US20050145341A1

US20050145341A1 - Plasma processing apparatus

Info

Publication number: US20050145341A1
Application number: US10/990,433
Authority: US
Inventors: Masaki Suzuki
Original assignee: Individual
Current assignee: Panasonic Holdings Corp
Priority date: 2003-11-19
Filing date: 2004-11-18
Publication date: 2005-07-07

Abstract

A plasma processing apparatus has a liquid storage vessel which is formed outside of a dielectric window and in which a plasma-exciting coil or electrode is placed inside and moreover in which an electrically insulative liquid is stored in the inside of the liquid storage vessel, as well as a cooling unit and a heating unit for the liquid. Temperature of the liquid stored in the liquid storage portion is adjusted, by which temperature of the plasma-exciting coil or electrode and the dielectric window is controlled via the liquid.

Description

BACKGROUND OF THE INVENTION

The present invention relates to plasma processing apparatuses such as dry etching apparatuses and plasma CVD apparatuses to be used for the manufacture of semiconductor or other thin-film circuits and electronic components or boards on which those electronic circuits and others are to be mounted.
Conventionally, as one of the plasma processing apparatuses to be used for the manufacture of semiconductor or other thin-film circuits, electronic components, or boards, there has been a plasma processing apparatus of the RF (Radio Frequency) plasma excitation method in which RF power is applied to a plasma-exciting coil or electrode positioned outside a vacuum vessel to excite a plasma in the vacuum vessel, and plasma processing is performed on a substrate (work piece) set within the vacuum vessel with the excited plasma. The plasma processing apparatus of this method is so designed with an RF magnetic field generated outside of the vacuum vessel, the RF magnetic field is transferred into the vacuum vessel via a dielectric window so that electrons are accelerated by this electromagnetic field to excite a plasma, by which the processing is carried out.
As an example of such a conventional plasma processing apparatus, a schematic sectional view of a plasma processing apparatus 500 is shown in FIG. 10 (see, e.g., Japanese unexamined patent publication No. 2003-59904, Specification of U.S. Pat. No. 5,540,824, Japanese unexamined patent publication No. H09-74089).
As shown in FIG. 10, the plasma processing apparatus 500 is equipped with a vacuum vessel 501 which has an opening at the top thereof and generally cylindrical shaped (only part of the vacuum vessel 501 is shown in FIG. 10), and a bell jar (dielectric window) 502 which is formed of a generally hemispherical-shell shaped dielectric material (e.g., quartz) and which is provided so as to cover the opening at the top of the vacuum vessel 501, where a processing chamber 503 is formed which is a space closed by the vacuum vessel 501 and the bell jar 502 and a space where plasma processing is performed. Further, the plasma processing apparatus 500 has a reactant gas supply portion 504 which is provided at an upper portion of a side face of the vacuum vessel 501 and which serves for introducing a specified reactant gas into the vacuum vessel 501, and a vacuum pump (not shown) which is an evacuator for discharging air or gas present in the vacuum vessel 501 (in the processing chamber 503). Also, near the top of the bell jar 502 are placed a plasma-exciting coil 505 formed of a wire conductor in a spiral shape, as well as a coil-use RF power supply 506 for applying RF power to the plasma-exciting coil 505. Further, a substrate electrode 507 is provided near a generally center in the vacuum vessel 501, and a substrate-electrode use RF power supply 508 for applying RF power to the substrate electrode 507 is provided. A substrate 509 which is to be subjected to plasma processing is held on the substrate electrode 507 within the vacuum vessel 501.
As shown in FIG. 10, in order that the electromagnetic field generated from the coil 505 to which RF power is applied is prevented from escaping to outside of the apparatus, the coil 505 and the bell jar 502 are covered with a ground shield 510 formed of a conductor member. In this ground shield 510, a vent hole 511 is provided at a left end in the figure, and a cooling fan 512 is provided at a right end in the figure, so that air in the ground shield 510 can be discharged to outside of the apparatus by the cooling fan 512, and that air outside the apparatus can be introduced into the ground shield 510 through the vent hole 511.
In the conventional plasma processing apparatus 500 of such a construction, air is discharged from interior of the vacuum vessel 501 (i.e., interior of the processing chamber 503) by the vacuum pump, while a specified gas is introduced thereinto from the reactant gas supply portion 504, so that the interior of the processing chamber 503 is kept at a specified pressure. In such a state, RF power is applied to the coil 505 by the coil-use RF power supply 506 so that an electromagnetic field is imparted to the reactant gas within the processing chamber 503 from the coil 505 via the bell jar 502, thereby exciting a plasma. Use of this excited plasma makes it possible to perform plasma processing such as etching, deposition or surface reforming on the substrate 509 held to the substrate electrode 507. In do this, applying RF power also to the substrate electrode 507 by the substrate-electrode use RF power supply 508 makes it possible to control ion energy which reaches the substrate 509.
In such a plasma processing, also, although temperature of the bell jar 502 or the coil 505 increases along with the application time of the RF power, yet the atmosphere in the internal space of the ground shield 510 is mechanically ventilated by the cooling fan 512 and the vent hole 511, so that the temperature increase can be reduced more or less.
Further, a schematic sectional view of a plasma processing apparatus 600 according to another prior art example is shown in FIG. 11 (see, e.g., Japanese unexamined patent publication No. 2000-21858, and Japanese unexamined patent publication No. H03-79025). As shown in FIG. 11, the plasma processing apparatus 600 differs in construction from the foregoing plasma processing apparatus 500 in terms of having a generally plate-shaped dielectric window 602 instead of the generally hemispherical-shell shaped bell jar 502. More specifically, the plasma processing apparatus 600 has generally cylindrical-shaped vacuum vessel 601 which has an opening, a dielectric window 602, a reactant gas supply portion 604, a flat spiral coil (planar spiral-shaped coil) 605, a coil-use RF power supply 606, a substrate electrode 607 on which a substrate 609 can be placed and held, a substrate-electrode use RF power supply 608, a ground shield 610, and a vacuum pump 613. The opening at the top of the vacuum vessel 601 is closed and sealed by the dielectric window 602, where a closed internal space serves as the plasma processing chamber 603. Further, a matching box 606 a is provided between the coil-use RF power supply 606 and the coil 605, and a matching box 608 a is also provided between the substrate-electrode use RF power supply 608 and the substrate electrode 607.
As shown in FIG. 11, a vent hole 611 is formed at a side face of the ground shield 610, a cooling fan 612 is provided at an upper portion of the matching box 606 a, and a large opening is formed at a center portion of the ground shield 610 coupled to the matching box 606 a. By the cooling fan 612 and the vent hole 611 being provided as shown above, the dielectric window 602 and the coil 605, which would increase in temperature during plasma processing, can be cooled by outside air, allowing their temperature increase to be suppressed to some extent.
Further, inside the substrate electrode 607 is formed an internal liquid passage 614 which allows a cooling/heating medium liquid to be circulated therealong, and this liquid passage 614 is communicated through a cooling/heating medium liquid circulation passage 616 with a chiller unit 615 installed outside the apparatus. It is noted that the cooling/heating medium liquid as shown above is given by the use of, for example, water, ethylene glycol, fluorine oil or the like. Further, the chiller unit 615 is provided with a pump for circulating the cooling/heating medium liquid, a refrigerator, a heater, a water cooling (air cooling) unit for the refrigerator, and the like. By such a chiller unit 615, the substrate electrode 607, which would increase in temperature during plasma processing, can be cooled to suppress the temperature increase. It is also possible to heat the substrate electrode 607 in advance for the preparation of plasma processing.

SUMMARY OF THE INVENTION

However, in the conventional plasma processing apparatus 500, since the bell jar 502 and the like that would increase in temperature are cooled by mechanically ventilating the internal space of the ground shield 510, which covers the bell jar 502 and the coil 505, by means of the small-diameter cooling fan 512 and the vent hole 511, there are some cases where the bell jar 502 may increase in temperature to, for example, about 200° C. along with an elapse of discharge time of the electromagnetic field due to a lack of cooling power. Discharge time of 3 minutes or longer makes this tendency to be more noticeable. Like this, in cases where the bell jar 502 is increased in temperature, there may occur emission of gas components from a deposited film deposited on an inner wall of the bell jar 502, causing the atmosphere of a plasma processing region R within the processing chamber 503 to be changed.
Also, in a halt of plasma processing or standby state of the plasma processing apparatus 500, the temperature of the bell jar 502 is also decreased to room temperature. In such a case, the low temperature of the dielectric window accelerates film deposition to the dielectric window during the next-time plasma processing, and moreover residual gas components within the plasma processing region R is adsorbed by the deposited film to make a degassing source in the next-time temperature increase. Repeated execution and halt of plasma processing shown above causes the atmosphere within the plasma processing region R to be unstable (unsteady), and increasing a thickness of the deposited film with increasing number of times of processing leads to change of the atmosphere. This gives rise to an issue that plasma processing of high repeatability cannot be implemented.
Further, repeating such plasma processing and plasma halt causes the quartz of the bell jar 502 and the deposited film to repetitively increase and decrease in temperature, so that peeling of the deposited film occurs due to a difference in coefficient of thermal expansion between the two members. As a result, dust adheres onto the substrate 509 placed on the substrate electrode 507, giving rise to an issue of device failures on the substrate to be processed.
Furthermore, in the plasma processing, ozone is generated by corona discharge around the coil 505 and ultraviolet rays in plasma emission, and the generated ozone may be diffused outside the plasma processing apparatus 500 by the cooling air. In such a case, there arise issues of a health problem of the operator as well as acceleration of deterioration of the apparatus component parts.
Such respective issues can occur also to the plasma processing apparatus 600 similarly. However, the plasma processing apparatus 600, which employs a not generally hemispherical-shell shaped but plate-shaped dielectric window 602, inevitably has to be large in its thicknesses so as to withstand the vacuum of the processing chamber 603 (i.e., to withstand the atmospheric pressure). Besides, the dielectric window 602 is formed of quartz or the like, which has a low heat transfer coefficient, thus giving rise to another issue that the dielectric window 602 becomes harder to cool.
Accordingly, an object of the present invention is to solve these and other issues and provide a plasma processing apparatus which is capable of performing stable plasma processing with enhanced repeatability, and which is smaller in dust generation within the processing chamber even with repetitive execution of plasma processing,
In order to achieve the aforementioned object, the present invention is constructed as follows.
According to a first aspect of the present invention, there is provided a plasma processing apparatus for imparting an electromagnetic field to reactant gas introduced into a evacuated processing chamber to excite plasma and performing plasma processing on a substrate set in the processing chamber, comprising:

- a vacuum vessel which defines the processing chamber in which the substrate is held and the plasma processing for the substrate is performed, and which includes a dielectric window forms a part of the vacuum vessel, for hermetically closing the vacuum chamber, and a gas supply portion for supplying the reactant gas into the processing chamber;
- a plasma-exciting coil which is placed so as to confront the processing chamber via the dielectric window, for imparting an electromagnetic field to interior of the processing chamber via the dielectric window with RF power applied;
- an evacuation unit for evacuating the interior of the processing chamber to draw a vacuum so that pressure in the processing chamber is kept generally constant;
- an RF power supply for applying the RF power to the plasma-exciting coil; and
- a liquid storage vessel which includes the dielectric window as a part thereof and which defines in interior thereof a liquid chamber for storing therein an electrically insulative liquid so that an opposite surface to a processing chamber-side surface of the dielectric window is immersed in the liquid and in which the plasma-exciting coil is placed.

According to a second aspect of the present invention, there is provided a plasma processing apparatus as defined in the first aspect, further comprising a liquid temperature adjusting unit which has a cooling unit and/or a heating unit for the electrically insulative liquid and for adjusting temperature of the liquid stored in the liquid storage vessel to control temperature of the plasma-exciting coil and the dielectric window via the liquid.
According to a third aspect of the present invention, there is provided a plasma processing apparatus as defined in the second aspect, wherein the liquid storage vessel except for the dielectric window is formed of an electrical conductor.
According to a fourth aspect of the present invention, there is provided a plasma processing apparatus as defined in the second aspect, wherein

- the liquid storage vessel is integrated with the dielectric window whereby an integrated dielectric window is formed, and the integrated dielectric window has a liquid flow passage for the electrically insulative liquid inside thereof as the liquid chamber in which the plasma-exciting coil is placed.

According to a fifth aspect of the present invention, there is provided a plasma processing apparatus as defined in the second aspect, wherein the liquid temperature adjusting unit is placed outside the liquid storage vessel, the plasma processing apparatus further comprising:

- a liquid circulating unit for circulating the electrically insulative liquid into the liquid chamber through a liquid flow passage communicated with the liquid chamber so that the liquid is circulatable therealong.

According to a sixth aspect of the present invention, there is provided a plasma processing apparatus as defined in the second aspect, wherein the liquid temperature adjusting unit has a heat exchange portion which is provided on a wall portion of the liquid storage vessel and which serves for heat exchange with the electrically insulative liquid stored in the liquid storage vessel, and

- a fluid stored in the heat exchange portion so as to be separable from the electrically insulative liquid is temperature-controlled by the cooling unit or the heating unit, whereby temperature of the electrically insulative liquid in the liquid storage portion is adjusted.

According to a seventh aspect of the present invention, there is provided a plasma processing apparatus as defined in the second aspect, wherein the cooling unit is an air cooling unit for air cooling an outer wall surface of the liquid storage vessel, and

- the heating unit is a heater placed inside or outside the liquid storage vessel.

According to an eighth aspect of the present invention, there is provided a plasma processing apparatus as defined in the second aspect, wherein the liquid temperature adjusting unit comprises:

- a supply portion of the electrically insulative liquid to the liquid chamber; and
- a discharge portion for discharge of liquid vapor generated by vaporization of the electrically insulative liquid from the liquid chamber, and wherein
- the electrically insulative liquid is a liquid which has a boiling point at or near an adjustment temperature of the dielectric window and the plasma-exciting coil or a temperature therearound.

According to a ninth aspect of the present invention, there is provided a plasma processing apparatus as defined in the first aspect, wherein in the liquid storage vessel, the electrically insulative liquid is stored so that the plasma-exciting coil is further immersed in the electrically insulative liquid.
According to a tenth aspect of the present invention, there is provided a plasma processing apparatus as defined in the first aspect, wherein the plasma-exciting coil is brought into close contact with the liquid chamber-side surface of the dielectric window with a pressure of the electrically insulative liquid supplied into the liquid storage vessel.
According to an eleventh aspect of the present invention, there is provided a plasma processing apparatus as defined in the tenth aspect, further comprising:

- a liquid chamber dividing member for dividing the liquid storage vessel into a first chamber to which the electrically insulative liquid is supplied, and a second chamber which is communicated with the first chamber so that the liquid supplied to the first chamber can be supplied to inside of the second chamber and in which the liquid chamber-side surface of the dielectric window and the plasma-exciting coil are placed inside; and
- a support guide member for, in the liquid chamber, supporting the liquid chamber dividing member while guiding a dividing position between the first chamber and the second chamber along a variable direction, wherein
  - the plasma-exciting coil is pressed against and brought into close contact with the surface of the dielectric window by a pressure difference between the liquid stored in the first chamber and the liquid stored in the second chamber.

According to a twelfth aspect of the present invention, there is provided a plasma processing apparatus as defined in the eleventh aspect, wherein in the second chamber of the liquid storage vessel is formed a generally spiral-shaped liquid flow passage in which gaps of the generally spirally turned plasma-exciting coil are surrounded by the liquid chamber dividing member and the dielectric window.
According to a thirteenth aspect of the present invention, there is provided a plasma processing apparatus as defined in the twelfth aspect, wherein a supply position of the electrically insulative liquid from the first chamber to the second chamber is set on a center side of the liquid flow passage so that the liquid is circulatable from center side toward outer peripheral side of the generally spiral-shaped liquid flow passage in the second chamber of the liquid storage vessel.
According to a fourteenth aspect of the present invention, there is provided a plasma processing apparatus as defined in any one of the second aspect through the thirteenth aspect, wherein the electrically insulative liquid is pure water having a resistivity of 1×10⁵Ω·cm or more.
According to a fifteenth aspect of the present invention, there is provided a plasma processing apparatus as defined in any one of the second aspect through the thirteenth aspect, wherein the electrically insulative liquid is a fluorine inert oil, a silicone oil, or organic oils and fats.
According to the first aspect or second aspect of the present invention, since the plasma processing apparatus includes a liquid storage vessel which is placed so as to confront the vacuum vessel and which is hermetically closed by the dielectric window to define in its interior a liquid storage vessel for storing therein an electrically insulative liquid, a cooling unit for the liquid and/or a heating unit, and a liquid temperature adjusting unit for adjusting temperature of the liquid stored in the liquid storage portion, the temperature of the dielectric window can be adjusted to a desired temperature by cooling or heating the plasma-exciting coil or electrode via the electrically insulative liquid.
For example, during the plasma processing on the held substrate, although the dielectric window is increased in temperature, cooling the electrically insulative liquid with the cooling unit allows the amount of heat due to the temperature increase to be eliminated from the surface of the dielectric window that is kept in contact with the electrically insulative liquid, by which temperature increase of the dielectric window can be suppressed. Such suppression of temperature increase makes it possible to suppress discharge of gas components into the processing chamber from the formed deposited film on the inner surface (i.e., a surface on the processing chamber side) of the dielectric window.
On the other hand, in the plasma non-processing state (e.g., in a standby state of the plasma processing or after completion of the plasma processing), the heating is applied to the temperature-decreased dielectric window by the heating unit, so that the temperature decrease of the dielectric window is suppressed, allowing the dielectric window to be maintained within the specified temperature range. Thus, film deposition onto the dielectric window during plasma processing is suppressed, so that adsorption of gas components in the processing chamber by the deposited film can be suppressed. Accordingly, discharge and adsorption of gas components caused by repetition of plasma processing and non-processing can be suppressed, thereby stabilizing the atmosphere in the plasma processing, so that a plasma processing of high repeatability can be achieved.
Also, since the plasma-exciting coil is placed in the liquid storage vessel in which the electrically insulative liquid shown above is to be stored, where, for example, the coil is immersed in the electrically insulative liquid, surface temperature of the coil can also be adjusted concurrently with the temperature control of the dielectric window. For instance, during the plasma processing, cooling the coil, which is increased in temperature with the application of the RF power, via the electrically insulative liquid allows the temperature increase to be suppressed. Actively lowering the surface temperature of the coil by such cooling can act to suppress increases of the substrate temperature due to infrared heating caused by excessive temperature increases of the coil so that deterioration due to thermal oxidation of the coil itself can also be prevented. The temperature adjustment for the dielectric window and the plasma-exciting coil as shown above exerts a sufficient effect even if the plasma processing time runs for 3 minutes to several hours, so that temperature changes are minimized.
Also, since such temperature control of the dielectric window and the plasma-exciting coil is performed not by conventional air ventilation but by heat transfer between the electrically insulative liquid and the dielectric window as well as the coil with the use of the electrically insulative liquid that is brought into contact with the dielectric window and the coil, it becomes implementable to improve efficiency and controllability of this temperature control depending on the improvement of heat transferability as well as on the temperature stability by the heat capacity of a high volume of the liquid against the intermittent plasma heating.
Further, in the plasma processing apparatus of the first aspect or second aspect, not that the cooling of the coil and the dielectric window is performed not by mechanically ventilating air around the coil (taking in fresh air from apparatus outside and discharging the ambient air to apparatus outside), as in the conventional plasma processing apparatus, but that the cooling or the like of the coil or the like is performed by adjusting the temperature of the electrically insulative liquid stored in the liquid storage vessel in which the coil is placed inside thereof. Accordingly, there occurs neither separation nor combination of oxygen molecules in the air due to corona discharge or ultraviolet rays in the air, and therefore there does not occur generation of ozone. Consequently, the health problem of the operator can be improved, and acceleration of deterioration of the apparatus and the component parts of peripheral units due to the diffusion of ozone can be prevented reliably.
According to the third aspect of the invention, the liquid storage vessel is formed as a space surrounded by an inner wall of the electrical conductor of ground potential and an outer surface of the dielectric window, and the plasma-exciting coil is housed in the liquid storage vessel. Accordingly, the liquid storage vessel can be formed as one which is completely hermetically closed with a simple construction and which serves also for ground shielding. Thus, there can be provided a plasma processing apparatus which is small in size and free from leakage of electromagnetic waves.
According to the fourth aspect of the invention, the liquid storage vessel is formed of a dielectric material, and a continued liquid flow passage formed by the liquid storage vessel and the dielectric window is provided as the liquid storage vessel. Thus, there can be provided a state that the liquid flow passage is formed inside one integrated dielectric window in which the liquid storage vessel and the dielectric window are integrated together. Even when the dielectric window has a large-aperture planar shape and has enough thickness to withstand atmospheric pressure, the distance between one surface of the dielectric window on the plasma processing chamber side and the liquid flow passage can be made smaller, thus making it possible to provide a plasma processing apparatus of high cooling and heating performance.
Also, since the plasma-exciting coil or the electrode is placed within the flow passage formed inside the dielectric window as shown above, the coil can be made closer to the inside of the processing chamber, as compared with the case where the coil is placed outer than the outer surface of the dielectric window, so that high-density plasma excitation can be fulfilled.
According to the other aspect of the invention, since the electrically insulative liquid is pure water having a large specific heat and electrical insulation property, there can be provided a plasma processing apparatus which has all of the electrical insulation property necessary for contact with the induction coil, an availability, successful handlability and safety and which is successful in handlability as a whole of the apparatus and high in practicability. Further, a dielectric constant of the pure water as large as about 70, although causing a somewhat large dielectric loss, acts to increase the electrostatic field effect for plasma excitation, thus providing a plasma processing apparatus of good ignitability.
Further, since the electrically insulative liquid is a fluorine inert oil, or a silicone oil having not only electrical insulation property but also properties of nonflammability, chemical inertness and a wide temperature range of usability, using the electrically insulative liquid in a closed circuit makes its applicability to the plasma processing apparatus more successful.
Further, since the liquid temperature adjusting unit is placed outside the liquid storage portion and since the plasma processing apparatus further comprises a liquid flow passage communicated with the liquid storage portion and a liquid circulating unit for circulating the electrically insulative liquid through the liquid flow passage, the degree of freedom for the installation of the liquid temperature adjusting unit can be enhanced, so that the cooling or heating performance can be enhanced. As such a liquid temperature adjusting unit shown above, applicable are commercially available articles called chiller, circulator or thermostat, producing an advantage of high availability.
Further, the liquid storage portion has a generally closed small capacity so that the storage volume of the electrically insulative liquid (e.g., electrically insulative fluorine inert oil or organic oils) to be stored in the liquid storage portion is made small, thus allowing the cost therefor to be reduced. Also, such a small capacity of the liquid storage portion makes it unlikely to occur that the stored electrically insulative liquid may leak. Further, in the heat exchange unit, the fluid to be stored so as to be separable from the electrically insulative liquid may be a fluid having no electrically insulation property, e.g. water (one other than pure water), instead of the electrically insulative liquid, allowing the cost required for the electrically insulative liquid to be reduced also from such a viewpoint.
Further, since there is no need for providing the liquid temperature adjusting unit of separate installation outside the liquid storage portion, the liquid temperature adjusting unit can be integrated compactly with the liquid storage portion. Thus, there can be provided a plasma processing apparatus which is small in size, small in the cost for the electrically insulative liquid and less liable to leakage or other troubles.
Further, since the electrically insulative liquid is a liquid which has a boiling point at a desired temperature, i.e., a temperature generally coincident with an adjustment temperature of the dielectric window and the plasma-exciting coil or the electrode, the need for providing any special cooling mechanism in the liquid temperature adjusting unit is eliminated, and latent heat of vaporization of the liquid itself is used. Thus, there can be provided a plasma processing apparatus which is capable of high cooling power and has a small-size, simple construction.
Further, the liquid is stored in such a fashion that not only the dielectric window is improved in the liquid but also the plasma-exciting coil as well is immersed therein, occurrence of ozone or the like that would be caused by the application of RF power with the plasma-exciting coil placed in the atmospheric air as in the prior art can reliably be prevented.
Further, since the plasma-exciting coil can be brought into close contact with the surface of the dielectric window with a pressure of the liquid supplied to the liquid storage portion, applying RF power to the coil in the close contact state makes it possible to induce a high voltage to a processing-chamber side surface of the dielectric window. Thus, it becomes easier to start or maintain discharge even with low pressure in the processing chamber.
Furthermore, the cooling or heating of the coil can be executed reliably and stably, and moreover the cooling or heating of the dielectric window can be executed uniformly.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects and features of the present invention will become clear from the following description taken in conjunction with the preferred embodiments thereof with reference to the accompanying drawings, in which:
FIG. 1 is a schematic sectional view of a plasma processing apparatus according to a first embodiment of the present invention;
FIG. 2 is a schematic sectional view of a plasma processing apparatus according to a second embodiment of the present invention;
FIG. 3 is a schematic sectional view of a plasma processing apparatus according to a modification example of the second embodiment of the present invention;
FIG. 4 is a sectional view taken along the line A-A in the plasma processing apparatus of FIG. 3;
FIG. 5 is a schematic sectional view of a plasma processing apparatus according to a third embodiment of the present invention;
FIG. 6 is a schematic sectional view of a plasma processing apparatus according to a fourth embodiment of the present invention;
FIG. 7 is a schematic sectional view of a plasma processing apparatus according to a fifth embodiment of the present invention;
FIG. 8 is a schematic sectional view of a plasma processing apparatus according to a sixth embodiment of the present invention;
FIG. 9 is a schematic sectional view of a plasma processing apparatus showing a state in which part of coil is exposed from a liquid level of the cooling/heating medium liquid stored in a liquid chamber in the plasma processing apparatus of the sixth embodiment;
FIG. 10 is a schematic sectional view (partial view) of a plasma processing apparatus according to a prior art example; and
FIG. 11 is a schematic sectional view of a plasma processing apparatus according to another prior art example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before the description of the present invention proceeds, it is to be noted that like parts are designated by like reference numerals throughout the accompanying drawings.
Hereinbelow, embodiments of the present invention are described in detail with reference to the accompanying drawings.

First Embodiment

A schematic sectional view of a plasma processing apparatus 800 which is an example of a plasma processing apparatus according to a first embodiment of the present invention is shown in FIG. 1.
As shown in FIG. 1, the plasma processing apparatus 800 is equipped with a vacuum vessel 801 which has an opening at the top thereof and generally cylindrical shaped, and a dielectric window (quartz plate) 802 which is formed of a generally disc-shaped dielectric material (e.g., quartz) and which is provided so as to close the opening at the top of the vacuum vessel 801, where a processing chamber 803 is formed which is a space closed by the vacuum vessel 801 and the dielectric window 802 and a space where plasma processing is performed.
Further, as shown in FIG. 1, the vacuum vessel 801 is divided into a lower vacuum vessel 801 b, which is a lower part of the generally cylindrical-shaped bottomed member, and an upper vacuum vessel 801 a, which is its upper portion and annular shaped, where the vacuum vessel 801 is constructed by coupling the upper vacuum vessel 801 a and the lower vacuum vessel 801 b to each other. In addition, a seal member, for example, an O-ring 828 is placed at the mutual coupling portion of the upper vacuum vessel 801 a and the lower vacuum vessel 801 b, so that airtightness at the coupling portion is ensured.
Also, the plasma processing apparatus 800 has a plurality of reactant gas supply holes 4, an example of the reactant gas supply portion, which are provided in upper portion of the inner side face of the upper vacuum vessel 801 a of the vacuum vessel 801 and which serve for introducing a specified reactant gas into the vacuum vessel 801, and a vacuum pump 13, an example of the evacuator, which is connected to a gas outlet 13 a provided at an inner side face of the lower vacuum vessel 801 b of the vacuum vessel 801 by means of a discharge passage 13 b and which serves for discharging air or gas present in the vacuum vessel 801 (i.e., in the processing chamber 803). Further, near the top of the dielectric window 802, a coil 805 (or plasma-exciting coil 805), which is an example of the plasma-exciting coil formed in spiral shape (helical shape) of a flat-shaped conductor having a rectangular cross section are arranged along the outer side face of the dielectric window 802 (i.e., a surface of the dielectric window 802 opposite to its surface confronting the processing chamber 803 so that the coil is placed so as to confront the processing chamber 803 via the dielectric window 802), and a coil-use RF power supply 806 for applying RF power to the coil 805 via a matching box 818 is provided outside the vacuum vessel 801. Further, a lower electrode 7 which is an example of the substrate electrode is provided near a generally center in the vacuum vessel 801, and a lower-electrode use RF power supply 8 for applying RF power to the lower electrode 7 via a matching box 19 is provided outside the vacuum vessel 801. Besides, a substrate 9 which is to be subjected to plasma processing by the plasma processing apparatus 800 is held on the lower electrode 7 within the vacuum vessel 801.
Also, as shown in FIG. 1, a ground shield vessel 810 (or an upper electrode casing 810) formed of an electrical conductor (a conductive material such as aluminum alloy) of ground potential is fixedly provided at an upper portion of the upper vacuum vessel 801 a of the vacuum vessel 801 so as to cover the entire coil 805 placed near the outer surface of the dielectric window 802. Further, near a generally center of this ground shield vessel 810, a center electrode 814 connected to the coil-use RF power supply 806 via the matching box 818 is fitted via an insulating bushing 815 so as not to make electrical contact with the ground shield vessel 810. This center electrode 814 is connected to a center-end of the spiral-shaped coil 805 via an application terminal 816. Also, an outer-end of the coil 805 is connected to the ground shield vessel 810 via a grounding terminal 817, and the ground shield vessel 810 is connected to a ground pole of the coil-use RF power supply 806. Thus, it is implementable to apply RF power to the coil 805 from the coil-use RF power supply 806 through the center electrode 814 and the application terminal 816. In addition, the coil 805, the center electrode 814, the application terminal 816 and the grounding terminal 817 are each plated with, for example, gold. A casing 819 for placing the matching box 818 inside thereof is fitted at an outer upper portion of the ground shield vessel 810 to eliminate the amount of heat generated from the matching box 818, and a cooling fan 860 for mechanically ventilating air inside the casing 819 is set in the casing 819.
Further, as shown in FIG. 1, in the state that the dielectric window 802 is placed so as to cover the opening portion at the top of the vacuum vessel 801, fixing the ground shield vessel 810 to the top of the vacuum vessel 801 allows the dielectric window 802 of the above placement to be fixed in that placement. Besides, with the dielectric window 802 fixed as shown above, the inside space of the ground shield vessel 810 is closed by the outer side surface of the dielectric window 802 (i.e., a surface of the dielectric window 802 opposite to its surface confronting the processing chamber), and a space in which the coil 805 is placed inside is formed. This space allows a cooling/heating medium liquid, which is an example of electrically insulating liquid, to be stored therein as will be described later, where the space serves as a liquid chamber 820, which is an example of the liquid storage portion, and further this ground shield vessel 810 closed by the dielectric window 802 is an example of the liquid storage vessel. Also, a lower-side surface of the dielectric window 802, as viewed in the figure, is a processing chamber-side surface (gas-seal-side surface) while its outside side surface is a liquid chamber closure-side surface (liquid-seal-side surface).
Further, as shown in FIG. 1, inside of this liquid chamber 820 is placed a disc-shaped coil holding plate 850 in which in its lower surface are formed recess portions 850 a to be engaged with upper portions of the spiral-shaped coil 805, as viewed in the figure, which is to be placed on the outer surface of the dielectric window 802. That is, the coil 805 is placed on the outer surface of the dielectric window 802 in the liquid chamber 820 in a state that the coil 805 is held to the lower surface of the coil holding plate 850, as viewed in the figure, so that its spiral shape is defined. Further, the coil holding plate 850, which is so formed that its disc-shaped external shape is generally equal in size to the shape of the inner side face of the ground shield vessel 810, is placed slidably along the side wall (peripheral face) of the liquid chamber 820. By guide bolts 851, which are examples of support guide members fixed to an inner top plate of the ground shield vessel 810, the coil holding plate 850 is supported so as to be guidable for its vertical move (i.e., sliding as described above) as viewed in the figure, where the coil holding plate 850 is prevented by this support from rotating and loosening off inside the ground shield vessel 810. Further, each of bias springs 852 is attached to each of the guide bolts 851, and the bias springs 852 have a function of normally biasing the coil holding plate 850 toward the dielectric window 802 along the guide bolts 851 placed in the vertical direction as viewed in the figure.
By the coil holding plate 850 and the coil 805 being placed in the liquid chamber 820 as shown above, the liquid chamber 820 is divided by the coil holding plate 850 into two chambers, an upper chamber 820 a, which is an example of a first chamber, and a lower chamber 820 b, which is an example of a second chamber. That is, in this first embodiment, the coil holding plate 850 is an example of a liquid chamber dividing member which divides the liquid chamber 820 into the two chambers. Also, by the coil holding plate 850 being made variable in its support position, the dividing position of the two chambers is made variable with, for example, external force imparted.
The upper chamber 820 a and the lower chamber 820 b are communicated with each other by through hole 850 a formed at a generally center of the coil holding plate 850. Further, in the lower chamber 820 b, since a lower surface of the coil 805 held to the coil holding plate 850 is kept in contact with the outer surface of the dielectric window 802, a space (spiral-shaped gap) of the spiral-shaped coil 805 is surrounded by the lower surface of the coil holding plate 850 and the outer surface of the dielectric window 802, as viewed in the figure, by which a spiral-shaped liquid flow passage 854 for the cooling/heating medium liquid is formed. That is, in the liquid chamber 820, the upper chamber 820 a is communicated through the through hole 850 a with center portion of the spiral-shaped liquid flow passage 854 formed in the lower chamber 820 b.
Moreover, in the ground shield vessel 810, a cooling/heating medium liquid supply hole 810 b to the upper chamber 820 a as well as a cooling/heating medium liquid discharge hole 810 a which is communicated with outer-peripheral end portions of the spiral-shaped passage 854 in the lower chamber 820 b and which is derived from the passage 854 are formed so as to extend through a side wall of the ground shield vessel 810. Thus, by virtue of the formation of the supply hole 810 b and the discharge hole 810 a for the cooling/heating medium liquid, a continued flow passage for the cooling/heating medium liquid is formed in the liquid chamber 820 so that the cooling/heating medium liquid supplied from the supply hole 810 b into the upper chamber 820 a flows into the lower chamber 820 b through the through holes 850 a, the cooling/heating medium liquid then being made to flow from the center toward the outer peripheral end portion of the spiral liquid flow passage 854, by which the cooling/heating medium liquid can be discharged through the discharge hole 810 a at the outer peripheral end portion. By virtue of the formation of such a continued liquid flow passage, temperature of the dielectric window 802, and the coil 805 can be adjusted by adjusting the temperature of the cooling/heating medium liquid to be put into flow.
Also, as shown in FIG. 1, a liquid flow passage 823 which allows the cooling/heating medium liquid to flow therethrough is formed inside the lower electrode 7, so that the lower electrode 7 can be maintained at a desired temperature by making the cooling/heating medium liquid, which has been adjusted to a desired temperature, flow from a supply hole 823 b, which is one end of the liquid flow passage 823, to a discharge hole 823 a, which is the other end.
Further, a cooling/heating medium liquid flow passage 853 formed in, for example, an annular shape is formed also in the upper vacuum vessel 801 a of the vacuum vessel 801, and a supply hole 853 b and a discharge hole 853 a for the cooling/heating medium liquid are formed in the liquid flow passage 853. The cooling/heating medium liquid that has been adjusted to a desired temperature is circulated so as to be supplied into the liquid flow passage 853 through the supply hole 853 b and discharged from the liquid flow passage 853 through the discharge hole 853 a, thus allowing the temperature in the processing chamber 803 to be adjusted through the inner side face of the upper vacuum vessel 801 a.
Further, a liquid flow passage 822, which is an example of the liquid flow passage that makes these supply holes 810 b, 853 b and 823 b communicated with the discharge holes 853 a, 823 a, and the liquid flow passage 822, and also makes discharge hole 810 a communicated with liquid flow passage 822 is provided so as to be connected to a chiller unit 821. The chiller unit 821 includes: a refrigerator (an example of the cooling unit) for cooling the cooling/heating medium liquid; a heater (an example of the heating unit) for heating the cooling/heating medium liquid; a cooling/heating medium liquid tank for storing therein the cooling/heating medium liquid; a pump which is an example of the liquid circulating unit for supplying (circulating) the cooling/heating medium liquid; a water/air cooling unit for eliminating heat generated by cooling operation of the refrigerator; a temperature control unit 821 a for controlling temperature of the cooling/heating medium liquid to a desired temperature by controlling operations of the above individual constituent sections; and a temperature sensor 821 b for detecting a temperature of the cooling/heating medium liquid and outputting the detected temperature to the temperature control unit 821 a. The chiller unit 821 constructed as shown above has both a function of adjusting (controlling) the temperature of the cooling/heating medium liquid to a desired temperature by cooling or heating the cooling/heating medium liquid, and a function of supplying the temperature-controlled cooling/heating medium liquid into the liquid chamber 820 or the like through the liquid flow passage 822 and moreover circulating and collecting the cooling/heating medium liquid, which has been stored in the liquid chamber 820 or the like, through the liquid flow passage 822.
More specifically, as shown in FIG. 1, a continued circulatory flow passage by the liquid flow passage 822 is formed so that the cooling/heating medium liquid fed out from the chiller unit 821 through the liquid flow passage 822 is supplied to the liquid flow passage 823 within the lower electrode 7, the cooling/heating medium liquid discharged from the liquid flow passage 823 is supplied into the liquid flow passage 853 in the upper vacuum vessel 801 a through the liquid flow passage 822, and that the cooling/heating medium liquid discharged from the liquid flow passage 853 is supplied into the liquid chamber 820 through the liquid flow passage 822, and the cooling/heating medium liquid discharged from the liquid chamber 820 is returned again to the chiller unit 821 through the liquid flow passage 822.
In FIG. 1, although the above description has been made on a case where the temperature sensor 821 b is placed near the outlet of the cooling/heating medium liquid in the chiller unit 821, yet the placement of the temperature sensor 821 b is not limited only to such a case. For example, the case may be that the temperature sensor 821 b is placed in the inner tank for the cooling/heating medium liquid or the like in the chiller unit 821, or that the temperature sensor 821 b is placed within the liquid chamber 820 so that the temperature of the cooling/heating medium liquid in the liquid chamber 820 can be detected.
The cooling/heating medium liquid as shown above may be selected from among, for example, fluorine inert oil typified by Fluorinert or Galden (both trade name or trademark), silicone oil, pure water, or insulating oils such as organic oils and fats. These liquids, having electrical insulation property, have a feature that there never occur short-circuits or current leakages even if they make contact with the coil 805 which is formed of a conductive material and to which RF power is applied. Further, those liquids, because of each being also a dielectric, are enabled to enhance an electrostatic field generated inside the processing chamber 803 via the dielectric window 802. In addition, as the pure water mentioned above, one having a resistivity of 1×10⁵Ω·cm or more is used to ensure its electrical insulation property.
Also, in the plasma processing apparatus 800, at a junction portion between the dielectric window 802 and the vacuum vessel 801, a junction portion between the vacuum vessel 801 and the ground shield vessel 810, and a junction portion between the aforementioned upper vacuum vessel 801 a and the lower vacuum vessel 801 b, O- rings 826, 827 and 828 are provided, respectively, so that airtightness of the processing chamber 803 and the liquid chamber 820 is ensured.
Further, the plasma processing apparatus 800 is provided with a control unit 90 for performing integrated control by associating one with another of individual operation controls for an RF power application operation by the coil-use RF power supply 806, an RF power application operation by the substrate-electrode use RF power supply 8, and an evacuation operation by the vacuum pump 13. By the integrated control performed by such a control unit 90, it is made implementable to perform plasma processing on the substrate 9 placed on the lower electrode 7. In addition, temperature adjustment operation for the cooling/heating medium liquid by the chiller unit 821 (i.e., temperature control operation by the temperature control unit 821 a) is autonomously performed in the chiller unit normally.
Now a method for performing plasma processing on the substrate 9 by the plasma processing apparatus 800 having a construction described above is explained. It is noted that individual operations shown below are performed while associated with one another as integrated control by the control unit 90.
Referring first to FIG. 1, the substrate 9 which is a processing object to be plasma-processed is placed on the lower electrode 7 in the vacuum vessel 801. Next, with the processing chamber 803 closed, air or gas in the processing chamber 803 is discharged through the gas outlet 13 a and the gas discharge passage 13 b by the vacuum pump 13, and subsequently a specified reactant gas is supplied from an unshown reactant gas supply unit through respective reactant gas supply holes 4 while interior of the processing chamber 803 is maintained at a specified pressure by adjusting the discharge flow rate with a discharge flow regulating valve (not shown) provided on the way of the gas discharge passage 13 b or other means.
Along with this, the cooling/heating medium liquid is circulated through the liquid flow passage 822 so that the cooling/heating medium liquid controlled to a specified temperature by the chiller unit 821 is supplied sequentially to the liquid flow passage 823 within the lower electrode 7, the liquid flow passage 853 within the upper vacuum vessel 801 a, and the liquid chamber 820 and moreover the supply cooling/heating medium liquid is collected to the chiller unit 821 through the liquid flow passage 822. By this circulation of the cooling/heating medium liquid, in the liquid chamber 820, the cooling/heating medium liquid is supplied from the liquid flow passage 822 through the supply hole 810 b into the upper chamber 820 a, this supplied cooling/heating medium liquid then flowing through the through hole 850 a into the lower chamber 820 b and further circulated from the central side toward the peripheral end portion side in the spiral liquid flow passage 854, thus discharged through the discharge hole 810 a to the liquid flow passage 822. By the cooling/heating medium liquid being circulated in the liquid chamber 820 as shown above, the coil holding plate 850 is biased toward the dielectric window 802 by the pressure difference of the cooling/heating medium liquid supplied into the upper chamber 820 a and the lower chamber 820 b.
The coil holding plate 850, while supported by the guide bolts 851, is normally biased at its support position toward the dielectric window 802 by the bias springs 852 so that the coil 805 is normally biased to the surface of the dielectric window 802. However, there are some cases where the coil 805 is not completely brought into contact with the surface of the dielectric window 802 due to manufacture precision or the like of the dielectric window 802 or the coil 805 or the coil holding plate 850. Yet, in such a case, slightly moving the support position of the coil holding plate 850 toward the dielectric window 802 side by biasing the coil holding plate 851 with the liquid pressure of the cooling/heating medium liquid having a force larger than the biasing force by the bias spring 852 allows the coil 805 held to the lower face of the coil holding plate 850 as viewed in the figure to be pressed against the outer surface of the dielectric window 802 so as to be brought into close contact therewith. Also, the pressing force of the coil 805 against the dielectric window 802 can be made generally uniform over the spiral-shaped contact surface by the coil 805 being pressed via the coil holding plate 850 with the pressure difference of the cooling/heating medium liquid supplied to the upper chamber 820 a and the lower chamber 820 b. From such a point of view, desirably, size and configuration of the through hole 850 a, the circulation flow rate of the cooling/heating medium liquid and the like are determined so as to generate a pressure difference that allows a necessary sufficient biasing force to be generated.
While this state is maintained, a specified RF power is applied from the coil-use RF power supply 806 to the coil 805 via the matching box 818, the center electrode 814 and the application terminal 816. As a result of this, an electromagnetic field is imparted from the coil 805 via the dielectric window 802 to the reactant gas in the processing chamber 803, so that electrons in the reactant gas molecules are accelerated and a plasma is excited to a plasma processing region R1 in the processing chamber 803. When this occurs, RF power is applied simultaneously also to the lower electrode 7 from the lower-electrode use RF power supply 8 via the matching box 19, thus' making it possible to control ion energy that reaches the substrate 9. With the plasma excited in this way, plasma processing such as etching, deposition or surface reforming can be carried out on the substrate 9 placed on the lower electrode 7.
Also, since the cooling/heating medium liquid adjusted to a specified temperature by the chiller unit 821 is circulated through the liquid flow passage 822, the dielectric window 802 and the coil 805 that are increased in temperature by the plasma processing can be cooled and their respective temperatures can be maintained within a specified temperature range while the plasma processing is carried out.
It is noted here that the term “specified temperature range” refers to such a temperature range that during plasma processing, formation of a deposited film, which is a deposit, can be suppressed and moreover the deposited film is prevented from coming off (peeling off) due to keep the dielectric window 802 in high temperature by reducing the amount of deposition of a thin film formed by deposition of reaction products onto the inner surface of the dielectric window 802.
Similarly, by the circulation of the cooling/heating medium liquid, the temperature of the lower electrode 7 can be maintained within a specified temperature range so that the substrate 9 to be processed, which would be increased in temperature by the plasma processing, is maintained at a suitable temperature during the plasma processing. Further, by the circulation of the cooling/heating medium liquid to the liquid flow passage 853 within the upper vacuum vessel 801 a, the temperature of the inner surface of the processing chamber 803 can be maintained within a specified temperature range so that plasma processing can be carried out while the formation of the deposited film is suppressed.
Even in a plasma non-processing state, by the cooling/heating medium liquid, which has been controlled to a desired temperature by the chiller unit 821, to the liquid chamber 820, the temperature of the dielectric window 802 can be maintained within the specified temperature range. In such a case, even in the plasma non-processing state, the temperature of the dielectric window 802 can be maintained within the specified temperature range, so that temperature changes due to repetition of plasma processing and plasma non-processing, i.e., the deposited film formed on the dielectric window 802 can be prevented from application of the heat cycle, so that the deposited film can be prevented from peeling off due to the heat cycle.
According to the first embodiment, various working effects as shown below can be obtained.
First, since the cooling/heating medium liquid controlled to a desired temperature can be circulated in the liquid chamber 820 formed so as to be surrounded by the outer surface of the dielectric window 802 and the inner surface of the ground shield vessel 810, the outer surface of the dielectric window 802 with which the cooling/heating medium liquid is put into contact can be cooled or heated through the cooling/heating medium liquid. More specifically, during the plasma processing, performing the cooling for the dielectric window 802 that is increased in temperature allows the temperature increase of the dielectric window 802 to be suppressed. Such suppression of temperature increase makes it possible to suppress discharge of gas components from the formed deposited film into the processing chamber 803. Further, in the plasma non-processing state, execution of heating on the dielectric window 802, which is decreased in temperature, makes it possible to suppress the temperature decrease of the dielectric window 802, so that the dielectric window 802 can be maintained within the specified temperature range. As a result of this, it becomes possible to prevent the deposited film from absorbing gas components in the processing chamber 803 or to prevent occurrence of film deposition on the inner surface of the dielectric window 802 at starting of the next-time plasma processing.
Accordingly, discharge and adsorption of gas components caused by repetition of plasma processing and non-processing can be suppressed, thereby stabilizing the atmosphere of the plasma processing region R1, so that a plasma processing of high repeatability can be achieved. Also, it becomes possible to prevent the deposited film stuck to the inner surface of the dielectric window 802 from peeling off due to the heat cycle, which would lead to failures of the processing-object substrate due to attaching dust or particles.
Further, since the coil 805 is placed within the lower chamber 820 b of the liquid chamber 820 through which the cooling/heating medium liquid is circulated and immersed in the cooling/heating medium liquid as shown above, surface temperature of the coil 805 as well as the dielectric window 802 can be controlled concurrently. More specifically, during the plasma processing, cooling the coil 805, which is increased in temperature with application of RF power, via the cooling/heating medium liquid allows the temperature increase to be suppressed. Actively lowering the surface temperature of the coil 805 by such cooling can prevent the processing-object substrate from being heated by infrared rays radiated by the increased surface temperature of the coil 805. Effects of the temperature adjustment for the dielectric window 802 and the coil 805 as shown above will never be impaired even if the plasma processing time runs for 3 minutes to several hours, so that temperature changes can be suppressed to the least.
Also, since the liquid chamber 820 is divided into the upper chamber 820 a and the lower chamber 820 b by the coil holding plate 850, which holds the coil 805, and since the cooling/heating medium liquid flow passage is so made up that the cooling/heating medium liquid supplied to the upper chamber 820 a is let to flow into the lower chamber 820 b, the coil holding plate 850 can be biased toward the lower chamber 820 b with the pressure difference of the cooling/heating medium liquid supplied to the upper chamber 820 a and the lower chamber 820 b so that the spiral coil 805 can be pressed against the surface of the dielectric window 802 with a uniform force so as to be brought into contact with the surface. Thus, by bringing the coil 805 into close contact with the surface of the dielectric window 802 like this, an RF high voltage applied to the coil 805 can be dielectrically led to one surface of the dielectric window 802 on the processing chamber 803 side, making it easier to start or maintain discharge even with low pressure. Accordingly, a strong electromagnetic field inducing effect by the coil 805 can be produced in the processing chamber 803, making it possible to provide a plasma processing apparatus which is capable of implementing discharge with low pressure, obtaining high plasma density and enhancing the etching rate.
Further, in the lower chamber 820 b of the liquid chamber 820, the liquid flow passage 854 is formed between the spiral-shaped coil 805 and so arranged that the cooling/heating medium liquid is circulated from the center side toward the outer peripheral end portion of the liquid flow passage 854. Thus, the dielectric window 802 and the coil 805 can be cooled or heated generally uniformly, allowing temperature control to be fulfilled with high temperature controllability.
Further, in the case where, for example, fluorine inert oil is used as the cooling/heating medium liquid described above, by virtue of its having high electrical insulating property, there occurs no current leakage or the like even if the coil 805 is immersed directly in the fluorine inert oil, so that its safety is ensured. Moreover, such fluorine inert oil, having a feature of a wide temperature range for usability, can be said to be suitable for temperature control of the dielectric window 802 or the like from a temperature below the freezing point until a temperature around 200° C. Still, since the fluorine oil is also a dielectric, a strong electrostatic field can be imparted into the processing chamber 803 through the fluorine inert oil and the dielectric window 802 with application of the RF power of the immersed coil 805, so that a successful ignitability of plasma can be obtained.
Further, since the spiral coil 805, the application terminal 816, the grounding terminal 817 and the center electrode 814 are plated at their surfaces with gold, and not with silver that has conventionally been used, corrosion and electrolytic corrosion can be prevented from occurring to the surface of the coil 805 or the like due to the application of the RF voltage and moisture contents or the like of the cooling/heating medium liquid.
In the conventional plasma processing apparatus 500, 600, cooling would be performed by mechanically ventilating air around the coil 505, 605 (taking in fresh air from apparatus outside and discharging the ambient air to apparatus outside). Instead, in the plasma processing apparatus 800 of the first embodiment, the cooling or the like of the coil 805 or the like is performed by using the closed-system circulatory path which is formed so as to be surrounded by the outer surface of the dielectric window 802 and the ground shield vessel 810 and which is made up of the liquid chamber 820 with the coil 805 placed inside, the liquid flow passage 822 and the chiller unit 821. Accordingly, there never occurs generation of ozone or the like or diffusion of the ozone to the apparatus outside due to the cooling. Consequently, the health problem of the operator can be improved, and acceleration of deterioration of the apparatus and the component parts of peripheral units due to the diffusion of ozone can be prevented reliably.

Second Embodiment

It is noted here that the present invention is not limited to the foregoing embodiment, and may be carried out in other various aspects. For instance, FIG. 2 shows a schematic sectional view of a plasma processing apparatus 100 which is an example of a plasma processing apparatus according to the second embodiment of the present invention. As shown in FIG. 2, the plasma processing apparatus 100 is different in construction from the plasma processing apparatus 800 of the first embodiment structurally in terms of having not the disc-shaped dielectric window 802 but a generally hemispherical-shell shaped dielectric window 2, but generally similar in construction to the plasma processing apparatus 800 in terms of the other structural components unrelated to the form of the dielectric window 2. The following description is given about this different construction. In addition, for an easier understanding of the description, constituent parts similar to those of the plasma processing apparatus 800 of the first embodiment are designated by like reference numerals in the plasma processing apparatus 100, and their description is omitted.
As shown in FIG. 2, the plasma processing apparatus 100 is equipped with a vacuum vessel 1, and bell jar (an example of the dielectric window) 2 formed of a generally hemispherical-shell shaped (or dome-shaped) dielectric material (e.g., quartz) provided so as to close an opening portion at the top of the vacuum vessel 1, where a processing chamber 3 is formed which is a space closed by the vacuum vessel 1 and the bell jar 2 and a space where plasma processing is performed.
Further, the plasma processing apparatus 100 has a plurality of reactant gas supply holes 4 provided at upper portions of a side face of the vacuum vessel 1, and a vacuum pump 13 which is connected to a gas outlet 13 a of the vacuum vessel 1 by means of a discharge passage 13 b and which serves for discharging air or gas present in the vacuum vessel 1 (i.e., in the processing chamber 3). Also, near the top of the bell jar 2, a coil 5 which is an example of the plasma-exciting coil formed of a wire conductor in a spiral shape is placed along an outer surface of the bell jar 2, and a coil-use RF power supply 6 for applying RF power to the coil 5 via a matching box 18 is provided outside the vacuum vessel 1. Further, a lower electrode 7 is provided near a generally center in the vacuum vessel 1, and a lower-electrode use RF power supply 8 for applying RF power to the lower electrode 7 via a matching box 19 is provided outside the vacuum vessel 1. A substrate 9 which is to be subjected to plasma processing by the plasma processing apparatus 100 is held on the lower electrode 7 within the vacuum vessel 1.
Also, as shown in FIG. 2, a ground shield vessel 10 (an example of the liquid storage vessel) formed of an electrical conductor (a conductive material) of ground potential is fixedly provided at an upper portion of the vacuum vessel 1 so as to cover the entire coil 5 placed near the outer surface of the bell jar 2. Further, near a generally center of this ground shield vessel 10, a center electrode 14 connected to the coil-use RF power supply 6 via the matching box 18 is fitted via an insulating bushing 15 so as not to make electrical contact with the ground shield vessel 10. This center electrode 14 is connected to an end portion of the center portion of the spiral-shaped coil 5 via an application terminal 16. Also, an end portion of the coil 5 on the outer peripheral side is connected to the ground shield vessel 10 via a grounding terminal 17, and the ground shield vessel 10 is connected to a ground pole of the coil-use RF power supply 6. Thus, it is implementable to apply RF power to the coil 5 from the coil-use RF power supply 6 through the center electrode 14 and the application terminal 16.
Further, as shown in FIG. 2, a space which is surrounded by the inner side of the ground shield vessel 10, the outer surface that is part of the bell jar 2 and the upper portion of the vacuum vessel 1 and in which the coil 5 is placed inside is defined as a liquid chamber 20, which allows a cooling/heating medium liquid to be stored therein. Besides, a discharge hole 10 a for the cooling/heating medium liquid derived from the inside of the liquid chamber 20 is formed near the upper portion of the ground shield vessel 10, and a supply hole 10 b of the cooling/heating medium liquid to the inside of the liquid chamber 20 is formed near a lower portion of the ground shield vessel 10.
These supply hole 10 b and discharge hole 10 a are connected to an upper-portion side chiller unit 21 through a passage 22, which is an example of the liquid flow passage, so that the cooling/heating medium liquid is circulatable therethrough. The upper-portion side chiller unit 21 is equipped with a cooling unit, heating unit, a pump, a temperature control unit 21 a for controlling temperature of the cooling/heating medium liquid to a desired temperature, and a temperature sensor 21 b for detecting a temperature of the cooling/heating medium liquid and outputting the detected temperature to the temperature control unit 21 a. The upper-portion side chiller unit 21 constructed as shown above is enabled to cool or heat the coil 5 and the bell jar 2 via the cooling/heating medium liquid to maintain them at a desired temperature, thus the upper-portion side chiller unit 21 being an example of the liquid temperature adjusting unit for the cooling/heating medium liquid.
Also, as shown in FIG. 2, a liquid flow passage 23 which allows the cooling/heating medium liquid to pass therethrough is formed inside the lower electrode 7, and a lower-portion side chiller unit 25 is connected to the liquid flow passage 23 via a passage 24. This lower-portion side chiller unit 25, which is similar in construction to the upper-portion side chiller unit 21, has a temperature control unit 25 a, a temperature sensor 25 b and the like, and is enabled to maintain the lower electrode 7 at a desired temperature by circulating within the liquid flow passage 23 the cooling/heating medium liquid that has been controlled to a desired temperature through the cooling/heating medium liquid passage 24.
Also, in the plasma processing apparatus 100, at a junction portion between the bell jar 2 and the vacuum vessel 1 and a junction portion between the vacuum vessel 1 and the ground shield vessel 10, O- rings 26, 27 are provided, respectively, so that airtightness of the processing chamber 3 and the liquid chamber 20 is ensured.
Further, the plasma processing apparatus 100 is provided with a control unit 90 for performing integrated control by associating one with another of individual operation controls for the aforementioned respective constituent sections to thereby control the plasma processing operation.
Here is described a working example showing various conditions in such a plasma processing. For example, in a case where via holes are etched to a depth of 100 μm in an InP (Indium-Phosphorus) substrate employed as the substrate, HI gas and Ar gas as reactant gases are supplied into the processing chamber 3 at a supply flow rate of 100 sccm (100 cc/min. in a normal state), and while the vacuum pressure is held at 1 Pa, an RF power of a 13.56 MHz frequency and a 1000 W output power is applied to the coil 5 by the coil-use RF power supply 6, and an RF power of a 13.56 MHz frequency and a 100 W output power is applied to the lower electrode 7 by the lower-electrode use RF power supply 8, by which the plasma processing is performed on the substrate 9 held on the lower electrode 7. In this case, with Galden used as the cooling/heating medium liquid, this Galden is circulated at 2 l/min. into the liquid chamber 20 so that the temperature of the bell jar 2 is held at about 100° C., and likewise the lower electrode 7 is held at about 50° C. Under such conditions, etching process on the substrate 9 can be carried out in a required time of about 100 minutes.
In the plasma processing apparatus 100 of such a construction, the coil 5 is placed in the liquid chamber 20 defined by the bell jar 2 and the ground shield vessel 10, and the cooling/heating medium liquid adjusted to a specified temperature is circulated into the liquid chamber 20 during the plasma processing. Thus, the temperature of the bell jar 2 and the coil 5 can be held within a specified temperature range, and working effects similar to those by temperature adjustment of the cooling/heating medium liquid in the first embodiment can be obtained.
Indeed the method of the second embodiment as shown FIG. 2 is applicable to the plate-shaped dielectric window and the flat spiral coil shown in the first embodiment of FIG. 1, but in particular, a hemispherical bell jar 2 allows the bell jar to be as small in thickness as possible even with a dielectric window made of a dielectric material having a low heat conductivity (e.g., quartz), thus advantageous for cooling of the dielectric window. Accordingly, from such a point of view, there is an advantage in the method for controlling the temperature of the bell jar 2 by forming the liquid chamber 20 by using the outside surface of the bell jar 2.
The above description has been made on a case where the coil 5 is placed in the liquid chamber 20 surrounded by the generally hemispherical-shell shaped bell jar 2 and the ground shield vessel 10, and where the cooling/heating medium liquid is circulated in the liquid chamber 20. However, the construction of the plasma processing apparatus 100 of this second embodiment is not limited to such a one. For example, in a plasma processing apparatus having a construction in which such a generally hemispherical-shell shaped bell jar 2 is used, the construction that the coil is brought into contact with the surface of the dielectric window is also applicable as in the plasma processing apparatus of the first embodiment. FIG. 3 is a schematic constructional view showing the construction of a plasma processing apparatus 900 according to a modification example of this second embodiment to which such a construction as described above is applied. Also, FIG. 4 is a sectional view taken along the line A-A in the plasma processing apparatus 900 shown in FIG. 3. It is noted that like parts similar in construction to those of the plasma processing apparatus 100 shown in FIG. 2 are designated by like reference numerals in the plasma processing apparatus 900 shown in FIGS. 3 and 4, and their description is omitted.
As shown in FIG. 3, in the plasma processing apparatus 900, a cone-shaped spiral coil 905 having a rectangular cross section is placed above the bell jar 2 within the liquid chamber 20, as viewed in the figure. Also, as shown in FIGS. 3 and 4, the coil 905 is held at a lower face of a coil holding member 950 having a planarly generally X-like shape. Such holding is, for example, implemented by an upper portion of the coil 905 being partly engaged with a plurality of recess portions 950 a formed at the lower face of the coil holding member 950.
Further, the coil holding member 950 is supported to inside of the ground shield vessel 10 via a plurality of guide bolts 951 at respective end portions of the X-like shape. The individual guide bolts 951 are placed along the vertical direction in the figure, and the coil holding member 950 is supported so as to be movable along the respective guide bolts 951. Furthermore, a bias spring 952 is attached to each of the guide bolts 951, and these bias springs 952 have a function of biasing the coil holding member 950 toward the upper face side, as viewed in the figure, of the bell jar 2 along the individual guide bolts 951. With such a construction, the coil 905 held to the lower face of the coil holding member 950 is normally pressed against the upper-side surface of the bell jar 2, as viewed in the figure, so that the coil 905 is maintained in close contact with the surface of the bell jar 2.
In the plasma processing apparatus 900, since the spiral-shaped coil 905 placed in the liquid chamber 20 is kept normally in close contact with the upper-side surface of the bell jar 2, as viewed in the figure, effecting the application of RF power to the coil 905 in the plasma processing makes it possible to generate a strong electromagnetic field inducing effect to a processing chamber 3 side surface of the bell jar 2, so that the working effect of allowing an easier start or holding of discharge even with low pressure, similar to a working effect of the first embodiment, can be obtained.
Although the configuration or placement of the grounding terminal 17 and the application terminal 16 in FIG. 3 differs from that of the plasma processing apparatus 100 of FIG. 2, yet such configuration and placement are determined depending on the configuration and placement of the coil 905, and there are no substantial differences in function or the like. Besides, as shown in FIG. 4, taking advantage of the coil member not being placed at a center portion of the spiral-shaped coil 905, a through hole 950 b is formed at a center portion of the coil holding member 950, while a through hole 10 a and an observation-use window portion 10 b (formed of, for example, quartz glass material) are provided at a position corresponding to the through hole 950 b in the ground shield vessel 10. Thus, the space within the processing chamber 3 can be made visually observable from the observation-use window portion 10 b through the through holes 10 a, 950 b and the bell jar 2.

Third Embodiment

Next, FIG. 5 is a schematic sectional view of a plasma processing apparatus 200 according to a third embodiment of the present invention. As shown in FIG. 5, the plasma processing apparatus 200 is different in construction from the plasma processing apparatus 100 of the second embodiment structurally in terms of having not the generally hemispherical-shell shaped dielectric window 2 but a generally plate-shaped dielectric window 202, but similar in construction to the plasma processing apparatus 100 in terms of the other structural components unrelated to the form of the dielectric window 202. Further, as shown in FIG. 5, the plasma processing apparatus 200 is similar in construction to the plasma processing apparatus 800 in terms of having the generally disc-shaped window 202, but different in terms of placing a liquid flow passage 220 and a coil 205 in the inside of the dielectric window 202. This different construction only is explained below. In addition, for an easier understanding of the description, constituent parts similar to those of the plasma processing apparatus 100 of the second embodiment are designated by like reference numerals in the plasma processing apparatus 200, and their description is omitted. Besides, although the plasma processing apparatus 200 is equipped with a control unit (corresponding to the control unit 90) for performing integrated control as in the plasma processing apparatus 100 of the second embodiment, it is similar in construction and therefore its representation is omitted in FIG. 5.
As shown in FIG. 5, the plasma processing apparatus 200 is equipped with a generally disc-shaped dielectric window 202 which is placed so as to close an opening portion at the top of the vacuum vessel 1 and which is formed of a dielectric material, where a processing chamber 203 is formed which is a space closed by the dielectric window 202 and a space where plasma processing is performed.
The dielectric window 202 is formed by mutual junction of an upper-portion side dielectric plate 202 a and a lower-portion side dielectric plate 202 b which are two generally disc-shaped dielectric plates formed of the dielectric material. Further, at the mutual junction surface of the upper-portion side dielectric plate 202 a and the lower-portion side dielectric plate 202 b is formed a continued recess portion having a generally concave-shaped cross section so that their formation placement coincide with each other. Then, by the upper-portion side dielectric plate 202 a and the lower-portion side dielectric plate 202 b being joined to each other, there is formed a continued liquid flow passage 220 for the liquid which is enclosed by respective concave-shaped inner walls and which allows the cooling/heating medium liquid to be circulated therethrough. Such a liquid flow passage 220 is formed, for example, so as to be spiraled from a generally center of the dielectric window 202 about the center. Also, a supply hole 220 a for the cooling/heating medium liquid is formed at a center-side end portion of the liquid flow passage 220 so as to extend through the upper-portion side dielectric plate 202 a, and a discharge hole 220 b for the cooling/heating medium liquid is formed at an spiral-periphery side end portion of the liquid flow passage 220 so as to extend through the upper-portion side dielectric plate 202 a. It is noted that the liquid flow passage 220 is also an example of the liquid chamber which is so formed that the inner wall of the recess portion formed inside the dielectric window 202 serves as a chamber wall and which is capable of storing the cooling/heating medium liquid therein. Further, in the plasma processing apparatus 200 of this third embodiment, the lower-portion side dielectric plate 202 b is an example of the dielectric window while the upper-portion side dielectric plate 202 a is an example of the liquid storage vessel, and moreover by the liquid storage vessel being formed of a dielectric material, it can be said that one dielectric window 202 in which the dielectric window and the liquid storage vessel are integrated together is formed.
Also, the supply hole 220 a and the discharge hole 220 b of the liquid flow passage 220 are communicated with the upper-portion side chiller unit 21 through a passage 222, which is an example of the liquid flow passage. Thus, the cooling/heating medium liquid can be circulated so that the cooling/heating medium liquid controlled to a desired temperature by the upper-portion side chiller unit 21 is supplied into the liquid flow passage 220 through the passage 222 and the supply hole 220 a, and moreover that the cooling/heating medium liquid within the liquid flow passage 220 is collected to the upper-portion side chiller unit 21 through the discharge hole 220 b and the passage 222.
Also, inside the liquid flow passage 220 formed into the generally spiral shape is formed the coil 205 which is an example of a plasma-exciting coil formed of a conductor wire continuously so as to generally coincide with the generally spiral-shaped configuration. A generally spiral-center side end portion of the coil 205 is connected via a matching box 218 to a coil-use RF power supply 206 placed outside the apparatus, and a generally spiral-periphery side end portion of the coil 205 is connected to the grounding terminal outside the apparatus.
At a junction portion between the dielectric window 202 and the vacuum vessel 1, an O-ring 226 is provided to ensure the airtightness inside the processing chamber 203. Further, in order to securely fix (releasably fix) the dielectric window 202 to the vacuum vessel 1, the dielectric window 202 is fixed at its end portion to the top of the vacuum vessel 1 with a presser metal fitting 228, which is a fixing member. Besides, a ground shield 210 formed of a conductive material is attached to the top of the vacuum vessel 1 so as to cover the outer surface of the dielectric window 202 as well as the space near the surface.
In the plasma processing apparatus 200 of such a construction, operation for performing plasma processing on the substrate 9 placed on the lower electrode 7 is similar to those of the plasma processing apparatus 800 of the first embodiment and the plasma processing apparatus 100 of the second embodiment. More specifically, the dielectric window 202 and the coil 205 can be controlled to a desired temperature by circulating the cooling/heating medium liquid so that the cooling/heating medium liquid controlled to a desired temperature is supplied from the supply hole 220 a via the passage 222 to the liquid flow passage 220 formed inside the dielectric window 202 and that the cooling/heating medium liquid supplied to the liquid flow passage 220 is discharged from the discharge hole 220 b to the passage 222.
Also, the dielectric window 202 having such a liquid flow passage 220 inside thereof can be joined together by bonding the upper-portion side dielectric plate 202 a, in which the concave-shaped recess portion is formed, and the lower-portion side dielectric plate 202 b to each other by means of adhesive or the like so that their mutual recess portions coincide with each other. Such adhesive may be given, preferably, by rubber-based adhesives capable of maintaining their elasticity after setting, for example, thermosetting silicone rubber based adhesives. Instead of joining with the use of adhesive as shown above, the upper-portion side dielectric plate 202 a and the lower-portion side dielectric plate 202 b can be joined together by providing a high-precision plane on the mutual junction surfaces of the upper-portion side dielectric plate 202 a and the lower-portion side dielectric plate 202 b by then evacuating the interior of the liquid flow passage 220 with their junction surfaces bonded together, or by pressing each other, and further by heating to high temperature those respective junction surfaces which are kept in secure close contact with each other, by which the upper-portion side dielectric plate 202 a and the lower-portion side dielectric plate 202 b are joined together by high-temperature interatomic junction.
According to the third embodiment, in a case where the dielectric window 202 is generally plate shaped, the liquid flow passage 220 is formed in the dielectric window 202, and the coil 205 is placed within this liquid flow passage 220. Thus, the surfaces of the dielectric window 202 and the coil 205 can be controlled to a desired temperature by circulating the cooling/heating medium liquid controlled to a desired temperature into the liquid flow passage 220, so that working effects similar to those of the second embodiment can be obtained.
As shown above, the coil 205 is placed in the liquid flow passage 220 formed inside the dielectric window 202. As a result of this, the distance between the coil 205 and the lower surface of the dielectric window 202 (the upper surface of the processing chamber 203) can be reduced, and therefore reliable temperature control of the dielectric window 202 and the coil 205 can be achieved while a higher plasma-exciting power is obtained.
Also, even in the case where the dielectric window 202 is made generally plate-shaped and formed large in thickness in order to obtain enough strength to withstand the atmospheric pressure as shown above, the liquid flow passage (liquid chamber) 220 and the coil 205 can be placed at a position close to the processing-chamber side surface of the dielectric window 202, so that reliable cooling of the dielectric surface can be achieved.
Further, in the plasma processing apparatus 200 of the third embodiment, since the liquid flow passage 220 is formed in a generally spiral shape inside the dielectric window 202, there is an advantage that the surface area for heat conduction can be made relatively large and the temperature controllability can be made successful. Furthermore, the amount of the cooling/heating medium liquid can be reduced, so that it is possible to come into being reducing in cost, downsizing, and saving power for temperature control for the apparatus.

Fourth Embodiment

Next, FIG. 6 is a schematic sectional view of a plasma processing apparatus 300 according to a fourth embodiment of the invention. In the following description, component parts similar in construction to those of the plasma processing apparatus 100 of the second embodiment are designated by like reference numerals, and their description is omitted.
As shown in FIG. 6, the plasma processing apparatus 300 is similar in construction to the plasma processing apparatus 100 of the second embodiment in that a liquid chamber 320 formed so as to be surrounded by the outer surface of a bell jar 2 and the inner surface of a ground shield vessel 310 is provided above the generally hemispherical-shell shaped or generally dome-shaped bell jar 2, but differs from the second embodiment in that the cooling/heating medium liquid stored in the liquid chamber 320 is not circulated through the chiller unit 325. This different construction only is explained below.
As shown in FIG. 6, the liquid chamber 320 is communicated with apparatus outside (i.e., atmospheric air) via a reserve tank 330 formed upward of the liquid chamber 320, and a cooling/heating medium liquid is stored inside the liquid chamber 320. It is noted that this reserve tank 330 has a role for absorbing and adjusting volumetric changes (or a little evaporation) due to temperature changes of the cooling/heating medium liquid stored inside the liquid chamber 320.
Further, on the perimeter of the liquid chamber 320, i.e., on the outer peripheral portion of the ground shield vessel 310, an outer-peripheral side cooling/heating medium liquid flow passage 331 is formed so as to surround the liquid chamber 320. This outer-peripheral side cooling/heating medium liquid flow passage 331 is enabled to cool or heat the cooling/heating medium liquid stored in the neighbored liquid chamber 320 by a temperature-controlled secondary cooling/heating medium liquid (an example of fluid stored so as to be separable from the cooling/heating medium liquid) being circulated inside the outer-peripheral side cooling/heating medium liquid flow passage 331, thus being an example of a heat exchanger section. Also, in this outer-peripheral side cooling/heating medium liquid flow passage 331 are formed a supply hole 331 a for supplying the secondary cooling/heating medium liquid as well as a discharge hole 331 b for discharging the same. The supply hole 331 a is communicated with the liquid flow passage 23 of the lower electrode 7 via a cooling/heating medium liquid passage 322, and the liquid flow passage 23 is communicated with a chiller unit 325 via a cooling/heating medium liquid passage 24. On the other hand, the discharge hole 331 b is communicated with the chiller unit 325 via a cooling/heating medium liquid passage 332.
With such a construction, it is made implementable to control the temperature of the lower electrode 7 by circulating the secondary cooling/heating medium liquid, which is controlled to a desired temperature by the chiller unit 325, along the liquid flow passage 23 of the lower electrode 7 through the cooling/heating medium liquid passage 24. Further, the cooling/heating medium liquid stored in the liquid chamber 320 can be controlled to a desired temperature by supplying the secondary cooling/heating medium liquid from the liquid flow passage 23 of the lower electrode 7 through the cooling/heating medium liquid passage 322 and the supply hole 331 a into the outer-peripheral side cooling/heating medium liquid flow passage 331, and by circulating the supplied secondary cooling/heating medium liquid through the discharge hole 331 b and the cooling/heating medium liquid passage 332 to the chiller unit 325.
Besides, the ground shield vessel 310 is equipped with a stirrer 333 for stirring the cooling/heating medium liquid stored in the liquid chamber 320, thus making it possible to uniformize the temperature of the cooling/heating medium liquid stored in the liquid chamber 320. Therefore, with the use of the cooling/heating medium liquid that is uniformized and temperature-controlled, it is made possible to control the surface temperature of the bell jar 2 and the coil 5.
The cooling/heating medium liquid to be stored in the liquid chamber 320 is given by using fluorine oil or silicone oil having electrical insulation property as in the first embodiment in view of being brought into direct contact with the coil 5. On the other hand, the secondary cooling/heating medium liquid to be circulated to the outer-peripheral side cooling/heating medium liquid flow passage 331 may be given by using a liquid which is commonly used as a cooling/heating medium such as tap water or ethylene glycol because of not being brought into contact with the coil 5 and therefore not being required to have electrical insulation property.
In this fourth embodiment, the chiller unit 325, which is equipped with a refrigerator (cooling unit) and a heater (heating unit), which is an example of the liquid temperature adjusting unit, is enabled to indirectly adjust the temperature of the cooling/heating medium liquid stored in the liquid chamber 320 with the use of the secondary cooling/heating medium liquid.
According to the fourth embodiment, in addition to the working effects of the second embodiment, it is further made possible to perform temperature control of the cooling/heating medium liquid stored in the liquid chamber 320 with the use of the secondary cooling/heating medium liquid indirectly temperature-controlled by the chiller unit 325 to thereby perform the temperature control of the bell jar 2 and the coil 5. Therefore, it is made possible to employ a common-use relatively low-price chiller unit 325 for water or ethylene glycol without using a relatively high-price chiller unit for fluorine oils and silicone oil, so that the plasma processing apparatus 300 can be reduced in cost.
Besides, by the provision of the stirrer 333 in the liquid chamber 320, it is made possible to accelerate the heat exchange with the secondary cooling/heating medium liquid present in the flow passage 331 and to uniformize the temperature of the cooling/heating medium liquid present in the liquid chamber 320, so that the temperature controllability of the bell jar 2 and the coil 5 can be improved.

Fifth Embodiment

Next, FIG. 7 is a schematic sectional view of a plasma processing apparatus 400 according to a fifth embodiment of the invention. As shown in FIG. 7, the plasma processing apparatus 400 is similar in construction to the plasma processing apparatus 300 of the fourth embodiment except for a construction for heating or cooling the cooling/heating medium liquid stored in a liquid chamber 420 formed so as to be surrounded by the bell jar 2 and a ground shield vessel 410. This different construction only is explained below.
As shown in FIG. 7, a multiplicity of cooling fins 410 a are formed on a generally cylindrical-shaped outer peripheral side wall of the ground shield vessel 410 in the plasma processing apparatus 400. Also, a cooling fan 440 for blowing air to the cooling fins 410 a is provided outside the ground shield vessel 410. It is noted that in this fourth embodiment, the cooling fins 410 a and the cooling fan 440 are an example of the air cooling unit.
Further, a heater 441 for heating the cooling/heating medium liquid stored in the liquid chamber 420 as well as a stirrer 333 are provided inside the ground shield vessel 410, i.e., in the liquid chamber 420.
As shown above, for the cooling/heating medium liquid stored in the liquid chamber 420, the cooling fins 410 a and the cooling fan 440 are provided as a cooling unit, the heater 441 is provided as a heating unit, and the stirrer 333 for uniformization of temperature of the internal liquid is provided. Thus, it is made possible to control the temperature of the cooling/heating medium liquid with the use of the cooling unit and the heating unit under their control. That is, in this fourth embodiment, the cooling fins 410 a, the cooling fan 440, the heater 441 and the stirrer 333 serve as an example of the liquid temperature adjusting unit.
According to the fifth embodiment, temperature control of the cooling/heating medium liquid stored in the liquid chamber 420 can be achieved without using any chiller unit but with the constructional provision of the cooling fins 410 a, the cooling fan 440, the heater 441 and the stirrer 333. This contributes to a downsizing of the apparatus as well as a simplification of the construction, so that manufacturing cost for the apparatus can be reduced and downsizing of the apparatus can be fulfilled.

Sixth Embodiment

Next, FIG. 8 is a schematic sectional view showing a schematic construction of a plasma processing apparatus 700 according to a sixth embodiment of the invention. As shown in FIG. 8, the plasma processing apparatus 700 is similar in construction to the plasma processing apparatus 400 of the fifth embodiment except that there is provided no externally cooling mechanism for the cooling/heating medium liquid stored in a liquid chamber 720 formed so as to be surrounded by the bell jar 2 and a ground shield vessel 710 and that there is a difference in the construction of supply and discharge holes for the liquid. This different construction only is explained below.
As shown in FIG. 8, the plasma processing apparatus 700 is provided with a liquid chamber 720 formed so as to be surrounded by the bell jar 2 and the ground shield vessel 710, and the cooling/heating medium liquid is stored in the liquid chamber 720. Also, a vapor discharge hole 710 a (an example of the discharge portion for liquid vapor) for discharging the vapor of the cooling/heating medium liquid vaporized within the liquid chamber 720 is formed at an upper portion of the ground shield vessel 710, and the vapor discharge hole 710 a is connected to open air or an evacuator (not shown) through the vapor discharge hole 710 a. The ground shield vessel 710 is provided with a cooling/heating medium liquid supply pipe 740 (an example of the supply portion) for supplying the cooling/heating medium liquid into the liquid chamber 720, and it is made possible to supply the cooling/heating medium liquid from the cooling/heating medium liquid supply pipe 740 so that the cooling/heating medium liquid stored in the liquid chamber 720 can be maintained at a specified liquid level. Within the liquid chamber 720, the heater 441 and the stirrer 333 are provided as in the plasma processing apparatus 400.
The cooling/heating medium liquid in the liquid chamber 720 is selected as one which is safe in electrical insulation property and which has a boiling point around a desired temperature (adjustment temperature) at which the bell jar 2 and the coil 5 to be maintained (adjusted). For example, when the desired temperature is around 100° C., pure water may be used appropriately. When the desired temperature is a cryogenic temperature, liquid nitrogen or liquefied carbonic acid gas may be used. For temperatures around normal temperature, chlorofluorocarbon based ones may be used.
By such a construction of the plasma processing apparatus 700, the amount of heat derived from the bell jar 2 and the coil 5 is imparted to (or lost from) the cooling/heating medium liquid in contact therewith, causing the cooling/heating medium liquid to be vaporized as vapor foams 750 with the amount of heat as latent heat of vaporization, by which the surfaces of the bell jar 2 and the coil 5 can be cooled. The vapor of the cooling/heating medium liquid is discharged from the vapor discharge hole 710 a outside the liquid chamber 720. Also, the amount of storage of the cooling/heating medium liquid decreased by this vapor discharge is compensated by supply from the cooling/heating medium liquid supply pipe 740. Also, for such supply of the cooling/heating medium liquid, the liquid chamber 720 is equipped with a sensor or the like (not shown) for detecting the liquid level of the cooling/heating medium liquid.
In addition, instead of using the heater 441 as the heating unit for the cooling/heating medium liquid as shown above, the heating of the bell jar 2 can be fulfilled via the cooling/heating medium liquid by heating the cooling/heating medium liquid stored in the liquid chamber 720 to a desired temperature with slight RF power applied to the coil 5. Further, for heating the bell jar 2 preparatorily to a desired temperature, the heater 441 and the stirrer 333 can be used as in the fifth embodiment.
According to the sixth embodiment, there can be provided an apparatus which has a sufficient cooling function, and which is simplified in the construction of the plasma processing apparatus 700 and further which is low in cost.
Although the plasma processing apparatuses of the foregoing individual embodiments have been described on a case where the coil to be placed in the liquid chamber is entirely immersed in the cooling/heating medium liquid supplied into the liquid chamber, the present invention is not limited only to such a case. Instead of such a case, the case may be that only part of the coil is immersed in the cooling/heating medium liquid.
Taking the plasma processing apparatus 700 of the sixth embodiment as an example, even in the case where, for example as shown in FIG. 9, the storage amount of the cooling/heating medium liquid is less than that of the state shown in FIG. 8 and part of the coil 5 is exposed from the liquid level of the stored cooling/heating medium liquid in the liquid chamber 720, the temperature control for the bell jar 2, which is of higher necessity, can reliably be fulfilled if the entire upper-face side surface of the bell jar 2, as viewed in the figure, is immersed in the cooling/heating medium liquid, so that the working effects by the sixth embodiment can be obtained. However, it is desirable that the entirety of the coil 5 is immersed in the cooling/heating medium liquid from the viewpoint of reliably fulfilling the temperature control of the coil 5 in addition to the bell jar 2.
Also, Although the foregoing individual embodiments have been described on a case where the dielectric window and the coil is cooled and heated by the cooling/heating medium liquid, the present invention is not limited only to such a case only. Even when only the cooling of the dielectric window by the cooling/heating medium liquid is performed during plasma processing, the present invention can be applied to obtain the working effects.
Furthermore, although the foregoing embodiments have been described on the assumption that so-called ICP (Inductively Coupled Plasma) excitation coil (or antenna) is shown in the drawings as the plasma-exciting coil or electrode, yet similar working effects can be obtained even with a CCP (capacitively coupled plasma) excitation electrode installed in the liquid chamber instead.
It is to be noted that, by properly combining the arbitrary embodiments of the aforementioned various embodiments, the effects possessed by them can be produced.
Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart therefrom.
The disclosure of Japanese Patent Application No. 2003-389251 filed on Nov. 19, 2003, including specification, drawings and claims are incorporated herein by reference in its entirety.

Claims

1. A plasma processing apparatus for imparting an electromagnetic field to reactant gas introduced into a evacuated processing chamber to excite plasma and performing plasma processing on a substrate set in the processing chamber, comprising:

a vacuum vessel which defines the processing chamber in which the substrate is held and the plasma processing for the substrate is performed, and which includes a dielectric window forms a part of the vacuum vessel, for hermetically closing the vacuum chamber, and a gas supply portion for supplying the reactant gas into the processing chamber;

a plasma-exciting coil which is placed so as to confront the processing chamber via the dielectric window, for imparting an electromagnetic field to interior of the processing chamber via the dielectric window with RF power applied;

an evacuation unit for evacuating the interior of the processing chamber to draw a vacuum so that pressure in the processing chamber is kept generally constant;

an RF power supply for applying the RF power to the plasma-exciting coil; and

a liquid storage vessel which includes the dielectric window as a part thereof and which defines in interior thereof a liquid chamber for storing therein an electrically insulative liquid so that an opposite surface to a processing chamber-side surface of the dielectric window is immersed in the liquid and in which the plasma-exciting coil is placed.

2. The plasma processing apparatus as claimed in claim 1, further comprising a liquid temperature adjusting unit which has a cooling unit and/or a heating unit for the electrically insulative liquid and for adjusting temperature of the liquid stored in the liquid storage vessel to control temperature of the plasma-exciting coil and the dielectric window via the liquid.

3. The plasma processing apparatus as claimed in claim 2, wherein the liquid storage vessel except for the dielectric window is formed of an electrical conductor.

4. The plasma processing apparatus as claimed in claim 2, wherein

the liquid storage vessel is integrated with the dielectric window whereby an integrated dielectric window is formed, and the integrated dielectric window has a liquid flow passage for the electrically insulative liquid inside thereof as the liquid chamber in which the plasma-exciting coil is placed.

5. The plasma processing apparatus as claimed in claim 2, wherein the liquid temperature adjusting unit is placed outside the liquid storage vessel, the plasma processing apparatus further comprising:

a liquid circulating unit for circulating the electrically insulative liquid into the liquid chamber through a liquid flow passage communicated with the liquid chamber so that the liquid is circulatable therealong.

6. The plasma processing apparatus as claimed in claim 2, wherein the liquid temperature adjusting unit has a heat exchange portion which is provided on a wall portion of the liquid storage vessel and which serves for heat exchange with the electrically insulative liquid stored in the liquid storage vessel, and

a fluid stored in the heat exchange portion so as to be separable from the electrically insulative liquid is temperature-controlled by the cooling unit or the heating unit, whereby temperature of the electrically insulative liquid in the liquid storage portion is adjusted.

7. The plasma processing apparatus as claimed in claim 2, wherein the cooling unit is an air cooling unit for air cooling an outer wall surface of the liquid storage vessel, and

the heating unit is a heater placed inside or outside the liquid storage vessel.

8. The plasma processing apparatus as claimed in claim 2, wherein the liquid temperature adjusting unit comprises:

a supply portion of the electrically insulative liquid to the liquid chamber; and

a discharge portion for discharge of liquid vapor generated by vaporization of the electrically insulative liquid from the liquid chamber, and wherein

the electrically insulative liquid is a liquid which has a boiling point at or near an adjustment temperature of the dielectric window and the plasma-exciting coil or a temperature therearound.

9. The plasma processing apparatus as claimed in claim 1, wherein in the liquid storage vessel, the electrically insulative liquid is stored so that the plasma-exciting coil is further immersed in the electrically insulative liquid.

10. The plasma processing apparatus as claimed in claim 1, wherein the plasma-exciting coil is brought into close contact with the liquid chamber-side surface of the dielectric window with a pressure of the electrically insulative liquid supplied into the liquid storage vessel.

11. The plasma processing apparatus as claimed in claim 10, further comprising:

a liquid chamber dividing member for dividing the liquid storage vessel into a first chamber to which the electrically insulative liquid is supplied, and a second chamber which is communicated with the first chamber so that the liquid supplied to the first chamber can be supplied to inside of the second chamber and in which the liquid chamber-side surface of the dielectric window and the plasma-exciting coil are placed inside; and

a support guide member for, in the liquid chamber, supporting the liquid chamber dividing member while guiding a dividing position between the first chamber and the second chamber along a variable direction, wherein

the plasma-exciting coil is pressed against and brought into close contact with the surface of the dielectric window by a pressure difference between the liquid stored in the first chamber and the liquid stored in the second chamber.

12. The plasma processing apparatus as claimed in claim 11, wherein in the second chamber of the liquid storage vessel is formed a generally spiral-shaped liquid flow passage in which gaps of the generally spirally turned plasma-exciting coil are surrounded by the liquid chamber dividing member and the dielectric window.

13. The plasma processing apparatus as claimed in claim 12, wherein a supply position of the electrically insulative liquid from the first chamber to the second chamber is set on a center side of the liquid flow passage so that the liquid is circulatable from center side toward outer peripheral side of the generally spiral-shaped liquid flow passage formed between the spiral-shaped plasma-exciting coil in the second chamber of the liquid storage vessel.

14. The plasma processing apparatus as claimed in claim 2, wherein the electrically insulative liquid is pure water having a resistivity of 1×10⁵Ω·cm or more.

15. The plasma processing apparatus as claimed in claim 2, wherein the electrically insulative liquid is a fluorine inert oil, a silicone oil, or organic oils and fats.

16. The plasma processing apparatus as claimed in claim 3, wherein the electrically insulative liquid is pure water having a resistivity of 1×10⁵Ω·cm or more.

17. The plasma processing apparatus as claimed in claim 4, wherein the electrically insulative liquid is pure water having a resistivity of 1×10⁵Ω·cm or more.

18. The plasma processing apparatus as claimed in claim 5, wherein the electrically insulative liquid is pure water having a resistivity of 1×10⁵Ω·cm or more.

19. The plasma processing apparatus as claimed in claim 6, wherein the electrically insulative liquid is pure water having a resistivity of 1×10⁵Ω·cm or more.

20. The plasma processing apparatus as claimed in claim 7, wherein the electrically insulative liquid is pure water having a resistivity of 1×10⁵Ω·cm or more.

21. The plasma processing apparatus as claimed in claim 8, wherein the electrically insulative liquid is pure water having a resistivity of 1×10⁵Ω·cm or more.

22. The plasma processing apparatus as claimed in claim 9, wherein the electrically insulative liquid is pure water having a resistivity of 1×10⁵Ω·cm or more.

23. The plasma processing apparatus as claimed in claim 10, wherein the electrically insulative liquid is pure water having a resistivity of 1×10⁵Ω·cm or more.

24. The plasma processing apparatus as claimed in claim 11, wherein the electrically insulative liquid is pure water having a resistivity of 1×10⁵Ω·cm or more.

25. The plasma processing apparatus as claimed in claim 12, wherein the electrically insulative liquid is pure water having a resistivity of 1×10⁵Ω·cm or more.

26. The plasma processing apparatus as claimed in claim 13, wherein the electrically insulative liquid is pure water having a resistivity of 1×10⁵Ω·cm or more.

27. The plasma processing apparatus as claimed in claim 3, wherein the electrically insulative liquid is a fluorine inert oil, a silicone oil, or organic oils and fats.

28. The plasma processing apparatus as claimed in claim 4, wherein the electrically insulative liquid is a fluorine inert oil, a silicone oil, or organic oils and fats.

29. The plasma processing apparatus as claimed in claim 5, wherein the electrically insulative liquid is a fluorine inert oil, a silicone oil, or organic oils and fats.

30. The plasma processing apparatus as claimed in claim 6, wherein the electrically insulative liquid is a fluorine inert oil, a silicone oil, or organic oils and fats.

31. The plasma processing apparatus as claimed in claim 7, wherein the electrically insulative liquid is a fluorine inert oil, a silicone oil, or organic oils and fats.

32. The plasma processing apparatus as claimed in claim 8, wherein the electrically insulative liquid is a fluorine inert oil, a silicone oil, or organic oils and fats.

33. The plasma processing apparatus as claimed in claim 9, wherein the electrically insulative liquid is a fluorine inert oil, a silicone oil, or organic oils and fats.

34. The plasma processing apparatus as claimed in claim 10, wherein the electrically insulative liquid is a fluorine inert oil, a silicone oil, or organic oils and fats.

35. The plasma processing apparatus as claimed in claim 11, wherein the electrically insulative liquid is a fluorine inert oil, a silicone oil, or organic oils and fats.

36. The plasma processing apparatus as claimed in claim 12, wherein the electrically insulative liquid is a fluorine inert oil, a silicone oil, or organic oils and fats.

37. The plasma processing apparatus as claimed in claim 13, wherein the electrically insulative liquid is a fluorine inert oil, a silicone oil, or organic oils and fats.