JPH10308439A - Method for detecting disconnection of electrostatic chuck circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for detecting disconnection in which disconnection detection can be exactly operated without being affected by a noise or the like, and any adverse influence on the peel characteristics of a substrate from an electrostatic chuck can be prevented. SOLUTION: This method includes a disconnection detection process and the following residual charge elimination process. In the disconnection detection process, when a substrate 4 is not placed on an electrostatic chuck 6, a voltage higher than that at the time of attracting and holding the substrate 4 is impressed from a DC power source 14 to the electrostatic chuck 6, currents I1 and I2 running between the DC power source 14 and the electrostatic chuck 6 at that time are measured by current meters 16 and 17, and the disconnection of the electrostatic chuck circuit is detected according to the size of the currents. In the residual charge elimination process, a changeover switch 20 is switched to a contact (b) side, a DC voltage with a polarity opposite to that in the disconnection detection process is impressed from the DC power source 14 to the electrostatic chuck 6, and a residual charge in the electrostatic chuck 6 in the disconnection detection process is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implantation apparatus, an ion beam etching apparatus, and a plasma CVD.
The present invention relates to a disconnection detection method of an electrostatic chuck circuit that detects a disconnection of a circuit that supplies a voltage to an electrostatic chuck that attracts and holds a substrate to be processed by static electricity in an apparatus, a thin film forming apparatus, and the like.

[0002]

2. Description of the Related Art FIG. 3 is a diagram showing an example of a conventional electrostatic chuck circuit. The electrostatic chuck circuit includes an electrostatic chuck 6 for attracting and holding a substrate (for example, a semiconductor wafer) 4 by static electricity, and applying a DC voltage to the electrostatic chuck 6 (more specifically, to each of the electrodes 10 and 11). A DC power supply 14 for applying and holding the substrate 4 by suction;
Switch 1 for turning on and off between the electrostatic chuck 6
8 is provided.

The electrostatic chuck 6 has a plurality of (two in this example) electrodes 10 and 11 embedded near a surface in an insulator 8. The electrodes 10 and 11 are, for example, embedded in the insulator 8 so as to have a semicircular shape, and to face each other to form a circular shape. This electrostatic chuck 6 is called a bipolar type because it has two electrodes 10 and 11 in this example, but there is also a type in which three or more electrodes are provided.

The DC power supply 14 is of a bipolar output type in this example, outputs output voltages + V and −V of the same value and of opposite polarities, and outputs the output voltages + V and −V to the respective electrodes 10, 11 of the electrostatic chuck 6.
Respectively. This DC power supply 14
Has two ammeters 16 and 17 for measuring their output currents I ₁ and I ₂ (usually | I ₁ | ≒ | I ₂ | because the electrostatic chuck 6 has symmetry). ing. However, since normally | I ₁ | ≒ | I ₂ | as described above, only one of the ammeters may be used. DC power supply 1
4 may be a normal DC power supply that outputs only an output voltage V of one polarity, and in that case, of course, only one ammeter may be used. The same applies to the embodiments of the invention described later.

When the switch 18 is turned on and the above voltage is applied from the DC power supply 14 to the electrostatic chuck 6, the substrate 4 and the electrode 1
Positive and negative charges accumulate between 0 and 11, and the electrostatic force (or Johnson-Rahbek force) acting between them causes the substrate 4 to be attracted and held on the electrostatic chuck 6. In that state, the substrate 4
The substrate 4 can be subjected to a treatment such as ion implantation by irradiating the substrate 4 with the ion beam 2.

During processing, heat input is applied to the substrate 4 by the ion beam 2 or the like.
Is normal, the substrate 4 is sufficiently cooled through the electrostatic chuck 6. The electrostatic chuck 6
Usually, it is cooled by a refrigerant or the like.

When the circuit from the DC power supply 14 to the electrostatic chuck 6 is disconnected during the processing of the substrate 4, the DC power supply 14
If no voltage is applied to the electrostatic chuck 6 while the voltage is output from the substrate 4, the substrate 4 is processed in a state where the substrate 4 is not attracted by the electrostatic chuck 6, and in this case, the substrate 4 The thermal conductivity between the electrostatic chucks 6 deteriorates, the cooling of the substrate 4 becomes insufficient, the temperature rise of the substrate 4 becomes excessive, and the substrate 4 is moved (more specifically, for example, on the surface of the substrate 4). (E.g., provided resist).

Conventionally, to prevent this, currents I ₁ and I ₂ flowing from the DC power supply 14 to the electrostatic chuck 6 are measured by an ammeter 1.
The voltage applied to the electrostatic chuck 6 was confirmed by measuring the currents I ₁ and I ₂ from time to time by measuring the currents 6 and 17.

[0009]

Since the electrostatic chuck 6 can be regarded as a kind of capacitor, there is a residual charge in the electrostatic chuck 6 even when the voltage applied thereto is cut off, as is well known. Thus, there is a problem that the substrate 4 cannot be peeled (separated) from the electrostatic chuck 6 until the residual charge is reduced. The longer it takes to peel the substrate 4 from the electrostatic chuck 6, the longer the waiting time and the lower the throughput of substrate processing. In addition, the substrate 4 will be damaged if it is forcibly peeled off. Therefore, the more the residual charges, the worse the peeling characteristics of the substrate.

Since the residual charge is proportional to the voltage applied to the electrostatic chuck 6, the voltage applied from the DC power supply 14 to the electrostatic chuck 6 has recently been reduced to avoid the above problem. In this case, the currents I ₁ and I ₂ flowing through the ammeters 16 and 17 become very small, and noise from the surroundings and leak current in the middle of the wiring (including the terminal block) cannot be ignored. It is difficult to confirm the voltage application to the electrostatic chuck 6, that is, to detect the disconnection of the electrostatic chuck circuit, depending on the magnitudes of the currents I ₁ and I ₂ flowing in the circuit 17.

For example, as shown in FIG.
The currents I ₁ and I ₂ flowing through the DC power supply 17 are the internal consumption currents of the DC power supply (hereinafter, referred to as “current disconnection” from the DC power supply 14 to the electrostatic chuck 6) even when the switch 18 is turned off. This is the sum of I _L and the increased current I _A that flows through the electrostatic chuck 6 when the switch 18 is turned on. Among the internal current I _L is approximately proportional to the output voltage V of the DC power supply 14, the increase current I _A is approximately proportional to the square of the output voltage V of the DC power supply 14.

Conventionally, the output voltage V of the DC power supply 14 is set to, for example, about 400 V. Therefore, when a disconnection does not occur from the DC power supply 14 to the electrostatic chuck 6, the ammeter 1 is used.
The difference between the current (about 60 .mu.A) flowing through the transistors 6 and 17 and the current (about 40 .mu.A) in the case of a disconnection was large, making it difficult to be affected by noise or the like. Output voltage is reduced to, for example, about 100 V.
The difference between the current (about 12 .mu.A) flowing through 6, 17 and the current (about 10 .mu.A) when the disconnection occurs is very small, which makes it difficult to accurately detect the disconnection due to the influence of noise and the like. is there.

Accordingly, the present invention mainly provides a disconnection detecting method which can accurately detect a disconnection without being affected by noise or the like and which does not adversely affect the peeling characteristic of a substrate from an electrostatic chuck. Aim.

[0014]

One of the disconnection detecting methods according to the present invention is a method for detecting a disconnection of a substrate from the DC power supply to the electrostatic chuck when the substrate is not held on the electrostatic chuck. A high voltage is applied, a current flowing between the DC power supply and the electrostatic chuck at that time is measured, and a disconnection detecting step of detecting a disconnection of the electrostatic chuck circuit based on the magnitude of the current, and a disconnection detecting step. Next, a DC voltage having a polarity opposite to that of the disconnection detecting step is applied to the electrostatic chuck to remove a residual charge in the electrostatic chuck during the disconnection detecting step. (Claim 1). The term "at the time of holding the substrate by suction" means that the processing is performed by holding the substrate by suction at the electrostatic chuck (the same applies hereinafter).

In another method of detecting a disconnection according to the present invention, when a substrate is not placed on an electrostatic chuck, a higher voltage is applied to the electrostatic chuck from the DC power supply than when the substrate is held by suction. Is applied, a current flowing between the DC power supply and the electrostatic chuck at that time is measured, and a disconnection detecting step of detecting disconnection of the electrostatic chuck circuit based on the magnitude of the current; and, following the disconnection detecting step, And a residual charge erasing step of applying a damped oscillation voltage to the electric chuck to erase residual charges in the electrostatic chuck at the time of the disconnection detecting step.

According to the above method, in the disconnection detecting step, the disconnection is detected by applying a higher voltage to the electrostatic chuck than at the time of holding the substrate by suction. Therefore, the current difference between the case and the case where it does not occur becomes large, so that disconnection detection can be accurately performed without being affected by noise or the like.

Furthermore, in the above-described disconnection detecting step alone, a relatively large voltage is applied for detecting the disconnection, that is, a voltage higher than that at the time of holding the substrate by suction. A large residual charge remains, and if left unchecked, adversely affects the subsequent peeling characteristics of the substrate. On the other hand, in the present invention, in the residual charge erasing step following the disconnection detecting step, a DC voltage having a polarity opposite to that in the disconnection detecting step is applied to the electrostatic chuck (claim 1), or the damped oscillation voltage is applied. Since the voltage is applied (claim 2), the residual charge in the electrostatic chuck due to the disconnection detecting step can be quickly erased. Therefore, it does not adversely affect the peeling characteristics of the substrate after the disconnection detecting step.

[0018]

FIG. 1 is a diagram showing an example of an electrostatic chuck circuit for implementing a disconnection detecting method according to the present invention. Parts that are the same as or correspond to those in the conventional example of FIG. 3 are denoted by the same reference numerals, and differences from the conventional example will be mainly described below.

In this example, the DC power supply 1 is connected between the DC power supply 14 and the electrostatic chuck 6, more specifically, between the switch 18 and the electrostatic chuck 6.
A switch 20 of a double-pole double-throw type for reversing the polarity of the voltage applied from 4 to the electrostatic chuck 6 is provided. When the changeover switch 20 is switched to the contact a side as shown in the illustrated example, the output voltages + V and -V from the DC power supply 14 become
When the voltage is applied to the electrodes 10 and 11 of the electrostatic chuck 6 and is switched to the contact b side, the output voltages + V and -V from the DC power supply 14 are reversed from the above, and the electrodes 11 and 10 respectively.

An example of a disconnection detecting method using this circuit will be described. First, the following disconnection detecting step is performed, and then the following residual charge erasing step is performed.

In the disconnection detecting step, the electrostatic chuck 6
When the substrate 4 is not placed on the substrate, the switch 18 is first turned off, and a voltage (for example, about ± 400 V) higher than that at the time of holding and holding the substrate (for example, about ± 100 V as described above) is output from the DC power supply 14. Then, the internal current I _L of the circuit from the DC power supply 14 to the switch 18 is
Measured by 17. In this case, for example, as described above with reference to FIG. 4, through the internal current I _L to about 40 .mu.A.

Next, the switch 18 is turned on and the DC power supply 1 is turned on.
4 is applied to the electrostatic chuck 6, and currents I ₁ and I ₂ flowing between the DC power supply 14 and the electrostatic chuck 6 at that time are measured by ammeters 16 and 17. At this time, as described above with reference to FIG.
Unless occurred disconnection circuit from the DC power supply 14 to the electrostatic chuck 6, about 20μA in addition to the internal current I _L
Of the current I _A of about 60 μA
₁ and I ₂ flow. If occurs disconnected, since increasing the current I _A does not increase as much as 20 .mu.A, current I ₁ and I ₂ is sufficiently smaller than 60 .mu.A. Therefore, depending on the magnitudes of the currents I ₁ and I ₂ when the switch 18 is turned on, that is, depending on whether predetermined currents (about 60 μA in this example) I ₁ and I ₂ flow when the switch 18 is turned on. Disconnection of the electrostatic chuck circuit can be detected.

As described above, in this disconnection detecting step,
Since the disconnection detection is performed by applying a higher voltage to the electrostatic chuck 6 than at the time of holding the substrate by suction, the current difference between when the disconnection occurs in the electrostatic chuck circuit and when the disconnection does not occur increases. Therefore, disconnection detection can be accurately performed without being affected by noise or the like.

However, if only the above-described disconnection detecting step is performed, a relatively large voltage is applied for detecting the disconnection, so that a relatively large residual charge remains in the electrostatic chuck 6 after the disconnection detecting step. If left unattended, it will adversely affect the subsequent peeling properties of the substrate. Therefore, in the present invention, a residual charge erasing step is performed following the disconnection detecting step.

In the residual charge erasing step, in this example, the changeover switch 20 is switched to the opposite side (that is, to the contact b side) in the above step, and the DC power supply 14
Then, a DC voltage having a polarity opposite to that of the disconnection detecting step is applied to erase residual charges in the electrostatic chuck 6 during the disconnection detecting step.

In more detail, the electrostatic chuck 6 (more specifically, its electrode 1
Assuming that the capacitance (between 0 and 11) is C ₀ and a DC voltage of ± V ₀ is applied during the disconnection detection step, the electrostatic chuck 6
Residual charge Q ₀ of the inner is generally expressed by the following equation. The coefficient has 2 because + V ₀ and −V ₀ are applied in series.

[0027]

## EQU1 ## Q ₀ = 2C ₀ V ₀

Therefore, in this residual charge erasing step, it is preferable to supply an amount of electric charge substantially equivalent to the residual electric charge Q ₀ in the opposite polarity. Can be.

[0029] For example, the current flowing to the electrostatic chuck 6 in residual charge erasing step and I ₀ (which corresponds to an increase current I _A described above with reference to FIG. 4), the application time of the reverse polarity voltage Assuming that t, the reverse polarity voltage may be applied so as to substantially satisfy the following equation.

[0030]

∫I ₀ dt = Q ₀ = 2C ₀ V ₀

However, it is not necessary to completely erase the residual charge in the electrostatic chuck 6 to zero, but it is sufficient to erase the residual charge as small as not to adversely affect the peeling characteristics of the substrate.

By providing the residual charge erasing step as described above, the residual charge in the electrostatic chuck 6 due to the disconnection detecting step can be quickly erased. The voltage can be applied to improve the disconnection detection accuracy, and the residual charge at that time can be quickly erased, so that the peeling characteristic of the substrate after the disconnection detection step is not adversely affected. That is, the substrate 4 can be quickly attached to and detached from the electrostatic chuck 6 without damaging the substrate 4.

The disconnection detecting step and the residual charge erasing step as described above are performed, for example, in each lot processing when a plurality of substrates 4 are processed as one lot. It is preferable to perform the processing in the interval between the processings of Steps 4 and 4. In such a case, even if the disconnection detection is performed, the processing does not cause a waiting time in the processing of the substrate 4, so that the throughput of the substrate processing does not need to be reduced. Further, when a plurality of electrostatic chucks 6 are provided and the substrates 4 are alternately processed one by one or one lot at a time on each electrostatic chuck 6, the electrostatic capacitor which is not used for the processing is used. The disconnection detection may be performed more frequently by the chuck 6, so that the reliability of the substrate processing is further improved and the throughput is not reduced.

FIG. 2 is a diagram showing another example of the electrostatic chuck circuit for implementing the disconnection detecting method according to the present invention. FIG.
In this example, a series resonance circuit 22 having a capacitor C and an inductor L is provided on the contact b side of the changeover switch 20. A resistor may be inserted in series between the capacitor C and the inductor L. However, since the wiring normally contains a resistance component, it is not necessary to insert a resistor.

Also in this example, the disconnection detecting step is performed in the same manner as in the example of FIG.

In the residual charge erasing step after the disconnection detecting step, it is only necessary to switch the changeover switch 20 to the contact b side. By doing so, a damped oscillating voltage is generated in the series resonance circuit 22 using the residual charges accumulated in the electrostatic chuck 6 in the disconnection detecting step as an energy source, and the damped oscillation voltage is generated in the electrostatic chuck 6 (more specifically, Are the electrodes 10 and 11
). This damped oscillation continues until the residual charge in the electrostatic chuck 6 becomes zero, but disappears in a very short time because the time constant of the circuit is usually very small. Thus, the residual charges in the electrostatic chuck 6 can be quickly erased.

Although the damped oscillation voltage can be easily applied to the electrostatic chuck 6 by providing the series resonance circuit 22, the static oscillation can be performed by other means, for example, by a separately provided damped oscillation voltage generating circuit. A damped oscillation voltage may be applied to the electric chuck 6.

[0038]

As described above, according to the present invention, in the disconnection detecting step, the disconnection is detected by applying a higher voltage to the electrostatic chuck than at the time of holding the substrate by suction. The current difference between the case where the disconnection has occurred and the case where the disconnection has not occurred becomes large, so that the disconnection can be accurately detected without being affected by noise or the like. Therefore, highly reliable substrate processing can be performed.

Further, in the residual charge erasing step following the disconnection detecting step, a DC voltage having a polarity opposite to that in the disconnection detecting step is applied to the electrostatic chuck (claim 1), or a damped oscillation voltage is applied ( According to the second aspect, the residual charge in the electrostatic chuck in the disconnection detecting step can be quickly erased, and therefore, the peeling characteristic of the substrate after the disconnection detecting step is not adversely affected. That is, the substrate can be quickly attached to and detached from the electrostatic chuck without damaging the substrate.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of an electrostatic chuck circuit that implements a disconnection detection method according to the present invention.

FIG. 2 is a diagram illustrating another example of an electrostatic chuck circuit that implements the disconnection detection method according to the present invention.

FIG. 3 is a diagram illustrating an example of a conventional electrostatic chuck circuit.

FIG. 4 is a diagram illustrating an example of a relationship between an output voltage of a DC power supply and a current flowing in an electrostatic chuck circuit.

[Explanation of symbols]

 4 Substrate 6 Electrostatic chuck 10, 11 Electrode 14 DC power supply 16, 17 Ammeter 18 Switch 20 Changeover switch 22 Series resonance circuit

Claims (2)

[Claims] An electrostatic chuck having a plurality of electrodes in an insulator and adsorbing and holding a substrate by static electricity, a DC power supply for applying a DC voltage to each electrode of the electrostatic chuck and adsorbing and holding the substrate. In the electrostatic chuck circuit provided with, when the substrate is not placed on the electrostatic chuck, a higher voltage is applied to the electrostatic chuck from the DC power supply than at the time of holding and holding the substrate. A disconnection detecting step of measuring a current flowing between the electrostatic chuck and the disconnection of the electrostatic chuck circuit based on the magnitude of the current, and a disconnection detecting step for the electrostatic chuck following the disconnection detecting step. And a residual charge erasing step of erasing residual charges in the electrostatic chuck at the time of the disconnection detecting step by applying a DC voltage having a reverse polarity. 2. An electrostatic chuck having a plurality of electrodes in an insulator and holding a substrate by electrostatic attraction, and a DC power supply for applying a DC voltage to each electrode of the electrostatic chuck to attract and hold the substrate. In the electrostatic chuck circuit provided with, when the substrate is not placed on the electrostatic chuck, a higher voltage is applied to the electrostatic chuck from the DC power supply than at the time of holding and holding the substrate. A disconnection detecting step of measuring a current flowing between the electrostatic chuck and the disconnection of the electrostatic chuck circuit based on the magnitude of the current, and applying an attenuated oscillation voltage to the electrostatic chuck following the disconnection detecting step And a residual charge erasing step of erasing residual charges in the electrostatic chuck at the time of the disconnection detecting step.