JP7438853B2 - Magnetron sputtering equipment - Google Patents

Description

The present invention includes a vacuum chamber, a stage that holds a substrate to be processed in the vacuum chamber , a target that is attached to the vacuum chamber facing the stage, and a substrate that is disposed on the back side of the target facing away from the stage. and a magnet unit that generates a leakage magnetic field in the space between the target and the target , and relates to a magnetron sputtering apparatus that uses plasma generated in a vacuum chamber to form a film on the processing surface of a substrate to be processed held on a stage. .

For example, in the manufacturing process of semiconductor devices, various plasma processing apparatuses are used that generate plasma in a vacuum chamber and use the generated plasma to perform predetermined processing on the processing surface of a processing target substrate held on a stage. has been done. For example, in the process of forming a metal film such as a Cu film as a seed layer on the inner surface (inner wall surface and bottom surface) of a via hole or contact hole, it is necessary to form a metal film over the entire surface of the substrate to be processed with good coverage. , sputtering apparatuses have been used conventionally (for example, see Patent Document 1). This type of sputtering apparatus is equipped with a vacuum chamber, and in the vacuum chamber, a target and a substrate to be processed are arranged with the sputtering surface of the metal target and the film forming surface of the substrate to be processed facing each other. Ru.

Further, the sputtering apparatus is arranged above the target in the Z-axis direction, with the axial direction orthogonal to the sputtering surface and the film-forming surface being the Z-axis direction, and the film-forming surface side being upward. A magnet unit that generates a leakage magnetic field in the space between the substrate to be processed, a magnetic field generation unit that generates a vertical magnetic field directed downward in the Z-axis direction passing through the film formation surface, and a bias power applied to the substrate to be processed during film formation. It is equipped with a high-frequency power supply that supplies power. Generally, a magnetic field generating unit is used, which includes a coil formed by winding a conductive wire around a ring-shaped yoke that is fixedly arranged on the outer wall of a vacuum chamber, and a power supply that energizes the coil.

When forming a metal film using the above sputtering apparatus, a sputtering gas such as argon is introduced into a vacuum chamber with a vacuum atmosphere, and a leakage magnetic field is applied to a metal target by a magnet unit. A predetermined power with a potential of . Then, plasma is formed in the space between the film forming surface and the sputtering surface, and ions of the sputtering gas ionized in the plasma collide with the sputtering surface of the target, causing sputtered particles to be scattered from the target. Because these scattered sputter particles have a positive potential, their direction is changed by a vertical magnetic field, and together with the fact that bias power is applied to the substrate to be processed, they are incident almost perpendicularly to the film-forming surface. A predetermined metal film is formed by adhesion and deposition.

When forming a metal film, if you want to increase the film forming rate to improve productivity, increase the current flowing through the coil while applying a predetermined bias power to the substrate to be processed. As the magnetic field strength increases (that is, as the magnetic field strength of the perpendicular magnetic field generated by the second magnetic field generating unit is increased), the film formation rate increases accordingly. On the other hand, it has been found that when the current applied to the coil is increased, the in-plane uniformity of the film thickness distribution decreases. Therefore, the inventors of the present application conducted extensive research, and in order to speed up the film formation rate, the in-plane uniformity of the film thickness distribution was reduced by increasing the magnetic field strength of the vertical magnetic field generated by the magnetic field generation unit. In this case, it has been found that the in-plane uniformity of the film thickness distribution can be adjusted by tilting the vertical magnetic field at an angle within a predetermined range (for example, within a range of −15 degrees to 15 degrees or less) with respect to the Z axis. For example, when forming trenches or holes on one surface (processing surface) of a silicon wafer using a dry etching device while generating a vertical magnetic field along the Z-axis direction passing through the processing surface, the perpendicular magnetic field is The configuration tilted with respect to the axis can also be expected to control the etching shape over the entire surface to be processed.

Japanese Patent Application Publication No. 2013-1965

The present invention has been made in view of the above points, and when a predetermined process is performed using plasma with a perpendicular magnetic field generated in the Z-axis direction passing through the processing surface, the perpendicular magnetic field is applied to the Z-axis. The object of the present invention is to provide a plasma processing apparatus that can be tilted at an angle within a predetermined range.

In order to solve the above problems, a vacuum chamber, a stage that holds a substrate to be processed in the vacuum chamber , a target that is attached to the vacuum chamber opposite to the stage, and a target that is placed on the back side of the target that is opposite to the stage are used. This book is equipped with a magnet unit that generates a leakage magnetic field in the space between the substrate to be processed and the target, and uses plasma generated in a vacuum chamber to form a film on the processing surface of the substrate to be processed held on a stage. The magnetron sputtering apparatus of the invention is provided on the side wall of a vacuum chamber , with the axial direction perpendicular to the processing surface being the Z-axis direction, and the processing surface side of the substrate to be processed facing upward, and generating a vertical magnetic field along the Z-axis direction passing through the processing surface. The magnetic field generating unit is characterized in that the magnetic field generating unit is provided with a tilting means for tilting the vertical magnetic field at an angle within a predetermined range with respect to the Z axis.

In the present invention, when the magnetic field generation unit includes a coil formed by winding a conductive wire around a ring-shaped yoke that is inserted on the side wall of the vacuum chamber extending in the Z-axis direction, and a power source that energizes this coil, A configuration may be adopted in which the tilting means includes at least one drive unit that moves a portion of the yoke upward or downward to tilt the coil as a whole with respect to the Z-axis direction. This makes it possible to realize a configuration in which the vertical magnetic field is tilted at an angle within a predetermined range with respect to the Z-axis simply by moving the coil portion upward or downward. For this reason, a plasma processing apparatus that performs a predetermined process using plasma is, for example, a magnetron sputtering apparatus. In such cases, in order to speed up the film formation rate, the in-plane uniformity of the film thickness distribution is reduced by increasing the current applied to the coil and increasing the magnetic field strength of the vertical magnetic field generated by the magnetic field generation unit. However, if the vertical magnetic field is tilted in a predetermined direction at an angle within a predetermined range (for example, within a range of -15 degrees to 15 degrees or less) with respect to the Z axis, the in-plane uniformity of the film thickness distribution can be adjusted. be able to. As a result, it becomes possible to deposit a metal film at a high deposition rate and with good in-plane uniformity of film thickness distribution.

By the way, in the above configuration in which the magnetic field generation unit is composed of a coil and the coil part is mechanically moved upward or downward, there are limitations on the direction and angle of inclination in which the vertical magnetic field can be tilted with respect to the Z axis. There are cases where this happens. Therefore, a magnetic field generation unit is arranged such that a plurality of electromagnets are arranged on the side wall of the vacuum chamber extending in the Z-axis direction, in the same plane perpendicular to the Z-axis direction, and at intervals in the circumferential direction. The tilting means may be configured with a controller that can energize the electromagnets selected from the electromagnet groups in each stage. According to this, by simply selecting the electromagnet to be energized by the controller, it is possible to freely change the inclination angle and direction that can tilt the magnetic field perpendicular to the Z-axis. It also becomes possible to rotate a vertical magnetic field that is tilted by the angle around the Z axis.

In addition, the present invention can be used to form a metal film with good coverage on each fine hole when a plurality of fine holes with a high aspect ratio are formed over the entire surface of the substrate to be processed. can also be applied. On the other hand, the present invention can also be applied, for example, to a case where a dry etching apparatus is used as the plasma processing apparatus and trenches or holes with uniform cross-sectional shapes are formed on the processing surface of a silicon wafer by the dry etching apparatus.

FIG. 1 is a schematic cross-sectional view showing a plasma processing apparatus according to a first embodiment of the present invention. FIG. 3 is a diagram showing the film formation rate and in-plane uniformity of film thickness distribution of a Cu film formed in an experiment showing the effects of the present invention. FIG. 3 is a plan sectional view showing a plasma processing apparatus according to a second embodiment of the present invention. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3;

Hereinafter, with reference to the drawings, the plasma processing apparatus is a magnetron type sputtering apparatus, the substrate to be processed is a silicon wafer (hereinafter referred to as "substrate Sw"), and the target is a copper one having a predetermined purity. The present embodiment will be described using an example in which a Cu film is formed on one surface (hereinafter referred to as "film formation surface Sw1"). In the following description, the orientation shown in FIG. 1 is used as a reference, and the axial direction perpendicular to the film-forming surface Sw1 of the substrate Sw is the Z-axis direction, and the direction toward the film-forming surface Sw1 is the bottom.

Referring to FIG. 1, SM ₁ is the magnetron sputtering apparatus of the first embodiment. The sputtering apparatus SM ₁ includes a vacuum chamber 1 defining a film forming chamber 1a, and a cathode unit Cu is attached to the upper part of the vacuum chamber 1. The cathode unit Cu includes a target assembly 2 and a magnet unit 3 located outside the vacuum chamber 1 and above the target assembly 2. The target assembly 2 includes a copper target 21 having a cylindrical profile and a predetermined composition ratio, and a backing plate 22 bonded to the upper surface of the target 21 via a bonding material (not shown) such as indium, using a known method. Equipped with Note that the target 21 is not limited to being made of copper, but may be made of other metals such as titanium or tungsten, or of metal compounds. Then, the target assembly 2 is detachably attached to the upper part of the vacuum chamber 1 via the insulator _I1 so that the lower surface (sputtering surface 21a) of the target 21 faces the film forming chamber 1a. The output from the power source E1 is also connected to the target 21, and a predetermined power having a negative potential, for example, is applied to the target 21 during sputtering. The magnet unit 3 generates a leakage magnetic field in the space below the lower surface (sputtering surface) 21a of the target 21, captures electrons etc. ionized below the sputtering surface 21a during sputtering, and efficiently removes sputtered particles scattered from the target 21. Since it is possible to use a material having a well-known structure that ionizes well, a detailed explanation will be omitted here.

At the bottom of the vacuum chamber 1, a stage 4 having a substrate mounting surface 41 facing the sputtering surface 21a of the target 21 is provided with an insulator _I2 interposed therebetween. Can be held in position. The output from the power source E2 is also connected to the stage 4, and during sputtering, bias power at a predetermined frequency is applied to the stage 4 and, by extension, the substrate Sw to actively draw sputtered particles having a positive potential to the substrate Sw. I can do it. The distance between the sputtering surface 21a and the film forming surface Sw1 is set, for example, in a range of 300 mm to 600 mm. An exhaust pipe 5a is connected to the lower wall of the vacuum chamber 1. The exhaust pipe 5a communicates with a vacuum pump unit Pu composed of a turbo molecular pump, a rotary pump, etc., and can evacuate the inside of the vacuum chamber 1 to a predetermined pressure or less. A gas pipe 5b for introducing argon gas as a sputtering gas is connected to the side wall 1b of the vacuum chamber 1. The gas pipe 5b communicates with a gas source (not shown) via a mass flow controller Mc, and can introduce argon gas whose flow rate is controlled into the film forming chamber 1a. Note that various components such as the target 21 as an electrode, the power sources E1 and E2, and the gas pipe 5b constitute the plasma generating means of this embodiment.

The side wall 1b of the vacuum chamber 1 is provided with a magnetic field generating unit ₆₁ that generates a vertical magnetic field _MF1 directed downward in the Z-axis direction passing through the film forming surface Sw1 of the substrate Sw. The magnetic field generating unit ₆₁ includes a coil 61 formed by winding a conducting wire 61b around a ring-shaped yoke 61a that is fitted onto the side wall 1b of the vacuum chamber 1 with a gap therebetween, and a coil 61 formed by connecting the free end of the conducting wire 61b. A power source 62 that enables energization of the power source 62 is provided. The position of the coil 61 with respect to the side wall 1b of the vacuum chamber 1 and the number of turns of the conducting wire 61b depend on, for example, the area of the sputtering surface 21a of the target 21, the distance between the target 21 and the substrate Sw, and the vertical magnetic field MF ₁ to be generated. It is set appropriately depending on the magnetic field strength. Further, a tilting means ₇₁ is connected to the yoke 61a to move a part of the yoke upward or downward to tilt the coil 61 as a whole with respect to the Z-axis direction.

The tilting means ₇₁ includes a feed screw 72 having a motor 71 as a driving portion and a slider 73 screwed into the feed screw 72, and the slider 73 is connected to a predetermined position of the yoke 61a via a hinge 74. In this embodiment, four tilting means ₇₁ are provided at intervals of 90 degrees in the circumferential direction. Thereby, for example, if the slider 73 of any one of the tilting means ₇₁ is moved upward (or downward) in the Z-axis direction, the coil 61 as a whole is tilted in the Z-axis direction, and accordingly, The vertical magnetic field MF ₁ generated by the coil 61 is inclined at an inclination angle θ (for example, within the range of −15 degrees to 15 degrees or less) with respect to the Z axis, as shown by the magnetic field MF ₂ shown by the imaginary line (see FIG. 1). ). In this case, by appropriately adjusting the amount of upward or downward movement of the slider 73 of each tilting means ₇₁ in the Z-axis direction, the inclination angle and direction of tilting the vertical magnetic field _MF1 can be appropriately adjusted. In this embodiment, an example will be described in which the drive unit of the tilting unit ₇₁ is provided with a feed screw 72, but the invention is not limited to this, and other actuators such as a single-axis robot may be used to move the coil. 61 may be tilted as a whole. The sputtering apparatus SM ₁ also has a known control controller Cr equipped with a microcomputer, a sequencer, etc., and the control controller Cr controls the operation of the power supplies E1, E2, 62, the mass flow controller Mc, and the evacuation means Pu. The operation, operation of the motor 71, etc. are collectively managed. Hereinafter, a film forming method using the sputtering apparatus SM ₁ will be described, taking as an example a case where a Cu film is formed on a substrate Sw.

A substrate Sw is set on the substrate mounting surface 41 of the stage 4 in the vacuum chamber 1 with its film forming surface Sw1 facing upward, and the vacuum chamber 1 is heated to a predetermined pressure (for example, 10 ^-5 Evacuate to Pa). When the inside of the vacuum chamber 1 reaches a predetermined pressure, the power supply 62 energizes the coil 61 with a predetermined current value to generate a vertical magnetic field MF ₁ directed downward in the Z-axis direction passing through the film-forming surface Sw1 of the substrate Sw. At this time, the slider 73 is moved upward in the Z-axis direction by the motor 71 of one of the tilting means 71, based on the correlation between the current value to the coil 61, which has been experimentally determined in advance, and the film thickness distribution in the plane of the substrate Sw at _that time. (or downward) and tilt the coil 61 as a whole at a predetermined angle with respect to the Z-axis direction (for example, the coil is oriented in the same direction as a region where the film thickness locally becomes thicker (or thinner) within the substrate Sw. 61 as a starting point, the tilting means ₇₁ that moves the slide 73 so that the coil 61 is moved upward or downward, and the amount of movement thereof may be selected. As a result, a vertical magnetic field MF ₂ tilted at an inclination angle θ (for example, within a range of -15 degrees to 15 degrees or less) with respect to the Z axis is generated in the substrate Sw.

Next, argon gas is introduced into the vacuum chamber 1 at a predetermined flow rate by controlling the mass flow controller Mc, and a predetermined power (10 to 30 kW) having a negative potential is applied to the target 21 from the power source E1 to form a film. Plasma is generated in the chamber 1a, and after a predetermined time has elapsed since the plasma is generated, the mass flow controller Mc is controlled to stop the introduction of argon gas while maintaining power input to the target 21, and self-discharge occurs. let As a result, the target 21 is sputtered by ions of the sputtering gas ionized in the plasma atmosphere, and sputtered particles from the target 21 are scattered. At this time, by applying a predetermined bias power (0 to 1250 W) to the stage 4 (substrate Sw) from the power source E2, sputtered particles with a positive potential are actively drawn into the substrate Sw, and the film is formed on the substrate Sw. A Cu film is formed on the surface Sw1. Thereby, a Cu film can be formed at a fast film formation rate and with good in-plane uniformity of film thickness distribution.

In order to confirm the above effects, the following experiment was conducted using the sputtering apparatus _SM1 . In the invention experiment, the substrate Sw was a silicon substrate with a diameter of 300 mm, and a Cu film was formed on the surface of the silicon substrate. That is, the target 21 was made of copper (99.9999% purity) with a diameter of 320 mm, the distance between the target 21 and the substrate Sw was set to 600 mm, and the coil 61 was energized with a current value of 3 A by the power source 62. A vertical magnetic field MF ₁ directed downward in the Z-axis direction was generated passing through the film-forming surface Sw1 of the substrate Sw. Then, after driving the motor 71 to tilt the vertical magnetic field MF ₁ at an inclination angle of 3.5 degrees with respect to the Z axis, the mass flow controller Mc is controlled to supply argon gas at a predetermined flow rate (for example, 20 sccm). (The pressure in the processing chamber 1a at this time was 0.4 Pa). At the same time, DC power (for example, 30 kW) having a negative potential is applied to the target 21 from the power source E1 to generate plasma in the film forming chamber 1a, and then the power applied to the target 21 is maintained. However, the introduction of argon gas was stopped to allow self-discharge (the pressure in the film forming chamber 1a at this time was 1×10 ⁻⁵ Pa). At this time, a predetermined bias power of 250 W or 400 W is applied to the stage 4 by the power source E2, and the sputtered particles are attached and deposited on the substrate Sw by sputtering the sputtering surface 21a of the target 21 to form a Cu film. The in-plane uniformity of the film thickness distribution and the film formation rate of the formed Cu film were measured. As a comparative experiment, a Cu film was formed on the substrate Sw except that the vertical magnetic field MF ₁ was tilted at a predetermined inclination angle with respect to the Z axis, and the thickness distribution of the formed Cu film was uniform in the plane. The properties and film formation rate were measured respectively. FIG. 2 shows the in-plane uniformity of the film thickness distribution and the film formation rate of the Cu films measured.

According to this, the in-plane uniformity of the film thickness distribution of a Cu film formed by tilting the vertical magnetic field MF ₁ at an inclination angle of 3.5 degrees with respect to the Z axis is determined by the power input to stage 4 of 250 W or At 400 W, the values were 1.82% and 1.34%, respectively, and compared with 2.30% and 1.46% in the comparative experiment, it was confirmed that the film could be formed with good in-plane uniformity in film thickness distribution. Furthermore, the deposition rate of the Cu film formed by tilting the vertical magnetic field MF ₁ at an inclination angle of 3.5 degrees with respect to the Z axis was 2.20 nm when the power input to the stage 4 was 250 W or 400 W, respectively. /sec, 1.80 nm/sec, which was confirmed to be the same film forming rate as 2.29 nm/sec, 1.98 nm/sec in the comparative experiment.

Next, referring to FIGS. 3 and 4, in which the same members and elements as in the first embodiment are given the same reference numerals, SM ₂ is a sputtering apparatus of the second embodiment. In the sputtering apparatus _SM2 , the second magnetic field generating unit ₆₂ provided on the side wall 1b of the vacuum chamber 1 is configured as follows. That is, a plurality of second magnetic field generating units ₆₂ (in this embodiment, eight units) are located in the same plane perpendicular to the Z-axis direction and are arranged at equal intervals in the circumferential direction of the side wall 1b. ) are arranged as magnet groups 63u, 63m, and 63d, and the magnet groups 63u, 63m, and 63d are arranged in three stages at equal intervals in the vertical direction so that the electromagnets 63 are aligned in the vertical direction. Each of the electromagnets 63 has the same configuration, and a known electromagnet having a coil wound around a cylindrical or prismatic core is used. The number of electromagnets 63 constituting the magnet groups 63u, 63m, and 63d and their positions depend on, for example, the area of the sputtering surface 21a of the target 21, the distance between the target 21 and the substrate Sw, and the perpendicular magnetic field MF ₁ to be generated. It is set appropriately according to the magnetic field strength.

Further, in the sputtering apparatus _SM2 , the tilting means ₇₂ is composed of a controller. In this case, the controller ₇₂ may be able to freely communicate with the controller Cr of the sputtering apparatus. The controller ₇₂ is a known controller including a microcomputer, a sequencer, a power supply circuit, etc., and includes at least one electromagnet 63 selected from the upper magnet group 63u and one selected from the middle magnet group 63m. Electricity can be applied to at least one electromagnet 63 and the winding of at least one electromagnet 63 selected from the lower magnet group 63d. Then, when an equal current is applied from the controller ₇₂ to all the electromagnets 63 constituting the magnet groups 63u, 63m, and 63d in each stage, a perpendicular magnetic field MF ₁ is generated with respect to the film-forming surface Sw1 of the substrate Sw. can be done. On the other hand, for example, any one electromagnet 63 of the upper magnet group 63u is used as the reference electromagnet 63s, and the electromagnet 63 (63n in FIG. 3) adjacent to the reference electromagnet 63s in the clockwise direction is de-energized. Energization is maintained to the electromagnets 63 in the middle magnet group 63u located directly below the electromagnet 63 that has been de-energized, and the electromagnets 63 adjacent in the clockwise direction to the electromagnets 63 in the middle magnet group 63u to which the energization is maintained are maintained. The energization is stopped, the energization is maintained to the electromagnet 63 of the lower magnet group 63d located directly below the electromagnet 63 whose energization has been stopped, and the electromagnet 63 of the lower magnet group 63d whose energization is maintained is connected to the clock. The energization to the electromagnets 63 adjacent in the direction is stopped. By repeating this, a magnetic field MF ₂ tilted at a predetermined tilt angle θ with respect to the Z-axis can be generated (see FIG. 4).

According to the above, by simply energizing the electromagnet 63 arbitrarily selected from the magnet groups 63u, 63m, and 63d in each stage by the controller ₇₂ , the vertical magnetic field _MF1 can be tilted at an angle with respect to the Z axis. The direction can be changed freely. Moreover, it is also possible to rotate the magnetic field MF ₂ tilted with respect to the Z-axis around the Z-axis during processing.

Although the embodiments of the present invention have been described above, various modifications can be made without departing from the scope of the technical idea of the present invention. In each of the first and second embodiments described above, a magnetron sputtering apparatus is used as an example of the plasma processing apparatus, but the invention is not limited to this. The technical concept of the present invention can be widely applied to a case where a predetermined process is performed using plasma while applying a downward vertical magnetic field to a processed substrate.

SM ₁ , SM ₂ ... sputtering device (plasma processing device), Sw ... substrate (substrate to be processed), Sw1 ... film forming surface (processing surface), E1, E2 ... power supply (plasma generation means), MF ₁ ... vertical magnetic field, DESCRIPTION OF SYMBOLS 1...Vacuum chamber, 1b...Side wall of vacuum chamber, 4...Stage, 5b...Gas tube (plasma generation means), ₆₁ , ₆₂ ...Magnetic field generation unit, ₇₁ ...Tilt means, 7 ₂ ...Controller (tilt means) , 61... Coil (magnetic field generation unit), 61a... Yoke, 61b... Conductor, 62... Power supply (magnetic field generation unit), 63... Electromagnet (magnetic field generation unit), 63u, 63m, 63d... Electromagnet group 71... Motor (drive unit) ).

Claims (3)

A vacuum chamber, a stage that holds a substrate to be processed within the vacuum chamber , a target that is attached to the vacuum chamber to face the stage, and a target that is placed on the back side of the target facing away from the stage to connect the substrate to be processed and the target. A magnetron sputtering apparatus that is equipped with a magnet unit that generates a leakage magnetic field in a space between the two , and that uses plasma generated in a vacuum chamber to form a film on the processing surface of a substrate to be processed held on a stage,
A magnetic field generating unit is provided on the side wall of the vacuum chamber and generates a vertical magnetic field along the Z-axis direction passing through the processing surface, with the axial direction perpendicular to the processing surface being the Z-axis direction and the processing surface side of the substrate being processed facing upward. In things,
A magnetron sputtering apparatus characterized in that the magnetic field generation unit is equipped with a tilting means for tilting the vertical magnetic field at an angle within a predetermined range with respect to the Z-axis. The magnetic field generation unit includes a coil formed by winding a conducting wire around a ring-shaped yoke that is fitted onto a side wall of the vacuum chamber extending in the Z-axis direction, and a power supply that energizes the coil. 2. The magnetron sputtering apparatus according to claim 1, further comprising at least one drive unit that tilts the coil as a whole with respect to the Z-axis direction by moving a portion upward or downward. An electromagnet group in which the magnetic field generation unit is formed by disposing a plurality of electromagnets on a side wall of the vacuum chamber extending in the Z-axis direction, located in the same plane orthogonal to the Z-axis direction, and spaced apart in the circumferential direction. Consisting of multiple stages of vertically arranged at predetermined intervals,
2. The magnetron sputtering apparatus according to claim 1, wherein the tilting means includes a controller capable of energizing the electromagnets selected from the electromagnet group at each stage.

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