JP6142305B2 - Electrostatic adsorption method and electrostatic adsorption device - Google Patents

Description

  The present invention relates to an electrostatic adsorption method and apparatus for adsorbing and fixing a substrate to a support member by electrostatic force in surface treatment such as etching and film formation of the substrate using plasma.

  When surface treatment such as etching or film formation using plasma is performed on the substrate, heat is generated by the surface treatment, and the temperature of the substrate rises. When the temperature of the substrate rises, there is a problem that a defect occurs in the surface treatment such as etching due to a change in the material and shape of the substrate. Therefore, as a method of preventing the temperature of the substrate from increasing, a method of cooling the substrate by bringing the substrate and a supporting member, which is a table for mounting and fixing the substrate, into close contact with each other and discharging the heat of the substrate through the supporting member is adopted. It is done. In addition, by providing a mechanism for flowing a He (helium) gas having a good thermal conductivity between the substrate and the support member, heat transfer between the two is improved.

  A mechanical chuck is known as one method for bringing a substrate into close contact with a support member. The mechanical chuck uses a mechanical structure of a claw or a ring to sandwich and hold the outer peripheral portion of the substrate or press it from the upper side, thereby closely contacting and holding the substrate and the support member. However, the central portion of the substrate to be surface-treated cannot be sandwiched or pressed, and the adhesion is weakened. Furthermore, there is a problem that the surface treatment cannot be performed on the portion of the outer periphery of the substrate covered with the claws or the ring.

  As a method different from the mechanical chuck, an electrostatic chuck is known. The electrostatic chuck uses a dielectric member in which an electrode is embedded as a support member. When a substrate is placed on such a support member and a DC voltage is applied to the electrodes, the back surface of the substrate is charged with a reverse polarity, and an electrostatic force is generated between the support member and the substrate so that the substrate is attracted to the support member. Is done. In the electrostatic chuck, by devising the shape of the electrode, the entire substrate including the central portion of the substrate, which has been difficult to adhere with the mechanical chuck, can be uniformly adhered to the support member. Of course, since the substrate is not mechanically pressed, there is no problem that the outer periphery of the substrate is covered and the surface treatment cannot be performed.

  For these reasons, a suction method using an electrostatic chuck is usually used for silicon substrates and the like. However, in the case of a substrate that is not silicon, the substrate may not be sufficiently adsorbed by the support member. In particular, there is such a problem in the case of a substrate having a large insulation resistance.

  In the case of a substrate having a high insulation resistance, a method of assisting electrostatic adsorption by forming a conductive film in advance on the back surface of the substrate is possible, but an extra step of forming a conductive film must be added. In addition to a decrease in plasma processing throughput and cost, there is a problem that the conductive film may interfere with other processing.

  Therefore, in Patent Document 1, with respect to these substrates, with the substrate placed on a stage that is a support member, first plasma discharge is performed to charge the back surface of the substrate to improve the adsorption performance. ing. As a result, the original (second) plasma treatment can be performed in a state where the substrate is stably held thereafter.

JP 2005-51098 A

  However, even if the adsorption performance is improved by the technique described in Patent Document 1, the adsorption force may still be insufficient or unstable. Therefore, a substrate having a large insulation resistance has not yet made the conductive film formed on the back surface of the substrate unnecessary.

  The problem to be solved by the present invention is to obtain sufficient adsorption performance without forming a conductive film on the back surface of a substrate even with a substrate having a large insulation resistance by further improving and stabilizing the adsorption force by the electrostatic chuck. It is an object of the present invention to provide an electrostatic adsorption method and apparatus that makes it possible.

The electrostatic attraction method according to the present invention, which has been made to solve the above-mentioned problems, provides a support provided with an electrostatic chuck made of a dielectric in which electrodes are embedded when processing the surface of a substrate to be processed with plasma. the substrate is placed on the member, the electrostatic adsorption to be causing an electrostatic force between the substrate and the support member substrate by applying a voltage to the electrode and fixed to adsorb to the support member A method,
Forming a gap between the back surface of the substrate and the substrate mounting surface of the support member , which is a step performed before generating an electrostatic force between the substrate and the support member ;
A pretreatment step of treating the substrate with a pretreatment plasma ;
It is characterized by providing.

In addition, the electrostatic chucking apparatus according to the present invention, which has been made to solve the above-described problems, fixes the substrate to the support member by electrostatic force when processing the surface of the substrate to be processed with plasma. An electrostatic adsorption device,
An electrostatic chuck having a dielectric with electrodes embedded in the support member;
Gap forming means for forming a gap between the back surface of the substrate and the substrate mounting surface of the support member;
Pretreatment plasma generation means for generating pretreatment plasma;
Controlling the gap forming means and the pretreatment plasma generation means so as to generate the pretreatment plasma with the gap formed, and applying a voltage to the electrode of the electrostatic chuck to apply the substrate Control means for sequentially performing a step of adsorbing the support member to the support member by electrostatic force ;
It is characterized by providing.

Here, “plasma for pretreatment” means plasma used for treatment (pretreatment) performed before the substrate is adsorbed to the support member by static electricity, but the target surface treatment (etching, It may be the same as the plasma (hereinafter referred to as “main processing plasma”) for performing film formation or the like, or may be another plasma weaker than that. When the same processing plasma is used, it is desirable that the time is shorter than the processing time of the main processing plasma. When the pretreatment plasma is weaker than the main treatment plasma, for example, high frequency power of 5.5 to 55000 mW / cm ² per area of the back surface of the substrate to be treated is supplied to a treatment gas of 0.01 to 100 Pa and generated. Further, it is more preferable that high frequency power of 2000 or more and 20000 mW / cm ² or less is generated in common with a processing gas of 0.1 or more and 10 Pa or less. If the high-frequency power is smaller than this range, the substrate tends not to be adsorbed to the support member due to static electricity. If it exceeds this range, the surface of the substrate tends to be etched depending on the gas type.
For example, Ar gas or He gas can be used as the processing gas for generating the pretreatment plasma, and is not limited thereto, and any gas that can be discharged may be used.
The substrate to be processed is made of, for example, glass including sapphire (Al ₂ O ₃ ), quartz (SiO ₂ ), alkali glass, resin, aluminum nitride (AlN), and has a resistance value of about 10 ⁹ to 10 ¹⁴ Ωm. The main object is a substrate, but the electrostatic adsorption method and apparatus according to the present invention is not limited to such a substrate, and can be applied to a substrate made of a material having a relatively small insulation resistance. Further, the material of the substrate is not limited to one type, and for example, the substrate may be a substrate whose back surface is made of an insulating material such as sapphire and whose surface is made of a conductor or a semiconductor material.

  As a result of diligent investigation by the inventors of the present invention on the point that sufficient adsorption performance cannot be obtained by the conventional electrostatic adsorption method, once the charge distribution on the back surface of the substrate becomes non-uniform, especially on a substrate having a large insulation resistance. It has been found that the cause is that it is difficult to uniformly charge the back surface of the substrate as compared with a substrate such as a silicon substrate or the like in which the charge is difficult to move. It was also found that uneven adsorption of moisture and the like occurs on the back surface of the substrate.

  And the board | substrate to which electrostatic adsorption is carried out differs in the charging state of a back surface and adsorption | suction states, such as a water | moisture content, for every board | substrate by the influence of the process performed previously. Therefore, if these substrates are electrostatically adsorbed without any treatment, all or part of the charge charged on the back surface of the substrate moves to the surface of the support member, and for that portion, the charge is canceled and the substrate It is considered that the electrostatic force between the support member and the support member cannot be obtained, and the adsorption performance is lowered as a whole.

Therefore, in the present invention, before the substrate is attracted by electrostatic force, the back surface of the substrate is generated by generating pretreatment plasma in a state where a gap is formed between the back surface of the substrate and the substrate mounting surface of the support member in advance. In addition to removing the electric charges, moisture adsorbed on the back surface of the substrate is also removed.
Since the pretreatment plasma of the present invention is used for the purpose of causing the above-described action on the back surface of the substrate, the pressure and type of the processing gas for generating the pretreatment plasma, and the input power per substrate area Or the like may be different from the plasma used for surface treatment (main treatment) such as substrate etching or film formation.

  According to the present invention, even if there is an influence of the past substrate processing, by removing the excessive charge on the back surface of the substrate, stable adsorption performance by the electrostatic chuck can be obtained. Therefore, even if the substrate has a high insulation resistance, there is no need to add an extra step of forming a conductive film on the back surface of the substrate, which can improve plasma processing throughput and reduce costs. There is no problem of hindering the processing. Further, in order to remove moisture and the like on the back surface of the substrate, even if the substrate does not have a large insulation resistance, if the conventional method fails to obtain sufficient electrostatic adsorption force, the present invention provides stable electrostatic adsorption. Power is obtained.

The cross-sectional block diagram of the plasma processing apparatus which implements the electrostatic adsorption method which concerns on a present Example. Schematic which shows the characteristic operation | movement of the electrostatic attraction method based on a present Example. The flowchart which shows the procedure of the plasma processing method which concerns on a present Example.

Hereinafter, an electrostatic adsorption method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional configuration diagram of a plasma processing apparatus according to the present embodiment. In the plasma processing apparatus 10, a high-frequency coil 12 for exciting plasma through a dielectric window 24 is provided on the top of the vacuum vessel 11. One end of the high-frequency coil 12 is connected to the high-frequency power source 20 via the matching unit 19, and the other end is directly connected to the high-frequency power source 20. In addition, a lower electrode 13 for exciting plasma is provided inside the vacuum vessel 11, and is connected to a first high-frequency power source 27 via a blocking capacitor 25 and a matching unit 26. On the upper surface of the lower electrode 13 is provided a dielectric layer 14 on which a substrate 16 to be subjected to plasma processing of the plasma processing apparatus 10 is placed. Here, the substrate 16 has a front surface and a back surface. The front surface is a surface opposite to the dielectric layer 14, and the back surface of the substrate 16 is a surface in contact with the dielectric layer 14.
An electrode is embedded in the dielectric layer 14 (not shown), and a voltage is applied to the electrode to generate an electrostatic force between the back surface of the substrate 16 and thereby attract the substrate 16 to the dielectric layer 14. (Suction by electrostatic chuck) and fix.
The dielectric layer 14 and the lower electrode 13 contain pins 21 for pushing up the substrate 16 from the back surface. The pin 21 is driven by the drive unit 22, and the drive unit 22 is controlled by the control device 23. The control device 23 also controls the high-frequency power supplies 20 and 27 having a function as pretreatment plasma generation means. Furthermore, control such as voltage application to the electrodes inside the dielectric layer 14 may be performed by the control device 23.

  A groove 15 for circulating a heat medium such as He gas is provided on the upper surface of the dielectric layer 14 in order to increase the thermal conductivity between the substrate 16 and the dielectric layer 14, and this groove 15 circulates the He gas. And a heat exchanger for adjusting the temperature of the He gas (not shown). Furthermore, the lower electrode 13 includes a cooling mechanism that cools the lower electrode by circulating cooling water therein. The gas introduction part 17 is a part for introducing a processing gas for generating the surface treatment plasma and the pretreatment plasma of the substrate 16 into the vacuum vessel 11. The exhaust port 18 is for exhausting the processing gas that is no longer required after the plasma processing to the outside of the vacuum vessel 11.

  FIG. 2 shows a characteristic operation of the electrostatic adsorption method of the present embodiment. The substrate 16 is placed. By driving the pin 21 up and down by the driving unit 22, the substrate 16 is pushed up to a predetermined height, and a gap is formed between the back surface of the substrate 16 and the dielectric layer 14. When the pretreatment plasma (P) is generated in the state where the gap is formed, the pretreatment plasma enters between the back surface of the substrate 16 and the dielectric layer 14, so that the back surface of the substrate 16 is in the pretreatment plasma. Exposed.

Here, the pins 21 may be coated with, for example, the same material as that of the substrate 16 or aluminum oxide having a high insulating property so that the charged state is not affected by contact with the back surface of the substrate 16. If the pin 21 and the back surface of the substrate 16 are in contact with each other at three or more locations, the substrate 16 can be pushed up substantially horizontally, and the back surface of the substrate 16 is uniformly exposed to the pretreatment plasma. The gap between the back surface of the substrate 16 and the dielectric layer 14 may be of a size that allows the back surface of the substrate 16 to be uniformly exposed in the pretreatment plasma. In the case of a substrate having a different diameter, it is preferable to set it to a value almost proportional to it.
Further, in the case where the pretreatment plasma is generated by applying high frequency power to the lower electrode 13, the driving unit 22 is controlled by the control device 23 and the substrate 16 is pushed up to a position above the sheath by the pin 21. preferable. This is to prevent the back surface of the substrate 16 from being contaminated by the substrate 16 being in the sheath.

Hereinafter, the plasma processing method of the present embodiment will be described with reference to FIG. First, the substrate is placed on the dielectric layer 14 as a support member (step S1). Next, the drive unit 22 is controlled by the control device 23, and the substrate 16 is pushed up by the pin 21 (step S2). In this state, Ar (argon) gas is introduced into the vacuum vessel 11 as a processing gas for exciting the pretreatment plasma inside the vacuum vessel 11 (step S3). By controlling and supplying high-frequency power to the high-frequency coil 12 (step S4), pretreatment plasma is generated (step S5).
The pretreatment plasma is generated at a pressure of 0.01 Pa or more and 100 Pa or less by applying high frequency power of 5.5 to 55000 mW / cm ² per substrate area to one of the high frequency coil 12 and the lower electrode 13. Further, it is more preferable that high frequency power of 2000 or more and 20000 mW / cm ² or less is generated in common with a processing gas of 0.1 or more and 10 Pa or less. The time for generating the pretreatment plasma is preferably about 10 to 60 seconds. The high-frequency power, pressure and time can be appropriately determined depending on the amount of charge charged on the back surface of the substrate 16, the material of the back surface of the substrate 16, the type of processing gas introduced into the vacuum vessel 11, etc. It is preferable that the surface of the substrate 16 is not etched.
The generated pretreatment plasma enters a gap formed between the back surface of the substrate 16 and the dielectric layer 14. Thereby, the back surface of the substrate 16 is exposed in the pretreatment plasma (step S6). Note that the high frequency power supply 20 and the high frequency power supply 27 may be controlled by the control unit 23 so that the high frequency power is simultaneously applied to the high frequency coil 12 and the lower electrode 13 by pushing the substrate 16 to a position above the sheath with the pin 21.

After a certain time (for example, about 10 to 60 seconds) elapses, the control unit 23 controls the high frequency power supply 20 to stop the supply of high frequency power to the high frequency coil 12 (step S7). When the supply of the high-frequency power to the high-frequency coil 12 is stopped, the power for generating plasma is not supplied to the Ar gas, and the pretreatment of the substrate 16 with the pretreatment plasma is completed. Here, the Ar gas inside the vacuum vessel 11 is discharged to the outside of the vacuum vessel 11 through the discharge port 18 (step S8), and the drive unit 22 is controlled by the control unit 23, and the pin 21 that has pushed up the substrate 16 is restored. The substrate 16 is again placed on the dielectric layer 14 (step S9). Then, a voltage is applied to the electrode embedded in the dielectric layer 14, and the substrate 16 is attracted and fixed to the dielectric layer 14 by electrostatic force (step S10, electrostatic chuck). Thereafter, a surface treatment (main treatment) of the substrate 16 is performed (step S11).
Note that the timing of pushing up the substrate 16 with the pin 21 (step S2) and the timing of generating the pretreatment plasma (steps S3 to S5) may be reversed. Even in this case, the pretreatment can be performed by exposing the back surface of the substrate 16 to the pretreatment plasma.

  In order to confirm the effect of this example, data obtained by measuring the attractive force by the electrostatic chuck when the back surface of the substrate 16 is exposed to the pretreatment plasma and when it is not exposed are shown in Table 1 below. . The numerical values in Table 1 indicate that the He gas circulating in the groove 15 is gradually increased in order to cool the substrate 16 in a state where the substrate 16 is attracted and fixed to the dielectric layer 14 by the electrostatic chuck. In this case, the pressure value when the substrate 16 is detached from the dielectric layer 14 is shown. This value can be regarded as an attractive force by the electrostatic chuck.

  As the substrate 16, a 6-inch sapphire substrate having a large insulation resistance was used. The size of the vacuum vessel 11 was such that one 6-inch substrate could be processed, and the inside of the vacuum vessel 11 was filled with 0.1 Pa Ar gas. The high frequency power for exciting the inductively coupled plasma from the Ar gas was 13.56 MHz, the input power was 500 W, and the processing time for the back surface of the substrate 16 was 2 minutes. The applied voltage of the electrode embedded in the dielectric layer 14 during electrostatic chucking was set to +1 kV. Under this condition, the experiment for measuring the adsorption force by the electrostatic chuck was performed five times, and the value of the adsorption force obtained in each experiment and the average value thereof were confirmed. The numerical value in the center column of Table 1 indicates the value of the adsorption force when the back surface of the substrate 16 is not exposed in the pretreatment plasma, and the numerical value in the right column of Table 1 indicates that the substrate 16 is exposed in the pretreatment plasma. The value of the adsorption force when it is made to show is shown. In the bottom column, the average value of five experiments is calculated.

  When the back surface of the substrate 16 was not exposed in the pretreatment plasma, the attractive force by the electrostatic chuck was 0.6 kPa to 1.0 kPa. This value is sufficiently large since it is smaller than 1.0 to 2.0 kPa, which is a normal pressure value of He gas circulated in the groove 15 in order to improve heat transfer between the substrate 16 and the dielectric layer 14. That's not it. On the other hand, when the back surface of the substrate 16 was exposed in the pretreatment plasma, it was confirmed that an adsorption force of 2.0 kPa or more was obtained in any of the five experiments.

  Further, Table 2 below shows the difference in the attractive force by the electrostatic chuck when the magnitude of the high-frequency power supplied to the Ar gas to excite the inductively coupled plasma and the processing time of the back surface of the substrate 16 are changed. Show. The experiment was conducted with three types of power supply OFF, 500 W, and 2000 W, and two processing times of 10 seconds and 60 seconds. Here, the supply power is OFF means that only Ar gas is introduced into the vacuum vessel 11, no high-frequency power is supplied to the high-frequency coil 12 and the lower electrode 13, and the Ar gas is not converted into plasma. . In the right column of Table 2, the value of the adsorption force is described. From this result, if the supplied power is 500 W or more, it is possible to stably obtain an adsorption force of 2.0 kPa or more by the electrostatic chuck by exposing the back surface of the substrate 16 to the pretreatment plasma for 10 seconds or more. It could be confirmed.

  In the above example, a sapphire substrate was used, but it was confirmed that an equivalent effect could be obtained even with a quartz substrate. Moreover, although the pressure of the process gas was 0.1 Pa in the above examples, it was confirmed that the same action and effect were obtained in the range of 0.1 to 10 Pa. Furthermore, helium can be used as the processing gas in addition to Ar gas.

DESCRIPTION OF SYMBOLS 10 ... Plasma processing apparatus 11 ... Vacuum vessel 12 ... High frequency coil 13 ... Lower electrode 14 ... Dielectric layer 15 ... Groove 16 ... Substrate 17 ... Gas introduction part 18 ... Outlet 19, 26 ... Matching device 20, 27 ... High frequency power supply 21 ... Pin 22 ... Driver 23 ... Control device 24 ... Dielectric window 25 ... Blocking capacitor

Claims (12)

When the surface of a substrate to be processed is processed with plasma, the substrate is placed on a support member having an electrostatic chuck made of a dielectric with an electrode embedded therein, and a voltage is applied to the electrode. the by causing an electrostatic force substrate between the substrate and the support member an electrostatic adsorption method of fixing by adsorption to the support member,
Forming a gap between the back surface of the substrate and the substrate mounting surface of the support member , which is a step performed before generating an electrostatic force between the substrate and the support member ;
A pretreatment step of treating the substrate with a pretreatment plasma ;
Electrostatic adsorption method, characterized in that it comprises a.   2. The electrostatic chucking method according to claim 1, wherein the substrate is a substrate made of an insulating material at least on the back surface.   The electrostatic chucking method according to claim 1, wherein the substrate is a substrate made of sapphire at least on the back surface.   The electrostatic chucking method according to claim 1, wherein the substrate is a substrate having at least a back surface made of quartz.   The pretreatment step is a step of generating plasma by supplying high-frequency power of 2000 to 20000 mW / cm2 per area of the back surface of the substrate to a processing gas of 0.1 to 10 Pa. 5. The electrostatic adsorption method according to any one of 4 above.   A plasma processing method comprising: adsorbing a substrate to a support member using the electrostatic adsorption method according to claim 1, and treating the surface of the substrate. An electrostatic adsorption device for adsorbing and fixing a substrate to a support member by electrostatic force when processing the surface of the substrate to be processed with plasma,
An electrostatic chuck having a dielectric with electrodes embedded in the support member;
Gap forming means for forming a gap between the back surface of the substrate and the substrate mounting surface of the support member;
Pretreatment plasma generation means for generating pretreatment plasma;
Controlling the gap forming means and the pretreatment plasma generation means so as to generate the pretreatment plasma with the gap formed, and applying a voltage to the electrode of the electrostatic chuck to apply the substrate Control means for sequentially performing a step of adsorbing the support member to the support member by electrostatic force ;
Electrostatic chuck, characterized in that it comprises a.   The electrostatic attraction apparatus according to claim 7, wherein the substrate is a substrate made of an insulating material at least on the back surface.   The electrostatic attraction apparatus according to claim 7, wherein the substrate is a substrate made of sapphire at least on the back surface.   The electrostatic attraction apparatus according to claim 7, wherein the substrate is a substrate having at least a back surface made of quartz. The pretreatment plasma generation means is means for generating plasma by supplying a high frequency power of 2000 to 20000 mW / cm ² per area of the back surface of the substrate to a process gas of 0.1 to 10 Pa. Item 11. The electrostatic attraction apparatus according to any one of Items 7 to 10. Means for adsorbing a substrate to a support member using the electrostatic attraction device according to any one of claims 7 to 11;
Means for treating the surface of the substrate;
A plasma processing apparatus comprising:

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