JP2009299191A - Plasma-assisted sputter film-forming apparatus - Google Patents

Abstract

Disclosed is a plasma-assisted sputter deposition apparatus having a wafer holder with good temperature controllability that can maintain good and required characteristics and is stopped during film deposition.
A plasma-assisted sputter deposition apparatus has the following configuration. A reaction vessel 1 into which a process gas used for plasma generation is introduced, and a donut-shaped electrode made of a material sputtered by the plasma, the lower surface of which is inclined with respect to the wafer surface 2 and a rotating plate 3 that rotates on its central axis while moving on a circle above the donut-shaped electrode, and includes a magnet array 4 attached to the lower surface thereof and parallel to the surface of the donut-shaped electrode And a power source 10 connected to the donut-shaped electrode, and a wafer holder 5 for placing the wafer 9 for film deposition, which is in a stopped state during film deposition.
[Selection] Figure 4

Description

 The present invention relates to a plasma assisted sputter film forming apparatus, and more particularly to a plasma assisted sputter film forming apparatus for depositing a thin film on a wafer, wherein the wafer holder is stopped during film deposition, and good film uniformity is achieved. The present invention relates to a plasma assisted sputtering film forming apparatus having high accuracy and high precision film thickness control.

 Magnetron DC or magnetron RF sputtering devices are widely applied to deposit thin films on substrates used in the semiconductor industry. One of the major requirements in depositing a film on a substrate is, for example, film uniformity on a silicon wafer. In order to deposit a film with higher film uniformity, a DC sputtering apparatus having an inclined electrode is invented and used with respect to the surface of the wafer (see Patent Document 1 and Patent Document 2). However, this apparatus has several problems in controlling the substrate temperature, sputtering the deposited film again, and reducing particles. These problems will be described in detail with reference to FIG.

 FIG. 5 shows a cross-sectional view of a DC sputtering apparatus having an inclined electrode. The reaction vessel 100 includes an electrode 101, a wafer holder 102, a gas introduction unit 103, and a gas discharge unit 104. The electrode 101 is made of a metal, such as Al, Ti, Ta, etc. that needs to be sputtered and deposited on the wafer 112. The electrode 101 is electrically insulated from the reaction vessel 100 using a dielectric material 105. In general, a plurality of magnets 106 having some special arrangement are arranged on the surface of the electrode 101. Further, the magnet 106 provided on the electrode 101 is rotated around the deflection axis or the central axis of the electrode 101. A circular arrow 121 indicates the state of rotation around the central axis. The electrode 101 is connected to a DC power source 107.

 In general, the wafer holder 102 includes a metal electrode 108, a dielectric material 109, a side wall 110, and a shaft portion 111. Shaft 111 is connected to an electric motor to rotate wafer holder 102 about its central axis as indicated by circular arrow 122. The electric motor is not shown in the figure.

 In the reaction vessel 100, a DC current is applied to the electrode 101 to generate DC plasma while maintaining the inside of the reaction vessel 100 at a low pressure. Due to the higher negative voltage of electrode 101, ions in the plasma are accelerated relative to electrode 101 and sputtered. These sputtered atoms then travel through the plasma, deposit on the wafer 112, and deposit on other surfaces exposed to the plasma.

 The flow of sputtered atoms coming from the tilt electrode 101 is not uniform over the surface of the wafer. In order to obtain a uniform film on the surface of the wafer, the wafer holder 102 is rotated about its central axis. This results in a uniform film.

 All problems in the PVD apparatus described above are due to the wafer holder 102 being made to rotate.

 The first problem is that the temperature of the wafer cannot be controlled during film deposition. This is because it is difficult to incorporate a liquid-based cooling mechanism into the metal electrode 108. It is similarly difficult to incorporate a heating mechanism into the metal electrode 108. These difficulties are mechanical difficulties and are caused by the rotation of the wafer holder 102. Depositing the film at a controlled temperature is important to obtain a film with desirable physical and electrical properties. For example, depositing a Cu (copper) film as a seed layer for the electroplating process must be performed at temperatures below zero degrees to obtain better surface smoothness.

 The second problem is that it is difficult to make an electrostatic chuck (ESC) on the metal electrode 108 to clamp the wafer using electrostatic forces due to the complexity of designing electrical connections. It is. Clamping the wafer using ESC is important when control over the temperature of the wafer is required during the film deposition process.

 A third problem is that supplying RF current to the metal electrode 108 is not as easy as it is also difficult to make an electrical connection to the rotating wafer holder 102. is there. Applying RF power to the metal electrode 108 is necessary when film deposition must be performed with soft ion bombardment or when the deposited film needs to be sputtered again.

 A fourth problem is that particles are generated in the reaction vessel due to the continuous rotation of the wafer holder 102. The rotation of the wafer holder 102 causes the outer portion and the peripheral portion to vibrate. This facilitates the separation of the deposited thin film as a flake from the vibrating surface, which ultimately causes particle contamination on the wafer surface.

 In addition, the following Patent Document 3 and Patent Document 4 can be cited as techniques relating to a donut-type cathode or target.

JP 2002-167661 A JP 2002-296413 A Japanese Patent Laid-Open No. 7-126847 Japanese Patent Laid-Open No. 5-189762

 An object of the present invention is to solve the four problems described above. In the magnetron DC or magnetron RF sputtering apparatus proposed by the present invention, the wafer holder is at rest when processing the wafer by changing or improving the structure of the electrodes and associated parts.

 An object of the present invention is to provide a donut-shaped electrode having an inclined surface, a structure of a magnet that rotates and revolves (satellite motion), and a wafer holder that has good controllability of temperature during a film deposition. By providing the plasma-assisted sputter deposition apparatus, the above-described problems can be solved, and the desired quality can be maintained in terms of film uniformity and thickness controllability. There is.

 The plasma assisted sputter deposition apparatus according to the present invention is configured as follows in order to achieve the above-described object.

 The plasma assisted sputter deposition apparatus has the following configuration. A reaction vessel into which a process gas used for plasma generation is introduced, and a donut-shaped electrode made of a material sputtered by the plasma, the lower surface of which is inclined with respect to the surface of the wafer; A rotating plate rotating on its central axis while moving on a circle above the donut-shaped electrode, the rotating plate including a magnet array attached to the lower surface thereof and parallel to the surface of the donut-shaped electrode, and a donut-shaped A power source connected to the electrodes and a wafer holder for placing the wafer for film deposition, the wafer holder being stopped during film deposition.

 In the above plasma assisted sputter deposition apparatus, the magnet arrangement on the lower surface of the rotating plate is preferably symmetrical about the rotation axis.

 In the above plasma assisted sputter deposition apparatus, the magnet array provided on the lower surface of the rotating plate is preferably asymmetric around the rotation axis.

 The plasma assisted sputter deposition apparatus has the following configuration. A reaction vessel into which a process gas used for plasma generation is introduced, and a donut-shaped electrode made of a material sputtered by the plasma, the lower surface of which is inclined with respect to the surface of the wafer; To create one or more closed loop magnetic flux lines under the donut-shaped electrode, facing the electrode, having alternating magnetic poles and having different diameters, placed above the donut-shaped electrode Two or more circular magnets, a power source connected to a donut-shaped electrode, and a wafer holder for placing a wafer for film deposition, wherein the wafer is in a stopped state during film deposition It consists of a holder.

 The plasma-assisted sputter deposition apparatus according to the present invention employs a donut-shaped electrode having an inclined surface, a rotating and revolving magnet configuration, and a temperature-controllable wafer holder that is stopped during film deposition. Good and required properties such as film uniformity and film thickness controllability can be maintained.

This figure is a longitudinal sectional view of the apparatus according to the first embodiment of the present invention. This figure is a perspective view of a donut-shaped electrode. This figure is a schematic plan view of the donut-shaped electrode accompanied by the movement of the rotating plate relative to the donut-shaped electrode. This figure is a longitudinal sectional view of an apparatus according to the second embodiment of the present invention. This figure is a longitudinal sectional view of a conventional apparatus.

 Hereinafter, preferred embodiments will be described with reference to the accompanying drawings. Details of the present invention will be clarified through the description of the embodiment.

 1st Embodiment of this invention is described according to FIGS. 1-3. FIG. 1 shows a longitudinal sectional view of a first embodiment of the plasma-assisted sputter deposition apparatus of the present invention.

 The reaction vessel 1 includes an electrode 2 provided on the ceiling wall 1A and a wafer holder 5 provided on the bottom plate 17 thereof. The upper support wall 1B supports the ceiling wall 1A. The ceiling wall 1A has a ring-shaped inclined peripheral portion. The electrode 2 is arranged on the ring-shaped inclined peripheral portion of the ceiling wall 1A.

 The electrode 2 is made of a metal, such as Al, Ti, Ta, etc., which needs to be sputtered and is deposited on a wafer 9 placed on the wafer holder 5. The electrode 2 is electrically insulated from the reaction vessel 1 using a dielectric material 8. The electrode 2 is connected to a DC power source 10.

 In the reaction vessel 1 of the first embodiment, the electrode 2 has a donut shape or a circular ring shape, and the bottom plate 17 has a gas introduction portion 6, and in the lower part of the side wall 20 near the bottom plate 17. Has a gas discharge part 7. In the space on the back side of the electrode 2, there is a rotating plate or a rotating disk 3 to which the magnet array 4 is attached.

 The electrode 2 is made of a material to be sputtered and deposited on the wafer 9. The shape of the electrode 2 is a circle having a hole in the center as shown in FIG. The inner and outer diameters of the electrode 2 are not critical and are determined by considering the wafer diameter and the height from the wafer to the electrode 2. The inner and outer diameter centers of the electrode 2 and the center of the wafer 9 are on the same straight line. The surfaces of the electrodes 2 are inclined so that the extended ones of these surfaces create a conical structure. The inclination angle between the electrode surface and the horizontal line, indicated by “α” in FIG. 1, is not important and is generally less than 45 degrees. The thickness of the electrode 2 indicated by “t” in FIG. 2 is likewise not critical and is in the range of 2 mm to 20 mm. A thinner electrode 2 is preferred because it creates a stronger magnetic flux on its lower surface. The electrode 2 is covered by an insulating material 8 to electrically insulate from the remaining portions of the reaction vessel 1 and is supplied with DC or rf power. As an example, a DC power supply 10 is shown in FIG.

 A magnet array 4 composed of a plurality of magnets is fixed to the rotating plate 3. The rotating plate 3 is usually made of metal. The diameter of the rotating plate 3 is usually set to be slightly shorter than the width of the electrode 2 indicated by “d” in FIG. However, rotating plates larger than the electrode width “d” may be employed with appropriate hardware modifications.

 The rotating plate 3 is constantly rotating around its central axis 16. In addition, the rotating plate 3 with the magnet array 4 moves in a circular orbit above the electrode 2 with a movement similar to satellite movement. In this case, the rotating plate 3 is parallel to the surface of the donut electrode 2. These movements are shown schematically in FIG. In FIG. 3, an arrow 31 indicates a spin motion (spinning motion), and an arrow 32 indicates a satellite motion (revolution motion). A mechanism for generating the spin motion and the satellite motion includes a motor 33 coupled to the central shaft 16, a ring-shaped guide member having a gear mechanism fixed to the side wall 20 of the upper support wall 1B, and the motor 33 and the ring-shaped guide. It is comprised from the connection member for connecting the member 34. As shown in FIG. When the motor 33 operates, the central shaft 35 is rotated, and the unit including the motor 33 and the rotating plate 3 moves along the ring-shaped guide member 34 by the gear mechanism.

 The magnet array 4 on the lower side of the rotating plate 3 is not important, and may be a magnet array having any symmetric or asymmetric form.

 The wafer holder 5 is fixed to the bottom plate 17. It is composed of a metal electrode 11, an electrostatic chuck (ESC) 12, and an insulator 13. A temperature control liquid is supplied to the metal electrode 11 via the liquid introduction part 14 and the liquid discharge part 15. The temperature control liquid is usually used to maintain a constant temperature in the range of 100 ° C. to −100 ° C. in the metal electrode 11. If higher temperatures are required, typically above 100 ° C., an electrical heating system can be provided inside the metal electrode 11. A thin dielectric layer 12 is present on the top surface of the metal electrode to form the ESC. In this dielectric layer 12, a very thin metal electrode or several electrodes may be provided as part of the ESC. Furthermore, a gas supply mechanism may be provided for the ESC in order to increase the thermal conductivity between the wafer 9 and the ESC. A detailed description of the structure of the ESC is not given here as it is available in the general literature. The wafer holder 5 is fixed on the bottom plate 17 of the reaction vessel 1. This facilitates the provision of electrical wiring and cooling / heating mechanisms. However, it is also possible to make the wafer holder 5 so as to move in the vertical direction with all the device configurations described above. An important feature of the wafer holder 5 is that the wafer and the wafer holder are stationary during film deposition compared to those described in the prior art. That is, there is no rotating part in the wafer holder 5.

 The operation of the structure described above will be described. The wafer 9 introduced into the reaction vessel 1 through the wafer loading / unloading door 18 is placed on the fixed wafer holder 5. The wafer 9 in the wafer holder 5 is electrostatically clamped on the ESC. The ESC is maintained at a constant temperature supported by a cooling medium or a heater. Gas is fed into the reaction vessel 1 and the reaction vessel is maintained at the desired pressure. The pressure inside the reaction vessel 1 is not critical and can be varied in the range of 0.1 mTorr to 100 mTorr. DC power is supplied from the DC power source 10 to the electrode 2, thereby generating and maintaining plasma. The power by the DC current supplied to the electrode 2 is not an important matter and is determined by the required deposition rate and other parameters. In particular, when precise control of the film thickness is required, the film formation must be performed at a low rate of, for example, 10 nm (nanometer) / min. In this case, a low DC power of, for example, 50 watts (W) is applied to the electrode 2. Even if the entire electrode 2 receives the same negative voltage provided by the DC power supply 10, the plasma is confined by the magnetic field, so that the plasma is concentrated on the lower side of the rotating plate 3. This high-concentration plasma moves on a circular orbit below the electrode 2 as the rotary plate 3 provided with the magnet array 4 moves. The phenomenon of sputtering occurs mainly in the presence of a dense plasma, and the sputtered atoms reach the wafer surface at an angle. Therefore, the film formation process is almost the same as that described in the prior art section, resulting in a film with very good film uniformity.

 The metal electrode 11 in the wafer holder 5 may or may not be supplied with an rf current. Even if the rf power is applied, the power due to the rf current from the rf power source 36 is usually kept at a low value so that excessive spattering in the deposited film does not occur.

 The sputtering apparatus according to the first embodiment can maintain a wafer temperature at a desired value, and can produce a highly uniform film with very high accuracy and good film thickness controllability. Further, film deposition is performed by a soft ion bombardment or resputtering process.

 According to the first embodiment, the wafer holder 5 is in a stopped state, and the plasma generated in the lower region of the electrode 2 corresponds to the magnet arrangement of the rotating plate 3 and the satellite motion (revolution) of the rotating plate 3. Rotate with motion). Therefore, even if the wafer holder 5 itself does not rotate, a uniform thin film is deposited on the wafer 9 on the wafer holder 5.

 Next, a second embodiment will be described with reference to FIG. It is a slight modification of the first embodiment. The only modification in this apparatus is to use a new structure of the magnet arrangement corresponding to the magnet arrangement 4 without using the rotating plate 3 as compared with the first embodiment. Here, two or more circular magnets 19a, 19b are arranged on the outer surface of the electrode 2, which face the surface of the electrode and have alternately different polarities. They do not move. In FIG. 4, for example, a configuration having two circular magnets 19a and 19b is shown. These two magnets 19a, 19b are either permanently fixed on the electrode or arranged slightly moved in parallel to the electrode surface with a narrow spacing of for example 1 mm. A magnetic flux line 37 exists between the two circular magnets 19a and 19b. The magnetic flux lines 37 penetrate the electrode 2 and reach the inside of the reaction vessel 1. A slight movement of the circular magnets 19a, 19b results in improved electrode utilization efficiency.

 The application of a DC power source or an rf power source to the electrode 2 is the same as that described in the first embodiment. However, by using the magnet arrangement, a strong donut-shaped plasma is generated on the lower side of the electrode 2 and, at the same time, a sputtering phenomenon occurs on the donut-shaped surface. Therefore, when this configuration is used, the film forming speed increases.

 Except for the modified part described above, all other structures, functions, procedures, and results are the same as those described in the first embodiment.

 The present invention is used for plasma-assisted magnetron sputtering without rotating a wafer holder, and is useful for film deposition on a wafer with good film uniformity, film thickness controllability, and temperature controllability.

DESCRIPTION OF SYMBOLS 1 Reaction container 2 Donut type electrode 3 Rotating plate 4 Magnet arrangement 5 Wafer holder 8 Insulation material 9 Wafer 10 DC power supply 11 Metal electrode 12 Dielectric layer (ESC)
13 Dielectric layer 19a Circular magnet 19b Circular magnet

Claims (1)

A reaction vessel into which a process gas used to generate plasma is introduced;
A donut-shaped electrode made of a material that needs to be sputtered by the plasma, the lower surface of which is inclined with respect to the surface of the wafer;
To generate one or more closed loop magnetic flux lines under the donut-shaped electrode, facing the electrode, having alternating magnetic poles and having different diameters, above the donut-shaped electrode Two or more circular magnets arranged in the
A power source connected to the donut electrode; and
Placing the wafer for film deposition, and a wafer holder stationary during film deposition;
A plasma assisted sputter deposition system comprising: