JP3964803B2 - Plasma processing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma processing apparatus. Furthermore, the present invention relates to a plasma processing apparatus having an electrostatic chuck in which electrodes that electrostatically form bipolar electrodes are disposed on a surface that attracts a wafer.
[0002]
[Prior art]
A conventional plasma processing apparatus using an alumite film as an adsorption film for an electrostatic chuck has a configuration in which the base material of the electrostatic chuck is made of aluminum, and an anodized film is formed by anodizing the surface. (For example, refer to Patent Document 1).
[0003]
An electrostatic chuck using an alumite film as an adsorption film has advantages such as a simple structure and low cost, and can be manufactured in a short period of time, compared with an electrostatic chuck using a ceramic sintered body as an adsorption film. However, the conventional electrostatic chuck using an alumite film as an adsorption film has two main problems. One of them is that it is easy to form a monopolar electrostatic chuck because of its low design freedom, but it is difficult to form a bipolar electrostatic chuck. Is that the electrical or mechanical integrity of the anodized film can often be reduced.
[0004]
Regarding the former problem, when using a single-pole electrostatic chuck in plasma, the plasma acts as a conductor and generates an adsorption force, so the plasma disappears for some reason during the plasma treatment. In this case, the suction force immediately disappears and the wafer cannot be held. However, for the purpose of promoting heat transfer between the electrostatic chuck and the wafer, a minute gap between the wafer and the electrostatic chuck is often filled with a gas such as helium. If the adsorption force disappears in a state where the gas pressure is applied, the wafer is pushed by the gas pressure and detached from the electrostatic chuck, and the wafer may be displaced, or the wafer may be damaged. This problem cannot occur in a bipolar electrostatic chuck that can generate an attractive force regardless of the presence or absence of plasma. Therefore, it is a very important issue to be able to manufacture bipolar electrodes with a higher degree of design freedom.
[0005]
On the other hand, with respect to the latter problem, when defects such as cracks and delamination exist in the adsorption film of the electrostatic chuck, problems such as a decrease in withstand voltage and desorption of the adsorption film may occur. In particular, an alumite film often contains a microcrack at the time of film formation, and the crack may develop with a relatively low stress starting from this crack. Therefore, tensile stress is applied to the alumite film. Structure should be avoided as much as possible. However, when aluminum having a relatively large thermal expansion coefficient is used as a base material and an alumite film having a relatively low thermal expansion coefficient is used as an adsorption film, the thermal expansion coefficients of the base material and the adsorption film are greatly different. A large thermal stress is generated near the interface between the substrate and the adsorption film. In particular, when the temperature rises, a tensile stress is applied to the adsorption film side, so that the adsorption film may crack and develop. Therefore, it is also a very important issue to suppress the generation and propagation of cracks due to this thermal stress.
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-160076
[Problems to be solved by the invention]
The present invention has been made in consideration of such problems. It is an object of the present invention to provide a plasma processing apparatus that is inexpensive, easy to use, or highly reliable.
[0008]
[Means for Solving the Problems]
The subject includes a vacuum container having a processing chamber that is depressurized inside, and a chuck that is placed in the processing chamber and has a mounting surface on which a wafer is mounted and held by static electricity. a plasma processing apparatus in which the holding surface of the wafer is processed, a member made of an insulating material placing surface is Ru is disposed on the upper surface, of different polarity arranged on surfaces of the insulator member made of two and membrane potential is separated is granted, covering the Makujo each of these are arranged with a predetermined plane shape that are separated from each other, the two having a anodized film on the surface This is achieved by a plasma processing apparatus having an aluminum layer, and the wafer is placed on the anodized film on the upper surface of each aluminum layer.
[0009]
Further, the above-mentioned problem is a plasma processing apparatus, wherein the anodized film is subjected to a predetermined treatment on the entire surface after the aluminum layer is disposed on the film on the insulator member. This is achieved by the structure formed by applying.
[0010]
Further, the above object is achieved by a plasma processing apparatus, wherein the anodized film is disposed by anodizing an upper surface and a side surface of the aluminum layer.
[0011]
Further, the above object is achieved by the plasma processing apparatus, wherein the upper corner portion of the aluminum layer is provided with a shape whose cross section is an arc shape or a chamfered shape.
[0012]
Furthermore, the above object is achieved by the plasma processing apparatus, wherein the two aluminum layers act as separated electrodes to which different polarities are given to hold the wafer on the mounting surface by static electricity. Is done.
[0013]
The above object is achieved by a plasma processing apparatus, further comprising an insulating thin film formed on the surface of the anodized film.
[0014]
Also. The above object is achieved by a plasma processing apparatus, wherein an insulating thin film made of ceramic is further formed on the surface of the anodized film.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
As described above, the point that the attractive force disappears when the plasma disappears can be solved by making the electrostatic chuck bipolar. This is because a bipolar electrostatic chuck generates an attracting force regardless of the presence of plasma, so that the attracting force is maintained even if the plasma disappears. However, the conventional method, that is, the method of anodizing a single aluminum substrate cannot form a bipolar electrostatic chuck. This is because the aluminum substrate just below the adsorption surface is a single electrode even if a bipolar electrode is formed on the adsorption surface. Therefore, in the embodiment of the present invention, a plurality of electrically insulated aluminum films are formed on an insulating base material, and a bipolar electrostatic chuck is formed by anodizing these aluminum films. To do.
[0016]
On the other hand, the point that the electrical or mechanical soundness of the alumite film is lowered can be solved by using, for example, ceramic as the material of the insulating base. This is because when the thermal expansion coefficient of the substrate is equivalent to the thermal expansion coefficient of anodized, the volume expansion and contraction are made uniform throughout the electrostatic chuck when the temperature changes. This is because generation of large thermal stress can be suppressed. Moreover, the reliability of the adsorption film is further improved by forming an insulating film such as a ceramic film on the surface of the alumite film.
[0017]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0018]
[Example 1]
FIG. 1 is a cross-sectional view schematically showing the configuration of a sample stage on which a wafer is placed according to a first embodiment of a semiconductor processing apparatus of the present invention. An electrostatic chuck 1 whose cutting model is shown in FIG. 1 is mainly used for the purpose of attracting a wafer 7 and processing it. The structure and usage of the electrostatic chuck according to the present invention will be described below.
[0019]
The basic components of the electrostatic chuck 1 according to the present invention are a base material 6, conductive thin films 4a and 4b, anodized films 2a and 2b, and power supply wirings 5a and 5b. The base material 6 is an insulator, and alumite films 2a and 2b are formed on its upper surface with the conductive thin films 4a and 4b interposed therebetween. Inside the base material 6, conductive power supply wirings 5a and 5b are formed through the base material 6, and one ends of the power supply wirings 5a and 5b are connected to the conductive thin films 4a and 4b, respectively. Further, a DC power source for electrostatic adsorption is connected to the other ends of the power supply wirings 5a and 5b, and an independent potential can be applied to the conductive thin films 4a and 4b.
[0020]
Next, a procedure for attracting the wafer 7 to the electrostatic chuck 1 in this embodiment will be described. First, the wafer 7 transported using a wafer transport means (not shown) is positioned on the electrostatic chuck 1 after the position of the wafer 7 is determined so that the outer periphery thereof substantially coincides with the outer periphery of the electrostatic chuck 1. Next, as shown in FIG. 1B, reverse-polarity potentials are applied to the conductive thin films 4a and 4b through the power supply wirings 5a and 5b, respectively. For example, when a positive charge is applied to the conductive thin film 4a and a negative charge is applied to 4b, the surface charge of the wafer 7 moves as shown in FIG. 1B, and the conductive thin films 4a and 4b and the wafer 7 The wafer 7 is attracted to the electrostatic chuck 1 by a force that attracts positive and negative charges on the surface, that is, a Coulomb force.
[0021]
In the state where the wafer 7 is attracted to the electrostatic chuck 1 by the above procedure, a desired plasma treatment is performed on the wafer 7. When the wafer 7 is removed from the electrostatic chuck 1 after the plasma processing is completed, the potential applied to the conductive thin films 4a and 4b may be returned to near 0 to level the charge distribution on the wafer surface.
[0022]
In addition, when the same potential of the same polarity is applied to the conductive thin films 4a and 4b, no adsorption force is generated as it is, but the difference between the potential of the wafer and the potential of the conductive thin films 4a and 4b is increased. As a result, a Coulomb force can be generated and adsorbed.
[0023]
Next, as an example of plasma processing, an embodiment of the plasma processing apparatus of the present invention will be described by taking an etching process which is one of important structures in semiconductor manufacturing as an example.
[0024]
An outline of the etching apparatus used in this example is shown in FIG. In FIG. 2, a processing chamber R is a vacuum vessel that can achieve a vacuum of about 10,000 Pa, an antenna 110 that radiates electromagnetic waves in the upper part, and a static electricity on which a sample 700 such as a wafer is placed in the lower part. A chuck 100 is provided. The antenna 110 and the electrostatic chuck 100 are installed so as to face each other in parallel. Around the processing chamber R, a magnetic field forming unit 101 made of, for example, an electromagnetic coil and a yoke is installed. Then, due to the interaction between the electromagnetic wave radiated from the antenna 110 and the magnetic field formed by the magnetic field forming means 101, the processing gas introduced into the processing chamber is turned into plasma, generating plasma P, and processing the sample 700. .
[0025]
On the other hand, the processing chamber R is evacuated by the evacuation system 106 and the pressure is controlled by the pressure control means 107. The processing pressure is adjusted to a range of 0.1 Pa to 10 Pa. The antenna 110 is held in a housing 114 as a part of the vacuum container. A processing gas for performing processing such as etching and film formation of a sample is supplied from a gas supply unit (not shown) with a predetermined flow rate and a mixing ratio, is controlled to a predetermined distribution, and is supplied to the processing chamber R.
[0026]
An antenna power source 120 and an antenna bias power source 122 are connected to the antenna 110 via a matching circuit / filter system 123 and 124 as an antenna power source 120, and are also connected to the ground through a filter 125. The antenna power supply 121 supplies power of a UHF band frequency from 300 MHz to 1 GHz. In this embodiment, the frequency of the antenna power supply 121 is 450 MHz. On the other hand, the antenna bias power supply 122 applies bias power having a frequency in the range of several tens of kHz to several tens of MHz to the antenna 110. In this embodiment, this frequency is 13.56 MHz.
[0027]
An electrostatic chuck 100 is provided below the processing chamber R so as to face the antenna 110. A bias power supply 141 that supplies a bias power in the range of 200 kHz to 13.56 MHz, for example, is connected to the electrostatic chuck 100 via a matching circuit / filter system 142 to control the bias applied to the sample 700 and the filter 143. It is connected to earth through In this embodiment, the frequency of the bias power supply 141 is 400 kHz.
[0028]
As described above, the electrostatic chuck 100 holds the sample 700 such as a wafer on the upper surface thereof, that is, the sample mounting surface. When the wafer 700 is etched using the plasma etching apparatus shown in this embodiment, a Coulomb force is generated by applying a DC voltage of several hundreds V to several kV from the DC power supply 144 and the filter 145 for electrostatic adsorption. appear. The surface of the electrostatic chuck 100 is controlled to a predetermined temperature by a temperature control means (not shown). An inert gas, for example, helium gas, is supplied to the gap between the surface of the electrostatic chuck 100 and the back surface of the wafer 700 at a predetermined flow rate and pressure, and heat transfer between the sample 700 and the sample is improved. It is increasing. Thereby, the surface temperature of the sample 700 can be accurately controlled within a range of, for example, about 20 ° C. to 110 ° C.
[0029]
The plasma etching apparatus according to this embodiment is configured as described above, and a specific process in the case of etching silicon, for example, using this plasma etching apparatus will be described.
[0030]
In FIG. 2, first, a wafer 700 as an object to be processed is loaded into a processing chamber R from a sample loading mechanism (not shown), and then placed and sucked on the electrostatic chuck 100, and if necessary, the electrostatic chuck. The height of 100 is adjusted and set to a predetermined gap. Next, gases necessary for etching the sample 700, such as chlorine, hydrogen bromide, and oxygen, are supplied from a gas supply unit (not shown) and supplied into the processing chamber R with a predetermined flow rate and mixing ratio. At the same time, the processing chamber R is adjusted to a predetermined processing pressure by the vacuum exhaust system 106 and the pressure control means 107. Next, an electromagnetic wave is radiated from the antenna 110 by supplying 450 MHz power from the antenna power supply 121. Then, the plasma P is generated in the processing chamber R by the interaction with the substantially horizontal magnetic field of 160 gauss (electron cyclotron resonance magnetic field intensity with respect to 450 MHz) formed inside the processing chamber R by the magnetic field forming means 101, and the processing is performed. The gas is dissociated to generate ions and radicals. Further, the wafer 700 is etched by controlling the composition ratio and energy of ions and radicals in the plasma by the antenna bias power from the antenna bias power source 122 and the bias power from the bias power source 141 for the lower electrode. Then, along with the end of the etching process, the supply of electric power / magnetic field and processing gas is stopped to end the etching.
[0031]
A method for carrying out the wafer 700 after completion of the etching will be described below. As described above, in order to reduce the attractive force between the wafer and the electrostatic chuck, the DC voltage applied to the conductive thin films 4a and 4b in FIG. The potential difference may be reduced. That is, the wafer 700 is separated from the alumite layers 2a and 2b by making the potential difference between the conductive thin films 4a and 4b substantially zero. Thereafter, the peeled wafer 700 is sent to the next process using a transfer mechanism (not shown).
[0032]
However, when the potential difference between the conductive thin films 4a and 4b is substantially zero, the wafer adsorption force may remain and may not be easily peeled off. If the wafer 700 is sufficiently conductive, this is because the charges accumulated in the alumite layers 2a and 2b are not neutralized. If the wafer is forcibly peeled off by the wafer peeling mechanism without sufficiently reducing the adsorption force between the wafer 700 and the electrostatic chuck, the wafer may jump up at the moment of peeling. In this case, since the accumulated charge can be neutralized by applying a voltage having a polarity opposite to that at the time of adsorption to the conductive thin films 4a and 4b, this risk can be reduced by using a wafer peeling mechanism thereafter. Can be avoided.
[0033]
[Example 2]
Hereinafter, embodiments of the method for manufacturing an electrostatic chuck according to the present invention will be described in detail. In this embodiment, first, as shown in FIG. 3A, power supply wirings 5a and 5b are installed and fixed at predetermined positions on the base material 6 so as to penetrate the base material 6. After processing so that a gap was not formed between the openings, the surface of the substrate 6 and the ends of the power supply wirings 5a and 5b were flushed. In this embodiment, the base material 6 is made of alumina, but other insulating materials such as ceramics such as aluminum nitride and silicon carbide, quartz and the like can achieve the object of the present invention. On the other hand, although the power supply wirings 5a and 5b are made of tungsten, other conductive materials can achieve the object of the present invention.
[0034]
Next, as shown in FIG.3 (b), the electroconductive thin films 4a and 4b were formed on the base material 6 in the desired shape. In this embodiment, the conductive thin films 4a and 4b are baked with a molybdenum-manganese alloy. However, the object of the present invention can be achieved by using other conductive thin films, for example, sputter films and plating films of various metals. The conductive thin films 4a and 4b are arranged so that the power supply wirings 5a and 5b are in electrical contact with each other.
[0035]
Next, as shown in FIG.3 (c), the aluminum layers 9a and 9b were formed on the electroconductive thin films 4a and 4b, and it equalized. In this embodiment, brazing is applied to the method of forming the aluminum layer, but other methods such as sputtering, plating, brazing, and pressure welding can achieve the object of the present invention.
[0036]
The aluminum layers 9a and 9b had a thickness of about 100 micrometers. The planar shapes of the aluminum layers 9a and 9b may be concentric circles and rings as shown in FIG. 1, respectively, or may be two semicircles. Furthermore, by adopting a so-called “comb-tooth type”, it is possible to generate an attracting force to an insulator such as raw glass. Furthermore, the surfaces of the aluminum layers 9a and 9b were finished to have a center line average roughness of 0.2 micrometers or less. Further, the corners of the aluminum layer were chamfered. This chamfering is very important in order to prevent cracks from occurring at the corners of the anodized film after the subsequent anodized treatment. The shape of the corner of the aluminum layer may be other than such chamfering, for example, an arc.
[0037]
Next, as shown in FIG.3 (d), the surface of the aluminum layers 9a and 9b was anodized. The alumite film was grown by applying a voltage to the aluminum layers 9a and 9b through the power supply wirings 5a and 5b in an oxalic acid solution. Film formation was completed when the thickness of the alumite films 10a and 10b in FIG. 3D reached 50 micrometers. However, since fine cracks in the film thickness direction remain inside the formed alumite films 10a and 10b as it is, the exposed alumite film is exposed to high-temperature water vapor so that the inside of the alumite films 10a and 10b The fine crack formed in was sealed.
[0038]
FIG. 4 shows an outline of a cross section of the electrostatic chuck manufactured by the above method. When the silicon wafer 7 was placed on the electrostatic chuck 1 manufactured by this method and DC voltages of +500 V and −500 V were applied to the power supply wirings 5a and 5b, respectively, the wafer 7 was attracted to the electrostatic chuck. As a result of applying a load for pulling the wafer 7 perpendicular to the adsorption surface of the electrostatic chuck 1, it was confirmed that an adsorption force of 4 kPa or more was generated. From the above, it was confirmed that a bipolar electrostatic chuck having sufficient adsorption performance can be manufactured by the method described in this example.
[0039]
Example 3
Hereinafter, another embodiment of the electrostatic chuck according to the present invention will be described in detail. FIG. 5 schematically shows the electrostatic chuck according to the present embodiment. In this example, an insulating thin film 10 was further formed on the surfaces of the alumite films 2a and 2b as shown in FIG. The reason and effect are as follows. That is, as described in Example 2, generally, fine cracks exist in the alumite film. Therefore, it seems very difficult to eliminate any cracks in the alumite film. However, if a large number of cracks remain in the film, the withstand voltage of the alumite film, that is, the adsorption film is lowered, and the performance as an electrostatic chuck may be impaired.
[0040]
In order to improve the withstand voltage of the alumite film, in Example 2, a sealing process of exposing to water vapor was performed after the formation of the alumite films 2a and 2b. This process is simple and certainly effective, but in some cases the effect may be insufficient. Therefore, as shown in the present embodiment, by forming the insulating film 10 on the surface of the alumite film, the withstand voltage of the adsorption film is further improved, and the occurrence of problems due to dielectric breakdown is significantly reduced, or By applying a higher voltage to the power supply wirings 5a and 5b, it is possible to obtain a larger adsorption force. Or the reliability at the time of using for a long period of time or repeated heating / cooling improves.
[0041]
In this example, an alumina CVD (chemical vapor deposition) film was used as the insulating thin film, and the film thickness was 5 micrometers. By this CVD treatment, the average withstand voltage of the adsorption film was improved from about 3 kV to about 5 kV. On the other hand, almost no change was observed in the adsorption force by this CVD treatment. From the above study, it has been clarified that forming an insulating thin film on the surface of the alumite film is very effective for improving the reliability of the electrostatic chuck.
[0042]
Example 4
In order to adjust the temperature of the wafer by increasing the heat transfer coefficient between the wafer and the adsorption film, it may be necessary to fill a gas such as helium at a predetermined pressure between the wafer and the adsorption film. In order to cope with this, as shown in FIG. 6, the groove G is processed on the surface of the adsorption film, and a predetermined roughness is provided on the adsorption surface, so that the gas pressure variation between the wafer and the adsorption film It is effective to reduce. In this case, it is necessary to provide a sealing structure for preventing gas from leaking from the back surface of the wafer into the vacuum container at the outermost peripheral portion of the electrostatic chuck. In this embodiment, as shown in FIG. 6, a structure is adopted in which the groove on the surface of the adsorption film is not penetrated to the outer peripheral end.
[0043]
In order to realize this, the shapes of the aluminum 9a and 9b in FIG. 3 may be appropriately set in advance so that the alumina film has a desired shape capable of suppressing gas leakage from the outermost periphery.
[0044]
Examples 1 to 4 described above are merely examples of the embodiment of the present invention, and needless to say, the present invention is not limited to the electrostatic chuck and apparatus.
[0045]
According to the present invention, a bipolar electrostatic chuck having high reliability such as withstand voltage and good usability can be manufactured at a low cost, thereby providing a plasma processing apparatus having a high degree of freedom in use. It becomes possible.
[Brief description of the drawings]
FIG. 1 is a perspective view and a sectional view of an electrostatic chuck according to an embodiment of the present invention.
FIG. 2 is a sectional view of an etching apparatus according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view illustrating a method for manufacturing an electrostatic chuck according to an embodiment of the present invention.
FIG. 4 is a sectional view of an electrostatic chuck according to another embodiment of the present invention.
FIG. 5 is a sectional view of an electrostatic chuck according to another embodiment of the present invention.
FIG. 6 is a perspective view of an electrostatic chuck according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Electrostatic chuck, 2a ... Anodized layer, 2b ... Anodized layer, 4a ... Conductive thin film, 4b ... Conductive thin film, 5a ... Feeding wiring, 5b ... Feeding wiring, 6 ... Base material, 7 ... Wafer

Claims (7)

A vacuum vessel having a processing chamber that is depressurized inside; and a chuck that is disposed in the processing chamber and has a mounting surface on which a wafer is placed and held by static electricity. A plasma processing apparatus for processing the surface of a wafer ,
And the member made of an insulating material placing surface is Ru is disposed on the upper surface, of the two potential of lined et Re different polarities on surfaces of the insulator made of member is separated is applied film and, each of these Anodized on the upper surface of each of the aluminum layers, the two anodized layers having an anodized film disposed on the surface of the aluminum layer. A plasma processing apparatus in which the wafer is placed on the formed film. 2. The plasma processing apparatus according to claim 1, wherein the anodized film is subjected to a predetermined treatment on the entire surface after the aluminum layer is disposed on the film on the insulator member. The plasma processing apparatus formed by giving. Claim 1 or a plasma processing apparatus according to claim 2, wherein the anodized film is a plasma processing apparatus upper surface and the side surface of the aluminum layer is arranged to be anodized. The billing A plasma processing apparatus according to claim 3, the corners of the upper of the aluminum layer is a plasma processing apparatus having a shape in cross-section is in an arc shape or chamfered shape. 5. The plasma processing apparatus according to claim 1, wherein the two aluminum layers hold the wafer on the mounting surface by static electricity and are given different polarities. Plasma processing apparatus which acts as a formed electrode. Wherein a plasma processing apparatus according to claim 1, the surface of the anodized film, further plasma processing apparatus to form an insulating thin film. The billing A plasma processing apparatus according to claim 1, wherein said anodized surface of the membrane, further plasma processing apparatus to form an insulating thin film made of ceramic.

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