JP2014159614A - Sputtering apparatus and sputtering method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sputtering apparatus which allows effectively suppressing generation of crosstalk when AC power with a single frequency is input from multiple of sputtering power supplies into multiple of targets disposed in a single vacuum chamber, and a sputtering method.SOLUTION: A sputtering apparatus includes: multiple of sputtering power supplies Ea to Ec which input AC power by synchronizing each frequency to multiple of targets 4a to 4c disposed in a vacuum chamber 1; and an oscillator Os, which is means to synchronize output timing from each sputtering power supply each other.

Description

  The present invention relates to a sputtering apparatus in which a plurality of targets are arranged in a vacuum chamber and a sputtering method using the same.

  Conventionally, for example, in the manufacturing process of a semiconductor device such as a non-volatile memory, the above kind of sputtering apparatus (so-called multi-source sputtering apparatus) is used to form a dielectric film on the surface of a film formation target (so-called multi-source sputtering apparatus) ( For example, see Patent Documents 1 and 2). This includes a plurality of targets arranged so as to face each film formation target in a vacuum chamber in which the film formation target such as a semiconductor wafer is arranged, and a plurality of spatters for supplying power to each target. Power supply. Then, a sputtering gas is introduced into the vacuum chamber, and a plasma atmosphere is formed in the vacuum chamber by applying DC power or AC power having a negative potential to each target from each sputtering power source, and each target is sputtered. The film is formed on the surface of the film formation target.

  Here, when an insulator is used as the target, it is common to use a high frequency power source (AC power source) as a sputtering power source. When the AC power is input to the target, the impedance is between the AC power source and the target. By interposing a matching device and matching the input impedance and the load impedance, a desired set AC power is always input to the target. On the other hand, if high-frequency power is applied to a plurality of targets arranged in a single vacuum chamber while matching input impedance and load impedance from a plurality of high-frequency power sources, so-called crosstalk is likely to occur. It has been known. When such crosstalk occurs, the load impedance fluctuates, the matching between the input impedance and the load impedance by the impedance matching device cannot follow, and the reflected power to the sputter power source increases. As a result, there is a problem that desired setting AC power is not input to the target and the sputtering rate is significantly reduced depending on the target.

  In order to solve such a problem, in Patent Document 2, the output frequency (for example, 4 MHz, 13, 56 MHz) is changed for each sputtering power source, and AC power is supplied to each target. However, in such a method, it is necessary to prepare a plurality of power supplies having different output frequencies, which increases the cost of the apparatus. Further, since the sputtering rate at the same set input power is different for each target, there is a problem that it is difficult to set process conditions so as to have desired film characteristics (film thickness and film quality).

JP 2009-133209 A International Publication No. 2007/066651

  In view of the above, the present invention is effective when AC power is applied at a single frequency from a plurality of sputter power sources to a plurality of targets arranged in a single vacuum chamber. It is an object of the present invention to provide a sputtering apparatus and a sputtering method capable of suppressing the occurrence of crosstalk.

  In order to solve the above-described problems, a sputtering apparatus of the present invention includes a plurality of sputtering power sources for supplying AC power to each of a plurality of targets arranged in a vacuum chamber with the same frequency and each sputtering power source. Synchronizing means for matching the timing of outputs from the power supply to each other is provided.

  The present inventors have conducted extensive research and applying high-frequency power to a plurality of targets arranged in a single vacuum chamber while matching input impedance and load impedance from a plurality of high-frequency power sources, respectively. The inventors have found that the occurrence of crosstalk can be effectively suppressed if the output timings from the AC power supplies are matched. Therefore, in the present invention, a synchronizing means is connected to each target, and the output timings from the respective sputtering power sources are made to coincide with each other by this synchronizing means. As a result, it is sufficient to prepare a single type of sputtering power source, so that the cost can be reduced and the sputtering rate at the same set input power is approximately the same for each target, so that desired film characteristics (film thickness) It becomes easy to set process conditions so as to have a film quality.

  In the present invention, in which the sputtering power source is a high frequency power source, and an output from each high frequency power source is input to a target via an impedance matching unit, each output cable includes an output cable for connecting each impedance matching unit and each target. It is preferable to use an equivalent one. Here, the equivalent output cable refers to a cable in which the characteristic impedance and the loss of high-frequency power coincide with each other, for example, a cable in which the cable length and the outer diameter of the conductor and the insulator are set to be the same. According to this, coupled with the fact that the occurrence of crosstalk can be suppressed as described above, impedance matching may be performed with high accuracy.

  In the sputtering method of the present invention using the above sputtering apparatus, sputtering gas is introduced into a vacuum chamber in which an object to be deposited is arranged, and AC power is supplied from each sputtering power source to each target at the same frequency. In the case where a plasma atmosphere is formed in the vacuum chamber and each target is sputtered to form a film on the surface of the film formation target, the output timings of the respective sputtering power sources are made to coincide with each other by the synchronizing means.

The top view explaining the structure of the sputtering device of embodiment of this invention. FIG. 2 is a schematic sectional view taken along line II-II in FIG. 1. (A) And (b) is a graph explaining the experimental result of this invention.

  Hereinafter, referring to the drawings, the target is made of alumina as a dielectric, the film formation target is a silicon wafer (hereinafter referred to as “substrate W”), high frequency power is applied to the target, and the alumina film is formed on the surface of the substrate W. The sputtering apparatus according to the embodiment of the present invention will be described with reference to the case of film formation.

  Referring to FIGS. 1 and 2, SM is a sputtering apparatus of the present embodiment, and the sputtering apparatus SM is a vacuum that can be maintained at a predetermined degree of vacuum via a vacuum exhaust means P such as a rotary pump or a turbo molecular pump. A chamber 1 is provided. A substrate stage 2 is disposed at the center of the bottom of the vacuum chamber 1, and the substrate stage 2 is mounted on a metal base 21 having an upper surface shape corresponding to the contour of the substrate W, for example, and the upper surface of the base 21. The chuck plate 22 is formed. Although not shown in particular, the chuck plate 22 has a monopolar or bipolar electrode embedded therein, and a chuck voltage is applied to the electrode from a chuck power source, whereby the substrate W is formed on the upper surface of the chuck plate 22. It can be held by suction. A rotating shaft 23 supported by a bearing 3 inserted through an opening provided in the bottom surface of the vacuum chamber 1 is connected to the center of the lower surface of the base 21. The rotating shaft 23 is connected to a driving unit (not shown) outside the vacuum chamber 1. ) To rotate the substrate stage 2 while holding the substrate W. The base 21 may be provided with a passage for circulating the refrigerant and a heater so that the substrate W can be controlled to a predetermined temperature during film formation by sputtering.

  The ceiling portion of the vacuum chamber 1 is formed in a substantially conical shape, and a plurality of targets 4 are arranged on the ceiling portion at predetermined intervals in the circumferential direction so that the sputtering surface 41 faces the substrate W, respectively. In the present embodiment, the three targets 4a, 4b, 4c are inclined and arranged at intervals of 120 ° in the circumferential direction. The target 4 is not limited to an oxide such as alumina, but the surface of the substrate W such as an insulator such as a nitride such as titanium nitride, tantalum nitride, or silicon nitride, or a carbide such as silicon carbide. It is made of a material appropriately selected according to the composition of the film to be formed. Although not shown in the drawings, a copper backing plate for cooling the target 4 is formed on the upper surface of the target 4 (the surface opposite to the sputtering surface 41) from a material having high thermal conductivity such as indium and tin during film formation by sputtering. It is joined via a bonding material. A known magnet unit is disposed above each target 4 to generate a magnetic field (known closed magnetic field or cusp magnetic field) in the space below the sputtering surface 41 of the target 4, and ionization is performed below the sputtering surface 41 during sputtering. The sputtered particles scattered from the target 4 by capturing the captured electrons and the like may be efficiently ionized.

  In the vacuum chamber 1, a deposition preventing plate 5 is provided so as to surround the target 4 and the substrate W, and adhesion of sputtered particles to the inner wall surface of the vacuum chamber 1 is prevented. A gas introduction pipe 6 for introducing a sputtering gas which is a rare gas such as argon (or a reaction gas of rare gas and oxygen or nitrogen gas in some cases) passes through the side wall of the vacuum chamber 1, and the tip of the gas introduction pipe 6 is a deposition plate. It is possible to introduce a sputtering gas up to 5. Although not shown, the gas introduction pipe 6 communicates with a gas source via a mass flow controller.

  A plurality of high-frequency power sources Ea to Ec as sputtering power sources are connected to the targets 4a to 4c, and high-frequency power (several to several tens of kW) of a predetermined frequency (for example, 13.56 MHz) is input to the ground during sputtering To be. Impedance matching devices Ma to Mc are interposed between the targets 4a to 4c and the high-frequency power sources Ea to Ec, and by matching the input impedance and the load impedance, a desired setting AC appropriately determined according to the process. Electric power is input to the targets 4a to 4c. The impedance matching devices Ma to Mc and the targets 4a to 4c are connected by output cables 7a to 7c, respectively. As each output cable 7a-7c, the same thing, ie, the thing in which the characteristic impedance and the loss of high frequency electric power mutually correspond, for example, the same cable length, the same outer diameter of a conductor, and an insulator, is used. In the present embodiment, the same output cables are used as the output cables for connecting the high-frequency power sources Ea to Ec and the impedance matching devices Ma to Mc.

  The sputtering apparatus SM further includes an oscillator Os that is a synchronization unit connected to each of the high-frequency power sources Ea to Ec. By synchronizing the frequency of the high-frequency power from each of the high-frequency power sources Ea to Ec with this oscillator Os, Timings of outputs from the power supplies Ea to Ec are made to coincide with each other. The sputtering apparatus SM has known control means including a microcomputer, a sequencer, and the like, and controls the operation of the oscillator Os, the operation of the mass flow controller, the operation of the vacuum exhaust means P, and the like. Hereinafter, the sputtering method according to the embodiment of the present invention will be described by taking as an example the case where an alumina film is formed on the surface of the substrate W using the sputtering apparatus SM.

First, the vacuum chamber 1 is evacuated to a predetermined degree of vacuum (for example, 2 × 10 ⁻⁷ Torr), the substrate W is transferred into the vacuum chamber 1 by a transfer robot (not shown), and the substrate W is transferred to the substrate stage 2. Deliver. Next, after applying a chuck voltage to the electrodes of the chuck plate 22 to electrostatically attract the substrate W, the substrate stage 2 is rotated at a predetermined rotational speed. At this time, the substrate stage 2 may be heated by a heater or the like, and the substrate W may be heated to a predetermined temperature. Next, argon gas as a sputtering gas is introduced at a predetermined flow rate, and for example, 100 W high frequency power is supplied from the high frequency power sources Ea to Ec to the targets 4 a to 4 c via the impedance matching units Ma to Mc at the same frequency (for example, 13.56 MHz). To form a plasma atmosphere in the vacuum chamber 1. Thereby, each of the targets 4a to 4c is sputtered, and an alumina film is formed on the surface of the substrate W.

  Here, for the plurality of targets 4 a to 4 c arranged in the single vacuum chamber 1, the present inventors have the respective frequencies from the plurality of high frequency power sources Ea to Ec via the impedance matching units Ma to Mc. When the high-frequency power is turned on and the output timings from the high-frequency power sources Ea to Ec are matched, it has been found that the occurrence of crosstalk can be effectively suppressed. Therefore, in this embodiment, the oscillators Os are connected to the targets 4a to 4c, and the output timings from the high-frequency power sources Ea to Ec are made to coincide with each other by the oscillators Os. Thereby, since it is only necessary to prepare a single type of high-frequency power source Ea to Ec, the cost can be reduced, and the sputtering rate at the same set input power is substantially the same for each target 4a to 4c. It becomes easy to set process conditions so as to have the film characteristics (film thickness and film quality).

  In addition, since the equivalent output cables 7a to 7c for connecting the targets 4a to 4c and the impedance matching devices Ma to Mc are used, the impedance can be reduced in combination with the suppression of the occurrence of crosstalk as described above. The alignment may be performed with high accuracy.

Next, an experiment was conducted to confirm the effect of the present invention using the sputtering apparatus SM. In the invention experiment, the substrate W was a silicon wafer having a diameter of 300 mm, and alumina targets having a diameter of 125 mm were used as the targets 4a to 4c. The substrate W is held by the substrate stage 2, and argon gas is introduced as a sputtering gas into the vacuum chamber 1 at a flow rate of 100 sccm (at this time, the pressure in the vacuum chamber 1 is 3.1 × 10 ⁻³ Torr), and the target 4a A plasma atmosphere was formed by applying high frequency power of 13.56 MHz and 100 W from high frequency power sources Ea to Ec to ˜4c, and each target 4a to 4c was sputtered to form an alumina film on the surface of the substrate W. At this time, the output timing from each of the high frequency power supplies Ea to Ec was matched using the oscillator Os. Vpp and Vdc in each of the targets 4a to 4c during sputtering film formation were measured, and the results are shown in FIG. According to this, it was confirmed that Vpp and Vdc are both substantially constant and stable during sputter deposition, and that crosstalk can be suppressed.

  On the other hand, in the comparative experiment, sputter film formation was performed under the same conditions as the inventive experiment except that the high-frequency powers Ea to Ec were operated without using the oscillator Os. Vpp and Vdc in each of the targets 4a to 4c during the sputtering film formation were measured, and the results are shown in FIG. According to this, it was confirmed that Vpp and Vdc continued to fluctuate during sputtering film formation (particularly, Vpp fluctuated by 200 V or more), and crosstalk occurred.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, the case where high frequency power is input from the high frequency power source to the target has been described, but another AC power source such as a low frequency power source may be used.

  In the above embodiment, the case where the plurality of targets are made of the same material has been described as an example. However, the present invention can also be applied to the case where the plurality of targets are made of different materials.

E (Ea, Eb, Ec) ... high frequency power supply (sputtering power supply), M (Ma, Mb, Mc) ... impedance matching unit, Os ... oscillator (synchronizing means), SM ... sputtering apparatus, W ... substrate (film formation target) 1) Vacuum chamber, 4 (4a, 4b, 4c) ... Target, 7 (7a, 7b, 7c) ... Output cable.

Claims (3)

  A plurality of sputtering power sources for supplying AC power to each of a plurality of targets arranged in a vacuum chamber by matching the respective frequencies, and a synchronizing means for mutually matching the timing of outputs from each sputtering power source A sputtering apparatus comprising: The sputtering apparatus according to claim 1, wherein the sputtering power source is a high frequency power source, and an output from each high frequency power source is input to a target via an impedance matching unit.
A sputtering apparatus comprising an output cable for connecting each impedance matching unit and each target, and using an equivalent one as each output cable. A sputtering method using the sputtering apparatus according to claim 1 or 2,
A sputtering gas is introduced into the vacuum chamber in which the film formation target is arranged, and AC power is applied to each target from each sputtering power source at the same frequency, thereby forming a plasma atmosphere in the vacuum chamber and each target. In order to form a film on the surface of an object to be formed by sputtering,
A sputtering method characterized in that output timings of the respective sputtering power sources are made to coincide with each other by the synchronizing means.

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