relates to electrostatic chuck releasing means, but this structure is applied to a plasma processing apparatus which does not employ an electrostatic chuck, for example, a method which does not use the dielectric 14. Also has the secondary effect of being beneficial in that the negative charges on the wafer surface can be removed instantaneously. This is because when the wafer is plasma-processed, negative charges are accumulated on the wafer surface regardless of whether an electrostatic chuck is used or not. Since this electric charge is retained even after the plasma treatment, a small amount of positively charged dust is electrostatically adsorbed on the wafer surface by this electric charge. Naturally, this dust will reduce the yield of semiconductor elements formed on the wafer. Adopting the present invention, by removing the negative charges on the wafer surface after plasma treatment, it is possible to prevent the attachment of dust due to static electricity,
It greatly contributes to the improvement in the yield of semiconductor device manufacturing.

[0017]

As described above, according to the present invention, the upper electrode installed so as to face the semiconductor wafer placed on the lower electrode of the plasma processing apparatus via the insulator plate is used. A positive bias was applied from a DC power source to the electrode, and this electrode could be moved in parallel to the vicinity of the semiconductor wafer by the gap adjustment device. Since the electrostatic chuck is released by eliminating the charge separation due to the negative charges accumulated on the wafer surface during processing, the wafer is not exposed to the plasma when the electrostatic chuck is released, and the wafer is not damaged by the plasma. The effect of completely disappearing is obtained. Further, when the electrostatic chuck is released, the surface charge of the wafer after the plasma processing can be instantaneously removed, so that there is an effect of eliminating the adhesion of dust to the wafer surface due to the electrostatic attraction force after the plasma processing. In addition, by applying the configuration of the present invention to a plasma processing apparatus that does not employ an electrostatic chuck for the purpose of eliminating the adhesion of dust to the wafer surface, which is just described, a similar result can be obtained. The following effects can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic principle view showing an embodiment of an electrostatic chuck releasing method according to the present invention.

FIG. 2 is a schematic explanatory view showing an embodiment of an apparatus configuration for realizing the electrostatic chuck releasing method according to the present invention.

FIG. 3 is a schematic cross-sectional view of a plasma processing apparatus showing a conventional electrostatic chuck releasing method.

FIG. 4 is a diagram illustrating the principle of a conventional electrostatic chuck.

FIG. 5 is a diagram illustrating the principle of a conventional electrostatic chuck releasing method.

[Explanation of symbols]

 1 Positive potential electrode 11 Processing chamber 12 Lower electrode 13 Upper electrode 14 Dielectric 15 Constant temperature water circulation path 16 Matching box 17 High frequency power supply 18 Vacuum exhaust port 19 Gap adjuster 20, 21 DC bias power supply 22 Semiconductor wafer (wafer) 23 Process gas introduction Mouth 24 Reverse bias voltage 25 Plasma

Claims (2)

[Claims] 1. An electrostatic chuck release of a semiconductor wafer in a plasma processing apparatus having electrostatic chuck means for bringing a semiconductor wafer placed on one electrode and subjected to plasma processing into close contact with the one electrode by electrostatic attraction force. In the method, by applying a positive potential to the other electrode facing the semiconductor wafer and bringing the other electrode close to the semiconductor wafer, the negative charge induced on the surface of the semiconductor wafer during plasma processing is reduced. A method of releasing an electrostatic chuck of a semiconductor wafer, which comprises releasing the electrostatic chuck. 2. The other electrode installed so as to face a semiconductor wafer placed on one electrode of a plasma processing apparatus via an insulator plate, and a positive bias is supplied to the other electrode. Electrostatic chuck release of a semiconductor wafer, characterized in that the plasma processing apparatus is equipped with a direct current power source connected to the semiconductor wafer and a gap adjusting device having a mechanism capable of moving the other electrode in parallel to the vicinity of the semiconductor wafer. apparatus.