JPH01112745A - Wafer separating method in semiconductor manufacturing device - Google Patents

Abstract

PURPOSE:To easily and securely separate from an electrostatic chuck a wafer, which has already been processed, without damaging the wafer by, upon interrupting the application of a voltage applied to the electrostatic chuck of a semiconductor manufacturing apparatus, turning off the application while alternating the polarity of the voltage. CONSTITUTION:Upon removing electric charges induced in an insulator 11 of an electrostatic chuck 10, an applied voltage to the electrostatic chuck is changed to -V1 which has a peak voltage less than the voltage V0 upon attraction of the chuck and has a reverse polarity, then changed to +V2 less than +V0, and to -V3 less than -V1. This is repeated in succession to bring the voltage to 0 volt. It is assumed that +100V is applied to a point A in the figure from a power supply 12 and -1000V to a point B from another power supply 14. The points A, B are branch points between lines connecting the power supplies 12, 14 to the electrodes 13, 13 and to the electrodes 15, 5. Upon interrupting the voltage, the voltage from the power supply 12 to the point A is decreased in succession by -1/2 time at each 1sec for example to 0V, like a voltage series: -500V, 250V, -125V, and 62.5V.... Electric charges induced in the electrostatic chuck are induced in the electrostatic chuck are surely reduced, to assure the separation of a wafer 16 from the electrostatic chuck by means of the operation of pins.

Description

[Detailed Description of the Invention] [Summary] When removing a semiconductor wafer from an electrostatic chuck used for dry etching of a semiconductor wafer, the voltage of the electrode of the electrostatic chuck is changed from alternating to Ov to reduce the residual adsorption force of the chuck. The purpose of this invention is to provide a method for easily and reliably releasing a processed wafer from an electrostatic chuck without damaging the wafer. The present invention includes a method for removing a wafer in a semiconductor manufacturing apparatus, characterized in that, in stopping the voltage applied to an electrostatic chuck of the apparatus, the polarity of the applied voltage is alternated and turned off.

[Industrial application field]

The present invention is a semiconductor device in which, when a semiconductor wafer is removed from an electrostatic chuck used for dry etching of a semiconductor wafer, the voltage of the electrode of the electrostatic chuck is changed from alternating to Ov to reduce the residual adsorption force of the chuck. The present invention relates to a wafer detachment method in a manufacturing apparatus.

[Conventional technology]

To perform dry etching on a semiconductor wafer (hereinafter simply referred to as a wafer), an apparatus shown in FIG. 4 is used, in which 21 is a chamber kept in vacuum, 22 is a wafer, 23 is an electrostatic chuck, 24 is an electrode connected to a 13.56 MHz power source 25, 26 is a counter electrode, and electrode 2
During 4.26, plasma is generated to perform dry etching on the wafer 22.

When the etching is finished, the power to the electrostatic chuck is turned off, and the wafer 22 is lifted up by a pin 27 which is moved up and down by a motor (not shown), and a robot arm (not shown) comes and grabs the wafer 22 and takes it out of the chamber 21. The next wafer is then brought to the position shown. During this operation, the chamber 21 is kept in a vacuum unless there is some problem.

This type of reactive ion etching (RIB)
), the wafer is heated by the plasma and may cause resist deterioration or etching profile deterioration, so to prevent this, the wafer is cooled. One way to do this is to combine a cooling source and a mechanical lamp, but there is also a method using a vacuum chuck or an electrostatic chuck in a higher vacuum, and the electrostatic chuck is superior in terms of damage to the wafer.

Referring to FIG. 5, which shows the electrostatic chuck in detail, the electrostatic chuck 10 is made of an insulator 10, and a + (for example, +IKV) power source 1 is connected to the side opposite to the side that attracts the wafer 16.
An electrode 13 connected to 2 and an electrode 15 connected to a − (for example −I KV) power source 14 are arranged.

[Problem that the invention seeks to solve]

Referring again to FIG. 5, the electrostatic chuck 10 has an IKν
A relatively high voltage is applied to the wafer, and the wafer is fixed by the Coulomb force between the wafer and the electric charge induced therein. Note that in the figure, + and - schematically represent positive and negative charges, respectively.

Even if the power is turned off and the voltage Vo applied to the power supply is reduced to zero in order to remove the wafer after dry etching or other processing is completed, the electrode 13. The wafer does not separate from the chuck due to the residual charge due to polarization of the dielectric material on top of the chuck (as mentioned above, electrostatic chucks are made of insulating material), and if you try to forcefully remove the wafer, the wafer may be damaged. . In FIG. 6, the horizontal axis represents time, and the vertical axis represents applied voltage in KV.

Returning to FIG. 4, as described above, the power is turned OFF, and then the pin 27 is moved upward to release the wafer from the electrostatic chuck. However, when the wafer does not separate from the electrostatic chuck for the reasons described above, the force of the pin is applied. If it is too large, the wafer will be damaged.

In such a case, it is necessary to break the vacuum in the chamber and remove the broken wafer. To avoid weakening the adsorption force of the chuck, wipe the electrostatic chuck with alcohol, for example, and then remove the moisture in the chamber.
The air must be purged and a vacuum drawn to return the vacuum level in the chamber to a predetermined value, which can take 1 to 3 hours.

When the wafer cannot be removed with the pins, even if you break the vacuum and use tweezers to remove the wafer in order to avoid damaging the wafer, even if you are careful, the wafer will be damaged and the above problem will occur. Even if the wafer is not damaged, it still takes about an hour to break the vacuum, remove the wafer, purge the air in the chamber, and return to the original vacuum.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method that allows a wafer that has been processed to be easily and reliably removed from an electrostatic chuck without damaging the wafer.

[Means for solving problems]

The above-mentioned problem is solved by a method for removing a wafer in a semiconductor manufacturing apparatus, which is characterized in that when stopping the voltage applied to the electrostatic chuck of the semiconductor manufacturing apparatus, the polarity of the applied voltage is alternated and turned off.

[Effect]

The charge on the electrode of an electrostatic chuck can be immediately released by grounding, but the problem is the charge induced in the insulator that makes up the electrostatic chuck. It is possible to make the insulator have some degree of conductivity, but this poses a problem because it weakens the insulation between the electrodes.

Therefore, in order to eliminate the charge induced in the insulator, the present invention has developed a method as shown in FIG. Set it to -v1, which is small and has the opposite polarity, then set it to +v2, which is smaller than +Vo, then set it to -v3, which is smaller than -v1, and then repeat this method successively to bring it closer to 0 volts, thereby reducing the induced charge. be.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to illustrated embodiments.

In the arrangement shown in FIG.
It is assumed that 1000V is applied to B from the other power supply 14. Here, A and B are the branching points of the lines from the power supply 12.14 to the electrodes 13.13 and 15.15, respectively.0 In one embodiment of the present invention, when this voltage is cut off, -500V to A,
For example, apply the applied voltages of 250 V, -125 V, and 62.5 V by multiplying them by 1 1/2 every second, and bring them to 0. This change is shown in the diagram in Figure 3, where the horizontal axis represents time (1).
is taken in seconds, and the voltage applied to A is taken in V on the vertical axis.

Similarly, a voltage having a value with the positive and negative signs opposite to those described above is applied to B.

By doing this, + induced in the electrostatic chuck
The charges at and - are definitely reduced, and when the voltage applied to A is 0, almost no charges remain, so the wafer can be reliably separated from the electrostatic chuck by operating the pins.

Alternatively, instead of the above method, the voltage applied to A can be set to 10
0OV, -900V, 800V, -700V,
It is also possible to change the absolute value of 600V, .

Furthermore, the above-mentioned applied voltage may be applied in the form of a pulse and the pulse width may be successively reduced (or the voltage may be applied in the form of a pulse in the above two methods).

The apparatus shown in FIG. 1 is used to carry out the above method.

In this device, voltage is applied to the branch point A in a switching manner from a power source 12 and an AC power source 17.

In order to gradually reduce the voltage to the electrostatic chuck to zero (0), let the voltage υ of the AC power source be −UP sin wt, and let C be the contact point of the variable resistor 17 between OD, then the potential true of A becomes 'JIA-(QCloo) 17p sin wt. Here, Vp is the amplitude of the AC power supply, and W is the angular frequency of the AC power supply. By driving the contact C, for example, by a motor (not shown), it is possible to reduce the voltage to 0 volts without alternating the voltage, and the same means as shown can be provided on the side of the power supply 14.

〔Effect of the invention〕

As described above, according to the present invention, the downtime caused by the wafer becoming impossible to remove due to the excessive residual adsorption force of the electrostatic chuck is reduced, and the operating rate of equipment used for etching etc. is improved. This prevents damage to the wafer due to unloading the wafer, which is effective in reducing costs.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of the present invention, Fig. 2 is a diagram showing the principle of the invention, Fig. 3 is a diagram showing the method of the invention, Fig. 4 is a sectional view of the dry etching apparatus, and Fig. 5 is a diagram showing the principle of the invention. The figure is a sectional view of an electrostatic chuck, and FIG. 6 is a diagram showing a conventional method. In the figure, 10 is an electrostatic chuck, 11 is an insulator, 12 and 14 are power supplies, 13 and 15 are electrodes, 16 is a wafer, 17 is an AC power supply, and 18 is a variable resistor. Patent Applicant Fujitsu Ltd. Representative Patent Attorney Akira Kukimoto Story of Electrostatic Sumatsu 2

Claims (4)

[Claims] (1) A method for removing a wafer in a semiconductor manufacturing device, characterized in that, in stopping the voltage applied to the electrostatic chuck (11) of the semiconductor manufacturing device, the applied voltage is turned off while alternating the polarity. (2) OF while gradually lowering the peak height of the alternating voltage.
The method according to claim 1, wherein the method is gradually reduced to F. (3) The method according to claim 1, wherein the applied voltage is turned off while successively decreasing the pulse width of the alternating voltage. (4) The method according to claim 1, in which the peak height is successively lowered by using pulsed alternating voltage.