JP2004128270A - Electrostatic attracting device and semiconductor manufacturing device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic attracting device capable of easily obtaining highly reliable electrostatic attraction abnormality judgement and a semiconductor manufacturing device using the electrostatic attracting device. <P>SOLUTION: In the device mounting a sample 1, a dielectric substance 2 and an electrostatic attracting part consisting of an electrode 3 on a sample board 61 and a cavity 61A is formed on a sample board 61. In the cavity 61A, a switch 4 for turning on/off electrostatic attracting voltage is connected to the electrode 3 arranged lower than the dielectric substance 2, and floating capacity existing in a circuit system from a DC voltage source 5 up to the switch 4 is allowed to be detected in the front of the switch 4, so that transient voltage for judging electrostatic attracting force abnormality can be accurately detected and stable judgment can be attained. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for electrostatically adsorbing a thin plate-shaped sample, and more particularly to an electrostatic adsorption apparatus suitable for a reduction projection exposure apparatus, an electron beam lithography apparatus, and the like, and a semiconductor manufacturing apparatus using the same.
[0002]
[Prior art]
In an apparatus that targets a thin sample such as a mask or a wafer, such as a reduction projection exposure apparatus, an electron beam lithography apparatus, and a semiconductor manufacturing apparatus, the sample needs to be mounted on a predetermined table (sample table) and fixed. Therefore, an electrostatic attraction device is generally used.
[0003]
Here, first, the basic principle of the electrostatic suction device will be described.
[0004]
Now, as shown in FIG. 7, a dielectric 2 such as a ceramic plate (plate thickness several mm) is prepared, and an electrode 3 is provided on the lower surface thereof. Then, it is assumed that a sample 1 to be an object to be fixed such as a wafer or a mask is placed on the dielectric 2.
[0005]
Then, the equivalent circuit at this time is represented by a parallel circuit of an equivalent resistor 6 and an equivalent capacitor 7, as shown in FIG.
[0006]
Here, the equivalent resistance 6 is equivalently formed because the dielectric 2 sandwiched between the sample 1 and the electrode 3 is not a perfect insulator, and the equivalent capacitance 7 is equivalent to the capacitance between the sample 1 and the electrode where the dielectric 2 is a conductor. 3 is equivalently formed by being sandwiched between the three.
[0007]
Therefore, when a DC voltage of a predetermined voltage (for example, 400 V DC) is applied from the DC voltage source 5 to the sample 1 and the electrode 3 via the switch 4 and the current detection resistor 65, the static electricity is applied between the sample 1 and the electrode 3. An electroadsorption force is generated, and the sample 1 can be fixed to the dielectric 2.
[0008]
By the way, when using this electrostatic adsorption device, after adsorbing the sample, it is necessary to confirm that a predetermined adsorption force is obtained before proceeding to subsequent processing. The adsorption abnormality determination method to be described has been conventionally applied.
[0009]
Now, in FIGS. 7 and 8, when the switch 4 is turned on (closed) to start electrostatic attraction, the equivalent capacitance 7 is charged from the DC voltage source 5, so that a current flows transiently, A voltage that changes as shown by a voltage waveform 31 in FIG. 9 appears at both ends of the current detection resistor 65. Therefore, it is determined from the voltage waveform 31 whether or not the electrostatic attraction force is normally obtained.
[0010]
Here, when a normal adsorption force is not obtained for some reason, the magnitude of the current transiently flowing between the sample 1 and the electrode 3 is smaller than that in the normal case, and the maximum of the voltage waveform 31 The value decreases. Therefore, as described above, it is possible to determine the abnormality of the attraction force from the voltage value of the voltage waveform 31.
[0011]
Specifically, in FIG. 9, after the voltage value of the voltage waveform 31 rises from the time when the switch is turned on at time 0, the voltage value becomes a normal region at the illustrated determination timing (usually, approximately 100 μS has elapsed). It is determined that it is in a normal suction state when it is touched, and is determined to be abnormal suction if it is out of the normal area.
[0012]
Note that the waveform of the transient current at this time should originally be the charging current waveform of the CR circuit as shown by the current waveform 41 in FIG. 10, and even after being converted into a voltage by the current detecting resistor 65 in FIG. Should be the voltage waveform 51 shown in FIG.
[0013]
However, in this case, since there is a delay time in the electric elements constituting the circuit (mainly, the elements constituting the switch 4), the rising edge is delayed (about 100 μS) as shown by the voltage waveform 31 in FIG. It will be.
[0014]
[Patent Document 1]
JP-A-6-45214 (FIG. 5)
[0015]
[Problems to be solved by the invention]
The above prior art does not take into account the stray capacitance existing in the circuit system, and has a problem in the reliability of the adsorption force abnormality determination.
[0016]
That is, in the circuit system, there is a stray capacitance other than the equivalent capacitance of the adsorbing portion, so that a transient current appears even when the stray capacitance is charged.
[0017]
Here, the transient current due to the stray capacitance has nothing to do with the electrostatic attraction force, so that the equivalent capacitance of the attraction portion cannot have a dominant effect on the transient current.
[0018]
In addition, at this time, the equivalent capacitance of the attracting portion is generally quite small (on the order of several hundred pF), so that the maximum value of the transient current also becomes a correspondingly small value. Will not be able to keep.
[0019]
SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrostatic attraction device capable of easily obtaining a highly reliable determination of an electrostatic attraction force abnormality, and a semiconductor manufacturing apparatus using the same.
[0020]
[Means for Solving the Problems]
The above object is to provide a switch for applying the attraction voltage in an electrostatic attraction device of a type that detects a transient current when an attraction voltage is applied from a DC voltage source to an electrostatic attraction unit to determine an electrostatic attraction abnormality. Is provided near the electrostatic attraction unit in a circuit system from the DC voltage source to the electrostatic attraction unit.
[0021]
At this time, the switch may be attached to an electrode on the lower surface of the dielectric material that forms the electrostatic attraction part, and the detection of the transient current has a dead zone, and the switch is present at the electrostatic attraction part. The effect of the transient current caused by the stray capacitance may be suppressed.
[0022]
The above object is further provided in the sample mounting chamber with an electrostatic attraction device of a type that detects a transient current when applying an attraction voltage from a DC voltage source to the electrostatic attraction portion to determine an electrostatic attraction abnormality. In the semiconductor manufacturing apparatus, the switch may be provided by applying a switch for applying the suction voltage in the vicinity of the electrostatic suction unit in the sample mounting chamber.
[0023]
At this time, the switch may be attached to an electrode on the lower surface of the dielectric material that forms the electrostatic attraction part, and the detection of the transient current has a dead zone, and the switch is present at the electrostatic attraction part. The effect of the transient current caused by the stray capacitance may be suppressed.
[0024]
This allows stable determination of the electrostatic attraction abnormality without being affected by the stray capacitance in the control circuit board and the capacitance of the harness. Further, by performing the dead zone processing, a stable determination of the adsorption abnormality can be similarly performed without being affected by the floating capacitance other than the floating capacitance in the control circuit board and the capacitance of the harness.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.
[0026]
FIG. 1 shows an embodiment of the present invention. Here, a portion related to fixing of a sample is a sample stage 61, a stage 62 for moving the sample stage 61 in the X direction and the Y direction, and a sample 1 is ground potential. And these are accommodated in a sample mounting chamber 64 of the semiconductor manufacturing apparatus.
[0027]
On the other hand, the DC voltage source 5 and the resistor 65 are mounted on a control board 68, and are connected to the sample mounting chamber 64 by a harness (wire harness) 71. Further, a current detection amplifier 66 and a dead zone circuit 67 are mounted on the control board 68.
[0028]
Here, the dielectric 2 having the electrode 3 is placed on a sample table 61, and the sample 1 is placed thereon, so that it is electrostatically attracted. The voltage (voltage drop) appearing at the resistor 65 is amplified by the current detection amplifier 66 and supplied to the external suction abnormality determination circuit 69 via the dead zone circuit 67.
[0029]
Therefore, when this embodiment is viewed as an electrostatic attraction device, it is constituted by other parts except the sample stage 61 and the stage 62 of the semiconductor manufacturing apparatus.
[0030]
Further, the sample stage 61 is usually made of a metal such as steel, and has a cavity 61A of a predetermined shape formed therein as shown in the figure. The hollow portion 61A is open to the upper surface of the sample stage 61 as shown in the figure, and the dielectric 2 is attached to the sample stage 61 so as to close the cavity portion 61A.
[0031]
Here, as shown in the figure, the dielectric 2 is attached to the upper surface of the sample table 61 with the surface on which the electrode 3 is provided facing downward, but at this time, although not shown in the figure, The electrode 3 is attached in a state where it is securely insulated from the sample table 61.
[0032]
Thus, the semiconductor switching element 40 serving as the switch 4 can be attached to a portion of the lower surface of the electrode 3 that is exposed in the cavity 61A.
[0033]
Here, the semiconductor switching element 40 operates as an electronic relay, and is constituted by, for example, an FET, and its ON / OFF switching operation is supplied via a wire 72 from an external control computer (not shown). Is controlled by an on / off signal.
[0034]
Next, the harness 71 has a coaxial cable shape as shown in the figure, and a voltage for adsorption is supplied from the control board 68 side to the sample mounting chamber 64 side via a conductor inside the harness 71. At this time, the external conductor is grounded (grounded) and held at the ground potential (common potential).
[0035]
The sample mounting chamber 64 side of the inner conductor of the harness 71 is connected to the switch 4 through a portion opened to the side of the cavity 61A formed in the sample table 61. At this time, a wire 72 for supplying an on / off signal to the switch 4 is also supplied from outside through this portion.
[0036]
Here, FIG. 2 is a simplified version of the embodiment of FIG. 1 as an electrostatic chucking device. In this case, the device for fixing the sample 1 to the dielectric 2 is a DC voltage source 5 and a current detecting resistor. 65, a current detection amplifier 66 for inputting, amplifying and outputting a voltage generated in the resistor 65, a control board 68 on which these are mounted, and a switch 4 for applying and cutting off a voltage for electrostatic attraction. And a harness 71 for supplying a voltage for electrostatic attraction thereto.
[0037]
Accordingly, the equivalent circuit in the case of the above embodiment is as shown in FIG. 3 and exists between the conductors of the control board 68 and the like in addition to the equivalent resistance 6 of the dielectric 2 and the equivalent capacitance 7 of the dielectric 2. The stray capacitance 81 and the stray capacitance 82 existing in the harness 71 are equivalently added. In FIG. 3, reference numeral 83 also denotes a stray capacitance, which will be described later.
[0038]
Next, the operation of this embodiment will be described.
[0039]
First, in the case of this embodiment, as is apparent from FIGS. 1 and 2, the switch 4 is mounted immediately below the dielectric 2 and almost in contact with the electrode 3.
[0040]
As a result, as apparent from FIG. 3, the stray capacitance 81 and the stray capacitance 82 exist in a portion before the switch 4 when viewed from the DC voltage source 5, and the DC voltage is always present regardless of the on / off state of the switch 4. It can be seen that it is connected to the source 5.
[0041]
Therefore, the stray capacitance 81 and the stray capacitance 82 are charged by the DC voltage source 5 before the switch 4 is turned on, and the accumulated charge is in a saturated state, so that the current i ₁ flowing through the stray capacitance 81 and the stray capacitance 82 in both 0 (zero) current i ₂ flowing through, when starting the electrostatic adsorption, it will turn on the switch 4 from this state.
[0042]
Therefore, if the switch 4 is turned on, a voltage is applied from the DC voltage source 5 between the sample 1 and the electrode 3, and as a result, the equivalent resistance 6 of the dielectric 2 and the equivalent capacitance 7 of the dielectric 2 are applied. Currents i ₃ and i ₄ respectively flow. Here, the current i ₃ becomes current of constant value, the current i ₄ becomes transient current. At this time, as described above, the stray capacitance 83 is not considered.
[0043]
When the equivalent capacitance 7 is charged by the current i ₄ and the electric charge is saturated, the voltage between the electrode 3 and the sample 1 becomes substantially equal to the voltage of the DC voltage source 5, and as a result, the electrostatic attraction force is reduced. appear. Further, the current _{i 4} is also 0 (zero) therewith.
[0044]
Attention is paid to the current at this time. At the moment when the switch 4 is turned on, the value determined by the voltage of the DC voltage source 5 and the resistance value of the current detection resistor 65 becomes the maximum value in the parallel circuit of the equivalent resistance 6 and the equivalent capacitance 7. , And the accumulation of electric charges in the equivalent capacitance 7 is started.
[0045]
Then, after the charge is saturated and a steady state is reached, only the voltage of the DC voltage source 5 and the current determined by the resistance values of the equivalent resistor 6 and the current detecting resistor 65 flow.
[0046]
Then, the waveform of the voltage appearing at the output of the current detection amplifier 66 at this time is a transient voltage waveform 91 shown in FIG.
[0047]
Here, in the case of this embodiment, the current i ₁ flowing through the stray capacitance 81 due to the control board and the current i ₂ flowing through the stray capacitance 82 due to the harness are both 0 (zero) even when the switch 4 is turned on, as before. It is.
[0048]
Therefore, according to this embodiment, the voltage detected by the current detection resistor 65 and appearing at the output of the current detection amplifier 66 is a constant current i ₃ flowing through the equivalent resistance 6 and a transient current i ₃ flowing through the equivalent capacitance 7. ₄ only.
[0049]
Here, the practical value of the equivalent resistor 6 is about 30 m [Omega], the resistance value of the current detection resistor 65 is a about 30 k.OMEGA, if the voltage of the DC voltage source 5 was 400V, the current i ₃ flowing through the equivalent resistance 6 At most, it is on the order of 10 μA.
[0050]
On the other hand, the maximum value of the transient current i ₄ flowing through the equivalent capacitance 7, since the common capacitance value of the equivalent capacitance 7 is about 1000pF, to say that a small current, also becomes 10mA order, thus for the transient current _{i 4,} the current _{i 3} is practically negligible.
[0051]
As a result, even if the transient current i ₄ has a very small value, in the case of this embodiment, it is substantially the same as the transient voltage waveform 91 due to the current of only the transient current i ₄ , which is hardly affected by external factors. Therefore, according to this embodiment, it is possible to accurately and stably determine the abnormality of the electrostatic attraction force.
[0052]
The transient voltage waveform 91 in FIG. 4 is a voltage waveform appearing at the output of the current detection amplifier 66 as described above. However, in the above embodiment, the output of the current detection amplifier 66 is supplied to the dead band circuit 67. The data is input, processed here, and then supplied to the suction abnormality determination circuit 68 to determine the electrostatic suction force abnormality. This is a result in which the stray capacitance 83 is also considered in this embodiment. .
[0053]
Here, the stray capacitance 83 is an equivalent expression of the capacitance that appears in the adsorption part composed of the electrode 3, the dielectric 2, and the sample 1. In this case, the stray capacitance 83 is the DC voltage source 5. As a result, it is located ahead of the switch 4 and, therefore, is connected in parallel to the equivalent capacitance 7 and the capacitance value is equivalently added.
[0054]
Therefore, the transient voltage waveform 91 in FIG. 4 is not only the equivalent capacitance 7, but is actually a sum of the transient voltage waveform 92 due to the current i ₅ flowing through the floating capacitance 83. The transient voltage waveform 92 not only does not contribute to the determination of the electrostatic attraction force abnormality, but also causes an error.
[0055]
That is, the current i ₄ maximum voltage value V ₄ of by flowing through the equivalent capacitance _7, if the maximum value of the voltage by the current i ₅ flowing through the stray capacitance 83 and the V _5, the maximum value V ₉₁ of the transient voltage waveform 91 As shown in the figure, (V ₄ + V ₅ ) is obtained, which cannot be said to be reflected only in the determination of the electrostatic attraction force abnormality. It will be.
[0056]
Therefore, in this embodiment, a dead zone circuit 67 is provided so that the voltage corresponding to the current value flowing through the stray capacitance 83 is deleted as shown in FIG. the, as shown in FIG. 5 does not contain a transient voltage waveform 92, the transient voltage waveform 101 by only the current i ₄ flowing through the correct equivalent capacitance 7 will be supplied.
[0057]
Therefore, according to this embodiment, the determination can always be performed under the ideal transient voltage waveform 101, and as a result, a stable and accurate electrostatic adsorption abnormality determination can be always obtained.
[0058]
Here, the dead zone circuit 67 is also called, for example, a clipper circuit or a blocking type limiter circuit, and is a circuit for removing a voltage value below a certain level as shown in FIG. Is what it is.
[0059]
Published by Tokyo Denki University Press, January 20, 1998, Yoshio Shirato, "Each Analog IC from Op Amps to Switched Capacitors"
P139-140
[0060]
Therefore, according to the above-described embodiment, a dielectric material having a small transient current at the time of electrostatic attraction ON, that is, a dielectric material having a small transient voltage, that is, a dielectric material having both high resistance and low capacitance, is provided with an electrostatic attraction apparatus and a semiconductor manufacturing apparatus. It can be mounted on.
[0061]
As a result, the heat generation of the dielectric can be reduced, the temperature rise of the sample can be further suppressed, the expansion and contraction of the sample can be further suppressed, and the accuracy of drawing or transfer can be improved in the semiconductor manufacturing apparatus. There is.
[0062]
Further, according to the above embodiment, the abnormality of the electrostatic attraction force can be stably determined when the voltage for electrostatic attraction is applied, so that the abnormality of the attraction can be determined before the processing of the sample is started. Thus, there is an effect that it is possible to avoid wasteful start of processing, prevent loss of a mask, a wafer, or the like, which is a property of the customer, and to avoid wasteful start-up time.
[0063]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, even if it uses the dielectric substance for which a transient voltage is not obtained too much for electrostatic attraction, since electrostatic adsorption abnormality can be determined stably, a highly reliable electrostatic attraction apparatus and semiconductor manufacturing The device can be easily provided.
[Brief description of the drawings]
FIG. 1 is a basic configuration diagram showing an embodiment of the present invention.
FIG. 2 is an electrical equivalent circuit diagram of one embodiment of the present invention.
FIG. 3 is an equivalent circuit diagram for explaining the operation of one embodiment of the present invention.
FIG. 4 is a waveform chart for explaining the operation of the embodiment of the present invention.
FIG. 5 is another waveform chart for explaining the operation of the embodiment of the present invention.
FIG. 6 is an explanatory diagram of a dead zone circuit used in one embodiment of the present invention.
FIG. 7 is a simplified configuration diagram illustrating an example of a conventional electrostatic attraction device.
FIG. 8 is an equivalent circuit diagram showing an example of a conventional electrostatic attraction device.
FIG. 9 is a waveform chart for explaining the operation of the conventional technique.
FIG. 10 is a waveform chart showing a change in current by the CR circuit.
FIG. 11 is a waveform chart showing a change in voltage by the CR circuit.
[Explanation of symbols]
1. Samples (wafers, etc.)
2 Dielectric 3 Electrode 4 Switch 5 DC voltage source 6 Dielectric equivalent resistance 7 Dielectric equivalent capacitance 31 Transient voltage waveform (by conventional technology)
40 Semiconductor switching element (for electronic relay)
41 Transient current waveform (by CR discharge)
51 Transient voltage waveform (by CR discharge)
61 sample stage 61A cavity 62 stage 63 ground needle 64 sample mounting chamber (semiconductor manufacturing equipment)
65 Current detection resistor 66 Current detection amplifier 67 Dead zone circuit 68 Control board 69 Absorption abnormality determination circuit 71 Harness (wire harness)
72 wires (for ON / OFF signal supply)
81 Stray capacitance (by control board)
82 Stray capacitance (by harness)
83 Floating capacity (depending on sample table)
91 Transient voltage waveform 92 Transient voltage waveform for stray capacitance 101 Transient voltage waveform

Claims (6)

In the electrostatic attraction device of the method of detecting a transient current when applying an attraction voltage from a DC voltage source to the electrostatic attraction unit to determine an electrostatic attraction abnormality,
An electrostatic attraction device, wherein a switch for applying the attraction voltage is provided near the electrostatic attraction unit in a circuit system from the DC voltage source to the attraction unit. The electrostatic chuck according to claim 1,
The switch according to claim 1, wherein the switch is attached to an electrode on a lower surface of the dielectric that forms the electrostatic chuck. The electrostatic chuck according to claim 1,
The detection of the transient current has a dead zone,
An electrostatic attraction device configured to suppress the influence of a transient current caused by a stray capacitance existing at the electrostatic attraction unit. In a semiconductor manufacturing apparatus in which a sample mounting chamber is provided with an electrostatic attraction device of a type that detects a transient current when an attraction voltage is applied to an electrostatic attraction unit from a DC voltage source and determines an electrostatic attraction abnormality,
A semiconductor manufacturing apparatus, wherein a switch for applying the suction voltage is provided near the electrostatic suction unit in the sample mounting chamber. The semiconductor manufacturing apparatus according to claim 1,
The semiconductor manufacturing apparatus, wherein the switch is attached to an electrode on a lower surface of a dielectric forming the electrostatic chuck. The semiconductor manufacturing apparatus according to claim 1,
The detection of the transient current has a dead zone,
A semiconductor manufacturing apparatus configured to suppress an influence of a transient current caused by a stray capacitance existing in the electrostatic attraction unit.

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