JP2022014978A - Sputtering apparatus and film deposition method of metal compound film - Google Patents

Abstract

To provide a sputtering apparatus capable of suppressing a deterioration of a stress distribution within a substrate surface when a metal compound film is deposited on a substrate to be deposited with a bias voltage applied thereto, and a film deposition method of the metal compound film.SOLUTION: A sputtering apparatus SM including: a vacuum chamber 1 in which a target 2 is arranged; gas introducing means 13a, 13b, 14 for introducing a sputtering gas into the vacuum chamber; a stage 4 which holds a substrate to be processed Sw in an attitude in which a surface to be deposited faces the target in the vacuum chamber; and a bias power source Pb for applying a bias voltage to the substrate to be processed held by the stage, further includes a plate-shaped electrode 5 arranged around the stage and a potential control power source Pc for controlling a surface potential of the plate shaped electrode.SELECTED DRAWING: Figure 1

Description

The present invention relates to a sputtering apparatus and a method for forming a metal compound film, and more particularly to an apparatus capable of improving the stress distribution in the plane of the substrate to be treated.

For example, in the process of manufacturing a high-frequency filter, there is a process of forming an AlN (aluminum nitride) film as a metal compound film on one surface (deposition surface) of a substrate to be processed such as a silicon wafer. A sputtering apparatus is generally used in this film forming step (see, for example, Patent Document 1). This type of sputtering apparatus includes a vacuum chamber in which a target is placed, and a gas introducing means for introducing a sputter gas containing a rare gas such as argon gas and a reaction gas such as a nitrogen-containing gas into the vacuum chamber, and a vacuum. A stage is provided in the chamber for holding the substrate to be processed in a posture in which the film forming surface faces the target. Then, the substrate to be processed is held on the stage with the film-forming surface facing the target side, spatter gas is introduced into the vacuum chamber in a vacuum atmosphere, and a predetermined electric power having a negative potential is applied to the target. Then, the target is sputtered by the ions of the rare gas ionized by the plasma generated in the vacuum chamber, the sputtered particles scattered from the target react with the nitrogen molecules, and the reaction product adheres to the film-forming surface of the substrate to be treated. , An AlN film is formed by depositing.

The AlN film formed on the film-forming surface as described above usually has tensile stress. On the other hand, in the manufacturing process of the high frequency filter, it may be desired that the tensile stress of the AlN film is as small as possible, or that the AlN film has a compressive stress. In such a case, it is conceivable to provide a bias power supply that applies a bias potential to the substrate to be processed held on the stage, and to apply a predetermined bias potential to the substrate to be processed during film formation. Here, when the AlN film is formed, the higher the bias potential, the smaller the tensile stress becomes as much as possible, and gradually the AlN film having compressive stress is obtained, but in the outer peripheral region of the substrate to be treated. It was found that the amount of change in stress locally increased, and on the contrary, the stress distribution in the substrate surface deteriorated. This is because the ions of the reaction gas ionized in the plasma are likely to be locally drawn into the outer peripheral region of the substrate to be processed during film formation, and the AlN film formed by these ions is excessively sputtered. It is thought that it will be done.

Japanese Unexamined Patent Publication No. 2011-135618

In view of the above points, the present invention makes it possible to suppress deterioration of the stress distribution in the surface of the substrate when forming a metal compound film in a state where a bias potential is applied to the substrate to be processed. It is an object of the present invention to provide an apparatus and a method for forming a metal compound film.

In order to solve the above problems, the vacuum chamber in which the target is arranged, the gas introducing means for introducing the sputter gas into the vacuum chamber, and the substrate to be processed are placed in a posture in which the film forming surface faces the target in the vacuum chamber. The sputtering apparatus of the present invention including a stage to be held and a bias power supply for applying a bias potential to the substrate to be processed held by the stage controls the plate-shaped electrodes provided around the stage and the surface potentials of the plate-shaped electrodes. It is characterized by further including a potential control power supply.

In the present invention, when the target is made of metal, the sputter gas contains a reaction gas, and a metal compound film is formed on the film-forming surface of the substrate to be processed by reactive sputtering, the plate-shaped electrodes are spaced apart from each other. The potential control power supply has an annular contour that surrounds the substrate to be processed, and the upper surface of the plate-shaped electrode facing the target side is arranged so as to be flush with the film-forming surface of the substrate to be processed. However, the surface potential of the plate-shaped electrode is controlled to a positive potential. The plate-shaped electrodes do not need to be integrally formed so as to surround the periphery of the substrate to be processed so as to surround the entire circumference thereof. For example, a plurality of arcuate electrodes are arranged at predetermined intervals in the circumferential direction. , It may be configured to have an annular contour as a whole. Further, the plate-shaped electrode is not limited to the one formed of the plate material as long as the upper surface thereof flush with the film-forming surface has a predetermined area, and may be formed of, for example, a mesh material or a punching metal. can.

Further, in order to solve the above-mentioned problems, a metal target and a substrate to be processed are arranged to face each other in a vacuum chamber, a sputter gas containing a reaction gas is introduced into the vacuum chamber, and power is applied to the target to generate plasma. In the method for forming a metal compound film of the present invention, which comprises a film forming step of forming and forming a metal compound film on the surface of the substrate to be processed by reactive sputtering, a bias potential is applied to the substrate to be processed during the film forming process. The film forming step is characterized by including a surface potential control step of controlling the surface potential of the plate-shaped electrode provided around the substrate to be processed.

In the present invention, when the bias potential applied to the substrate to be processed is set in the range of -100 to -10V when the aluminum nitride film is formed as the metal compound film, in the surface potential control step. It is preferable to control the surface potential of the plate-shaped electrode to a positive potential in the range of 5 to 150 V.

Based on the above, when a bias potential is applied to the substrate to be processed held in the stage when a metal target is sputtering to form a metal compound film by reactive sputtering, the higher the bias potential, the higher the bias potential. , The tensile stress becomes as small as possible, and a metal compound film having a compressive stress is gradually obtained. Then, if a plate-shaped electrode is provided around the substrate to be processed and a configuration is adopted in which the surface potential of the plate-shaped electrode is controlled to a positive potential during film formation, the amount of change in stress in the outer peripheral region of the substrate to be processed can be increased. It was confirmed that it could be suppressed, and as a result, it was confirmed that the deterioration of the stress distribution in the substrate surface could be suppressed. This is because a part of the reaction gas ions (for example, nitrogen ions) toward the outer peripheral region of the substrate to be treated is reflected by the plate-shaped electrode controlled to a positive potential, so that the reaction gas is drawn into the outer peripheral region. It is considered that this is because the number of ions is reduced and the metal compound film formed on the outer peripheral region of the substrate to be treated is suppressed from being excessively sputtered by the ions of this reaction gas.

The figure schematically explaining the sputtering apparatus of embodiment of this invention. The graph which shows the experimental result which confirms the effect of this invention.

Hereinafter, referring to the drawings, the sputtering apparatus of the present invention takes as an example a case where the substrate to be processed is a silicon wafer (hereinafter referred to as “substrate Sw”) and an AlN film (aluminum nitride film) is formed on the surface of the substrate Sw. And an embodiment of a method for forming a metal compound film will be described. In the following, the terms indicating the directions such as up and down are based on the installation posture of the sputtering apparatus shown in FIG.

With reference to FIG. 1, the SM is a sputtering apparatus, and the sputtering apparatus SM includes a vacuum chamber 1 capable of forming a vacuum atmosphere. An exhaust pipe 11 leading to a vacuum pump unit Pu composed of a turbo molecular pump, a rotary pump, or the like is connected to the vacuum chamber 1 so that the inside of the vacuum chamber 1 can be evacuated to a predetermined pressure (for example, 1 × 10 ^-5 Pa). ing. A gas pipe 14 having a flow rate control valve composed of mass flow controllers 13a, 13b, etc., which communicates with the gas sources 12a and 12b of the spatter gas, is connected to the side wall of the vacuum chamber 1 to control the flow rate. The gas can be introduced into the vacuum chamber 1. The sputter gas includes a reaction gas (for example, a nitrogen-containing gas such as nitrogen gas), and may further contain a rare gas (for example, argon gas). In this embodiment, the mass flow controllers 13a and 13b and the gas pipe 14 constitute the gas introduction means.

A cathode unit C is attached to the upper part of the vacuum chamber 1. The cathode unit C has a target 2 made of Al and a magnet unit 3 arranged above the target 2 and rotatable about the center of the substrate Sw as the center of rotation. The target 2 has a shape corresponding to the contour of the substrate Sw (for example, a circular shape in a plan view), and is mounted on the backing plate 21 with the sputter surface 2a facing downward, and is mounted on the backing plate 21 through the insulator Io1 in a vacuum chamber. It is attached to the upper part of 1. The output from the DC power supply Ps as a sputter power supply is connected to the target 2, and DC power having a negative potential can be input to the target 2. The magnet unit 3 has a known structure in which a magnetic field is formed in the space below the sputtering surface 2a of the target 2 and electrons and the like ionized below the sputtering surface 2a are captured during sputtering to efficiently ionize the sputtering gas. Since it can be used, a detailed description is omitted here.

A stage 4 is arranged at the lower part of the vacuum chamber 1 so as to face the target 2. The stage 4 includes a base 41 made of a thermally conductive metal (for example, made of SUS) provided on the lower wall of the vacuum chamber 1 via the insulator Io2, and a chuck plate 42 provided on the base 41. .. The chuck plate 42 has an electrode for an electrostatic chuck, and the substrate Sw is electrostatically adsorbed (held) with the film formation surface facing up by energization from an external power supply for the chuck (the target 2 and the substrate Sw at this time). The TS distance between and is, for example, 40 mm to 60 mm). Further, the output from the high frequency power supply as the bias power supply Pb is connected to the base 41, and by applying high frequency power of a predetermined frequency (for example, 13.56 MHz) to the base 41 during sputtering, a predetermined frequency is applied to the substrate Sw. A bias potential can be applied. Although not particularly illustrated, a heater and a refrigerant circulation path are attached to the base 41 to energize the heater from an external power source or to circulate the refrigerant to the refrigerant circulation path from a chiller unit (not shown). The substrate Sw can be controlled to a predetermined temperature by heat conduction from the base 41. The heater may be attached to the chuck plate 42, and in this case, the chuck plate 42 also serves as a hot plate.

A plate-shaped electrode 5 having an annular contour is arranged around the stage 4 so as to surround the substrate Sw. The plate-shaped electrode 5 having a flat upper surface 5a is formed by processing from a plate material of a metal (for example, SUS or Cu) having relatively good conductivity, and a cylindrical support 51 is provided on the lower surface of the plate-shaped electrode 5. There is. Then, the plate-shaped electrode 5 is installed on the lower wall of the vacuum chamber 1 via the insulator Io3 with the support 51 facing down. In this case, the height of the support 51 is fixed so that the upper surface 5a of the plate-shaped electrode 5 is flush with the upper surface (deposition surface) of the substrate Sw. Further, the gap Dw between the outer peripheral edge portion of the substrate Sw and the inner peripheral edge portion of the plate-shaped electrode 5 is set as much as possible so that the stability of the plasma generated in the vacuum chamber 1 at the time of film formation is not impaired. It is set small (for example, within the range of 5 mm to 30 mm). Further, the output from the potential control power supply Pc composed of the DC power supply is connected to the plate-shaped electrode 5, and the surface potential of the plate-shaped electrode 5 can be controlled to a positive potential within the range of 0V to 200V. The plate-shaped electrodes 5 do not need to be integrally formed so as to surround the substrate Sw over the entire circumference. For example, a plurality of arc-shaped portions are arranged at predetermined intervals in the circumferential direction to form an annular shape as a whole. It may be configured to have the contour of. In this case, although not particularly illustrated and described, if an adjusting plate for adjusting the scattering distribution of sputtered particles is provided between the target 2 and the substrate Sw, any of the arcuate portions is provided accordingly. Can be omitted. Further, the plate-shaped electrode 5 can be formed of a metal plate material, but if the upper surface 5a thereof has a predetermined area, it may be formed of a mesh material or a punching metal.

The sputtering apparatus SM has known control means (not shown) equipped with a microcomputer, a sequencer, and the like, and operates mass flow controllers 13a and 13b, vacuum pump unit Pu, DC power supply Ps, and bias power supply Pb. Operation, potential control The operation of the power supply Pc, etc. are controlled in an integrated manner. Hereinafter, an example of forming an AlN film on the surface of the substrate Sw by reactive sputtering using the sputtering apparatus SM will be specifically described.

The substrate Sw is placed on the upper surface of the stage 4 arranged in the vacuum chamber 1, the inside of the vacuum chamber 1 is evacuated to a predetermined pressure, and when the predetermined pressure is reached, argon gas and nitrogen gas are evacuated into the vacuum chamber 1, respectively. When introduced at a predetermined flow rate (for example, argon gas flow rate: 0 to 100 sccm, nitrogen gas flow rate: 20 to 100 sccm) and a pulsed DC power (frequency: 29.4 kHz) having a negative potential is applied to the target 2 from the DC power supply Ps. , Plasma is formed in the vacuum chamber 1. The target 2 is sputtered by the argon ions and nitrogen ions ionized in the plasma, and the sputtered particles scattered from the target 2 along the cosine side react with the nitrogen molecules, and the reaction product adheres to and deposits on the surface of the substrate Sw. An AlN film is formed.

By the way, when a bias potential is applied from the bias power supply Pb to the substrate Sw during the film formation of such an AlN film, the higher the bias potential, the smaller the tension of the AlN film becomes as much as possible, and gradually compression. Although it becomes stressed, the amount of change in stress locally increases in the outer peripheral region of the substrate Sw, and on the contrary, the stress distribution in the substrate surface may deteriorate.

Therefore, according to the present embodiment, by providing a plate-shaped electrode 5 around the substrate Sw and adopting a configuration in which the surface potential of the plate-shaped electrode 5 is controlled to a positive potential during film formation, the outer periphery of the substrate Sw is adopted. It was confirmed that the amount of change in stress in the region could be suppressed, and as a result, it was confirmed that the deterioration of the stress distribution in the substrate surface could be suppressed (improved). This is because a part of the argon ion or the nitrogen ion toward the outer peripheral region of the substrate Sw is reflected by the plate-shaped electrode 5 controlled to a positive potential, so that the nitrogen ion drawn into the outer peripheral region is reduced and the substrate is used. It is presumed that this is due to the fact that the AlN film is suppressed from being excessively sputtered by nitrogen ions in the outer peripheral region of Sw.

Next, in order to confirm the above effect, the following experiment was performed using the above sputtering apparatus SM. In the invention experiment, the target 2 is made of Al of φ300 mm, the substrate Sw is a silicon wafer of φ200 mm, and the substrate Sw is held by the stage 4 in the vacuum chamber 1 (TS distance is 50 mm), and around the stage 4. The plate-shaped electrode 5 was arranged so that the upper surface 5a was flush with the film-forming surface of the substrate Sw (the gap Dw at this time was 12 mm). Then, argon gas is introduced into the vacuum chamber 1 in a vacuum atmosphere at a flow rate of 0 sccm and nitrogen gas is introduced at a flow rate of 35 sccm (the pressure in the vacuum chamber 1 at this time is about 0.25 Pa). By inputting 4 kW of pulsed DC power (frequency: 29.4 kHz, off time: 34 μs, Duty: 70%) to 2 and 30 W of high frequency power of 13.56 MHz as bias power to stage 4 (at this time, the substrate). The bias potential applied to Sw was -23V), and an AlN film was formed on the surface of the substrate Sw by reactive sputtering to a thickness of 1150 nm. During the film formation, the surface potential of the plate-shaped electrode 5 was controlled to a positive potential of 40 V. During the film formation, the temperature of the substrate Sw was controlled to 350 ° C. After film formation, use a stress measuring device (manufactured by Toho Technology Co., Ltd., trade name "FLX-2000-A") to form an AlN film at four points (2 mm, 25 mm, 48 mm, 75 mm from the center of the substrate) on the substrate surface. The result of measuring the stress of is shown by a solid line in FIG. The stress of the AlN film at each measurement point in FIG. 2 is standardized by the average value of the stress measured at four points in the substrate surface of the comparative experiment 3 described later. When the stress difference Δ at the four measured points was obtained, it was 0.515 when the stress difference Δ in the comparative experiment 3 described later was 1.

Next, a comparative experiment with respect to the above-mentioned invention experiment will be described. First, in Comparative Experiment 1, an AlN film was formed under the same conditions as in the above-mentioned invention experiment, except that the height of the upper surface 5a of the plate-shaped electrode 5 was 7 mm higher than that in the above-mentioned invention experiment. After the film formation, the results of measuring the stress of the AlN film at four points on the substrate surface in the same manner as in the above invention experiment are shown by the alternate long and short dash line in FIG. The stress difference Δ at this time was 0.799 when the stress difference Δ in Comparative Experiment 3 described later was 1. Next, in Comparative Experiment 2, an AlN film was formed under the same conditions as in the above-mentioned invention experiment, except that the height of the upper surface 5a of the plate-shaped electrode 5 was 10 mm lower than that in the above-mentioned invention experiment. After the film formation, the results of measuring the stress of the AlN film at four points on the substrate surface in the same manner as in the above invention experiment are shown by a two-dot chain line in FIG. The stress difference Δ at this time was 0.823 when the stress difference Δ in Comparative Experiment 3 described later was 1. Further, in Comparative Experiment 3, an AlN film was formed under the same conditions as in the above-mentioned invention experiment except that the plate-shaped electrode was not provided. After the film formation, the results of measuring the stress of the AlN film at four points on the substrate surface in the same manner as in the above invention experiment are shown by broken lines in FIG. The stress difference Δ at this time is normalized to 1.

According to the above-mentioned invention experiment, it was confirmed that the amount of stress change in the outer peripheral region of the substrate Sw was suppressed and the stress difference could be suppressed to about half as compared with the above-mentioned comparative experiment 3 in which the plate-shaped electrode was not provided. It was confirmed that the deterioration of the stress distribution in the substrate surface can be suppressed. It is presumed that this is because the nitrogen ions drawn into the outer peripheral region are reduced and the AlN film formed on the outer peripheral region of the substrate Sw is suppressed from being excessively sputtered by the nitrogen ions. When the upper surface 5a of the plate-shaped electrode 5 is not flush with the film-forming surface of the substrate Sw as in the comparative experiments 1 and 2, the stress difference can be suppressed by only about 20% as compared with the comparative experiment 3. It was confirmed that.

Although the embodiments of the present invention have been described above, various modifications are possible as long as they do not deviate from the scope of the technical idea of the present invention. In the above embodiment, the case of forming an AlN film as an example has been described, but the present invention is not limited to this, and the substrate is formed during the film formation, for example, as in the case of forming a metal compound film such as a TiN film or TaN. It can be suitably applied when the amount of stress change in the outer peripheral region of the substrate becomes large by applying the bias potential.

In the above embodiment, the case where the surface potential of the plate-shaped electrode 5 is controlled to a positive potential has been described as an example, but depending on the bias potential applied to the substrate Sw, the thin film formed in the outer peripheral region of the substrate is sputtered by anions. In this case, the surface potential of the plate-shaped electrode 5 can be controlled to a negative potential.

Pb ... Bias power supply, Pc ... Potential control power supply, SM ... Sputtering device, Sw ... Substrate (processed substrate), 1 ... Vacuum chamber, 2 ... Target, 4 ... Stage, 5 ... Plate electrode, 5a ... Plate electrode 5 13a, 13b ... Mass flow controller (gas introduction means), 14 ... Gas pipe (gas introduction means).

Claims (4)

A vacuum chamber in which a target is placed, a gas introducing means for introducing sputter gas into the vacuum chamber, a stage in which the film-forming surface faces the target in the vacuum chamber, and a stage for holding the substrate to be processed, and holding the stage. In a sputtering apparatus provided with a bias power supply that applies a bias potential to the surface to be processed.
A sputtering apparatus further comprising a plate-shaped electrode provided around the stage and a potential control power supply for controlling the surface potential of the plate-shaped electrode. The sputtering apparatus according to claim 1, wherein the target is made of metal, the sputtering gas contains a reaction gas, and a metal compound film is formed on the film forming surface of the substrate to be processed by reactive sputtering. ,
The plate-shaped electrode has an annular contour that surrounds the substrate to be processed at intervals, and the upper surface of the plate-shaped electrode facing the target side is flush with the film-forming surface of the substrate to be processed. A sputtering apparatus, wherein the potential control power supply controls the surface potential of the plate-shaped electrode to a positive potential. A metal target and a substrate to be processed are placed facing each other in a vacuum chamber, a sputter gas containing a reaction gas is introduced into the vacuum chamber, power is applied to the target to form a plasma, and the substrate to be processed is subjected to reactive sputtering. In a method for forming a metal compound film including a film forming step of forming a metal compound film on the surface of the above, in which a bias potential is applied to a substrate to be processed during the forming step.
The film forming step is a method for forming a metal compound film, which comprises a surface potential control step for controlling the surface potential of a plate-shaped electrode provided around the substrate to be processed. The method for forming a metal compound film according to claim 3, wherein the metal compound film is an aluminum nitride film and the bias potential is set in the range of -100 to -10 V.
A method for forming a metal compound film, wherein the surface potential is controlled in the range of 5 to 150 V in the surface potential control step.

Images