JPS58114437A - Electrostatic attracting method - Google Patents

Abstract

PURPOSE:To prevent the lowering of attractive force by repeating polarity at every once electrostatic attraction. CONSTITUTION:Copper foil is shaped onto a supporter with approximately 0.1mm. in necessary form, the copper foil side is bonded onto a flat insulating substrate, and an electrode is manufactured. Polarity is changed over at every once adsorption by a switch 5. According to such constitution, since the polarity of residual charges is inverted at every once, the charges are adsorbed under a state in which there is hardly residual charges, and attractive force does not lower.

Description

[Detailed Description of the Invention] (1) Technical Field of the Invention This invention relates to an electrostatic adsorption method used to adsorb and handle objects such as semiconductor wafers and semiconductor chips.
In particular, it concerns a method in which the adsorption force is stable and strong. (2) Prior art and problems FIG.
Supported and surrounded by 9, switch 3 is turned on
Then, a voltage of the DC power supply number is applied to the electrode 1 to attract the object, and the object is released by turning off the switch 4. Figure 2 shows the second conventional example. , a plurality of pairs of electrodes 1 are supported and surrounded by insulators 2, the switch 3 is turned OFF', the full voltage of the DC power supply 4 is applied to the electrodes 1, the object is attracted, and the switch 3 is turned ON to apply the applied voltage. It lowers the value of the object and makes the object i. Here, R1 and R1 are voltage dividing resistors, and R1>>Rt.

The first conventional example has the disadvantage that, after the switch 3 is turned off and the object is released, charges remain on the attracting surface of the insulator 2'', which significantly reduces the success of subsequent attracting operations. -!Also, in the second conventional example, the voltage is lowered without opening the wiring when separating the object, so the charge remaining on the attraction surface of the insulator 2 is smaller than in the first conventional example. However, when this adsorption is repeated continuously, the residual charge is added up and the adsorption force gradually decreases.◇In either case, if the adsorption is repeated continuously, When repeating this process, a decrease in adsorption force is inevitable.

Although the first conventional example shows a pair of electrodes, and the second conventional example shows a mantissa pair of electrodes, the above-mentioned phenomenon does not change whether the electrodes are a negative pair or a plurality of pairs.

(3) Purpose of the Invention The purpose of the present invention is to provide a method that does not cause the above-mentioned decrease in suction force, and has a strong and stable suction force even when suction is repeatedly performed continuously. (4) Structure of the Invention The present invention is characterized in that a polarity changeover switch 5 is newly provided as shown in FIG. 3, and the polarity is changed every - times of suction.

FIG. 4 shows the insulator 2 when a voltage V is applied to the electrode l and a conductive object 6 such as a semiconductor wafer is attracted.
The polarization (↑ mark) and trout electrostatic charge (+ or 1 symbol) are shown. (a) is adsorbed with no residual charge,
(b) is (0) when adsorbed with residual charge.
is the case where there is no residual charge and the polarity of the voltage V is reversed and applied.

In the case of (b), the polarization effect caused by the voltage VK is partially canceled out by the residual charge, and the adsorption force becomes weaker than in the case of (a), but in the case of (C), the effect of the residual charge is due to the polarization effect. Since it is added, the adsorption force becomes stronger than in the case of (&). When adhesion is repeated while switching the polarity of the applied voltage as in the present invention, unlike the first and second conventional examples described above, the polarity of the residual charge is reversed each time, so charges of the same polarity are added. There's no way you'll be left behind. Therefore (
Almost the same adsorption force as in case a) can be obtained by %N. If the residual charge caused by the first adsorption cannot be completely erased by the second adsorption, the adsorption force of the second (!lJ) is (0). If this residual charge is carried over to the third adsorption, the K will be carried over as in the case of the third adsorption force e(b). However, this decreases slightly.

As described above, the method of the present invention may cause slight fluctuations in the adsorption force, but unlike the first and second conventional examples, the adsorption force does not unilaterally decrease with each repetition. This can be understood conceptually.

(5) Embodiments of the Invention The electrodes used for electrostatic adsorption of semiconductor wafers, etc. are different from conventional known technology, but it is convenient to use, for example, a copper-clad laminate used for printed boards. .

There is a method of selecting a thin support of about 01 wJ, shaping the steel foil on it into the desired electrode shape by photo-etching, and bonding the copper foil side to a flat insulating substrate.

FIG. 5 shows a circuit for supplying DC voltage to the electrodes as described above, which automatically performs polarity switching according to the present invention. The transistors 'rr1. Try is a general flip-flop circuit, and 'rrs is a drive transistor for the polarity switching relay 9. When the switch is turned ON, the voltage V applied to the electrode appears at the output terminal 10 by the ON/OFF relay 8. When the switch is turned on, the voltage applied to the excitation coil of relay 8 is simultaneously applied to the 7 lip-flop circuit, and Try and Try are turned on.
OF'? The state is reversed, and the polarity of the voltage applied to the electrodes is reversed. Therefore, the polarity is automatically switched to ONO[ of the switch 1, and the operator can carry out the method of the present invention without any extra operations.

In order to prevent chattering due to switch-off, it is desirable to make the time constant determined by C and R (shown in the figure $5) of the 7-lip 70-tub circuit somewhat larger.

In addition, in order to adsorb a normal silicon wafer, when the copper-clad laminate is set between αl, the applied voltage V is 20
(6) Effects of the invention The following table shows the adsorption results when adsorption is repeated continuously in the first conventional example, the second conventional example, and the embodiment of the present invention. This is an example of measuring changes in force) 1st measurement 2nd measurement jI 3rd measurement 4th measurement 6th measurement
40g 80g 2nd O@3j@14 560g 4
10g 220g 240g 1801ki-01
Example 500g 630g 5EiOg MaOOg
530g As can be seen from this table, according to the present invention, although there is a slight fluctuation in the adsorption force, there is no decrease in adsorption force to the extent that adsorption becomes impossible as in the conventional example, and stable adsorption is possible. be. In addition, although the embodiment of the present invention of the clothing uses one pair of electrodes, the same effect can be obtained even if multiple pairs of electrodes are used.

[Brief explanation of drawings]

FIG. 1 shows a first conventional example, FIG. 2 shows a second conventional example, and FIG. 3 shows an embodiment of the present invention. FIG. 4 is a diagram illustrating changes in adsorption force due to residual charge, and FIG. 5 is a diagram showing a voltage supply circuit according to an embodiment of the present invention. Here, 1 is an electrode, 2 is an insulator, 3 is a switch, number is a DC power supply, 5 is a polarity switch, 6 is a conductive object, 1 company switch, 8
9 is a relay that switches the voltage applied to the electrode on and off, 9 is a relay that switches the polarity of the voltage applied to the electrode, and 0 is an output terminal.

Claims (1)

[Claims] In a method in which a voltage is applied to one or more pairs of electrodes surrounded by an insulator and an object is attracted by electrostatic attraction, the voltage applied to the electrodes each time an object is attracted is An electrostatic adsorption method characterized by reversing polarity.