JPH0982787A - Plasma treating apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma treat apparatus which makes it possible to hold a wafer by an electrostatic attraction force even before a plasma is generated and to prevent the positional deviation of the wafer. SOLUTION: A holder base for holding a wafer 4 is formed of a high-frequency electrode 2 connected to a ground potential side, an electrostatic chuck electrode 3 having an opening provided via a first dielectric film 5 on the electrode 2, and a second dielectric thin film 6 covering the electrode 3 and mounting the wafer 4. A DC high-voltage power source 7 for controlling the potential is provided at the electrode 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus and a plasma processing method characterized by a holding table for holding a substrate to be processed.

[0002]

2. Description of the Related Art An electrostatic chuck method is known as one of means for holding a wafer on an electrode in vacuum (Japanese Patent Laid-Open No. 52-67353). In this method, as shown in FIG. 6, a wafer 103 is placed on an electrostatic chuck electrode 102 whose surface is covered with a dielectric film 101, and a high voltage power source 10 is used.
4, a high voltage is applied between the electrostatic chuck electrode 102 and the wafer 103.

Since the positive electrode and the negative electrode of the high voltage power source 104 are connected to the electrostatic chuck electrode 102 and the wafer 103, respectively, the wafer 103 and the electrostatic chuck electrode 10 are connected.
Negative charge 105 and positive charge 106 are induced in 2 respectively. Therefore, the wafer 103 and the electrostatic chuck electrode 10
An attraction force (electrostatic attraction force) is generated in which the two attract each other by an electrostatic force.

In this way, the wafer 103 is held by the electrostatic chuck electrode 102. By using the electrostatic force in this way, the wafer 1 is mechanically clamped or the like.
Wafer 103 in vacuum without pressing 03
Can be held.

Further, there has been proposed a plasma processing apparatus such as an etching apparatus or a plasma CVD apparatus using the above method as a wafer holding means (Japanese Patent Laid-Open No. 55-9022).
8, JP-A-57-149734).

In such a plasma processing apparatus, plasma existing between the vacuum container and the wafer is used as a means for applying a potential to the wafer, thereby inducing charges having different polarities on the wafer and the electrostatic chuck electrode. ,
The electrostatic attraction force is generated (1 pole type electrostatic chuck method). According to this method, since it is not necessary to connect the wafer to the high voltage power source, it is possible to prevent metal contamination due to a metal wire or the like connecting the wafer and the high voltage power source.

However, this type of plasma processing apparatus has the following problems. First, in the one-pole type electrostatic chuck method, since the electrostatic attraction force is generated by generating plasma above the wafer, the wafer cannot be held before the generation of plasma.

Therefore, in order to control the temperature of the wafer (for example, temperature control for preventing a rapid temperature rise of the wafer in the initial stage of plasma processing), heat conduction is provided between the back surface of the wafer and the electrostatic chuck electrode. If you want to flow the gas for cooling (cooling gas), if you do not introduce the cooling gas after the plasma is generated, the wafer moves due to the gas pressure,
The wafer is displaced. Therefore, the temperature of the wafer cannot be controlled before and immediately after the plasma is generated.

This becomes a problem in the film forming process in which the initial growth process is extremely important. Further, there is a problem in an etching process in which a large amount of heat is applied to the wafer from the moment plasma is generated (for example, an oxide film etching process performed by applying high power). That is, in the case of the etching process, unless the temperature of the wafer is controlled before the generation of plasma, the cooling becomes insufficient, and the etching mask deteriorates immediately and becomes unusable.

In contrast to such a plasma processing apparatus using the one-pole type electrostatic chuck method, a plasma processing apparatus using the two-pole type electrostatic chuck method has been proposed (Japanese Patent Laid-Open No. 5-58200).
7-60074).

In this plasma processing apparatus, as shown in FIG. 7, a pair of electrostatic chuck electrodes (a first electrostatic chuck electrode 111 and a second electrostatic chuck electrode 112) are provided, and a high voltage power supply 117 is used to provide a first electrostatic chuck electrode. A high voltage is applied between the first electrostatic chuck electrode 111 and the second electrostatic chuck electrode 112.

Since the positive electrode and the negative electrode of the high voltage power source 104 are connected to the first electrostatic chuck electrode 111 and the second electrostatic chuck electrode 122, respectively, the wafer starts from the first electrostatic chuck electrode 111. A line of electric force 113 passing through 103 and ending at the second electrostatic chuck electrode 112 is generated.

As a result, the electrostatic chuck electrodes 111, 1
12, a positive charge 106 and a negative charge 105 are respectively induced, and a negative charge 105 and a positive charge 106 are respectively induced in the portions of the wafer 103 facing the electrostatic chuck electrodes 111 and 112, and as a result, An electrostatic attraction force is generated between the electrostatic chuck electrodes 111 and 112.

According to the plasma processing apparatus using the two-pole type electrostatic chuck method, the electrostatic adsorption force can be obtained without generating plasma, and the wafer 103 does not need to be connected to a high voltage power source. There is no problem of metal pollution. That is,
The problem of the plasma processing apparatus using the one-pole type electrostatic chuck method is solved.

However, the plasma processing apparatus using such a system has the following problems. That is, a phenomenon occurs in which the electrostatic attraction force of one of the electrostatic chuck electrodes 111 and 112 becomes weaker than that of the other, and the wafer 10
There was a problem that the position of 3 shifted. The cause of the above phenomenon is that when plasma is generated, a potential (self-bias voltage Vdc) is generated on the surface of the wafer 103.

The self-bias voltage Vdc depends on the process conditions,
It changes depending on the material on the outermost surface of the wafer, and it is also difficult to measure the self-bias voltage Vdc. Therefore, it is difficult to control the high-voltage power supply 104 to make the electrostatic attraction force within the surface of the wafer 103 uniform.

Further, in the electrostatic chuck mechanism, the electrostatic chuck electrode is a portion in which a failure is likely to occur. Therefore, if the electrostatic chuck electrode is increased to two, the failure problem becomes remarkable. In addition, since the number of electrostatic chuck electrodes is increased to two, a power supply of two systems is required, which causes a problem that the device becomes complicated.

Further, as described below, there is a problem regarding the uniformity of temperature control within the wafer surface. The electrostatic chuck electrodes 111 and 112 are usually slightly smaller than the wafer 103 in order to avoid direct exposure to plasma. For example, the outer peripheral portion of the wafer 103 having a portion of several mm is below the electrostatic chuck electrodes 111 and 112. There is no. Further, for controlling the temperature of the wafer 103, a cooling gas is flown between the wafer 103 and the electrostatic chuck electrodes 111 and 112. Therefore, the outer peripheral portion of the wafer 103 without the electrostatic chuck electrodes 111 and 112 is not cooled and the temperature rises.

As a result, a temperature gradient is generated from the outer peripheral portion of the wafer 103 to the inner portion thereof, which causes, for example, a problem that the etching rate and the etching shape become nonuniform on the wafer surface. Such problems are especially
It becomes remarkable as the diameter of 03 increases.

[0020]

As described above, the problem of using the one-pole type electrostatic chuck system as the electrostatic chuck system can be solved by using the two-pole type electrostatic chuck system. The method has a problem that the electrostatic attraction force of one of the two electrostatic chuck electrodes may be weakened and the wafer may be displaced.

The present invention has been made in view of the above circumstances, and an object thereof is to hold a substrate to be processed by electrostatic attraction even before generation of plasma and to displace the substrate to be processed. An object of the present invention is to provide a plasma processing apparatus and a plasma processing method capable of preventing the above.

[0022]

[Means for Solving the Problems]

[Outline] To achieve the above object, a plasma processing apparatus (Claim 1) according to the present invention includes a processing container for performing a plasma processing on a substrate to be processed, and the processing container is provided in the processing container to hold the substrate to be processed. And a high-frequency electrode connected to the ground potential via a high-frequency impedance, and a high-frequency electrode connected to the high-frequency electrode. An electrostatic chuck electrode having an opening provided through a first dielectric film, and a second dielectric film that covers the electrostatic chuck electrode and on which the substrate to be processed is placed, The electrostatic chuck electrode is provided with potential control means for controlling the potential thereof.

Here, it is possible to add means for controlling the high-frequency electrode to a constant temperature and means for flowing a gas for controlling the temperature of the substrate to be treated between the substrate to be treated and the second dielectric film. preferable. Further, as the plasma generating means, for example, there is a means for discharging the reactive gas introduced into the processing container by grounding the processing container and applying high frequency power to the high frequency electrode using a high frequency power source.

Another plasma processing apparatus (Claim 2) according to the present invention is the plasma processing apparatus (Claim 1), wherein the opening is provided on the high frequency electrode below the opening and on the opening. It is formed so as to induce electric charges having opposite polarities to the substrate to be processed and to induce electric charges having opposite polarities to the electrostatic chuck electrode and the substrate to be processed on the electrostatic chuck electrode, respectively. And

Further, in another plasma processing apparatus (claim 3) according to the present invention, in the plasma processing apparatus (claim 1), the area of the electrostatic chuck electrode is 40 to 80% of the area of the substrate to be processed. Is characterized in that.

A plasma processing method according to the present invention (claim 4) is a plasma processing method using the plasma processing apparatus (claim 1), which comprises a step of placing a substrate to be processed on a holding table. , A potential control means for controlling the potential of the electrostatic chuck electrode so that an electric force line passing through the substrate to be processed and the opening of the electrostatic chuck electrode is formed between the high frequency electrode pole and the electrostatic chuck electrode. Controlled by the above, the step of holding the substrate to be processed on the holding table by an electrostatic force, and the step of forming plasma above the substrate to be processed by plasma forming means and performing plasma processing on the substrate to be processed. It is characterized by

Another plasma processing method (Claim 5) according to the present invention is the plasma processing method (Claim 4), wherein after the plasma processing, the potential control means controls the electrostatic chuck electrode. It is characterized by changing the electric potential to the opposite polarity.

[Operation] According to the present invention, electrostatic lines of force are formed between the high-frequency electrode and the electrostatic chuck electrode so as to form lines of electric force that pass through the substrate to be processed and the openings of the electrostatic chuck electrode. By controlling the potential of the chuck electrode by the potential control means, electric charges of opposite polarities are induced in the high-frequency electrode below the opening and the substrate to be processed thereon, and the electrostatic chuck electrode and the substrate to be processed on it are also induced. It is possible to induce charges of opposite polarities in the respective.

For example, if the potential of the electrostatic chuck electrode is controlled to be higher than the potential of the high frequency electrode, the high frequency electrode has a negative charge, the electrostatic chuck electrode has a positive charge, and the substrate to be processed on the electrostatic chuck electrode has a negative charge. It is possible to induce a negative charge and a positive charge on the substrate to be processed on the high frequency electrode below the opening.

Therefore, according to the present invention, the substrate to be processed can be held on the holding table by the electrostatic attraction force before the plasma is generated. After the plasma is generated, in addition to the electrostatic attraction force (first electrostatic attraction force), the electrostatic attraction force (second electrostatic attraction force) generated by the same mechanism as in the one-pole electrostatic chuck method is used.
Electrostatic attraction force) between the electrostatic chuck electrode and the wafer above it, and between the high-frequency electrode below the opening and the wafer above it. As a result, after the plasma is generated, the substrate to be processed is held on the holding table by the electrostatic attraction force (synthetic electrostatic attraction force) that is the combination of the first electrostatic attraction force and the second electrostatic attraction force. It

Here, depending on the location, the combined electrostatic attraction force becomes smaller than the first electrostatic attraction force, but this decrease in electrostatic attraction force is sufficient as described in the embodiments of the invention. It's a small one.

Therefore, after the plasma is generated, the holding force of the substrate to be treated becomes high as a whole by the amount of the second electrostatic attraction force applied, and therefore, unlike the case of the two-pole type electrostatic chuck system. The problem that the electrostatic attraction force becomes non-uniform and the position is displaced does not occur.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. (First Embodiment) FIG. 1 is a schematic diagram showing a schematic configuration of a plasma processing apparatus according to a first embodiment of the present invention.

In the figure, reference numeral 1 denotes a vacuum container, which is normally maintained at ground potential. A gas inlet 11 is provided in the upper part of the vacuum container 1, and a constant flow rate of the reactive gas is introduced from the gas inlet 11.
The introduced reactive gas is exhausted from the gas exhaust port 12 provided in the lower portion of the vacuum container 1 by an exhaust means (not shown), and the inside of the vacuum container 1 is maintained at a predetermined gas pressure.

Further, in the figure, reference numeral 4 denotes a wafer, and the wafer 4 is carried into the vacuum container 1 by a load lock mechanism (not shown) and placed on a holding table. In the case of the present embodiment, the holding table is composed of the high frequency electrode 2, the first dielectric thin film 5, the electrostatic chuck electrode 3, and the second dielectric film 6.

A high frequency power of 8, for example, 13.56 MHz is applied to the high frequency electrode 2 from a high frequency power source 8 through a matching circuit 13. The high-frequency power forms plasma of the reactive gas in the vacuum container 1.
Further, the high frequency power source 8 is connected to the ground potential via a high frequency impedance composed of a high frequency filter 14 and a high resistance body 15. These 14 and 15 are high frequency power sources 8
Is for keeping the potential of the high-frequency electrode 2 at the ground potential when is off.

Further, the high frequency electrode 2 is provided with a coolant inlet 19 and a coolant outlet 20, whereby a coolant set at a predetermined temperature is flown into the high frequency electrode 2,
The temperature of the high frequency electrode 2 can be controlled. Further, the high frequency electrode 2 facing the space where plasma is generated
The surface of is covered with the first dielectric thin film 5 and the insulating member 21, so that the surface of the high frequency electrode 2 does not come into direct contact with plasma. Further, the insulating member 21 is provided with a shield member 22.

An electrostatic chuck electrode 3 having an opening is provided on the high frequency electrode 2 via a first dielectric film 5. That is, the electrostatic chuck electrode 3 insulated from the high frequency electrode 2 by the dielectric thin film 5 is provided on the high frequency electrode 2. The surface of the electrostatic chuck electrode 3 is covered with the second dielectric thin film 6. The wafer 4 is placed on the dielectric thin film 6.

These dielectric thin films 5 and 6 are firmly adhered to each other with, for example, an epoxy-based adhesive, and exhibit high thermal conductivity.
Further, it is possible to obtain high durability against a heat load.

The electrostatic chuck electrode 3 is formed of, for example, a copper thin film having a thickness of about several tens of microns, and its pattern covers a predetermined area in the area where the wafer 4 is arranged when viewed from above in FIG. Has become. Specifically, for example, a concentric plane pattern as shown in FIG. The width L1 of each torus-shaped electrode 3t is preferably about half or more and four times or less of the width L2 of the gap (opening) between the electrodes 3t. Further, two adjacent torus-shaped electrodes 3t are electrically connected by the strip-shaped electrode 3s.

Here, the area of the electrostatic chuck electrode 3 is preferably used in the range of 40 to 80% of the area of the wafer 4 to be processed. For example, in an apparatus that requires high cooling capacity during plasma processing, increase the area of the electrostatic chuck electrode, and conversely, in an apparatus in which temperature control before and after plasma processing is important, conversely It is appropriately selected depending on the application of the device, such as making the areas of the electrodes equal.

Further, the electrostatic chuck electrode 3 is connected to the DC high-voltage power supply 7 through the high frequency electrode 2, the insulating member 21, and the through passage 23 formed in the shield member 22.
The inner wall of the through passage 23 is covered with a dielectric film.

Further, the electrostatic chuck electrode 3 is adapted to be applied with a DC voltage of about several hundred V to 2 kV by the DC high voltage power supply 7. The DC high-voltage power supply 7 is connected to the high frequency filter 16 and the capacitor 17.

The high frequency filter 16 and the capacitor 17 are for preventing the high frequency power applied to the high frequency electrode 2 from flowing into the high voltage DC power supply 7. Further, when the DC high voltage power supply 7 is off, the electrostatic chuck electrode 3
Also has a role of maintaining the potential of the ground potential.

Further, in order to flow the cooling gas into the gap between the electrostatic chuck electrode 3 and the wafer 4, the cooling gas penetrating the high frequency electrode 2, the first dielectric thin film 5 and the second dielectric thin film 6. An inlet 18 is provided.

In the figure, 9 and 10 respectively indicate a peripheral ring and a baffle plate. Peripheral ring 9 is wafer 4
It is for protecting the surface of the high frequency electrode 2 in the periphery of the plasma from plasma, and is usually formed of other material such as quartz, carbon, silicon carbide, silicon or resin which is durable to plasma. ing. The baffle plate 10 is a plate having many fine holes for preventing plasma from entering the gas exhaust port 12.

Next, a plasma processing method using the plasma processing apparatus thus configured will be described. First, the wafer 4 is loaded into the vacuum container 1 by a load lock mechanism and a wafer transfer arm (not shown), then the wafer 4 is received from the wafer transfer arm by a pusher pin (not shown), and the wafer 4 is lowered by lowering the pusher pin. Is placed on a holding table (second dielectric thin film 6).

Next, a DC high voltage power supply 7 is applied to the electrostatic chuck electrode 3.
A high voltage DC voltage (for example, 2 kV) is applied. As a result, as will be described later, charges are induced in the high frequency electrode 2, the electrostatic chuck electrode 3 and the wafer 4, and the wafer 4 is held by the electrodes 2 and 3 by the electrostatic attraction force. That is, according to the present embodiment, the wafer 4 can be held on the holding table (electrodes 2 and 3) by the electrostatic attraction force before the plasma is generated.

Next, a gas (cooling gas) having a high thermal conductivity is flown through the gap between the wafer 4 and the second dielectric thin film 6. The cooling gas may be the same as the conventional gas. Since the wafer 4 is held by the electrodes 2 and 3 by the electrostatic attraction force, there is no problem that the wafer 4 is displaced due to the cooling gas.

Since a step is formed on the base of the second dielectric thin film 6 by the electrostatic chuck electrode 3, this causes a cooling gas between the wafer 4 and the second dielectric thin film 6. A gap is secured to allow for flushing. It should be noted that a path for flowing the cooling gas may be separately provided.

By flowing the cooling gas in this way,
The thermal conductivity between the wafer 4 and the high frequency electrode 2 becomes high,
The temperature rise of the wafer 4 can be prevented. In order to effectively prevent the temperature rise of the wafer 4, the pressure of the cooling gas is set to several Torr.
It may be set in the range of r to about 20 Torr.

Next, after introducing the reactive gas into the vacuum container 1 through the gas inlet 11 and keeping the pressure of the reactive gas constant, the high frequency power source 8 applies high frequency power to the high frequency electrode 2, and A plasma of reactive gas is generated.

Here, in the present embodiment, as will be described later, unlike the case of the two-pole type electrostatic chuck method, the electrostatic attraction force in the wafer surface becomes weak after the generation of plasma, and the position of the wafer 4 is reduced. The problem of slippage does not occur.

Next, after the plasma processing (for example, plasma etching, plasma CVD) is completed, the introduction of the reactive gas is stopped and the gas in the vacuum container 1 is exhausted. At the same time, the cooling gas flowing in the gap between the wafer 4 and the dielectric thin film 6 is also exhausted. After that, the DC high voltage power supply 7 and the high frequency power supply 8 are turned off.

Then, the pusher pin is raised to move the wafer 4
Is peeled off from the electrostatic chuck electrode 3 which is the electrostatic chuck electrode. Finally, the wafer 4 is unloaded to the outside through the load lock chamber by the wafer transfer arm. Actually, since a plurality of wafers are subjected to plasma processing, the above operation is repeated.

According to this embodiment, the wafer 4 can be held on the holding table by the electrostatic attraction force before the plasma is generated. Therefore, the cooling gas for improving the thermal conductivity can be introduced to the back surface of the wafer 4 before the wafer 4 is exposed to the plasma, and the temperature of the wafer 4 can be controlled from the start of the process. The temperature control is also performed by the coolant flowing inside the high frequency electrode 2.

Further, there is no problem that the electrostatic attraction force becomes weak after the generation of plasma and the wafer 4 is displaced. Further, the polarity and level of the applied voltage to the electrostatic chuck electrode 3 can be selected regardless of the self-bias voltage Vdc, and the electrostatic attraction force corresponding to the applied potential can be generated at any applied potential.

The principle of generation of the electrostatic attraction force of the plasma processing apparatus of this embodiment will be described below. FIG. 3 shows that when the DC high-voltage power supply 7 is on and the high-frequency power supply 8 is off, that is,
Electric field (electromotive force line,
It is a figure which shows the mode of electric charge distribution.

In this case, the high frequency electrode 2 is maintained at the ground potential by the high impedance composed of the high frequency filter 14 and the high resistance body 15. On the other hand, the electrostatic chuck electrode 3
The potential of is a positive potential (for example, 2V) by the DC high-voltage power supply 7.
Becomes

As a result, as shown in FIG. 3, the lines of electric force that start from the electrostatic chuck electrode 3, pass through the wafer 4, pass through the opening (gap) of the electrostatic chuck electrode 3, and end at the high-frequency electrode 2. 31 occurs.

When an electric field having such lines of electric force 31 is formed, a negative charge 32 is induced in the high frequency electrode 2 and a positive charge 33 is generated in the electrostatic chuck electrode 3, as shown in FIG.
Is induced, and a negative charge 32 is induced on the wafer 4 on the electrostatic chuck electrode 3, and a positive charge 33 is induced on the wafer 4 on the opening of the electrostatic chuck electrode 3.

The wafer 4 is fixed on the electrodes 2 and 3 by the electrostatic attraction force (first electrostatic attraction force) due to the negative charge 32 and the positive charge 33 attracting each other by the electrostatic force. That is, in the region 36 where the electrostatic chuck electrode 3 exists, the positive charge 33 of the electrostatic chuck electrode 3 and the negative charge 32 of the wafer 4 attract each other, and in the region 37 where the opening of the electrostatic chuck electrode 3 exists, The negative charge 32 of the high frequency electrode 2 and the positive charge 33 of the wafer 4 attract each other.

As described above, according to this embodiment, since the wafer 4 can be held on the electrodes 2 and 3 before the plasma is generated (when the high frequency power source 8 is off), the conventional one-pole type electrostatic chuck method is used. No problems occur when used.

FIG. 4 is a diagram showing a state of the electric field (electric force lines, charge distribution) of the electrostatic chuck portion when the DC high voltage power source 7 is turned on and the high frequency power source 8 is turned on, that is, after the plasma 34 is generated. Is. However, only new electric lines of force and charge distribution generated by generation of plasma 34 are shown.

When the plasma 34 is generated, the plasma 34
A sheath 35 is formed on the surface of the wafer 4 exposed to
Usually, a positive voltage (self-bias voltage Vdc) of about several tens of volts to several hundreds of volts, for example, a self-bias voltage Vdc of 300V is generated. As a result, the potential of the wafer 4 becomes lower than the ground potential by the amount of the self-bias voltage Vdc and becomes a negative potential. The potential of the plasma 34 is, for example,
It is 30V.

Therefore, a potential difference is generated between the electrostatic chuck electrode 3 and the wafer 4 by adding the self-bias voltage Vdc to the voltage of the DC high voltage power source 7, and the electric force line 31 'as shown in FIG. The distribution of charges 32 'and 33' is newly generated. As a result, a new electrostatic attraction force (second electrostatic attraction force) is generated by the charges 32 'and 33'.

At this time, the distribution of the actually induced electric force and electric charge 3 is the same as the distribution of electric force line 31, electric charges 32 and 33 before generation of plasma 34 shown in FIG. The lines of electric force 31 'and the charges 32' and 33 'generated in the above are superposed.

Here, in the region 36 where the electrostatic chuck electrode 3 exists, the lines of electric force become dense due to the generation of the plasma 34, and the electrostatic attraction force becomes stronger. On the other hand, in the area 37 of the opening of the electrostatic chuck electrode 3, since the electrostatic chuck electrode 3 is not under the wafer 4, the direction of the electric force line is different before and after the plasma 34 is generated, and the electrostatic attraction force is weakened. .

However, the region 37 after the plasma is generated
The new electrostatic attraction force is only the potential difference between the high-frequency electrode 2 and the wafer 4, that is, the self-bias voltage Vdc, which is sufficiently weaker than that before plasma generation. In other words, the electrostatic attraction force in the region 37 is substantially reduced, and the holding force of the wafer 4 is increased in the entire region.

Specifically, the self-bias voltage Vdc is given by
On the order of 0V to several 100V, the potential difference between the high frequency electrode 2 and the wafer 4 before plasma generation is several kV.
Of the order.

Therefore, after the plasma is generated, the holding force of the wafer 4 is increased as a whole due to the addition of the second electrostatic attraction force, and the electrostatic attraction is different from the case of the two-pole type electrostatic chuck method. There is no problem that the force becomes weak and the position shifts. (Second Embodiment) Next, a plasma processing method according to another embodiment of the present invention will be described. In this embodiment, the plasma processing apparatus of FIG. 1 is used.

When the electrostatic chuck portion of the plasma processing apparatus of FIG. 1 is repeatedly used in the above-described sequence to perform the plasma processing, the electrostatic attraction force becomes weak. In addition, the phenomenon that the reproducibility of the adsorptivity deteriorates occurs. That is,
When plasma processing is performed on a plurality of wafers, the electrostatic attraction force may be strong or weak. If the electrostatic attraction force is weak, the wafer 4 is peeled off from the electrodes 2 and 3 during the plasma treatment.

The reason is that a part of the negative charges induced on the wafer 4 is the dielectric thin film 6 on the electrostatic chuck electrode 3.
To move to remain. The negative charges (residual charges) remaining after the movement cancel out a part of the positive charges induced in the electrode 3, and the electrostatic attraction force between the electrode 3 and the wafer 4 is reduced. Therefore, if the amount of residual charge differs for each wafer, the reproducibility of the attraction force deteriorates.

Here, in the conventional case, the reproducibility of the adsorption force is improved by exposing the surface of the electrode corresponding to the electrode 2 to the plasma for a moment to constantly keep the charge amount of the electrode constant.

However, in this case, since processing such as exposure to plasma is required, there arises a problem that throughput is lowered. In addition, since members such as electrodes are exposed to plasma during the above-described plasma processing in addition to the original plasma processing such as plasma etching, they are easily damaged and the life of the members such as electrodes is shortened. Occurs.

On the other hand, in this embodiment, the polarity of the voltage applied to the electrostatic chuck electrode 3 is reversed before the wafer 4 is peeled off in order to improve the reproducibility of the attraction force. That is, a voltage (negative voltage) having the same polarity as the residual charge (negative charge) is applied to the electrostatic chuck electrode 3.

As a result, the negative charges of the dielectric thin film 6 can be prevented from moving to the wafer 4 and the negative charges remaining on the dielectric thin film 6. After that, the high voltage DC power supply 7 is turned off for the electrostatic chuck electrode 3, and the electrostatic chuck electrode 3 is grounded via the high frequency filter 16 and the capacitor 17.

Therefore, when a new wafer 4 is loaded into the vacuum container 1 and held by the electrodes 2 and 3, the electrostatic attraction force due to the residual charge (negative charge) does not decrease, and the attraction force is reduced. The reproducibility becomes high, and it becomes possible to prevent the decrease in reliability due to the reproducibility of the suction force.

Further, since plasma processing other than the original plasma processing is unnecessary, throughput does not decrease. That is, generation of residual charges can be prevented by controlling the DC high-voltage power supply 7, which is a simpler method than plasma processing. Also, the life of the electrostatic chuck electrode 3 (usually the dielectric breakdown of the dielectric thin film 6 covering the electrode 2 determines the life).
The cost can be reduced without shortening.

Further, since the residual charge is eliminated, the problem that the wafer 4 becomes difficult to peel off does not occur. That is, when peeling the wafer 4 from the electrostatic chuck electrode 3,
Since the power supplies 7 and 8 are off, the electrostatic attraction force is not generated in principle, but there is a possibility that the electrostatic attraction force is generated due to the residual charge. However, in the present embodiment, since a voltage of opposite polarity is applied to the electrostatic chuck electrode 3 to prevent the generation of residual charges, such a problem does not occur.

Further, the method of the present embodiment uses the dielectric thin film 6
Since the remanent polarization is reduced, the time until the dielectric breakdown of the dielectric thin film 6 (life of the electrostatic chuck electrode) can be extended.

Although the method of the present embodiment is such that the step of preventing the generation of residual charges is added after the plasma treatment, the voltage applied to the electrostatic chuck electrode 3 in two consecutive plasma treatments is Similar effects can be obtained even if the polarities are different from each other. (Third Embodiment) A feature of the plasma processing apparatus of the present embodiment is that the surface shape of the high-frequency electrode 2 is not flat but has a concave shape that is the most depressed in the central portion, as shown in FIG. Therefore, the gap between the wafer 4 and the electrodes 2 and 3 is wide at the central portion of the wafer 4 and narrow at the peripheral portion.

The thermal conductivity between the wafer 4 and the electrostatic chuck electrode 3 is introduced by the distance between the wafer 4 and the electrostatic chuck electrode 3 (the size of the gap into which the cooling gas is introduced). It is determined by the pressure with the cooling gas. That is, the closer the distance is and the higher the gas pressure is, the higher the thermal conductivity is.

When the plasma treatment of the wafer 4 is performed, energy is uniformly applied to the wafer 4 from the plasma,
This given energy becomes heat. This heat causes the temperature of the wafer to rise rapidly, but in the present embodiment, since a cooling mechanism made of a cooling gas or the like that can be used before plasma generation is provided, the wafer 4 is kept at a predetermined temperature. Can be controlled.

Here, the electrostatic chuck electrode 3 is covered with the dielectric thin film 6 with high durability against heat load, but in order to reduce the influence of plasma, the electrostatic chuck electrode 3 is formed.
Is smaller than the wafer 4. For this reason, the effect of temperature control is small in the peripheral portion of the wafer 4, and a large temperature difference may occur between the central portion and the peripheral portion of the wafer 4.

In order to prevent the occurrence of such a temperature difference, in the present embodiment, the high frequency electrode 2 has a concave shape. With such an electrode shape, the distance between the wafer 4 and the high-frequency electrode is increased in the central portion, and the thermal conductivity in the central portion is lowered, so that the temperature difference between the central portion and the peripheral portion is sufficiently small. It becomes possible to do.

Therefore, according to the present embodiment, the non-uniformity of the temperature generated in the wafer surface is reduced, so that, for example, uniform etching characteristics can be obtained over the entire surface of the wafer. Is not limited to the embodiment described above. For example, although the above embodiments have been described on the assumption of a plasma processing apparatus for film formation and etching, the present invention is applicable to other purposes such as ion implantation, ion plating, and surface treatment such as removal of contaminants. It can also be applied to a plasma processing apparatus.

Further, the pattern of the electrostatic chuck electrode is not limited to the torus pattern shown in the above embodiment, and various patterns such as a strip shape and a lattice shape can be used. As the plasma source, a capacitively coupled plasma source (parallel plate type plasma source), an ECR (electron cycloton resonance) type plasma source, an ICP (inductively coupled) type plasma source, a helicon wave excited type plasma, a magnetron type A plasma source or the like can be used.

Further, the present invention is particularly effective for a wafer having a diameter as large as 8 inches or more, such as 12 or 15 inches. The substrate to be processed is not limited to the wafer, but may be a large area substrate such as a display panel substrate. Also in this case, a remarkable effect can be obtained as in the case of a large diameter wafer.

[0090]

As described above in detail, according to the present invention, the substrate to be processed can be held by the electrostatic adsorption force even before the plasma is generated, and the displacement of the substrate to be processed can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a schematic configuration of a plasma processing apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a plane pattern of an electrostatic chuck electrode.

FIG. 3 is a diagram showing a state of an electric field (electric force lines, charge distribution) of the electrostatic chucking section before plasma generation.

FIG. 4 is a diagram showing a state of an electric field (electric force lines, charge distribution) of the electrostatic chucking section after plasma generation.

FIG. 5 is a diagram showing a surface shape of a high frequency electrode of a plasma processing apparatus according to a third embodiment of the present invention.

FIG. 6 is a diagram for explaining a conventional electrostatic chuck method.

FIG. 7 is a diagram for explaining another conventional electrostatic chuck method.

[Explanation of reference numerals] 1 ... Vacuum container 2 ... High frequency electrode 3 ... Electrostatic chuck electrode 4 ... Wafer 5 ... First dielectric thin film 6 ... Second dielectric thin film 7 ... DC high voltage power supply 8 ... High frequency power supply 9 ... Peripheral Ring 10 ... Baffle plate 11 ... Gas inlet 12 ... Gas outlet 13 ... Matching circuit 14 ... High frequency filter 15 ... High resistance element 16 ... High frequency filter 17 ... Capacitor 18 ... Cooling gas inlet 19 ... Refrigerant inlet 20 ... Refrigerant outlet 21 ... Insulation member 22 ... Shield member 23 ... Penetration path 31, 31 '... Electric force line 32, 32' ... Negative charge 33, 33 '... Positive charge 34 ... Plasma 35 ... Sheath

Claims (5)

[Claims] 1. A processing container for performing plasma processing on a substrate to be processed, a holding table provided in the processing container for holding the substrate to be processed, and a plasma forming means for forming plasma for performing the plasma processing. And an electrostatic chuck having a high-frequency electrode connected to a ground potential via a high-frequency impedance and an opening provided on the high-frequency electrode via a first dielectric film. An electrode and a second dielectric film that covers the electrostatic chuck electrode and on which the substrate to be processed is placed, and the electrostatic chuck electrode is provided with potential control means for controlling the potential thereof. A plasma processing apparatus characterized in that 2. The opening induces charges of opposite polarities in the high-frequency electrode below the opening and the substrate to be processed above the opening, and the electrostatic chuck electrode and the electrostatic chuck electrode are connected to each other. The plasma processing apparatus according to claim 1, wherein the plasma processing apparatus is formed so as to induce electric charges of opposite polarities on the substrate to be processed. 3. The area of the electrostatic chuck electrode is 40 to 80% of the area of the substrate to be processed.
3. The plasma processing apparatus according to 1. 4. A plasma processing method using the plasma processing apparatus according to claim 1, wherein the step of placing the substrate to be processed on a holding table, and the step of placing the substrate between the high frequency electrode pole and the electrostatic chuck electrode. The electric potential of the electrostatic chuck electrode is controlled by the potential control means so that the electric force lines that pass through the substrate to be processed and the opening of the electrostatic chuck electrode are formed, and the substrate to be processed is electrostatically force A plasma processing method comprising: a step of holding on a holding table; and a step of forming plasma above the substrate to be processed by a plasma forming means to perform plasma processing on the substrate to be processed. 5. The plasma processing method according to claim 4, wherein after the plasma processing, the potential control means changes the potential of the electrostatic chuck electrode to a reverse polarity.