JP4226101B2 - Substrate removal method from electrostatic chuck plate surface - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for fixing (chucking) a substrate onto an electrostatic chuck plate, and more particularly to a technique for removing the substrate from the surface of the electrostatic chuck plate after the electrostatic adsorption is released.
[0002]
[Prior art]
Conventionally, in a vacuum processing apparatus that performs thin film formation, plasma etching, and the like, an electrostatic chuck plate is disposed in the vacuum chamber, the substrate is electrostatically adsorbed on the surface of the electrostatic chuck plate, Processing is performed in a vacuum atmosphere while controlling the temperature of the substrate with a cooling device.
[0003]
Reference numeral 102 in FIG. 4A is an electrostatic chuck plate schematically shown, on which a substrate 103 made of a glass substrate, a semiconductor wafer, or the like is disposed.
[0004]
Lift pins 104 are inserted into the electrostatic chuck plate 102, the substrate 103 is placed in a vacuum atmosphere, a voltage is applied to the electrodes in the electrostatic chuck plate 2, and the electrostatic chucking force is applied to the surface of the electrostatic chuck plate 102. The process is performed while the substrate is in close contact, and after the electrostatic attraction is released, the lift pins 104 are moved upward to separate the substrate 103 from the electrostatic chuck plate 102.
[0005]
Reference numeral 113 in FIG. 4B indicates a substrate that is normally placed on the lift pins 104. In this state, when the arm of the substrate transfer robot is inserted between the lift pins 104 and the lift pins 104 are lowered, 113 can be transferred onto the arm.
If such an electrostatic chuck plate 102 is used, the substrate can be electrostatically attracted in a vacuum atmosphere, so that a complicated substrate holding mechanism and contact mechanism are not required.
[0006]
However, even if the voltage application to the electrode is stopped and electrostatic attraction is released, the charge accumulated between the electrostatic chuck plate 102 and the substrate 103 does not disappear completely, and the charge remains. Due to the residual charge, an electrostatic attraction force remains between the substrate 103 and the electrostatic chuck plate 102, and when the substrate 103 is detached from the electrostatic chuck plate 102, the substrate vibrates or the substrate is displaced. There are problems such as.
[0007]
Reference numeral 123 in FIG. 4C indicates a substrate that has been lifted off from the lift pins 104 by being lifted from the electrostatic chuck plate 102 by the lift pins 104 due to the influence of the residual adsorption force. Also, reference numeral 133 in FIG. 4D indicates a substrate that has been displaced on the lift pins 104 due to the residual attracting force and has been displaced.
[0008]
In order to prevent the above-mentioned dropout and displacement, the electrostatic charge is released, and then a voltage having a polarity opposite to that at the time of electrostatic adsorption is applied to the electrode in the electrostatic chuck plate 102 to reduce the residual charge. A method of making it possible is considered.
[0009]
The inventors of the present invention, when releasing the substrate 103 from the surface of the electrostatic chuck plate 102, knows the residual charge amount and its polarity from the electrostatic induction current pulse caused by the residual charge and its time integral value. (Japanese Patent Application Nos. 10-66132 and 66133).
[0010]
However, when the electrostatic chuck plate adopts a bipolar system, a positive and negative voltage is applied between the two electrodes inside to electrostatically attract the substrate. It was found that the residual charge amount between the electrostatic chuck plate and the substrate on the electrode to which the positive voltage was applied was different from the residual charge amount on the electrode to which the negative voltage was applied when released.
[0011]
For example, if the process is sputtering or etching and plasma is generated on the substrate, the substrate will be negatively charged, so that static electricity on the electrode to which a positive voltage is being applied during the process. Electroadsorptive power increases. As a result, there is also a difference in the amount of residual charge on both the positive and negative electrodes, and even if a reverse voltage of the same applied amount is applied to the positive and negative electrodes, the amount of residual charge on both electrodes is reduced. There was also a difference.
[0012]
For example, when the reverse bias is applied, the residual charge amount on the positive electrode disappears, but when there is a residual charge on the negative electrode, an electrostatic adsorption force is generated on the negative electrode due to the residual charge. When trying to detach, the substrate detaches without resistance on the positive electrode, but the wafer is adsorbed by the residual charge on the negative electrode, so the substrate rises as if it was caught, so-called one-side-up state End up. As a result, the substrate vibrates on the lift pins, and in an extreme case, the substrate falls off the lift pins.
[0013]
As a worse case, the substrate may be damaged because the substrate is removed by applying a strong force with a lift pin or a robot arm.
[0014]
[Problems to be solved by the invention]
The present invention was created to solve the above problems, and even when there is a difference between the residual charge on the positive electrode and the residual charge on the negative electrode, the substrate can be smoothly removed from the electrostatic chuck plate. It is to provide a technology that can be detached.
[0015]
[Means for Solving the Problems]
When the electrostatic chuck plate has a pair of positive and negative electrodes, the inventors of the present invention apply a voltage (reverse voltage) opposite in polarity to that at the time of electrostatic attraction. The cause of the vibration or jumping up from the electrostatic chuck plate is considered to be the deviation of the residual charge amount between the positive and negative electrodes. When the deviation is reduced, the substrate is smoothly detached from the electrostatic chuck plate. I found out.
[0016]
The present invention was created based on the above knowledge, and the invention according to claim 1 is characterized in that a substrate is disposed on a bipolar electrostatic chuck plate in which a pair of electrodes are disposed in a dielectric body, and the pair of electrodes is disposed. The substrate is treated in a vacuum atmosphere with positive and negative voltages applied to the electrodes and the substrate is electrostatically adsorbed, and then a reverse voltage having a polarity opposite to that during the electrostatic adsorption is applied to the pair of electrodes. A method for removing a substrate from the bipolar chuck plate after applying and reducing a residual charge, wherein when the reverse voltage of the same applied amount is applied to the pair of electrodes, Depending on the type of substrate and the content of the treatment, the reverse voltage is applied in advance to a bipolar electrostatic chuck plate in which the residual charge of the electrode is zero when the residual charge of the other electrode is zero. Applied amount and remaining after application The charge amount relation to previously obtain individually for each of the electrodes, from the relationship, a applying amount of the reverse voltage, is applied to the respective electrodes, wherein the same reference numerals residual charge amount not zero for each electrode An application amount having an equal absolute value is obtained, and a reverse voltage of the obtained application amount is applied to each electrode of the pair of electrodes in a state where a substrate is disposed on the bipolar electrostatic chuck plate. To do.
[0017]
The invention according to claim 2 is the substrate removal method according to claim 1, wherein the relationship between the absolute value of the reverse voltage application amount and the residual charge amount for each of the electrodes is graphed, and from the intersection, The application amount is obtained.
[0018]
[0019]
[0020]
The present invention is configured as described above, and a voltage is applied to an electrode disposed in a dielectric body of a bipolar or unipolar electrostatic chuck plate, and the substrate is electrostatically adsorbed in a vacuum atmosphere. In addition, processes such as sputtering and etching are performed.
[0021]
The electrostatic chuck plate includes a bipolar electrostatic chuck plate in which a pair of electrodes (positive and negative electrodes) are disposed in a dielectric body, and a monopolar electrostatic chuck plate in which one electrode is disposed. is there. In the case of a bipolar electrostatic chuck plate, a positive voltage is applied to one electrode and a negative voltage is applied to the other electrode to electrostatically attract the substrate. In many cases, a negative charge remains on the electrode to which is applied, and a positive charge remains on the electrode to which a negative voltage is applied.
[0022]
Such residual charges are caused by exoelectrons being emitted due to thermal expansion of the substrate after electrostatic adsorption of the substrate, or electron emission (field emission) between the wafer and the electrostatic chuck plate due to voltage application. Although it is presumed to occur, the causal relationship is not described here.
[0023]
In any case, if a voltage having a polarity opposite to that at the time of electrostatic attraction is applied to the electrode before releasing the substrate from the surface of the electrostatic chuck plate after releasing the electrostatic attraction, the residual charge amount may be reduced. Are known.
[0024]
However, the residual charge amount (absolute value) between a pair of electrodes is not always equal, so if the same amount of reverse voltage is applied to each electrode, the residual charge of one electrode disappears, but the other electrode May remain. On the other hand, if the application amount of the reverse voltage is too large, charges are injected in reverse, and residual charges having a reverse polarity are generated.
Therefore, it is necessary to set the reverse voltage applied to the substrate to an appropriate amount.
[0025]
In the case of the present invention, the relationship between the amount of applied reverse voltage and the amount of residual charge after application is obtained for each electrode in advance, and from the relationship, the amount of applied reverse voltage at which the amount of residual charge of each electrode becomes substantially equal After performing vacuum processing, a reverse voltage of the applied amount is applied.
[0026]
As described above, not only the residual charge amount itself becomes small, but also the adsorption force due to the residual charge on the positive and negative electrodes becomes equal. be able to.
[0027]
When making the absolute value of the reverse voltage applied to each electrode substantially equal, write the relationship between the absolute value of the reverse voltage applied and the residual charge amount after applying the reverse voltage on a graph for each electrode, What is necessary is just to read the application amount of the intersection of two graphs. Since the application amount of the reverse voltage is determined by the voltage value and the application time, if one of the application time and the voltage value is fixed, the other magnitude can be obtained.
[0028]
In the case of a unipolar electrostatic chuck plate in which a single electrode is placed in a dielectric, electrostatic chucking applies a voltage between the electrode and a member placed at a ground potential such as a vacuum chamber. It is thought that this is done. The member placed at the ground potential always has a residual charge amount of zero, so for the electrodes in the dielectric, write the relationship between the amount of reverse voltage applied and the amount of residual charge after application in a graph. What is necessary is just to obtain | require the intersection with the straight line whose residual charge is zero.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
Reference numeral 1 in FIG. 1 is an example of a vacuum processing apparatus to which the present invention can be applied, and has a vacuum chamber 10.
A sputtering target 5 is disposed on the ceiling side of the vacuum chamber 10, and a mounting table 11 is disposed on the bottom wall.
[0030]
A bipolar electrostatic chuck plate 2 having a dielectric 7 and a pair of electrodes 8 ₁ and 8 ₂ disposed in the dielectric 7 is fixed on the mounting table 11. A lift pin 4 is disposed below the electrostatic chuck plate 2, and an upper end portion thereof is inserted into a hole 9 provided in the dielectric 7.
[0031]
A DC power source 21, an electrostatic chuck power source 22, a substrate lifting / lowering mechanism 17, and a computer 23 are disposed outside the vacuum chamber 10, and a lower end portion of the lift pin 4 is led out to the outside of the vacuum chamber 10. And attached to the substrate lifting mechanism 17. A motor or the like is disposed in the substrate lifting mechanism 17 so that the lift pins 4 can be lifted and lowered while maintaining the vacuum atmosphere in the vacuum chamber 10.
[0032]
Insulators 12 ₁ and 12 ₂ are airtightly attached to the external position of the bottom wall of the vacuum chamber 10, and the electrostatic chuck power supply 22 is connected to the electrodes 8 ₁ and 8 ₂ via the insulators 12 ₁ and 12 _2. It is connected. Here is one electrode ₈₁ is connected to the positive voltage side of the electrostatic chuck power supply 22, it is assumed that the other electrode 8 ₂ is connected to the negative voltage side. The electrostatic chuck power source 22 immediately installs the chuck electrode when the voltage application is completed (when the chuck is OFF).
The DC power source 21 is connected to the target 5 and is configured to apply a negative voltage to the target 5 while the vacuum chamber 10 is placed at the ground potential.
[0033]
When the substrate removal method of the present invention is applied to the vacuum processing apparatus 1, the residual charges of the electrodes 8 ₁ and 8 ₂ are individually measured in advance according to the type of substrate and process.
The measurement method will be described. After the vacuum chamber 10 is evacuated, the substrate is loaded into the vacuum chamber 10 and placed on the electrostatic chuck plate 2. Reference numeral 3 in FIG. 1 indicates the substrate in that state.
[0034]
The substrate lifting mechanism 17, the DC power source 21, and the electrostatic chuck power source 22 are connected to a computer 23, and are configured to operate according to the control of the computer 23. The electrostatic chuck power source 22 is activated, and positive and negative voltages are respectively applied to the pair of electrodes 8 ₁ and 8 ₂ to generate an electrostatic adsorption force so that the substrate 3 is brought into close contact with the surface of the dielectric 7 of the electrostatic chuck plate 2. .
[0035]
In this state, when sputtering gas such as argon gas is introduced into the vacuum chamber 10, the DC power source 21 is activated and a negative voltage is applied to the target 5, plasma is generated in the vacuum chamber 10, and sputtering of the target 5 is performed. Is called.
When a thin film having a predetermined thickness is formed on the surface of the substrate 3, the DC power source 21 is stopped and the plasma is extinguished.
[0036]
Next, the electrostatic chuck power source 22 is stopped, and voltage application to the pair of electrodes 8 ₁ and 8 ₂ is terminated. At this time, in the electrostatic chuck power source 22, the electrodes 8 ₁ and 8 ₂ are connected to the ground potential, and charges accumulated between the substrate 3 and the electrodes 8 ₁ and 8 ₂ are released.
[0037]
However, if the electrodes 8 ₁ and 8 ₂ are simply connected to the ground potential, the charges at the time of electrostatic attraction do not disappear completely, and residual charges remain. Moreover, since the plasma is generated on the substrate 3, the residual charges accumulated in the positive and negative electrodes 8 ₁ and 8 ₂ have different sizes.
[0038]
When the lift-in 4 is moved upward in this state, if there is a residual charge between each electrode 8 ₁ , 8 ₂ and the substrate, it is proportional to the amount of residual charge between the electrode 8 ₁ , 8 ₂ and the ground. Electrostatic induction current flows. As the current values measured by the ammeters 13 ₁ and 13 ₂ , currents proportional to the residual charges on the electrodes 8 ₁ and 8 ₂ flow.
[0039]
Ammeters 13 ₁ and 13 ₂ are respectively inserted between the electrostatic chuck power source 22 and the electrodes 8 ₁ and 8 ₂ , and these ammeters 13 ₁ and 13 ₂ are connected to a computer 23. The magnitude of the current flowing through each ammeter 13 ₁ , 13 ₂ can be automatically recorded by the computer 23.
Therefore, the currents flowing through the electrodes 8 ₁ and 8 ₂ when the substrate 3 is detached are measured by the ammeters 13 ₁ and 13 ₂ , and the values are recorded in the computer 23.
[0040]
Here, after the process is completed, assuming that the current (discharged charge amount) when the substrate 3 is detached without applying a reverse voltage is measured, another substrate 3 is then placed in the vacuum chamber 10. Then, a voltage having the same magnitude as described above is applied to the electrodes 8 ₁ and 8 ₂ and sputtering is performed in the same manner to form a thin film having a predetermined thickness on the surface of the substrate 3.
[0041]
After canceling the electrostatic adsorption, the electrostatic chuck power supply 22 applies a voltage having a polarity opposite to that at the electrostatic adsorption to each of the electrodes 8 ₁ and 8 ₂ (a positive voltage is applied during the electrostatic adsorption). the electrodes 8 ₁ which has a negative voltage is applied, the electrode ₈₂ which has a negative voltage is applied to a positive voltage.).
[0042]
Next, the lift pins 4 are lifted, the substrate 3 is detached from the surface of the electrostatic chuck plate 2, and the current value flowing through the ammeters 13 ₁ and 13 ₂ at that time is matched with the amount of reverse voltage applied in the computer 23. Record.
[0043]
A reverse voltage with a different application amount is applied to a plurality of substrates, the substrate is detached, a current value is measured, and the current value is recorded in the computer 23 in association with the application amount of the reverse voltage. The application amount of the reverse voltage is determined by the magnitude of the reverse voltage and the application time. Here, the application time of the reverse voltage is set to a constant value, and the magnitude of the reverse voltage is varied.
[0044]
FIG. 1 is a graph showing the relationship between the applied reverse voltage value and the residual charge amount measured by the ammeters 13 ₁ and 13 _{2. The} positive electrode is applied to the electrode 8 ₁ applied with a positive voltage during electrostatic adsorption, and the negative voltage is applied. the applied electrode 8 ₂ are described as the negative electrode.
[0045]
When the graph of FIG. 1 is obtained, the substrate 3 is a silicon wafer having a silicon oxide film having a thickness of 1 μm formed on the back surface, and sputtering is performed by energizing the ceramic heater inside the electrostatic chuck plate 2. Was carried out with the temperature raised to 300 ° C.
[0046]
Further, during electrostatic adsorption, voltages of +100 V and −100 V were applied to the electrodes 8 ₁ and 8 ₂ . The electrostatic adsorption time was set to 60 seconds. In addition, the application time of the reverse voltage after releasing the electrostatic adsorption was fixed to 3 seconds, and the substrate 3 was detached from the electrostatic chuck plate 2 when 15 seconds passed after the application of the reverse voltage.
[0047]
The horizontal axis of the graph in FIG. 2 indicates the absolute value of the magnitude of the applied reverse voltage (the magnitude of the negative voltage applied to the positive electrode and the magnitude of the positive voltage applied to the negative electrode. The vertical axis represents the amount of residual charge obtained from the current value that flows when the substrate 3 is detached after application.
[0048]
In this graph, when a voltage of ± 130 V is applied, the residual charge of the positive electrode 8 ₁ becomes zero, but the residual charge of 1.5 μC remains on the negative electrode 8 ₂ . Therefore, when applying a reverse voltage of ± 130 V, the substrate 3 will be adsorbed on the negative electrode ₈₂ with a force of 1.5MyuC.
[0049]
On the other hand, the graphs of the positive and negative electrodes 8 ₁ and 8 ₂ intersect at 150V. Therefore, each of the positive and negative electrodes _{81, 82,} -150 V, by applying a reverse voltage of + 150 V, the residual charge amount of the respective electrodes _81, on 8 ₂ equal (about 0.8μ coulombs).
[0050]
When thin films are continuously formed on a large number of substrates using the vacuum processing apparatus 1, the reverse voltage applied amount set in the computer 23 in advance is ± 150 V × 3 seconds, and the substrate on which the thin films are actually formed On the other hand, when the target 5 is sputtered while being electrostatically attracted under the same conditions as described above, and after the electrostatic attraction is released, a reverse voltage is applied to each of the electrodes 8 ₁ and 8 ₂ under the conditions set in the computer 23. The residual charge amounts of the electrodes 8 ₁ and 8 ₂ are equal.
Accordingly, if the lift pins 4 are raised in this state, the substrate can be smoothly detached from the electrostatic chuck plate 2.
[0051]
As described above, according to the substrate removal method of the present invention, the residual charge amount of the positive electrode (electrode 8 ₁ ) is equal to the residual charge amount of the negative electrode (electrode 8 ₂ ), and electrostatic adsorption due to the residual charge is performed. Since the force is applied evenly to the substrate, vibrations and falling off from the lift pins 4 are eliminated.
[0052]
Further, as described above, when a reverse voltage having an optimum applied amount is applied to the electrodes 8 ₁ and 8 ₂ , the residual charge amount remaining on the electrostatic chuck plate 2 after the substrate is detached becomes extremely small (0.1 μC). Less than).
Therefore, when a large number of substrates are successively processed by the substrate removing method of the present invention, the static elimination processing of the electrostatic chuck plate 2 becomes unnecessary.
[0053]
In the graph of FIG. 2, the residual charges of the electrodes 8 ₁ and 8 ₂ did not become zero. However, depending on the process conditions and the type of the substrate, as shown in FIG. It may be an intersection of graphs. In the graph of FIG. 3, when −200 V and +200 V are applied, the residual charges of the electrodes 8 ₁ and 8 ₂ disappear.
[0054]
As described above, the application time is fixed, the magnitude of the reverse voltage is changed to create a graph, and the optimum reverse voltage application amount (voltage value × application time) is obtained from the intersection of the graph. Even when the magnitude of the reverse voltage is fixed and the graph is created by changing the application time, the application amount of the reverse voltage becomes the same value.
[0055]
In the above embodiment, the substrate detachment method for the bipolar electrostatic chuck plate 2 has been described. However, depending on the type of the electrostatic chuck plate, a single-pole system in which the substrate is electrostatically attracted by one electrode is adopted. There is something. In the case of the unipolar electrostatic chuck plate, if one of the reverse voltage and the application time is fixed and the other is changed, a graph composed of one curve is obtained.
[0056]
In a monopolar type electrostatic chuck plate, it can be considered that a pair of electrodes are formed between an electrode in the electrostatic chuck plate and a member placed at a ground potential such as a vacuum chamber. A straight line with zero charge (the horizontal axis in FIGS. 2 and 3) is considered as a virtual electrode curve, and the amount of application at the intersection with the straight line may be obtained.
[0057]
In the above example, the intersection point is obtained from the graph. However, the computer 23 may obtain the intersection point by numerical calculation such as a spline method.
In that case, before starting the process, the relationship between the applied amount of the reverse voltage and the residual charge amount is obtained by the computer 23, and the reverse voltage of the applied amount at which the residual charge amounts of the positive and negative electrodes are the same in each substrate. May be applied.
[0058]
Although the vacuum processing apparatus 1 which forms a thin film by sputtering method was demonstrated above, this invention is not limited to it, All using electrostatic chuck plates, such as a CVD apparatus, an etching apparatus, a vapor deposition apparatus, and an annealing apparatus, are used. It is effective in the device of.
[0059]
In the above example, the method of using the lift pins when detaching the substrate from the electrostatic chuck plate has been described. However, the present invention also applies to the case where the substrate is detached using a transfer robot having a moving mechanism in the Z-axis direction (vertical direction). include.
[0060]
【The invention's effect】
According to the present invention, non-uniform electrostatic adsorption due to residual charges is eliminated, so that the substrate does not jump up or drop off.
[Brief description of the drawings]
FIG. 1 shows an example of a vacuum processing apparatus to which the method of the present invention can be applied. FIG. 2 shows an example of a graph showing a relationship between a reverse voltage application amount and a residual charge amount. FIG. 3 shows a relationship between a reverse voltage application amount and a residual charge amount. Other examples of graphs [Fig. 4] (a) to (d): diagrams for explaining the state of separation of the substrate [Explanation of symbols]
7 …… Dielectric 8 ₁ , 8 ₂ …… Electrode 2 …… Electrostatic chuck plate 3 …… Substrate

Claims (2)

A substrate is disposed on a bipolar electrostatic chuck plate having a pair of electrodes disposed in a dielectric;
The substrate is treated in a vacuum atmosphere while positively and negatively applying a voltage to the pair of electrodes and electrostatically adsorbing the substrate.
Next, after applying a reverse voltage having a polarity opposite to that during the electrostatic adsorption to the pair of electrodes to reduce the residual charge,
A substrate detachment method for detaching the substrate from the bipolar chuck plate,
A bipolar electrostatic chuck plate in which, when applying the reverse voltage of the same applied amount to the pair of electrodes, applying a reverse voltage that makes the residual charge of one electrode zero, the residual charge of the other electrode does not become zero Whereas
According to the type of the substrate and the content of the treatment, in advance, the relationship between the application amount of the reverse voltage and the residual charge amount after application is individually determined for each electrode,
From the above relationship , when the application amount of the reverse voltage is applied to each electrode, the residual charge amount of each electrode is not zero but the application amount with the same sign and the absolute value is equal , and the bipolar type A substrate detachment method, wherein a reverse voltage of an applied amount is applied to each electrode of the pair of electrodes in a state where the substrate is disposed on an electrostatic chuck plate. 2. The substrate removal method according to claim 1, wherein the relationship between the absolute value of the reverse voltage application amount for each electrode and the residual charge amount is graphed, and the application amount is obtained from the intersection.

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