JP2007042919A - Sputtering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sputtering system which can form a film with a uniform composition, and prevents the state of a plasma from changing with time, thereby not reducing a productivity. <P>SOLUTION: In the sputtering system, chucking-proof plates 7a, 7b are installed by a plurality of metal members doubly and in a non-contact state therebetween, and also, an amount of a residual gas obtained from a residual gas detecting means 15 is analyzed and a DC negative potential is applied to the outside chucking-proof plate 7b. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention particularly relates to a sputtering apparatus provided with a deposition preventing plate that prevents an insulator or the like from adhering to the wall surface of the vacuum vessel.

  In the manufacturing process of a semiconductor integrated circuit (IC), various dielectric films are formed. The purpose of use is, for example, film formation for interlayer insulation films, mask formation, passivation or capacitor dielectric films, etc., and various sputtering methods are used by selecting materials or plasma processing methods for each purpose. ing.

  In recent years, in order to reduce the size of this IC, a sputtering method has been studied in which a dielectric material having a high dielectric constant such as barium strontium titanate (BST) or strontium titanate (STO) is plasma-treated on the capacitor dielectric film. It is being done.

  Further, a sputtering method using plasma of a ferroelectric material such as lead zirconate titanate (PZT) or strontium bismastantalate (SBT) has been studied for sensors, actuators, and nonvolatile memory devices.

  In order to achieve performance and quality stability in the dielectric materials and ferroelectric materials having a high dielectric constant described above, the material composition of the dielectric material or ferroelectric material should be uniformly formed. is necessary.

  Therefore, in the sputtering method using plasma processing, it is necessary to stabilize the plasma conditions during the film forming process. On the other hand, it is also strongly required to improve the productivity by increasing the film formation rate.

  Hereinafter, the configuration of a conventional sputtering apparatus will be described with reference to the drawings.

  FIG. 2 is a conceptual diagram showing a schematic configuration of a conventional sputtering apparatus. In this sputtering apparatus, a sputtering chamber is formed by a vacuum vessel 101 that can be evacuated by using a suction means.

  A target 102 is fixedly held on the electrode 103 below the sputtering chamber. The electrode 103 is electrically insulated from the vacuum vessel 101 and incorporates a water cooling mechanism (not shown) in order to prevent the temperature of the target 102 from rising.

  Above the vacuum vessel 101, a wafer holder 104 is arranged in parallel to face the electrode 103. The wafer holder 104 is electrically insulated from the vacuum vessel 101 and has a floating potential. A substrate, for example, a semiconductor wafer (hereinafter referred to as a wafer) 105 is placed on the wafer holder 104. Wafer holder 104 incorporates a heating mechanism (not shown) for maintaining wafer 105 at a predetermined temperature set in advance.

  Then, plasma is generated by applying a predetermined high-frequency power determined by sputtering conditions from the high-frequency power source 106 between the electrode 103 and the grounded vacuum vessel 101. The high frequency power is adjusted by the impedance matching unit 120 so that the maximum power can be supplied by matching. The high frequency power is applied under a predetermined negative DC bias.

  Next, in order to perform the film forming process with this sputtering apparatus, the wafer 105 is placed on the wafer holder 104, and is evacuated by a vacuum pump (not shown) connected to the exhaust port. A variable conductance valve interposed between the exhaust port and the vacuum pump is adjusted to a predetermined pressure while introducing a gas (for example, Ar gas) at a predetermined flow rate. Then, high frequency power is applied to generate plasma to sputter the target.

  In this way, components scattered from the target 102 are deposited on the wafer 105 to form a film. The components scattered from the target 102 are not only directed toward the wafer 105 but also directed toward other directions. If an object other than the wafer 105 adheres to the inner wall of the vacuum vessel 101 or a structure inside the vacuum vessel 101, the cleaning becomes difficult. Therefore, the adhesion preventing plate 107 a and the outer side of the electrode 103 and the wafer holder 104 are surrounded. A protective plate 107b is disposed on the surface.

  These adhesion prevention plates 107a and 107b are made of metal, and are electrically connected to the vacuum vessel 101 to be at a ground potential. When the deposit attached to the surface becomes thick with an easily removable structure, they are removed and cleaned. To be able to. Further, these adhesion prevention plates 107 a and 107 b can be partially retracted for taking in and out of the wafer 105.

Then, as the film formation proceeds, deposits adhere to the deposition plate 107a and the wafer 105 and the grounding surface cannot be seen, and the plasma tends to spread out from the gap between the wafer holder 104 and the deposition plates 107a and 107b. However, since it is difficult for deposits to adhere to the inner surface of the protective plate 107b, it is a ground potential surface, and discharge occurs between them, so that plasma spreads outside the dual-layered protective plates 107a and 107b. (For example, refer to Patent Document 1).
JP 2004-31493 A

  However, in such a sputtering apparatus provided with the conventional adhesion preventing plates 107a and 107b, when a dielectric material or a piezoelectric material is used as a target and a film is formed during the plasma processing, the dielectric material that is also an insulator or The piezoelectric material adheres also to the adhesion preventing plates 107a and 107b, and the surfaces of the adhesion preventing plates 107a and 107b which should be conductors are insulated, so that the adhesion preventing plate 107b which plays a role as a ground electrode in particular. The ground potential area is reduced.

  When the ground potential area is sufficiently larger than the area of the electrode 103, the DC bias of the high frequency power applied to the electrode 103 is a negative large value, and the average potential of the plasma is also approximately equal to the ground potential. However, as described above, when the ground area of the plasma decreases due to the adhesion of the insulator, the DC bias potential increases, and the average potential of the plasma increases to a value larger than the ground potential. The plasma state changes. As a result, there arises a problem that the composition of the formed film becomes non-uniform.

  The present invention is intended to solve the above-described problems, and an object of the present invention is to provide a sputtering apparatus capable of forming a desired film having a uniform composition.

  Furthermore, the present invention provides a sputtering apparatus in which productivity is not lowered by preventing the plasma state from changing over time.

  In order to solve the above problems, the present invention has the following configuration.

  The invention according to claim 1 of the present invention particularly provides the anti-adhesion plate in a non-contact state with a plurality of metal materials in a double and non-contact state with the residual gas detection means from the residual gas detecting means. It is configured to apply a DC negative potential that is determined by analyzing and determining the amount of residual gas to be obtained. This makes it possible to secure the ground contact area of the deposition preventive plate and achieve a desired composition that does not contain foreign matter. It has the effect of forming a film.

  The invention according to claim 2 of the present invention is particularly configured to determine the time for applying the DC negative potential by analyzing the residual gas amount obtained from the residual gas detecting means. The film formation can secure the ground contact area of the deposition preventing plate, and has the effect of forming a film having a desired composition with no foreign matter mixed therein. Furthermore, it is possible to prevent the plasma state from changing over time, and since the film formation rate is constant, there is an effect that productivity does not decrease.

  Sputtering apparatus of the present invention, a vacuum container, a residual gas detection means installed in the vacuum container, a wafer holder placed inside the vacuum container, an electrode disposed facing the wafer holder, A sputtering apparatus comprising: an impedance matching unit connected to the electrode; a high-frequency power source connected to the impedance matching unit; and an adhesion preventing plate disposed so as to surround the electrode. In addition to being installed in a non-contact state with each other, a DC negative potential determined by analyzing and determining the amount of residual gas obtained from the residual gas detection means is applied to the outer deposition plate. In addition, the ground contact area of the deposition preventing plate can be ensured, and a film having a desired composition can be formed without foreign matter being mixed therein.

(Embodiment 1)
Hereinafter, the sputtering apparatus in Embodiment 1 of this invention is demonstrated, referring drawings.

  FIG. 1 is a conceptual diagram for explaining the configuration of a sputtering apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, a switch 11 for switching the potential of the deposition prevention plate 7b between a ground potential and a negative DC potential is connected to the deposition prevention plate 7b arranged on the outside.

  An electrode 3 on which a target 2 is placed is installed at the lower part of the vacuum vessel 1 capable of forming and maintaining a vacuum, and a wafer holder 4 is opposed to the electrode 3 in parallel at the upper part of the vacuum vessel 1. The wafer holder 4 is electrically insulated from the vacuum vessel 1 and has a floating potential.

  A wafer 5 such as a silicon substrate is placed on the wafer holder 4. Furthermore, the adhesion prevention board 7a, 7b which consists of a double metal cylindrical body is provided so that the target 2 may be enclosed, and the adhesion prevention board 7a installed inside this is made into the floating electric potential.

  A switch 11 for switching the potential of the deposition plate 7b between a ground potential and a DC negative potential by the DC power source 12 is disposed and connected to the deposition plate 7b installed on the outside. Normally, the switch 11 is connected to the ground potential during film formation, and the switch 11 is configured such that when the switch 11 is switched, the potential of the deposition preventing plate 7b becomes a DC negative potential.

  The vacuum vessel 1 is equipped with a residual gas detection means 15 such as a gas sensor for detecting and measuring the residual gas inside the vacuum vessel 1, and measures the residual gas amount inside the vacuum vessel 1 when necessary. The result can be output. A control circuit for switching the switch 11 and changing the set voltage of the DC power source 12 by using the measured value of the residual gas output from the residual gas detection means 15 as a monitor output and analyzing or analyzing the measured value. 10 is provided.

An example in which a piezoelectric thin film, for example, lead zirconate titanate (PZT: Pb (Ti _x Zr) O ₃ ) is formed on a Si wafer in the sputtering apparatus configured as described above will be described.

  In order for a predetermined PZT thin film to function as a piezoelectric device, it is necessary to form electrodes on the upper and lower layers of the PZT thin film in order to apply an electric field to the PZT thin film, and a metal film (for example, Ti A film having a thickness of 10 nm and a Pt film having a thickness of 400 nm is preliminarily formed on one surface of the wafer 5.

The wafer 5 is placed on the wafer holder 4, and the inside of the vacuum vessel 1 is brought into a predetermined vacuum state by a vacuum pump, and then a predetermined gas (for example, Ar gas and reactive gas as an inert gas) is supplied from a gas inlet. O ₂ gas) is introduced at a predetermined flow rate (for example, Ar gas flow rate: 0.2 sccm, O ₂ gas flow rate: 20 sccm), and a variable conductance valve interposed between the exhaust port and the vacuum pump is adjusted to adjust the vacuum container The inside of 1 is adjusted to a predetermined pressure (for example, 0.2 Pa).

  Next, when a high frequency power (for example, 1000 W) is applied between the electrode 3 and the vacuum vessel 1 by the high frequency power source 6, plasma is generated immediately above the target 2 and the formation of a PZT thin film is started.

  The high frequency power is adjusted by the impedance matching unit 20 so that the maximum power can be supplied by matching.

  Then, after elapse of time for obtaining the desired thickness of the PZT thin film, the application of the high frequency power is stopped and the film formation of the PZT thin film is completed.

  Here, there is a close relationship between the piezoelectric characteristics required for the piezoelectric thin film and the composition ratio of Pb, Zr, Ti, and O of PZT. In order to obtain the desired piezoelectric characteristics, the composition control of the dense piezoelectric thin film is required. is important.

In particular, the composition ratio of Pb, Zr, Ti, and O of the PZT thin film formed on the wafer 5 is mainly governed by the composition ratio of the target 2 and the substrate temperature of the wafer 5, and further has a desired piezoelectric composition. In order to obtain an oxide, it is necessary to accurately supply O ₂ gas corresponding to the amount of Pb, Zr, Ti particles sputtered from the target 2 by sputtering.

  In particular, at the initial stage, the inner surface of the deposition preventive plate 7b is a ground potential surface, and discharge occurs between them, so that the plasma does not spread outside the dual-layered deposition preventive plates 7a and 7b. However, as the number of piezoelectric thin film formations increases, an insulating film (oxide scattered from the target 2) adheres to the first deposition plate 7a and the wafer 5, and the ground plane becomes invisible. An attempt is made to spread outside the gap between the wafer holder 4 and the adhesion preventing plates 7a and 7b.

  However, since the insulating film is attached to the deposition preventing plate 7b by repeatedly performing the film forming process of the piezoelectric thin film, the ground contact area of the plasma is reduced. The DC bias potential rises as the plasma ground area decreases. As the DC bias potential increases, the efficiency of sputtering the target 2 also decreases, resulting in a problem that productivity decreases.

  Accordingly, the amount of reactive gas necessary for the formation of the piezoelectric thin film also decreases, so that the amount of reactive gas becomes excessive under a constant gas supply, resulting in residual gas. This residual gas becomes oxygen-neutral particles in the vacuum vessel 1 and damages the wafer 5, causing problems such as reverse sputtering of the wafer 5, resulting in the production of a PZT thin film having a desired piezoelectric thin film composition. It becomes difficult.

  Therefore, it is possible to determine whether the PZT film is formed with the desired piezoelectric thin film composition by monitoring the residual amount of excess oxygen gas in the vacuum vessel 1, so that it remains during the formation of the piezoelectric thin film. The residual gas amount output from the gas detection means 15 is taken into the control circuit 10 as a monitor signal, and the residual gas amount is measured.

  The residual gas detection means 15 preferably uses, for example, a quadrupole mass spectrometer or an optical gas analyzer. Further, the place where the residual gas detecting means 15 is placed may be in the vacuum vessel 1, but it is more desirable that the place is close to the place where the piezoelectric thin film is formed.

Next, after the formation of the piezoelectric thin film, the introduction of O ₂ gas from the gas inlet is stopped.

  Thereafter, it is determined whether or not to remove the insulator adhered to the surface of the second deposition preventing plate 7b by sputtering the surface of the second deposition preventing plate 7b based on the measured residual gas amount. This criterion is determined by separately checking the correlation between the composition analysis of the PZT thin film after the piezoelectric thin film is formed and the residual gas amount.

When the residual gas amount becomes larger than a specified value, the switch 11 is switched to the DC power supply 12 side, and the potential of the deposition preventing plate 7b is set to a DC negative potential. As a result, a sputtering phenomenon occurs on the surface of the deposition preventing plate 7b, and it is possible to remove substances such as insulators attached to the surface of the deposition preventing plate 7b. Further, the switch 11 is switched to the DC power source 12 until the time when the substance adhering to the surface of the deposition preventing plate 7b can be removed. There is a method in which the amount of O ₂ gas is measured and it is determined that the oxide such as an insulator in the substance attached to the surface of the deposition preventing plate 7b has disappeared when the O ₂ gas is no longer detected.

  As a result, the ground contact area of the deposition preventing plate 7b is secured, and the DC bias potential can be maintained at a large negative value, so that the efficiency of sputtering the target 2 is also improved.

  Therefore, under a predetermined gas supply, necessary and sufficient reactive gas is consumed and no residual gas is generated.

  As described above, it is possible to realize a PZT thin film with a highly accurate composition that functions as a piezoelectric thin film having excellent piezoelectric characteristics.

  Further, the monitoring signal of the residual gas amount is taken into the control circuit 10, and the time for switching the switch 11 to the DC power source 12 side is controlled so that the potential becomes a constant value, thereby stabilizing the DC bias potential. It is desirable to realize. As a result, the plasma state is stabilized and the film formation rate can be made constant at all times.

  In this case, not only can a piezoelectric thin film having an excellent composition uniformity be formed, but also the effect that productivity is not lowered because the film forming rate is constant.

  Since the sputtering apparatus according to the present invention can stably secure the ground contact area of the deposition preventing plate, it has the effect of forming a thin film having a predetermined uniform composition, and forms various functional materials. It is useful as a sputtering apparatus that can be used.

The conceptual diagram for demonstrating the structure of the sputtering device in Embodiment 1 of this invention. Conceptual diagram of conventional sputtering equipment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Target 3 Electrode 4 Wafer holder 5 Wafer 6 High frequency power supply 7a Depositing plate 7b Depositing plate 10 Control circuit 11 Switch 12 DC power supply 15 Residual gas detection means 20 Impedance matching device

Claims (2)

Vacuum container, residual gas detection means installed in the vacuum container, wafer holder placed inside the vacuum container, an electrode disposed opposite to the wafer holder, and impedance connected to the electrode In a sputtering apparatus comprising a matching unit, a high-frequency power source connected to the impedance matching unit, and an adhesion preventing plate disposed so as to surround the electrode, the adhesion preventing plate is made of a plurality of metal materials in a double manner and mutually. A sputtering apparatus, wherein the sputtering apparatus is installed in a non-contact state and applies a DC negative potential to the outer deposition plate by analyzing the residual gas amount obtained from the residual gas detecting means. 2. The sputtering apparatus according to claim 1, wherein the time for applying the negative DC potential applied to the outer deposition preventing plate is determined by analyzing the residual gas amount obtained from the residual gas detecting means.

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