JP2014070275A - Plasma treatment method, and plasma treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma treatment method, in which a processing object electrostatically attracted by a stage can be released as soon as possible with a simple construction.SOLUTION: In a vacuum treatment chamber 1a, a processing object W is electrostatically attracted by a chuck plate 52 of an electrostatic chuck mounted on a surface of a metallic base 51. A gas to be excited into plasma is introduced into the vacuum treatment chamber evacuated. An electric power is applied to an electrode 2 disposed in that vacuum treatment chamber thereby to establish a plasma atmosphere, in which the processing object W is subjected to the plasma treatment. A potential of the base is made floating, and a positive potential is applied to the base for a predetermined time period for the plasma treatment.

Description

  The present invention relates to a plasma processing method and a plasma processing apparatus, and more particularly, a simple configuration when a processing object is electrostatically adsorbed on a plate mounted on a metal base surface during plasma processing. And to which the object to be treated can be detached from the plate after the plasma treatment as soon as possible.

  In order to obtain a desired device structure in a semiconductor manufacturing process, various types of plasma processing such as film formation processing, ion implantation processing, and etching processing are performed on a processing target such as a silicon wafer by a sputtering method and a plasma CVD method. In a plasma processing apparatus that performs these plasma processes, a stage with an electrostatic chuck is provided in order to position and hold an object to be processed in a vacuum processing chamber in a vacuum atmosphere. In this case, the stage has, for example, a metal base and an aluminum nitride ceramic plate (chuck plate) mounted on the surface thereof, and positive and negative electrodes are embedded in the chuck plate, and the surface of the chuck plate is processed. It is configured as an electrostatic chuck that electrostatically attracts an object (for example, see Patent Document 1).

  Here, when a desired plasma treatment is performed in a state where a processing object is electrostatically adsorbed by applying a voltage from the chuck power supply to the electrode of the chuck plate, the chucked processing object is detached from the chuck plate. The voltage application to the electrode is stopped. At this time, in order to keep the object to be removed from the chuck plate as quickly as possible, it is desirable to positively remove the charge charged on the object by the plasma treatment. Conventionally, as such a static elimination method, there is a gas static elimination method. For example, Patent Document 2 discloses that a heat transfer gas supply unit that ejects a heat transfer gas toward the processing target is provided, and that the ionized gas is supplied from the heat transfer gas supply unit toward the processing target. Has been.

  However, as in Patent Document 2, if a process for supplying an ionized gas is provided after the plasma process is completed to neutralize the object to be processed, the process time is increased by that process, which is an obstacle to improving the throughput. In addition, since the components for supplying the ionized gas toward the object to be processed are provided, the configuration of the apparatus becomes complicated. In addition, since such parts are expensive, the cost of the apparatus is increased.

JP 2008-277545 A JP 2010-199239 A

  In view of the above, the present invention has an object to provide a plasma processing method and a plasma processing apparatus capable of detaching a processing object electrostatically attracted with a simple configuration as quickly as possible. It is.

  In order to solve the above problems, a processing object is electrostatically adsorbed on a plate mounted on the surface of a metal base in a vacuum processing chamber, and a gas for plasma excitation is introduced into the vacuum processing chamber that has been evacuated. The plasma processing method of the present invention in which power is applied to the electrode provided in the vacuum processing chamber to form a plasma atmosphere and the plasma processing is performed on the object to be processed. A positive potential is applied to the base for a certain period of time.

  According to the above, when the object to be processed can be electrostatically adsorbed to the plate during the plasma processing, when a positive (DC) potential is applied to the base during the plasma processing, for example, immediately before the end of the plasma processing, Electrons charged in the object to be processed flow to the ground through the low resistance plasma, and the object to be processed is discharged. Therefore, the object to be processed immediately after the end of the plasma processing is in a state where it can be detached from the plate as quickly as possible. As a result, it is possible to improve the throughput by omitting the step of supplying the ionized gas to the object to be processed and removing the static electricity as in the conventional case, and further, no parts for supplying the ionized gas are required. Therefore, the apparatus configuration is simple and the cost of the apparatus can be reduced.

  In the present invention, the term “plate” means that a processing object such as a wafer is installed. If plasma processing is performed in this state, the processing object can be charged. The chuck can be a chuck plate, and charging of the object to be processed on the plate can occur even with an insulating plate such as a quartz plate.

  In order to solve the above problems, a plasma processing apparatus of the present invention includes a vacuum processing chamber provided with an electrode, gas introduction means for introducing a plasma excitation gas into the vacuum processing chamber, and powering the electrode. A first power source, a stage having a metal base and a plate mounted on the surface thereof, and a stage for electrostatically attracting an object to be processed in the vacuum processing chamber, the base being vacuum processed through an insulating material A second power source is further provided, which is installed indoors and applies a positive potential to the base for a certain period. In this case, the plate can be a chuck plate of an electrostatic chuck.

  According to this, it is possible to realize a simple and low-cost configuration capable of detaching the processing object electrostatically attracted to the plate as quickly as possible.

  In the present invention, the plate is a chuck plate of an electrostatic chuck, the electrode is an insulating target, the first power source is a high frequency power source, and the surface of the object to be processed by high frequency sputtering as plasma processing. The present invention can be applied to a film to be formed.

The schematic diagram of the sputtering device of this invention. The graph which shows the change of the substrate surface potential when a high frequency power supply and a DC power supply are turned on / off at the time of sputtering.

  Hereinafter, referring to the drawings, a plasma processing apparatus and method thereof are described in which a plate is an electrostatic chuck chuck plate, a target is an insulator, and a processing target is a silicon wafer (hereinafter referred to as a substrate W). Next, an embodiment applied to a sputtering apparatus and method for forming an insulating film will be described.

  With reference to FIG. 1, SM is the high-frequency sputtering device of this embodiment. The high-frequency sputtering device SM includes a vacuum chamber 1 that defines a vacuum processing chamber 1a, and a cathode unit C is detachably attached to a ceiling portion of the vacuum chamber 1. In the following description, in FIG. 1, the direction facing the ceiling portion side of the vacuum chamber 1 is referred to as “up” and the direction facing the bottom portion side is described as “down”.

  The cathode unit C includes a target 2 and a magnet unit 3 disposed above the target 2. The target 2 is made of an insulator such as alumina, silicon nitride, or silicon carbide, and is formed in a circular shape or a rectangular shape in plan view by a known method according to the contour of the substrate W. The target 2 is attached to the upper portion of the vacuum chamber 1 via the first insulator 41 provided on the upper wall of the vacuum chamber 1 with the sputtering surface 22 facing downward while being mounted on the backing plate 21. The target 2 is connected to a high-frequency power source (first power source) E1 having a known structure, and high-frequency (alternating current) power having a predetermined frequency (for example, 13.56 MHz) is supplied to the ground during sputtering. I am doing so. The magnet unit 3 disposed above the target 2 generates a magnetic field in a space below the sputtering surface 22 of the target 2, captures electrons etc. ionized below the sputtering surface 22 during sputtering, and spatters from the target 2. It has a known closed magnetic field or cusp magnetic field structure for efficiently ionizing particles, and detailed description thereof is omitted here.

  A stage 5 is disposed in the center of the bottom of the vacuum chamber 1 so as to face the target 2. The stage 5 includes a metal base 51 having an upper surface shape corresponding to the outline of the substrate W, for example, and a chuck plate (plate) 52 bonded to the upper surface of the base 51. The chuck plate 52 has an outer diameter that is slightly smaller than the upper surface of the base 51, and electrostatic chuck electrodes 52a and 52b to which a voltage is applied from a chuck power supply (not shown) are embedded to constitute an electrostatic chuck. ing. In this case, the chuck plate 52 is detachably attached to the upper surface of the base 51 by a ring-shaped first attachment plate 53. The first deposition preventing plate 53 is attached to the upper surface of the base 51 via the second insulator 42 in order to reduce the bias potential generated in the substrate W during sputtering. As the structure of the electrostatic chuck, known ones such as a monopolar type and a bipolar type can be widely used, and thus detailed description thereof is omitted here.

  The base 51 is held by a third insulator 43 that is L-shaped in cross-sectional view and is hermetically attached to an opening provided on the bottom surface of the vacuum chamber 1, is separated from the grounded vacuum chamber 1, and is electrically floating. Has been. An upper portion of the third insulator 43 is covered with a first deposition preventing plate 53. There is no restriction | limiting in particular as a material of each 1st-3rd insulator 41,42,43, A glass-containing fluororesin (polytetrafluoroethylene), a glass-filled epoxy resin, etc. can be used. In addition, an output from a DC power supply (second power supply) E2 that applies a positive DC potential to the electrically floating base 51 is connected to the stage 5 via a switching element 54. As the DC power supply E2, a known structure can be used, and a positive potential of 400 V or less is applied in consideration of the input power to the target 2 and the like. In other plasma processing apparatuses such as an etching apparatus, the applied voltage is appropriately set according to the plasma processing performed in the vacuum processing chamber. A resistor for protecting the switching element 54 may be provided. The base 51 further includes a refrigerant circulation passage 55a and a heater 55b so that the substrate W can be controlled to a predetermined temperature during sputtering.

  A gas pipe 6 serving as a gas introduction means for introducing sputtering gas is connected to the side wall of the vacuum chamber 1, and the gas pipe 6 communicates with a gas source (not shown) via a mass flow controller 6a. The sputtering gas includes not only a rare gas such as an argon gas introduced when forming plasma in the vacuum processing chamber 1a but also a reactive gas such as an oxygen gas or a nitrogen gas. The side wall of the vacuum chamber 1 is also connected to an exhaust pipe 7 leading to a vacuum pump P composed of a turbo molecular pump, a rotary pump, or the like so that the vacuum processing chamber 1a can be evacuated at a constant speed and maintained at a predetermined pressure. I have to.

  Around the stage 5 in the vacuum chamber 1, an annular second adhesion-preventing plate 8 is provided as a ground electrode with a predetermined distance from the third insulator 43. The second adhesion-preventing plate 8 is formed so as to incline downward radially outward from the inner peripheral edge thereof. Although not specifically illustrated and described, a plurality of through holes penetrating in the vertical direction may be formed in the second deposition preventing plate 8. And the 2nd adhesion prevention board 8 is installed in the bottom face of the vacuum chamber 1 of earth ground, and plays a role as earth at the time of sputtering. In the vacuum chamber 1, a third deposition plate 9 that surrounds the space between the target 2 and the substrate W is disposed in order to prevent adhesion of sputtered particles to the inner wall surface of the vacuum chamber 1. .

  The third deposition preventive plate 9 is made of a known material such as alumina or stainless steel, and the upper deposition preventive plate 91 suspended from the upper wall of the vacuum chamber 1 and the lower protection plate erected on the bottom surface of the vacuum chamber 1. Between the attachment plate 92 and the upper prevention plate 91 and the lower prevention plate 92, both the attachment prevention plates 91 and 92 are provided inside the vacuum chamber 1 so that the upper and lower attachment plates 91 and 92 are in the vertical direction. And a movable protection plate 93 that overlaps with each other. The driving shaft Cr of the cylinder Cy provided through the bottom surface of the vacuum chamber 1 at 90 ° intervals in the circumferential direction is connected to the outer surface of the movable protection plate 93 and supported by each driving shaft Cr. Then, the cylinder Cy is used to move the lower adhesion position (position shown in FIG. 1) to prevent the sputter particles from adhering to the inner wall surface of the vacuum chamber 1 and the movable adhesion prevention plate 93 by moving to the upper adhesion prevention plate 91 side. A gap is formed between the lower protection plate 92 and the upper moving position where the substrate W can be carried out and carried into the stage 5 through a through hole To for opening and closing by a gate valve (not shown). The movable adhesion preventing plate 93 is movable. Below, the sputtering method by the said high frequency sputtering device SM is demonstrated.

  Referring also to FIG. 2, the substrate is transferred onto the stage 5 through the through hole To for transfer to the vacuum processing chamber 1 a in a vacuum atmosphere at the upward movement position of the movable protection plate 93 by a vacuum transfer robot (not shown). W is carried out, and the substrate W is placed on the upper surface of the chuck plate 52 of the stage 5. At this time, the switching element 54 is in an off state, and the stage 5 is in a floating state. When the vacuum transfer robot is retracted, the movable adhesion preventing plate 93 is moved to the downward movement position to prevent the sputter particles from adhering to the inner wall surface of the vacuum chamber 1. When a predetermined voltage is applied from the chuck power source to the electrostatic chuck electrodes 52 a and 52 b, the substrate W is electrostatically attracted to the surface of the chuck plate 52.

Next, when the inside of the vacuum processing chamber 1a is evacuated to a predetermined pressure (for example, 10 ⁻⁵ Pa), the argon gas as the sputtering gas is supplied through the gas introduction means 6 at a constant flow rate (for example, the argon partial pressure is In addition to this, a predetermined high-frequency power (for example, 1 to 5 kW) is input from the high-frequency power source E1 to the target 2. As a result, plasma is formed in the vacuum processing chamber 1a, and the target 2 is sputtered by argon gas ions in the plasma for a sputtering time set in accordance with the target film thickness, and the sputtered particles from the target 2 are transferred to the substrate. An insulating film is formed by adhering to and depositing on W. In this case, a high-frequency current flows to the ground via the plasma, but in this embodiment, the stage 5 and the first deposition plate 53 around the substrate W are in an electrically floating state. The film is formed in a state where the flowing high-frequency current is restricted and the bias potential is not applied to the substrate W.

  Here, during film formation by sputtering, electrons in the plasma are charged on the surface of the substrate W, so that the potential of the substrate W gradually decreases as shown by a line a in FIG. Therefore, in this embodiment, before the set sputtering time elapses, the switching element 54 is turned on and a positive potential is applied from the DC power source E2 to the base 51 of the stage 5 for a certain period. As a result, the substrate W potential becomes a potential near zero V (see FIG. 2). In this case, the positive potential may be applied during sputtering (during plasma processing), but at the end of sputtering, the substrate W is not charged (that is, the substrate W potential is about 0 V). It is preferable that it is just before the end of sputtering.

  After the film formation by sputtering is finished, the application of high-frequency power to the target 2 and the introduction of gas are stopped, the voltage application from the chuck power supply is stopped, and the suction of the substrate W is released by short-circuiting to the ground. Then, the film-formed substrate W on the stage 5 is carried out to the vacuum processing chamber 1a through the through hole To for transfer by a vacuum transfer robot (not shown).

  According to the above embodiment, since a positive potential is applied to the base 51 for a certain period of time during the film-forming process by sputtering with respect to the substrate W electrostatically attracted by the chuck plate 52 of the stage 5, the substrate W The charged electrons flow to the ground via low-resistance plasma, and the substrate W is discharged. Therefore, the substrate W immediately after the end of sputtering can be detached from the chuck plate 52 as quickly as possible. In this case, as in the above-described conventional example, the process of supplying ionized gas toward the substrate can be omitted, throughput can be improved, and components for supplying ionized gas are not required. In addition, the cost of the apparatus can be reduced.

  Here, in a plasma processing apparatus including not only the high-frequency sputtering apparatus SM but also an etching apparatus or the like, a processing object exposed to plasma may have a negative potential called a so-called self-bias during the plasma processing. For example, when the object to be processed is placed on an insulating plate such as quartz, the object to be processed is statically fixed to the insulating plate by charging unless the charging of the object to be processed generated at this time is eliminated. Electroadsorption may make it difficult to desorb from the plate after plasma treatment. Even in such a case, if a positive DC potential is applied to a metal base supporting the plate by applying the present invention, the same effect as described above can be obtained and advantageous.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said thing. In the above-described embodiment, the high-frequency sputtering apparatus has been described as an example. However, as long as the substrate can be prevented from being quickly conveyed due to the charging of the substrate during film formation, not only a sputtering apparatus having another configuration but also an etching apparatus, etc. The present invention can be widely applied to other plasma processing apparatuses. As such a plasma processing apparatus, for example, a DC power is applied to a conductive target and a bias voltage is applied to a stage to form a film by sputtering, or an electrode is used as an insulator, and a coil and a flat plate are formed. There is a type that performs plasma processing by supplying high frequency power to at least one to excite IPC plasma in a vacuum processing chamber.

  Moreover, in the said embodiment, although the base 51 was metal, if it is a material which has heat resistance and electroconductivity, it can substitute. Further, the chuck plate 52 has been described as an example of the plate. However, as described above, in the case where the insulating plate does not include the electrostatic chuck and the object to be processed is electrostatically attracted by the plasma processing, the present plate is used. By applying the invention, the object to be processed can be detached as soon as possible after the plasma processing. Furthermore, the object to be processed is not particularly limited as long as it can be charged during plasma processing, such as a glass substrate or a sapphire substrate, as well as a wafer.

SM: high frequency sputtering apparatus, 1 ... vacuum chamber, 1a ... vacuum processing chamber, 2 ... target, 5 ... stage, 52 ... chuck plate (plate), 52a, 52b ... electrode (electrostatic chuck), 6 ... gas tube (gas Introducing means), 8... Second deposition plate (ground electrode), C... Cathode unit, E1 .high frequency power source, E2 .. DC power source, W .. substrate (processing object).

Claims (5)

In the vacuum processing chamber, the object to be processed is electrostatically adsorbed to a plate mounted on the surface of the metal base, and a gas for plasma excitation is introduced into the vacuum processing chamber which has been evacuated, and is provided in the vacuum processing chamber. In a plasma processing method for forming a plasma atmosphere by applying power to the electrodes, and performing plasma processing on the processing object,
A plasma processing method, wherein a potential of the base is made floating, and a positive potential is applied to the base for a certain period during the plasma processing.   2. The plasma processing method according to claim 1, wherein a chuck plate of an electrostatic chuck is used as the plate. A vacuum processing chamber provided with electrodes, gas introduction means for introducing a gas for plasma excitation into the vacuum processing chamber, a first power source for supplying power to the electrodes, a metal base, and a plate mounted on the surface thereof And a stage for electrostatically attracting an object to be processed in a vacuum processing chamber,
A plasma processing apparatus, further comprising a second power source that is installed in a vacuum processing chamber via an insulating material and applies a positive potential to the base for a certain period of time.   The plasma processing apparatus according to claim 3, wherein the plate is a chuck plate of an electrostatic chuck. 5. The plasma processing according to claim 3, wherein the electrode is an insulating target, the first power source is a high-frequency power source, and a film is formed on the surface of the object to be processed by high-frequency sputtering as plasma processing. apparatus.

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