JP2018104738A - Deposition method - Google Patents

Abstract

Provided is a magnetron sputtering apparatus capable of effectively suppressing a deviation in film thickness distribution with a simple configuration. A substrate-like substrate W and a target 2 are arranged opposite to each other, and a tunnel-like leakage magnetic field is formed in a space below the target by a magnet unit arranged above the target with the direction from the substrate to be processed toward the target being upward. Is generated while being unevenly distributed from the center of the target toward the periphery of the target, and this leakage magnetic field is circulated around the center of the target, and when the sputtering of the target is started, the position of the substrate to be processed where the substrate to be processed and the target face each other is determined. A step of forming a film with a first film thickness that is smaller than the target film thickness at the reference position, and a position of the substrate to be processed that is rotated from the reference position by a predetermined rotation angle θ with the center of the substrate to be processed as a rotation center. And forming a film with a second film thickness that is thinner than the target film thickness at at least one correction position. [Selection] Figure 3

Description

  In the present invention, a substrate to be processed and a target are arranged opposite to each other in a deposition chamber, a sputtering gas is introduced into the deposition chamber, power is applied to the target, the target is sputtered, and sputtered particles are attached to the surface of the substrate to be processed. The present invention relates to a film forming method for depositing and forming a film with a predetermined target film thickness.

  In the manufacturing process of a semiconductor device, there is a step of forming an insulating film such as an aluminum oxide film, and the sputtering method is used as a film forming method for forming such an insulating film with high productivity. In this case, with the direction from the target substrate to the target facing upward, during the sputtering of the target, a magnet-like unit placed above the target causes a tunnel-like leakage magnetic field to flow into the space below the target from the target center to the periphery of the target. It is possible to increase the film formation rate by increasing the electron density in the lower space of the target, and hence the plasma density. In this case, in the target region where the leakage magnetic field acts, the portion of the target facing the high-density plasma is locally sputtered, so that the thickness of the portion of the substrate to be processed facing the portion becomes relatively thick. . Therefore, during film formation, the magnet unit is rotated around the center of the target so that the leakage magnetic field is rotated around the center of the target so that the film can be formed on the substrate to be processed with a good in-plane film thickness distribution ( For example, see Patent Document 1).

  However, it has been found that even when the magnet unit is rotated as in the conventional example, the film thickness distribution of the thin film formed on the substrate to be processed is biased in the radial direction. This is because an insulating target is generally produced by sintering, but the density of the insulating particles is biased during sintering, so that the scattering distribution of the sputtered particles when sputtering the target is biased. It is thought to do. In next-generation semiconductor devices, it is required to control the in-plane thickness distribution within, for example, 2%, more preferably within 1%. To satisfy this requirement, the radial deviation of the thickness distribution is required. How to suppress is important, but there is a limit to the improvement by the magnet unit.

Japanese Patent Laid-Open No. 9-41137

  In view of the above points, it is an object of the present invention to provide a film forming method capable of effectively suppressing the radial deviation of the film thickness distribution of a thin film formed on a substrate to be processed. It is.

  In order to solve the above-described problems, a substrate to be processed and a target are disposed facing each other in a film formation chamber, a sputtering gas is introduced into the film formation chamber, power is applied to the target, the target is sputtered, and the surface of the substrate is processed. The film forming method of the present invention for depositing and depositing sputtered particles to form a film with a predetermined target film thickness is arranged above the target during sputtering of the target with the direction from the substrate to be processed to the target as the top. A magnet-like magnetic unit generates a tunnel-like leakage magnetic field in the space below the target from the target center to the periphery of the target, and circulates the generated leakage magnetic field around the center of the target to start sputtering the target. The position of the substrate to be processed where the substrate to be processed and the target face each other is taken as a reference position, and the target film is A step of forming a film with a thinner first film thickness, and a position of the substrate to be processed rotated at a predetermined rotation angle from the reference position with the center of the substrate to be processed as a rotation center, and at least one correction position And forming a film with a second film thickness that is smaller than the target film thickness. The present invention includes a case where the first film thickness and the second film thickness are set to be the same.

  According to the present invention, the sputtered particle scattering distribution with respect to the substrate to be processed can be changed by rotating the substrate to be processed from the reference position at a predetermined rotation angle to the correction position. In this way, by performing film formation intermittently while changing the scattering distribution of the sputtered particles with respect to the substrate to be processed, the radial deviation of the film thickness distribution of the thin film formed on the substrate to be processed is effectively suppressed. As a result, the film thickness in-plane distribution can be remarkably improved. According to the experiments by the present inventors, it was confirmed that the in-plane film thickness distribution can be controlled within 2%.

  In the present invention, a plurality of the correction positions may be provided, and the target film thickness may be obtained by film formation at the first film thickness at the reference position and film formation at the second film thickness at the plurality of correction positions. In this case, the film may be formed with the second film thickness different from the first film thickness at at least one correction position among the plurality of correction positions.

  In the present invention, it is preferable that the rotation angle, the first film thickness, and the second film thickness are set based on a film thickness distribution generated when the film is formed without rotating the substrate to be processed. According to this, the in-plane distribution of the film thickness can be further improved, and in the experiments of the present inventors, the in-plane distribution of the film thickness of the thin film formed on the substrate to be processed can be controlled within 1%. confirmed.

The typical sectional view showing the sputtering device which enforces the film-forming method of the embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of the film forming chamber shown in FIG. 1. The figure explaining the reference position and correction position of a to-be-processed substrate. (A)-(c) is a figure which shows the experimental result which confirms the effect of this invention.

  Hereinafter, with reference to the drawings, a sputtering apparatus composed of a cluster tool for performing a film forming method according to an embodiment of the present invention will be described. As shown in FIG. 1, the sputtering apparatus SM includes a central transfer chamber T in which the transfer robot R is disposed, and a film formation chamber C1, a rotation chamber C2, and a load lock chamber L1 that are disposed so as to surround the transfer chamber T. , L2. The transfer chamber T, the load lock chambers L1 and L2, the film formation chamber C1, and the rotation chamber 2 can be evacuated by a vacuum pump (not shown), respectively. As the transfer robot R, for example, a so-called frog-leg type known robot having a robot arm 10a and a robot hand 10b attached to the tip of the robot arm 10a and holding the substrate W to be processed can be used. Detailed description is omitted here. Such a transfer robot R can transfer the substrate W to be processed to a predetermined position in each chamber. Further, the transfer chamber T and the load lock chambers L1 and L2, the film forming chamber C1, and the rotating chamber C2 are connected to each other via a partition valve Iv so that the chambers can be isolated from each other.

  Referring also to FIG. 2, the film forming chamber C <b> 1 is defined by the vacuum chamber 1, and a gas pipe 11 serving as a gas introducing means for introducing a sputtering gas is connected to the side wall of the vacuum chamber 1. It communicates with a gas source (not shown) via the mass flow controller 12. The sputtering gas includes not only a rare gas such as an argon gas introduced when forming plasma in the film forming chamber C1, but also a reactive gas such as an oxygen gas or a nitrogen gas used for reactive sputtering. The side wall of the vacuum chamber 1 is also connected to an exhaust pipe 13 communicating with an evacuation means P constituted by a turbo molecular pump, a rotary pump, or the like, and the film formation chamber C1 can be evacuated at a constant speed and maintained at a predetermined pressure. I am doing so.

A cathode unit C is detachably attached to the ceiling of the vacuum chamber 1. The cathode unit C includes a target 2 and a magnet unit 3 disposed above the target 2. The target 2 is a sintered target made of an insulator such as aluminum oxide, silicon nitride, or silicon carbide, and is formed in a circular or rectangular shape in plan view by a known method according to the contour of the substrate W to be processed. . The target 2 is attached to the upper portion of the vacuum chamber 1 through an insulator I ₁ provided on the upper wall of the vacuum chamber 1 with the sputtering surface 22 to be sputtered downward while being mounted on the backing plate 21. The target 2 is connected to a known high-frequency power source E so that high-frequency (alternating current) power having a predetermined frequency (for example, 13.56 MHz) is supplied between the target 2 and the ground during sputtering.

  The magnet unit 3 includes, for example, a yoke 31, a plurality of first magnets 32 provided on the lower surface of the yoke 31, and a plurality of second magnets 33 provided around the first magnets 32. It can be used, and a tunnel-like leakage magnetic field is unevenly distributed in the space below the sputtering surface 22 from the center of the target 2 toward the periphery of the target 2. Further, a drive shaft 34 of a drive source (not shown) is connected to the upper surface of the yoke 31, and the magnet unit 3 is driven to rotate around the center of the target 2, so that the leakage magnetic field is moved around the center of the target 2. I try to go around.

A stage 4 is disposed in the center of the bottom of the film formation chamber C1 so as to face the target 2. The stage 4 includes a metal base 41 having a cylindrical outline, for example, and a chuck plate 42 bonded to the upper surface of the base 41. The chuck plate 42 has an outer diameter that is slightly smaller than the upper surface of the base 41, and electrostatic chuck electrodes 42 a and 42 b are embedded. When a voltage is applied from a chuck power supply (not shown), the chuck plate 42 is opposed to the target 2. Thus, the substrate W to be processed can be held. The chuck plate 42 is detachably attached to the upper surface of the base 41 by a ring-shaped first attachment plate 43. The first deposition preventing plate 43 is attached to the upper surface of the base 41 via the insulator I ₂ in order to reduce the bias potential generated in the substrate W to be processed during sputtering. In addition, about the structure of an electrostatic chuck, since well-known things, such as a monopolar type and a bipolar type, can be utilized, detailed description is abbreviate | omitted here. Base 41 is held by the insulator I ₃ attached airtightly to an opening provided on the bottom surface of the vacuum chamber 1, and is in an electrically floating. Further, the base 41 may be provided with a refrigerant circulation passage and a heater so that the substrate W to be processed can be controlled to a predetermined temperature during sputtering.

  An annular second deposition preventing plate 5 is provided around the stage 4 in the film forming chamber C1. The 2nd adhesion prevention board 5 is formed so that it may incline below to the radial direction outer side from the inner peripheral edge part. And the 2nd adhesion prevention board 5 is installed in the bottom of vacuum chamber 1 of earth ground, and plays a role of an earth electrode at the time of sputtering. In addition, the 2nd adhesion prevention board 5 may be provided with the several through-hole penetrated in the up-down direction.

  A third deposition plate 6 that surrounds the space between the target 2 and the substrate W to be processed is disposed in the film forming chamber C1 in order to prevent the sputter particles from adhering to the inner wall surface of the vacuum chamber 1. ing. The third protective plate 6 includes an upper protective plate 61 suspended from the upper wall of the vacuum chamber 1, a lower protective plate 62 erected on the bottom surface of the vacuum chamber 1, and the upper protective plate 61 and the lower protective plate. A movable deposition plate 63 is provided between the deposition plate 62 and the deposition plates 61, 62 inside the vacuum chamber 1 and overlaps the upper deposition plate 61 and the lower deposition plate 62 in the vertical direction. Has been. The driving shaft Cr of the cylinder Cy provided through the bottom surface of the vacuum chamber 1 at intervals of 90 ° in the circumferential direction is connected to the outer surface of the movable deposition preventing plate 63. Then, the cylinder Cy moves to the lower movement position (position shown in FIG. 2) for preventing the sputter particles from adhering to the inner wall surface of the vacuum chamber 1 at the time of film formation, and the movable adhesion by moving to the upper adhesion plate 61 side. A gap is formed between the plate 63 and the lower prevention plate 62, and is movable between an upper movement position at which the substrate W to be processed can be carried out or carried in through a through hole To for opening and closing by the partition valve Iv. The adhesion prevention plate 63 becomes movable.

  Further, in the rotation chamber C2 shown in FIG. 1, a rotation stage St that holds and rotates the substrate W to be processed and an optical edge sensor Se are provided. The notch formed in the edge portion of the substrate W to be processed is detected while rotating the substrate W to be processed by the rotation stage St. The to-be-processed substrate W from which the notch has been detected is transferred by a transfer robot R to a later-described reference position facing the target 2 in the film forming chamber C1. In the present embodiment, the rotation stage St provided in the rotation chamber C2 also serves to rotate the substrate to be processed W at a predetermined rotation angle in order to transport the substrate to be processed W to the correction position. In addition, since a well-known thing can be used as rotation stage St and edge sensor Se, detailed description is abbreviate | omitted here.

  The sputtering apparatus SM has a known control means Ct provided with a microcomputer, a sequencer, etc., and operates the gate valve Iv, the operation of the transfer robot R, the operation of the mass flow controller 12, the operation of the vacuum exhaust means P, the drive source It is designed to control the driving of the machine. Further, the control means Ct controls the operation of the rotation stage St in the rotation chamber C2 in order to rotate the substrate W to be processed from the reference position to the correction position by the rotation angle θ. Hereinafter, using the sputtering apparatus SM, the substrate W to be processed is a silicon substrate (hereinafter referred to as “substrate W”), a sintered target made of aluminum oxide is used as the target 2, and an aluminum oxide film is formed on the surface of the substrate W. As an example, a film forming method according to an embodiment of the present invention will be described.

  First, the substrate W is put into the load lock chamber L1 in the atmosphere, and the load lock chamber L1 is evacuated, and then the substrate W is transferred from the load lock chamber L1 to the rotation chamber C2 via the transfer chamber T by the transfer robot R. . In the rotation chamber C2, the notch N formed in the substrate W is detected by the edge sensor Se while the substrate W is rotated by the rotation stage St, and the detected notch N is located on the partition valve Iv side (transfer chamber T side). The rotation stage St is stopped.

  Next, the substrate W is transferred from the rotation chamber C2 to the stage 4 in the film formation chamber C1 by the transfer robot R. The substrate W transferred to the film formation chamber C1 is held by the stage 4 with the notch N positioned on the partition valve Iv side (transfer chamber T side) and facing the target 2, and the position of the substrate W is set as a reference. Position. Then, while rotating the magnet unit 3, argon gas is introduced into the film forming chamber C1 at a flow rate of, for example, 150 to 250 sccm (at this time, the pressure in the vacuum chamber 1 is 2 to 4 Pa). 2 is supplied with high frequency power (for example, 13.56 MHz, 0.2 kW to 3.0 kW) to form plasma in the vacuum chamber 1, sputter the sputter surface 2 a of the target 2, An aluminum oxide film is formed by adhering and depositing on the surface of the substrate W.

  Here, when the target film thickness is formed on the surface of the substrate W at the reference position, the film thickness distribution of the aluminum oxide film may be biased in the radial direction. Therefore, in this embodiment, the film formation on the substrate W at the reference position is stopped at the first film thickness that is smaller than the target film thickness, that is, when the film formation time corresponding to the first film thickness has elapsed, The introduction and power supply to the target 2 are stopped. Then, when the residual gas in the film formation chamber C1 is exhausted and the inside of the film formation chamber C1 reaches a predetermined pressure, the substrate W is transferred to the rotation chamber C2 by the transfer robot R, and the substrate W is rotated by a predetermined rotation by the rotation stage St. Rotate the corner. The substrate W thus rotated is transferred again to the film forming chamber C1 by the transfer robot R.

  The substrate W re-transferred to the film forming chamber C1 is held by the stage 4 in a state where the substrate W is rotated from the reference position by a predetermined rotation angle θ (for example, 90 ° counterclockwise as shown in FIG. 3). Is the first correction position. At this first correction position, an aluminum oxide film is formed under the same conditions as the film formation conditions at the reference position. At this time, since the substrate W is twisted with respect to the target 2 at the first correction position, the sputtered particle scattering distribution with respect to the substrate W at the first correction position is different from that at the reference position. It will be. Then, when the film formation time corresponding to the second film thickness that is thinner than the target film thickness has elapsed, the introduction of the sputtering gas and the application of power to the target 2 are stopped, and the residual gas in the film formation chamber C1 is exhausted. .

  The second film thickness at the first correction position may be set to be different from the first film thickness at the reference position, or may be set to be the same. These first film thickness, second film thickness, and rotation angle θ are preferably set based on the film thickness distribution generated when the target film thickness is formed without rotating the substrate W (see the experiment described later). ).

  Such rotation in the rotation chamber C2 and film formation at the correction position in the film formation chamber C1 are alternately repeated until the film thickness of the aluminum oxide film reaches the target film thickness. In the example shown in FIG. 3, a second correction position that is further rotated 90 ° counterclockwise from the first correction position, and a third correction position that is further rotated 90 ° counterclockwise from the second correction position, Further, an aluminum oxide film having a target film thickness is formed on the surface of the substrate W by performing film formation twice. In other words, an aluminum oxide film having a target film thickness can be obtained by intermittently rotating the substrate W by 90 ° and performing film formation four times in total. Thereafter, the substrate W is transferred from the film forming chamber C1 to the load lock chamber L2 by the transfer robot R, and the load lock chamber L2 is vented to atmospheric pressure to take out the substrate W.

  As described above, according to the present embodiment, the substrate W is rotated from the reference position by the predetermined rotation angle θ to obtain a correction position in which the substrate W is twisted with respect to the target 2. The scattering distribution of the sputtered particles with respect to W can be changed. As described above, by performing film formation intermittently while changing the scattering distribution of the sputtered particles with respect to the substrate W, it is possible to effectively suppress the radial deviation of the film thickness distribution of the thin film formed on the substrate W. As a result, the in-plane distribution of the film thickness can be remarkably improved.

  Next, in order to confirm the effect, the following experiment was performed using the sputtering apparatus SM. Here, the substrate W to be processed is a silicon substrate of φ300 mm (hereinafter referred to as “substrate W”), a sintered target made of aluminum oxide of φ400 mm is used as the target 2, and an aluminum oxide film is formed on the surface of the substrate W with a target film thickness of 30 nm. It was decided to form a film.

  First, as a comparative experiment, the film thickness distribution generated when the target film thickness was formed at the reference position without rotating the substrate W was obtained. That is, after holding the substrate W on the stage 4 in the film formation chamber C1, the magnet unit 3 is rotated at a rotational speed of 40 rpm, and argon gas is introduced into the film formation chamber C1 at a predetermined flow rate (the film formation at this time). The pressure in the chamber C1 was 0.36 Pa), 600 W of 13.56 MHz high frequency power was input to the target 2 to generate plasma, and an aluminum oxide film was formed on the surface of the substrate W. The film formation time was 120 sec. According to this comparative experiment, the film thickness in-plane distribution (σ) of the formed aluminum oxide film is 7.50%, and as shown in FIG. It was confirmed that Based on this film thickness distribution, the rotation angle θ in Invention Experiments 1 and 2 described below was set to 45 °. Further, the first film thickness and the second film thickness in Invention Experiment 1 are set to the same 7.1 nm, and in Invention Experiment 2, the second film thickness at one correction position (seventh correction position) is 1.2. Doubled to 8.5 nm.

  Next, as Invention Experiment 1, a film is formed for 15 sec corresponding to the first film thickness on the substrate W at the reference position in the film forming chamber C1 under the same film forming conditions as in the comparative experiment. Thereafter, the step of transporting the substrate W to the rotation chamber C2 and rotating it by the rotation angle θ = 45 °, and the second film thickness (in this experiment, the first film thickness) with respect to the substrate W at the correction position transferred again to the film formation chamber C1 The aluminum oxide film having the target film thickness was formed on the surface of the substrate W by alternately repeating the process of forming the film for 15 sec corresponding to the same film thickness) seven times. According to Experiment 1 of the present invention, the film thickness distribution (σ) of the formed aluminum oxide film is 1.16%, and the portions having the same film thickness are substantially concentric as shown in FIG. Thus, it was confirmed that the radial deviation of the film thickness distribution was suppressed.

  Next, as Invention Experiment 2, an aluminum oxide film was formed in the same manner as Invention Experiment 1 except that the film formation time at one correction position (seventh correction position) was 1.2 times. According to Experiment 2 of the present invention, the film thickness distribution (σ) of the formed aluminum oxide film is 0.87%, and the portions having the same film thickness are substantially concentric as shown in FIG. Thus, it was confirmed that the deviation in the radial direction of the film thickness distribution was further suppressed.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. In the above embodiment, the case where the insulating film is formed using the sintered target has been described as an example. However, the present invention can also be applied to the case where the metal film is formed using the metal target. The metal target is generally manufactured through a rolling process, but there may be a radial deviation in film thickness distribution due to the rolling direction. In this case, if the present invention is applied, it is possible to effectively suppress the radial deviation of the film thickness distribution of the metal film formed on the substrate to be processed.

  In the above embodiment, the case where the substrate W to be processed is rotated at a predetermined rotation angle using the rotation stage St provided in the rotation chamber C2 has been described as an example, but the substrate W to be processed is held in the film formation chamber C1. In the case of having a rotatable stage that can be rotated in this state, the substrate W to be processed may be rotated using this rotatable stage. In this case, after the film is formed with the first film thickness at the reference position, the rotation stage is rotated at a predetermined rotation angle and the film is formed with the second film thickness at the correction position. Transport between the chamber C2 is not necessary, and throughput can be improved. However, since components such as the adhesion preventing plates 5 and 6 are installed in the film forming chamber C1, there are cases where the rotation stage cannot be installed in the film forming chamber C1 due to space constraints. In such a case, if the rotary stage St of the rotary chamber C2 is used as in the above-described embodiment, it is possible to prevent an increase in apparatus cost, which is advantageous.

  Further, in Invention Experiment 2, the film is formed with the second film thickness different from the first film thickness at one correction position, but the film with the second film thickness is formed at two or more correction positions. Good. In this case, if the correction position for forming the film with the second film thickness is set based on the radial deviation of the film thickness distribution that occurs when the film is formed without rotating the substrate W, the radial direction of the film thickness distribution is set. The bias can be further suppressed.

  C1 ... deposition chamber, W ... substrate to be processed, θ ... rotation angle, 2 ... target, 3 ... magnet unit.

Claims (5)

The substrate to be processed and the target are placed opposite to each other in the film formation chamber, a sputtering gas is introduced into the film formation chamber, power is applied to the target, the target is sputtered, and sputter particles are attached and deposited on the surface of the substrate to be processed. A film forming method for forming a film with a predetermined target film thickness,
With the direction from the target substrate to the target facing upward, during the sputtering of the target, a magnet-like unit placed above the target causes a tunnel-like leakage magnetic field to be unevenly distributed from the center of the target to the periphery of the target. In addition to causing the generated leakage magnetic field to circulate around the center of the target,
A step of forming a first film thickness that is thinner than the target film thickness at the reference position, with the position of the substrate to be processed facing the target substrate and the target at the reference position when starting sputtering of the target;
The position of the substrate to be processed rotated at a predetermined rotation angle from the reference position with the center of the substrate to be processed as the center of rotation is defined as a correction position, and at least one correction position is formed with a second film thickness smaller than the target film thickness. Forming a film with a target film thickness. The film forming method according to claim 1, wherein the correction position has a plurality of locations.
A film forming method comprising forming a film at the reference position and a plurality of correction positions to obtain a target film thickness.   3. The film forming method according to claim 2, wherein the film is formed with the second film thickness different from the first film thickness at at least one correction position among a plurality of correction positions. Membrane method.   The film forming method according to claim 1, wherein the rotation angle is set based on a film thickness distribution generated when the film is formed without rotating the substrate to be processed.   5. The first film thickness and the second film thickness are set based on a film thickness distribution generated when a film is formed without rotating a substrate to be processed. The film forming method.

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