JP2004319840A - Wafer chucking apparatus and chucking method - Google Patents

Abstract

An object of the present invention is to make it possible to prevent the wafer from being lifted up and displaced when securing electrical conductivity of the wafer covered with an insulator film from the back surface of the wafer and to remove the wafer from a chuck. It enables the residual charge to be reduced as much as possible.
A first and second electrode (4, 6), an insulator (8) that electrically separates the first and second electrodes and a back surface of a wafer is mounted on a main surface, and a back surface of the insulator portion Chucking portion 2 having a through hole 9 penetrating through the main surface, a conducting needle 20 having one end connected to a reference potential through a wiring and being able to pass through the through hole, and a conducting needle from the back of the insulator portion. A conductive needle driving device 24 that moves the inside of the through hole toward the main surface to drive the other end of the conductive needle to protrude from the back surface of the wafer, and can apply voltages having different polarities to the first and second electrodes. And a voltage controller 10 capable of applying voltages having the same polarity to the first and second electrodes and capable of changing the value of the voltage applied to the first and second electrodes. It is characterized by.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus and a method for chucking a wafer.
[0002]
[Prior art]
In general, cross contamination is prevented by covering the surface of a wafer flowing in a processing line during a semiconductor manufacturing process with an insulating film (for example, a silicon oxide film or a silicon nitride film). In an apparatus for processing a wafer covered with an insulating film in a vacuum, a vacuum chuck method cannot be used for fixing the wafer, and thus a mechanical chuck method or an electrostatic chuck method is used.
[0003]
However, the mechanical chuck method is not used due to problems such as uneven stress applied to the wafer and deterioration of the flatness of the wafer. Further, two electrodes are brought into contact with the wafer, a high voltage (for example, 1 to 3 kV) is applied between the two electrodes, and the two electrodes are discharged, so that the outer periphery of the wafer (portion where no element is formed) is formed. A method of partially breaking an insulating film to achieve conduction is also known (for example, see Patent Document 1). However, when this method is used, the element being manufactured is damaged inside the wafer, and therefore, it is necessary to perform a step of removing the insulating film only in a portion where it is desired to secure conduction.
[0004]
The electrostatic chuck system includes a monopolar system and a bipolar system. In the case of the single-pole type, it is necessary to control the voltage between the wafer and the electrode in the electrostatic chuck, and it is necessary to secure electrical conduction to the wafer.
[0005]
In the case of the bipolar type, it is not always necessary to secure electrical conduction directly with the wafer. When voltages of different polarities are applied to the two types of electrodes in the electrostatic chuck, charges different from those of the opposing electrostatic chuck electrodes are collected on the surface of the wafer that is in surface contact with the insulating layer. Therefore, an electric force acts between the wafer and the electrostatic chuck, and the wafer is held.
[0006]
[Patent Document 1]
JP-A-59-135574
[0007]
[Problems to be solved by the invention]
However, in a device using an electron beam, for example, an electron beam lithography device, it is desirable that the wafer be at the same potential in order to irradiate an arbitrary position on the wafer, and the best condition is that the wafer has a uniform zero potential. It is that you are. For this reason, conventionally, the use of a bipolar electrostatic chuck has been avoided in an electron beam lithography apparatus.
[0008]
In addition, as described above, in the single-electrode type electrostatic chuck, it is necessary to secure electrical conduction to the wafer. However, the insulating film formed around the wafer, such as a silicon oxide film or a silicon nitride film, is harder than a metal oxide film, and penetrates the insulating film with a contact needle to ensure electrical conduction. Requires relatively large contact pressure.
[0009]
If this contact pressure is applied from the lower surface of the wafer before holding the wafer, the wafer will be lifted or displaced, making it difficult to secure electrical conduction. If the contact needle is made considerably thin, the contact pressure can be reduced, but there is a problem that the life of the tip of the contact needle becomes extremely short. Therefore, in general, the contact needle is often pressed from the upper surface of the wafer. However, in this case, it is necessary to provide an area on the upper surface of the wafer where irradiation is prohibited by the electron beam lithography apparatus for the contact needle and a mechanism for operating the contact needle. However, there is a problem that the yield of chips is deteriorated.
[0010]
Further, in a vacuum apparatus in a semiconductor manufacturing apparatus, there is a step of automatically holding a wafer in a vacuum or removing the wafer from the chuck in a vacuum. In particular, the wafer often has residual charges when it is removed from the chuck. For this reason, when the wafer is detached from the chuck plate or a push-up pin or an arm comes into contact, the following problem occurs.
[0011]
Even though the chucking force between the chuck plates due to the residual charge in the wafer is acting, a large force is required for the push-up pin or arm in order to peel it off with the push-up pin or arm. Furthermore, the wafer jumps up at the moment when the peeling force by the push-up pin or the arm overcomes the above-mentioned suction force, so that the wafer falls off and automatic transfer becomes impossible.
[0012]
Further, when the wafer is removed from the chuck, a discharge phenomenon occurs between the residual charges in the wafer and the push-up pins or arms, and a high-voltage small current flows through the wafer, thereby damaging the semiconductor device formed on the wafer. There is a problem.
[0013]
The present invention has been made in view of the above circumstances, and when the wafer covered with an insulator film is kept conductive from the back surface of the wafer, it is possible to prevent the occurrence of the lifting and displacement of the wafer. It is an object of the present invention to provide a wafer chucking device and a chucking method capable of reducing residual charges as much as possible while removing a wafer from a chuck.
[0014]
[Means for Solving the Problems]
A wafer chucking device according to a first aspect of the present invention is configured to electrically separate a first and a second electrode, which are arranged so as not to overlap each other, from a first surface and a second surface of a wafer. An insulator portion on which a back surface is mounted, an electrostatic chuck portion having a through hole penetrating from the back surface of the insulator portion to the main surface, and one end connected to a reference potential via a wiring and passing through the through hole A possible conducting needle, and a conducting needle that drives the conducting needle to move in the through hole from the back surface of the insulator portion toward the main surface to push the other end of the conducting needle to the back surface of the wafer. A driving device, a voltage having a different polarity can be applied to the first and second electrodes, and a voltage having the same polarity can be applied to the first and second electrodes; and the first and second electrodes can be provided. The value of the voltage applied to the electrode is variable Characterized by comprising a voltage controller capable of it.
[0015]
The voltage controller includes a first switch and a second switch, one of which is turned off when the other is turned on, a first power supply for applying a voltage to the first electrode, and the second switch via the first switch. A second power supply for applying a voltage of a different polarity to the first power supply to the two electrodes; and a third power supply for applying a voltage of the same polarity as the first power supply to the second electrode via the second switch. You may comprise so that it may be.
[0016]
The voltage controller includes a first switch and a second switch, one of which is turned off when the other is turned on, a voltage applied to the first electrode, and a voltage applied to the second electrode via the first switch. And a second power supply that applies a voltage having a polarity different from that of the first power supply to the second electrode via the second switch.
[0017]
Further, in the method of chucking a wafer according to the second aspect of the present invention, the first and second electrodes are arranged so as not to overlap each other and are electrically separated by an insulator, and penetrate from the back surface to the main surface. Placing a wafer on the main surface of the electrostatic chuck portion having a through hole, applying a voltage having the same absolute value and a different polarity to the first and second electrodes, one end of which is connected to a reference potential; The other end of the conducting needle is protruded from the back surface of the wafer through the through hole, and the quality of chucking of the wafer is determined based on one of a current flowing through the conducting needle and a contact resistance of the conducting needle. And applying a voltage having the same absolute value and polarity to the first and second electrodes when it is determined that the chucking of the wafer is good.
[0018]
Further, in the method of chucking a wafer according to the second aspect of the present invention, the wafer is placed on a main surface of an electrostatic chuck portion having an electrostatic chuck electrode, and then a conductive needle is applied to the back surface of the wafer. By applying a fritting voltage, conduction between the wafer and the conduction needle is established, and thereafter, a voltage is applied to the electrostatic chuck electrode of the electrostatic chuck unit to chuck the wafer to the electrostatic chuck unit. It is characterized by King.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
[0020]
(1st Embodiment)
FIG. 1 shows the configuration of a wafer chucking device according to a first embodiment of the present invention. The wafer chucking device according to this embodiment includes an electrostatic chuck unit 2, a voltage controller 10, a conduction needle 20, and a conduction needle driving mechanism 24. The electrostatic chuck section 2 includes a first electrode 4, a second electrode 6, and an insulator section 8. The insulator portion 8 has a flat main surface on which the wafer 100 is mounted, and has a through hole 9 penetrating from the back surface to the main surface at an end. The main surface of the insulator portion 8 is in contact with the back surface of the wafer 100, that is, the surface opposite to the surface on which semiconductor elements and the like are formed. The through hole 9 has a size that allows the conduction needle 20 to pass through. The first and second electrodes 4, 6 are embedded in the insulator portion 8 and are arranged so as not to overlap with each other when viewed from the main surface side.
[0021]
The voltage controller 10 includes power supplies 12, 14a, 14b and switches 16a, 16b. The power supply 12 has one end connected to the reference potential GND and the other end connected to the first electrode. The power supply 14a has one end connected to the reference potential GND and the other end connected to the second electrode 6 via the switch 16a. The power supply 14b has a polarity different from that of the power supply 14a, and has one end connected to the reference potential GND and the other end connected to the second electrode 6 via the switch 16b. When a voltage is applied to the electrode 6, one of the switches 16a and 16b is turned on and the other is turned off.
[0022]
The conduction needle 20 is driven by the conduction needle driving mechanism 24 so as to be movable in the through hole 9 of the insulator portion 8 from the back surface of the insulator portion to the main surface side and from the main surface side to the back surface side. The tip of the conduction needle 20 is configured to be pressed by the drive mechanism 24 against the back surface of the wafer 100 placed on the main surface of the insulator portion 8. The conduction needle 20 is connected to a reference potential GND via a wiring 26 and an ammeter 28.
[0023]
Next, the operation of the wafer chucking device according to the first embodiment will be described with reference to FIGS. FIG. 2 is a flowchart showing an outline of a method of chucking the wafer 100 by the chucking device according to the present embodiment. First, the wafer 100 is placed on the main surface of the electrostatic chuck section 2 (see step F0), and then a first chucking step is executed (see step F1).
[0024]
Details of the first chucking step will be described with reference to FIG. First, voltages Ea1 and Ea2 having the same absolute value but different polarities are applied to the two electrodes 4 and 6 of the electrostatic chuck section 2 on which the wafer 100 is mounted, and the two electrodes 4 and 6 are provisionally chucked by the bipolar method (see step F10). . Subsequently, the surface height of the wafer 100, that is, the flatness, is measured using a light lever type height sensor, not shown in FIG. 1 (see step F11). Thereafter, it is determined whether or not the measured flatness is within an allowable value (see step F12). If the measured flatness is within the tolerance, the first chucking step is completed (see step F13). In addition, as the number of films formed on the wafer 100 increases, “undulation” occurs in the wafer 100, and the flatness of the wafer 100 deteriorates. Therefore, the flatness of the wafer 100 is improved by chucking before drawing with an electron beam.
[0025]
In step F12 of FIG. 3, if the measured flatness is out of the allowable value, the wafer is determined to be defective (see step F14), the wafer 100 is removed from the electrostatic chuck unit 2, and step F0 shown in FIG. (See step F15 in FIG. 3), and a wafer to be newly chucked is placed on the electrostatic chuck section 2. If the measured flatness is out of the permissible value in step F12 in FIG. 3, the process returns to step F10 to perform the temporary chuck again without replacing the wafer, and the flatness is measured again. Is also good. In this case, when the measurement result of the flatness again is outside the allowable value, the process proceeds to step F14.
[0026]
Next, when the above-mentioned first chucking step is completed, the process proceeds to step F2 in FIG. Details of the step of conducting to the back surface of the wafer 100 will be described with reference to FIG. First, the conduction needle 20 is raised by the conduction needle driving mechanism 24 (see step F20), and the conduction needle 20 is pushed up on the back surface of the wafer 100 placed on the electrostatic chuck unit 2. Then, the current flowing to the wafer 100 and the ground GND via the conduction needle 20 is measured by the ammeter 28 (see step F21).
[0027]
Thereafter, the voltage E applied to one of the electrodes 4 and 6, for example, the electrode 4_s1Is changed (see step F22). As a result, the voltage E applied to the electrode 4 is_s1And the voltage E applied to the electrode 6_s2Balance is lost, the potential of the neutral wafer 100 changes to a potential having any polarity, and the leakage current I between the wafer 100 and the reference potential GND via the conduction needle 20._ΔEsFlows. This leak current I_ΔEsIs measured by the ammeter 28. As described above, by flowing the leak current, the charge charged in the wafer 100 can be released to the reference potential GND, and the residual charge of the wafer 100 can be reduced as much as possible.
[0028]
The leakage current I obtained in step F22 in FIG._ΔEsIs determined to be a value within the specified value in step F23. Leakage current I_ΔEsIs within the specified value, the conduction step with the back surface of the wafer 100 is completed. Leakage current I_ΔEsIf the value is outside the specified value, the process proceeds to step F24, in which the conduction needle 20 is lowered and separated from the wafer 100. Thereafter, the process returns to step F20, and the conduction process with the back surface of the wafer 100 is performed again. Even if the conduction step is performed again, the leakage current I_ΔEsIs outside the specified value, the wafer 100 is removed from the electrostatic chuck unit 2, and the process proceeds to step F <b> 0 in FIG. 2, and a new wafer 100 is placed on the electrostatic chuck unit 2.
[0029]
Next, when the above-described conduction step is completed, the process proceeds to step F3 in FIG. 2, and a second chucking step of the wafer 100 is performed. Details of the second chucking step will be described with reference to FIG. First, the voltage applied to one of the electrodes 4, 6 of the electrostatic chuck section 2, for example, the electrode 6, is reduced to the reference potential GND (see step F30). At this time, the voltage of the other electrode 4 is not changed. Thereby, the charge charged on the wafer 100 escapes to the reference potential GND, and the remaining charge on the wafer 100 can be reduced as much as possible. At this time, the leakage current I flowing between the wafer 100 and the reference potential GND via the conduction needle 20_ΔEsIs measured by the ammeter 28 (see step F31). Then, the measured leakage current I_ΔEsIt is determined in step F32 whether or not is within a specified value. Leakage current I_ΔEsIs outside the specified value, the process returns to step F30 and repeats the above steps. Leakage current I_ΔEsIs within the specified value, the process proceeds to step F33, where the voltage E applied to the electrode 6 is_s2Is the voltage E applied to the electrode 4 from the reference potential GND level._s1And the same value as That is, the wafer 100 is chucked by a monopolar electrostatic chuck method.
[0030]
Subsequently, the leakage current I flowing between the wafer 100 and the reference potential GND via the conduction needle 20_ΔEsIs measured by the ammeter 28 (see step F34). Then, the measured leakage current I_ΔEsIt is determined in step F35 whether or not is within a specified value. Leakage current I_ΔEsIs outside the specified value, the process returns to step F33 and repeats the above steps. Leakage current I_ΔEsIs within the specified value, the process proceeds to step F36, and the flatness of the wafer 100 is measured by a height sensor (not shown). It is determined in step F37 whether or not the measured flatness is within the allowable value, and if it is within the allowable value, the second chucking process is completed. If not, the wafer 100 is determined to be defective (see step F38), and the process returns to step F0 of FIG. 2 to place a new wafer 100 on the electrostatic chuck unit 2.
[0031]
In the conduction step and the second chucking step, the quality of conduction between the wafer 100 and the conduction needle 20 is determined based on the current value. And the voltage value E_s1, E_s2, The contact resistance of the conduction needle 20 may be calculated, and may be determined based on the calculated contact resistance of the conduction needle 20.
[0032]
A method of calculating the contact resistance will be described with reference to FIG. FIG. 6A is a block diagram of the chucking device when the voltage applied to one of the electrodes 4 and 6 is changed, and FIG. 6B is a circuit diagram at this time. It is. ΔE shown in FIG._sIs the difference between the voltages applied to the electrodes 4 and 6. As shown in FIG. 6B, the resistance value of the insulator 8 between the electrode 4 and the wafer 100 is represented by R_es1, The resistance of the insulator portion 8 between the electrode 6 and the wafer 100 is represented by R_es2And the contact resistance of the conducting needle 20 is R_sAnd the internal resistance of the ammeter 28 is R_c, The current flowing through the system consisting of the electrode 4 and the conducting needle 20 is represented by I_s1, The current flowing through the system consisting of the electrode 6 and the conducting needle 20 is represented by I_{s 2}And Then, the current I actually flowing through the conduction needle 20_ΔEsIs
I_ΔEs  = I_s1  + I_s2            ... (1)
Becomes And I_s1And I_s2Is
I_s1  = E_s1/ (R_es1+ R_es2+ R_c) (2)
I_s2  = E_s2/ (R_es1+ R_es2+ R_c・ ・ ・ ・ ・ ・ (3)
Becomes From these equations (1), (2) and (3), the contact resistance R_sIs required. If the resistance R_es1And resistance R_es2Are the same value R_es, Ie, R_es1= R_es2= R_es, The contact resistance R of the conducting needle 20_sIs
R_s  = ΔEs / I_ΔEs  − (R_es+ R_c)
Becomes
[0033]
As described above, in the present embodiment, the residual charges on the wafer 100 are allowed to escape to the reference potential via the conduction needle 20, so that the residual charges can be reduced as much as possible. Accordingly, when the wafer 100 is detached from the chucking device, even if the peeling force by the push-up pins or the arm acts on the wafer 100, it is possible to prevent the wafer 100 from being lifted up and to prevent the displacement thereof. Can be.
[0034]
Further, when the wafer 100 is removed from the chucking device, in the related art, a discharge phenomenon occurs between the wafer and the push-up pins or the arms. Since the potential is released to the reference potential through the contact, it is possible to prevent a discharge phenomenon from occurring between the wafer and the push-up pins or arms. Thus, the semiconductor device can be prevented from being broken.
[0035]
In the first embodiment, the voltage controller 10 includes three power supplies 12, 14a, and 14b. However, as illustrated in FIG. 7, the voltage controller 10 may be configured to include two power supplies 12, 14. good. In this case, the power supply 12 is connected to the first electrode 4 and also to the second electrode 6 via the switch 17a. The power supply is connected to the second electrode 6 via the switch 17b.
[0036]
Further, specific examples of the first electrode 4 and the second electrode 6 used in the present embodiment will be described with reference to FIGS.
[0037]
FIG. 8 shows a configuration of a first specific example of the electrodes 4 and 6 used in the present embodiment. FIG. 8 is a plan view of the electrodes 4 and 6 of the first specific example. In FIG. 8, the electrodes 4 and 6 have a shape combined with each other in a nested manner. The space between the electrodes 4 and 6 is covered with an insulator portion 8. These electrodes 4 and 6 are fixed to the insulator 8 by screws 70.
[0038]
FIG. 9 shows a configuration of a second specific example of the electrodes 4 and 6 used in the present embodiment. FIG. 9 is a plan view of the electrodes 4 and 6 of the second specific example. In FIG. 9, the electrodes 4 and 6 have a shape that is nested with each other. The electrodes 4 and 6 are covered with an insulator portion 8.
[0039]
FIG. 10 shows a configuration of a third specific example of the electrodes 4 and 6 used in the present embodiment. FIG. 10 is a plan view of the electrodes 4 and 6 of the third specific example. In FIG. 10, the electrodes 4 and 6 have a half-moon shape and are surrounded by the insulator portion 8.
[0040]
FIG. 11 shows a configuration of a fourth specific example of the electrodes 4 and 6 used in the present embodiment. FIG. 11 is a plan view of the electrodes 4 and 6 of the fourth specific example. In FIG. 11, the electrodes 4 and 6 have a quadrant shape and are surrounded by the insulator portion 8.
[0041]
FIG. 12 shows a configuration of a fifth specific example of the electrodes 4 and 6 used in the present embodiment. FIG. 12 is a plan view of the electrodes 4 and 6 of the fifth specific example. In FIG. 12, the electrodes 4 and 6 are each annular, and the electrode 4 is surrounded by the electrode 6 and is electrically separated by the insulator portion 8.
[0042]
The conducting needle 20 used in this embodiment is made of conductive diamond, tungsten carbide, alumina titanium carbide based ceramic (Al₂O₃+ TiC), cermet (TiC + TiN), tungsten, palladium, iridium, beryllium-copper alloy. Particularly important properties of the material used for the conducting needle 20 are (1) conductivity, (2) hardness, and (3) non-magnetic.
[0043]
(2nd Embodiment)
Next, a wafer chucking device according to a second embodiment of the present embodiment will be described with reference to FIGS. The wafer chucking device according to this embodiment uses the fritting phenomenon to break the insulating film of the wafer and electrically connect the wafer to the conductive needle. The fritting phenomenon is a phenomenon in which the contact resistance increases when a film formed by oxidation or the like on the wafer surface becomes 5 nm or more, but the contact resistance sharply decreases when a certain voltage is applied. When the coating is a metal oxide film, it is known that a fritting phenomenon occurs when the potential gradient reaches 105 to 106 V / cm. The wafer chucking device according to this embodiment includes an electrostatic chuck section 2A, an electrostatic chuck power supply 10B, conduction needles 20A and 20B, a conduction needle driving mechanism 40, and a fritting voltage application device 60. I have.
[0044]
The electrostatic chuck section 2A includes an electrostatic chuck electrode 5 and an insulator section 8. The electrostatic chuck electrode 5 is embedded in the insulator portion 8. The insulator portion 8 has a flat main surface on which the wafer 100 is mounted, and has through holes 9A and 9B penetrating from the back surface to the main surface at end portions. The main surface of the insulator portion 8 is in contact with the back surface of the wafer 100, that is, the surface opposite to the surface on which semiconductor elements and the like are formed. The through holes 9A and 9B have a size that allows the conducting needles 20A and 20B to pass through.
[0045]
The electrostatic chuck power supply 10B includes a power supply 12 and a switch 13. By switching the switch 13, the potential applied to the electrostatic chuck electrode 5 is changed to the power supply potential E._sAlternatively, it is configured to have the reference potential GND.
[0046]
The conduction needle driving mechanism 40 includes a guide 42, a motor 44, a screw 46 coupled to a shaft of the motor 44 and rotating with the rotation of the shaft of the motor 44, a moving member 48 movable up and down along the guide 42, A horizontal member 49 fixed to the moving member 48 and extending in the horizontal direction; a fixing member 50 fixed to the horizontal member 49 and internally threaded and screwed with the screw 46; a conduction needle fixed to the horizontal member 49 It has a force detecting section 52 for detecting a force applied to 20A, 20B, and insulators 54A, 54B provided on the horizontal member 49 and having one ends of the conducting needles 20A, 20B embedded therein. When the motor 44 rotates, the screw 52 rotates, whereby the fixing member 50 moves up and down. This movement of the fixing member 50 causes the horizontal member 49, that is, the moving member 48 to move along the guide 42. If the horizontal member 49 moves upward, the conducting needles 20A and 20B will strike the back surface of the wafer 100 placed on the main surface of the insulator portion 8.
[0047]
The fritting voltage application device 60 includes a programmable voltage source 61, a buffer amplifier 62, a current detection resistor 64, a current limiting amplifier 66, and a switch 68, and applies a fritting potential to the conduction needle 20A. The conduction needle 20B is always supplied with the reference potential GND.
[0048]
Next, the operation of the wafer chucking device according to the present embodiment will be described with reference to FIG.
[0049]
First, as shown in Step F50 of FIG. 13, the wafer 100 is placed on the electrostatic chuck 2A. Subsequently, the conduction needles 20A and 20B are moved to the back surface of the wafer 100 by the conduction needle driving mechanism 40 (see step F51). Further, the conducting needles 20A and 20B are pressed against the back surface of the wafer 100 by the conducting needle driving mechanism 40, and the pressing force at this time is detected by the force detecting unit 46 (see step F52). It is determined in step F53 whether or not the detected pressing force is within a specified value range. If not, the process returns to step F51 to adjust the position of the conduction needle and repeat the above. If the pressing force detected in step F53 is within the specified value range, the process proceeds to step F54.
[0050]
In step 54, a fritting voltage is applied to the conduction needle 20A by the fritting voltage application device 60. When the insulating film of the wafer 100 is destroyed by the fritting voltage, an electric circuit including the buffer amplifier 62, the current detection resistor, the switch 68, the conductive needle 20A, the insulating film of the wafer 100, the underlayer of the wafer 100, and the conductive needle 20B is formed. Electric current flows. At this time, a reference potential GND is applied to the electrostatic chuck electrode 5 from the electrostatic chuck power supply 10B.
[0051]
Subsequently, the current flowing through the electric circuit is detected by the current detection resistor 64 (see step F55). In step F56, it is determined whether the detected current value is within the specified value. If the detected current value is out of the specified value range, the voltage applied to the conduction needle 20A by the fritting voltage application device 60 is increased (see step F57), and the process returns to step F54 to repeat the above. When the voltage is increased, a current suddenly flows at a certain point. This sudden increase in current is detected, and is used as a substitute for ensuring the conduction between the conduction needle 20A and the wafer 100. If the detected current value is within the specified value range, the process proceeds to Step F58.
[0052]
In step F58, the reference potential GND is applied to the conduction needle 20A by the switch 68 of the fritting voltage application device 60 to separate the conduction needle 20A from the electric circuit. Thereafter, by switching the switch 13 of the power supply 10B for electrostatic chuck, the electrostatic chuck voltage E is applied to the electrostatic chuck electrode 5._s(See step F59). At this time, an electric current is supplied to an electric circuit of the electrostatic chuck power supply 10B, the electrostatic chuck electrode 5, the insulator section 8 of the electrostatic chuck section 2, the insulating film of the wafer 100, the base of the wafer 100, the conductive needle 20B, and the reference potential GND. Flows. Then, in step F60, a current flowing through the conduction needle 20B is detected by a current detector (not shown). If the detected current value is within the specified value range, it is determined that chucking of the wafer 100 is complete, and the next operation, for example, drawing using an electron beam is performed. If the detected current value is out of the specified value range, the process returns to step F60 and repeats the above. If the number of repetitions exceeds a predetermined value, the wafer 100 is peeled off from the electrostatic chuck 2A, and the process returns to step F50 to repeat the above.
[0053]
Note that the fritting voltage is about 1 to 20 V, and at most 100 V or less. For this reason, it is different from the discharge phenomenon that occurs when a voltage of several kV is applied as in the case of breaking the insulating film described in the related art. The pressing force of the conduction needles 20A and 20B is about 1 g. Therefore, the life of the conduction needles 20A and 20B can be made longer than in the conventional case.
[0054]
The conducting needles 20A and 20B used in the present embodiment are made of any one of conductive diamond, tungsten carbide, tungsten, palladium, iridium, and beryllium-copper alloy.
[0055]
Therefore, when the wafer is removed from the chuck, the potential applied to the electrostatic chuck electrode 5 by the electrostatic chuck power supply 10B is set to the reference potential GND, thereby preventing the wafer from being lifted and displaced. And the residual charge can be reduced as much as possible.
[0056]
As described above, according to the present embodiment, good chucking can be performed without damaging the semiconductor device formed on the wafer 100.
[0057]
In the first embodiment, one end of the power supply 12, 14a, 14b is connected to the reference potential GND, and one end of the conduction needle 20 is connected to the reference potential GND via the ammeter 28. As shown in FIG. 15, a configuration may be adopted in which the power supply 29 is grounded via a certain power supply 29.
[0058]
The chucking apparatuses of the first and second embodiments can be used as a vacuum apparatus used in a semiconductor manufacturing apparatus or a chucking apparatus of an electron beam lithography apparatus. In particular, when used in an electron beam lithography apparatus, the chucking apparatus according to the above embodiment can reduce the residual charge on the wafer, so that it is possible to prevent displacement during electron beam irradiation, Accurate electron beam irradiation can be performed.
[0059]
【The invention's effect】
As described above, according to the present invention, when a wafer covered with an insulator film is to be electrically connected from the back surface of the wafer, it is possible to prevent the wafer from being lifted and displaced. At the same time, the residual charge can be reduced as much as possible when the wafer is removed from the chuck.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a configuration of a wafer chucking device according to a first embodiment of the present invention.
FIG. 2 is a flowchart illustrating the operation of the chucking device according to the first embodiment.
FIG. 3 is a flowchart illustrating details of a first chucking step shown in FIG. 2;
FIG. 4 is a flowchart illustrating details of a conduction step shown in FIG. 2;
FIG. 5 is a flowchart illustrating details of a second chucking step shown in FIG. 2;
FIG. 6 is a view for explaining how to determine the contact resistance when the determination of the quality of chucking is performed using the contact resistance of the conductive needle.
FIG. 7 is a diagram showing a configuration of a first modification of the first embodiment.
FIG. 8 is a plan view of a first specific example of an electrode used in the first embodiment.
FIG. 9 is a plan view of a second specific example of the electrode used in the first embodiment.
FIG. 10 is a plan view of a third specific example of the electrode used in the first embodiment.
FIG. 11 is a plan view of a fourth specific example of an electrode used in the first embodiment.
FIG. 12 is a plan view of a fifth specific example of an electrode used in the first embodiment.
FIG. 13 is a diagram showing a configuration of a wafer chucking device according to a second embodiment of the present invention.
FIG. 14 is a flowchart showing the operation of the wafer chucking device according to the second embodiment.
FIG. 15 is a diagram showing a configuration of a second modified example of the first embodiment.
[Explanation of symbols]
2 Electrostatic chuck
2A Electrostatic chuck
4 First electrode
5 Electrostatic chuck electrode
6 Second electrode
8 Insulator
9 Through hole
9A Through hole
9B Through hole
10 Voltage controller
10B Power supply for electrostatic chuck
12 Power supply
13 switches
14a power supply
14b power supply
16a switch
16b switch
20 Conductive needle
20A Conductive needle
20B Conductive needle
24 Conduction needle drive mechanism
26 Wiring
28 ammeter
40 Conduction needle drive mechanism
60 Fritting voltage application device

Claims (5)

First and second electrodes arranged so as not to overlap each other, an insulator portion electrically separating the first and second electrodes, and a back surface of a wafer placed on a main surface; An electrostatic chuck portion having a through hole penetrating from the back surface to the main surface,
A conductive needle having one end connected to a reference potential via a wire and capable of passing through the through hole;
A conduction needle driving device that drives the conduction needle to move in the through hole from the back surface of the insulator portion toward the main surface to push the other end of the conduction needle to the back surface of the wafer,
Voltages having different polarities can be applied to the first and second electrodes, voltages having the same polarity can be applied to the first and second electrodes, and voltages applied to the first and second electrodes can be applied. A voltage controller capable of changing the value of
A wafer chucking device comprising: The voltage controller includes a first and a second switch, one of which is turned off when the other is turned on, a first power supply for applying a voltage to the first electrode, and the second electrode through the first switch. A second power supply for applying a voltage having a polarity different from that of the first power supply, and a third power supply for applying a voltage having the same polarity as the first power supply to the second electrode via the second switch. 2. The wafer chucking device according to claim 1, wherein: The voltage controller is configured to apply a voltage to the first electrode while applying a voltage to the second electrode via the first switch, the first and second switches being turned off when one is in an ON state. 2. A wafer chuck according to claim 1, further comprising a first power supply for applying a voltage having a polarity different from that of said first power supply to said second electrode via said second switch. King device. A wafer is placed on the main surface of an electrostatic chuck portion having first and second electrodes arranged so as not to overlap with each other and electrically separated by an insulator, and a through hole penetrating from the back surface to the main surface. Applying a voltage having the same absolute value but different polarity to the first and second electrodes;
The other end of the conduction needle, one end of which is connected to the reference potential, is protruded through the through-hole to the back surface of the wafer, and based on one of the current flowing through the conduction needle and the contact resistance of the conduction needle, Determining the quality of the chucking of the wafer,
Applying a voltage having the same absolute value and polarity to the first and second electrodes when it is determined that chucking of the wafer is good;
A method for chucking a wafer, comprising: The wafer is placed on the main surface of an electrostatic chuck portion having an electrostatic chuck electrode, and thereafter, a conducting needle is applied to the back surface of the wafer to apply a fritting voltage, whereby the wafer and the conducting needle are connected to each other. A method of chucking a wafer, comprising establishing electrical continuity and thereafter applying a voltage to the electrostatic chuck electrode of the electrostatic chuck unit to chuck the wafer on the electrostatic chuck unit.

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