JP2014091861A - Sputtering method and sputtering apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sputtering method capable of densifying a film formed by a simple method, when a film is formed by applying AC power (high-frequency power) to a target of an insulator.SOLUTION: A substrate W is installed on a metal stage 5 provided in a vacuum treatment chamber 1a, and sputter gas is introduced into the vacuum treatment chamber subjected to vacuum drawing, and AC power is inputted into a target 2 provided in the vacuum treatment chamber to sputter the target, and to thereby form a film on the substrate surface. During sputtering, the electric potential of the stage 5 is set in the floating state.

Description

  The present invention relates to a sputtering method and a sputtering apparatus, and in particular, a target composed of an insulator is used, and the target is sputtered by supplying AC power (for example, a frequency of 13.56 MHz) to and from the ground. Further, the present invention relates to a structure in which an insulating film such as an oxide or a nitride is formed on a surface of a substrate to be processed facing a target.

  Conventionally, for example, an insulator composed of an oxide such as alumina or silicon oxide, or a nitride such as silicon nitride is used as a target, and the oxide or nitride is formed on the surface facing the target of the substrate to be processed by sputtering. In the case of forming an insulating film such as a high-frequency sputtering apparatus, it is widely known to use a high-frequency sputtering apparatus including a high-frequency power source for supplying high-frequency (alternating current) power to and from a ground (see, for example, Patent Document 1). . When a film is formed with this high-frequency sputtering apparatus, the substrate may be cooled or heated. In such a case, a heating means or a cooling means is incorporated in a vacuum processing chamber in which the film is formed. In general, a substrate stage is disposed, and a so-called electrostatic chuck is provided on the surface of the substrate stage facing the target to hold the substrate (see, for example, Patent Document 2).

  By the way, in the manufacturing process of a semiconductor device, an oxide film formed on the surface of a silicon wafer which is a substrate to be processed is locally removed, or a metal film deposited on the surface is locally processed to form an electrode and a wiring structure. Etching is performed to obtain. As one of such etchings, there is so-called wet etching in which a material to be removed is dissolved with a chemical substance. For example, by utilizing the fact that silicon dioxide dissolves in hydrofluoric acid but silicon hardly dissolves, an etching solution (chemical solution) composed of an oxidizing agent and hydrofluoric acid is used to remove the oxide film. .

  Prior to wet etching, a mask is provided to limit the etching range, and alumina films and silicon nitride films are widely used as such mask materials. The high frequency sputtering apparatus is also used for forming an alumina film or a silicon nitride film. Here, the alumina film and the silicon nitride film for the above-described use are required to have a performance that is difficult to be removed by a chemical solution used during wet etching. In other words, if the alumina film or the silicon nitride film has high chemical resistance, there is an advantage that the film thickness can be reduced and the productivity can be improved. However, when such a nitride film or oxide film is formed by the above-described high-frequency sputtering apparatus, the formed film is not sufficiently dense. For example, in the above application, it has sufficient chemical resistance. It turned out that I could not say.

  Therefore, the present inventors have made extensive studies and, when the stage holding the substrate in the high-frequency sputtering apparatus is grounded, a bias potential is applied to the substrate during sputtering, so that the plasma is supposed to collide with the target. The positive ions are attracted to the substrate side, and the film formed by the positive ions is not only reverse-sputtered, but the positive ions are taken into the film, so that the formed film is sufficiently dense. I got the knowledge that it wouldn't be.

JP 2002-4042 A JP 2010-21510 A

  In view of the above, the present invention provides a sputtering method capable of densifying a film formed by a simple technique when an AC power (high frequency power) is applied to an insulating target for film formation. It is an object of the present invention to provide a sputtering apparatus having a simple configuration capable of performing this sputtering method.

  In order to solve the above problems, a substrate is placed on a metal stage provided in a vacuum processing chamber, a sputtering gas is introduced into the vacuum processing chamber that has been evacuated, and an AC power is supplied to a target provided in the vacuum processing chamber. The sputtering method of the present invention in which a target is sputtered and a target is sputtered to form a film on the substrate surface is characterized in that the potential of the stage is made floating during sputtering.

  According to the above, since the potential of the stage was made floating during sputtering, the amount of positive ions in the plasma drawn into the substrate and taken into the film by a simple method could be greatly reduced, and the film was formed. The film can be made sufficiently dense. In this case, if the stage is installed with an insulator interposed in a vacuum chamber that defines the vacuum processing chamber, which is normally grounded, the potential of the stage can be made floating during sputtering.

  In the present invention, the stage potential is preferably set to the ground potential before and after the sputtering. According to this, when the substrate is electrostatically adsorbed during sputtering and held in the vacuum processing chamber, when the voltage application to the electrode for chucking is stopped, the potential of the stage is the ground potential. It is possible to easily detach the substrate from the stage without causing a problem that the charge charged on the surface flows to the ground and the substrate remains stuck on the surface of the electrostatic chuck.

  Further, in the present invention, for example, when alumina, silicon carbide, or silicon nitride is used as a target, it is confirmed that positive ions such as argon ions taken into the film formed on the substrate can be suppressed as much as possible. It was.

  By the way, when efficiently cooling or heating the substrate during sputtering, it is desirable to provide a so-called electrostatic chuck on the stage to hold the substrate, but when the stage is installed in a vacuum chamber via an insulator, Even if the application of voltage to the chuck electrode is stopped, the substrate remains attached to the surface of the electrostatic chuck due to the influence of the residual charge, and this makes it impossible to remove the substrate from the stage. In such a case, it is conceivable to incorporate a grounding pin that can be moved forward and backward in the substrate and to remove the static electricity from the substrate prior to removal from the stage, but this complicates the structure of the stage.

  Accordingly, a sputtering apparatus of the present invention includes a vacuum processing chamber in which a target is detachably attached, a gas introduction means for introducing a sputtering gas into the vacuum processing chamber, a sputtering power source for supplying AC power to the target, and a vacuum processing chamber. And a metal stage for holding the substrate, wherein the stage is installed in a vacuum processing chamber via an insulating material, and further includes a potential switching means for switching the stage between floating and ground potential. .

  According to the above, if only the wiring from the ground is connected to the stage, the stage can be grounded by switching the potential switching means provided in the wiring outside the vacuum processing chamber. As a result, the film can be formed with a simple configuration. It is advantageous that the substrate and the stage can be neutralized prior to detachment of the used substrate from the stage.

  In the present invention, if a configuration further including an annular ground electrode that surrounds the periphery of the stage in the vacuum processing chamber is adopted, there is a ground around the stage, so that AC power is supplied to the target and the target is formed in the vacuum processing chamber. It may be possible to stabilize the plasma discharge.

The schematic diagram of the sputtering device of this invention. The graph of the experimental result which shows the effect of this invention.

  Hereinafter, a sputtering method and a sputtering apparatus according to an embodiment of the present invention will be described with reference to the drawings, taking as an example a case where an insulating film is formed on the surface of a substrate W such as a sapphire substrate using an insulator.

  Referring to FIG. 1, SM is a high-frequency sputtering apparatus capable of forming a film by the sputtering method 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 E having a known structure, and high-frequency (alternating current) power having a predetermined frequency (for example, 13.56 MHz) is supplied between the target 2 and the ground during sputtering. The magnet unit 3 disposed above the target 2 generates a magnetic field in the space below the sputtering surface 22 of the target 2, captures electrons etc. ionized below the sputtering surface 22 during sputtering, and sputters 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 a cylindrical outline, for example, and a chuck 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, embedded with electrostatic chuck electrodes 52a and 52b, and is applied with a voltage from a chuck power supply (not shown). 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. In this case, 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 during sputtering. In addition, about the structure of an electrostatic chuck, since well-known things, such as a monopolar type and a bipolar type, can be utilized, detailed description is abbreviate | omitted here.

  The base 51 is held by a third insulator 43 that is airtightly attached to an opening provided on the bottom surface of the vacuum chamber 1, and is separated from the grounded vacuum chamber 1 and is electrically floating. 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. The stage 5 is connected to a potential switching means 54 for switching the base 51 between a floating state and a ground potential. The potential switching means 54 includes a wiring 54a connected to the base 51. The wiring 54a is positioned outside the vacuum processing chamber 1a, and a resistor 54b and a switching element 54c are interposed and grounded. . In this case, the resistor 54b stops the voltage application from the chuck power supply and shorts to the ground to release the adsorption of the substrate W. When the resistor 54b switches the switching element 54c in synchronization with this to ground the stage 5 to the ground. This is to prevent an overcurrent from flowing (for example, 1 MΩ).

  A known element can be used as the switching element 54c. However, if the switching element 54c has a large capacitance, a high-frequency current may flow during sputtering. For example, capacitance: 0.9 pF). The base 51 includes a refrigerant circulation passage 55a and a heater 55b so that the substrate W can be controlled to a predetermined temperature during sputtering.

  Further, a gas pipe 6 serving as a gas introducing means for introducing sputtering gas is connected to the side wall of the vacuum chamber 1, and this 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 surface of the vacuum chamber 1 is also connected to an exhaust pipe 7 leading to a vacuum pump P constituted by 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. 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.

  An unillustrated vacuum transfer robot unloads the substrate W onto the stage 5 through the transfer through hole To to the vacuum processing chamber 1a in the vacuum atmosphere at the upward movement position of the movable protection plate 93, and the stage 5 The substrate W is placed on the upper surface of the chuck plate 52. When the vacuum transfer robot is retracted, the movable deposition plate 93 is moved to the downward movement position so that the sputtered particles do not adhere to the inner wall surface of the vacuum chamber 1. The switching element 54c of the potential switching means 54 is off, and the stage 5 is in a floating state. When a predetermined voltage is applied from the chuck power source to the electrostatic chuck electrodes 52a and 52b, the substrate W is electrostatically attracted.

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 at a constant flow rate (for example, the argon partial pressure is 2 Pa through the gas introducing means). In accordance with this, predetermined high frequency power (for example, 1 to 5 kW) is supplied from the high frequency power source E to the silicon nitride target 2. Thereby, plasma is formed in the vacuum processing chamber 1a, the target 2 is sputtered by ions of argon gas in the plasma, and sputtered particles from the target 2 adhere to and deposit on the substrate W to form a silicon nitride film. The In this case, a high-frequency current flows to the ground through the plasma. However, in this embodiment, the stage 5 and the first deposition plate 53 around the substrate are in an electrically floating state, and therefore flow to the substrate W. The film is formed in a state where the high-frequency current is limited and the bias potential is not applied to the substrate W.

  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 short circuit to the ground is released to release the adsorption of the substrate W, and the switching element 54c Is switched on and the stage 5 is grounded. 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 the potential of the stage 5 is made floating during sputtering, the amount of argon ions in the plasma drawn into the substrate W and taken into the film by a simple method can be greatly reduced. The formed film can be made sufficiently dense. In addition, if only the wiring 54a from the ground is connected to the stage 5, the stage 5 can be grounded by switching the switching element 54c interposed in the wiring 54a outside the vacuum processing chamber 1a. It is advantageous that the stage 5 can be neutralized before the film-deposited substrate W is detached from the stage 5. In addition, since the second protective plate 8 serving as an annular ground electrode surrounding the stage 5 is further provided, it is possible to stabilize the plasma discharge formed in the vacuum processing chamber 1a by supplying high frequency power to the target 2. it can.

  Next, in order to confirm the above effects, the following experiment was performed using the high-frequency sputtering apparatus SM shown in FIG. In this experiment, the substrate W was a silicon wafer. Then, alumina was used as the target 2 and an alumina film was formed on the silicon wafer surface. As the sputtering conditions, the distance between the target 2 and the substrate W was set to 60 mm, the input power was set to 1 kW by the high frequency power source E, and the sputtering time was set to 70 sec. In this experiment, argon gas was used as the sputtering gas, and the partial pressure of the sputtering gas was set to about 2 Pa during sputtering. As a comparative experiment, in the high frequency sputtering apparatus, films were formed with the switching element 54c turned on and the stage 5 grounded (the input power was set to 1, 1.5 and 2 kW, respectively).

  FIG. 2 is a graph obtained by measuring the etching rate when wet etching is performed using a chemical solution (0.2% hydrofluoric acid) on an alumina film formed on the substrate surface with respect to input power. According to this, it can be seen that, in the comparative experiment, the etching rate was 280 Å / min, whereas in this experiment, it decreased to 200 Å / min. Further, when the formed alumina film was analyzed by XPS, it was confirmed that, unlike the comparative experiment, argon ions were not taken into the film in the alumina film of this experiment. This does not particularly indicate experimental results, but it was confirmed that the same was true for silicon nitride and silicon carbide.

  As mentioned above, although embodiment of this invention was described, this invention is not limited above. In the above embodiment, an example in which a stage is provided with an insulator interposed in a grounded vacuum chamber has been described as an example, but any method may be used as long as the stage can be electrically floated. Further, the configuration of the electrical switching means 54 is not limited to the above. In the above embodiment, alumina, silicon nitride, and silicon carbide are mentioned. However, the present invention is not limited to these, and the present invention can be used as long as an insulator target is sputtered by applying a high-frequency power source. Can be widely applied.

SM: high frequency sputtering apparatus, 1 ... vacuum chamber, 1a ... vacuum processing chamber, 2 ... target, 5 ... stage, 54 ... potential switching means, 6 ... gas pipe (gas introduction means), 8 ... second deposition plate (earth) Electrode), C ... cathode unit, E ... high frequency power supply, W ... substrate.

Claims (5)

A substrate is placed on a metal stage provided in the vacuum processing chamber, a sputtering gas is introduced into the vacuum processing chamber that has been evacuated, and AC power is supplied to the target provided in the vacuum processing chamber to sputter the target. In the sputtering method of forming a film on the substrate surface,
A sputtering method characterized by floating a potential of a stage during sputtering.   2. The sputtering method according to claim 1, wherein the potential of the stage is set to the ground potential before and after the sputtering.   The sputtering method according to claim 1 or 2, wherein alumina, silicon carbide, or silicon nitride is used as the target. A vacuum processing chamber in which a target is detachably attached, a gas introducing means for introducing sputtering gas into the vacuum processing chamber, a sputtering power source for supplying AC power to the target, and a metal stage for holding a substrate in the vacuum processing chamber And
A sputtering apparatus characterized in that a stage is installed in a vacuum processing chamber via an insulating material, and further comprises a potential switching means for switching the stage between floating and ground potential.   The sputtering apparatus according to claim 4, further comprising an annular ground electrode surrounding the stage in the vacuum processing chamber.

Images