JP4436350B2 - Thin film forming method and thin film forming apparatus - Google Patents

Description

  The present invention relates to a thin film forming method such as sputtering and a thin film forming apparatus, and in particular, includes a thin film forming method in which a plurality of target pairs are arranged in parallel in a vacuum chamber and a thin film is formed on a substrate to be processed, and this AC power supply. The present invention relates to a thin film forming apparatus.

  When forming a thin film on a substrate to be processed having a large area by sputtering, a plurality of target pairs are arranged in parallel in a vacuum chamber so as to face the substrate to be processed, and a predetermined power source is connected via an AC power source connected to each target pair. An alternating voltage is applied alternately with a frequency, and two targets constituting each target pair are alternately switched between an anode electrode and a cathode electrode, and a glow discharge is generated between the anode electrode and the cathode electrode to generate plasma. There is a method of forming an atmosphere and sputtering each target pair.

  In this case, when glow discharge is simultaneously started in each target pair, a phenomenon in which the discharge is unstablely fluctuated due to a minute difference in frequency or a phase difference inherent in each oscillator included in the AC power supply. This fluctuation of discharge may cause in-plane distribution of film thickness to be non-uniform, which may hinder good film formation.

Therefore, conventionally, a sputtering apparatus has been proposed in which the glow discharge does not fluctuate in an unstable manner by synchronizing the output frequency and output phase of each AC power source (see, for example, Patent Document 1). In this sputtering apparatus, only target oscillators of a predetermined AC power source (master AC power source) are used to perform oscillation output with all target pairs, and oscillators provided in AC power sources other than the master AC power source are used. The synchronization process was performed without doing so.
WO2003 / 014410 (claims 1 and 2)

  By the way, among the plurality of target pairs arranged side by side, targets adjacent to each other connected to different AC power sources are coupled via a floating electrostatic capacitance.

  In the above conventional sputtering apparatus, although the output frequency and output phase of each AC power supply can be synchronized, the output between the targets adjacent to each other is not adjusted. The glow discharge fluctuates and a stable plasma atmosphere is not formed.

  In addition, when an abnormal discharge occurs when the output potential difference of each AC power source between the targets adjacent to each other is large, a large arc energy is generated, resulting in a splash in which the target is melted and huge droplets are attached, There was a problem of inhibiting good thin film formation.

  Furthermore, in the above-mentioned conventional sputtering apparatus, when a large arc energy is actually generated in association with the occurrence of the abnormal discharge, by simply shutting off the output of the AC power source connected to the target pair in which the arc discharge has occurred, Since energy is supplied from the plasma generated in the target pair adjacent to the target pair and coupled via the floating capacitance, there is a problem that the generated arc discharge is difficult to extinguish.

  Therefore, in view of the above problems, the present invention forms a stable plasma atmosphere while suppressing fluctuations in glow discharge caused by an output potential difference between mutually adjacent targets connected to the different AC power sources. A thin film forming method capable of suppressing generation of large arc energy and further minimizing damage due to arc discharge even when the arc discharge occurs, and a thin film forming apparatus capable of performing these thin film forming methods The issue is to provide.

In order to solve the above problems, a thin film forming method according to the present invention includes a plurality of target pairs arranged in parallel in a vacuum chamber so as to face a substrate to be processed, and a predetermined frequency via an AC power source connected to each target pair. The AC voltage is output alternately with the alternating current, and the two targets constituting each target pair are alternately switched between the anode electrode and the cathode electrode, and a glow discharge is generated between the anode electrode and the cathode electrode to generate a plasma atmosphere. Forming a thin film on the substrate to be processed by sputtering each target pair,
Compare the outputs between adjacent targets connected to different AC power sources among the parallel target pairs, and adjust the output of the AC power source when the output potential difference exceeds a predetermined value The potential difference is converged below the predetermined value.

  According to this method, the output potential difference between the targets adjacent to each other can be converged and adjusted, so that a stable plasma atmosphere can be formed, and even when abnormal discharge occurs, large arc energy is generated. Can be suppressed.

  When the AC power supplies are simultaneously output and the outputs of the AC power supplies are the same, the output phase is substantially inverted between the targets adjacent to each other. Therefore, in such a case, the adjustment of the output may be performed by converging the output potential difference by inverting the polarity by shifting the output phase between the adjacent targets by 180 degrees.

  The order of adjusting the output is, for example, such that the output of each AC power supply is sequentially adjusted from any one AC power supply as a starting point toward the outside in the juxtaposition direction from the target pair serving as the starting point. That's fine.

  In this case, after adjusting the output of the AC power supply that is adjacent to the AC power supply that is the starting point, the output of each AC power supply that is adjacent to the outside in the juxtaposed direction is sequentially adjusted using the adjusted AC power supply as a further starting point. You may make it do.

  The output adjustment may be performed by generating a signal for controlling the output of the AC power source and transmitting this signal to the AC power source for adjusting the output. The control signal may be generated by the AC power source serving as the starting point, and transmitted from the AC power source serving as the starting point to an AC power source that adjusts the output.

  When an arc discharge occurs in any one of the plurality of target pairs arranged in parallel, the output to the target pair in which the arc discharge has occurred is cut off and no arc discharge has occurred. What is necessary is just to interrupt | block the output to another target pair simultaneously.

  In this way, when a large arc energy is generated due to the occurrence of the abnormal discharge, when the output of the AC power source connected to the target pair where the arc discharge is generated is cut off, It is possible to prevent energy from being supplied from the plasma generated in the above.

  In order to solve the above-mentioned problems, a thin film forming apparatus according to the present invention includes a plurality of target pairs arranged in parallel so as to face a substrate to be processed disposed in a vacuum chamber, and includes an AC power source connected to each target pair. The thin film forming apparatus compares the outputs between adjacent targets connected to different AC power sources among the target pairs arranged side by side, and the AC power source when the output potential difference exceeds a predetermined value And adjusting means for adjusting the output potential to converge the output potential difference to the predetermined value or less.

  The adjusting unit may include a signal generating unit that generates a signal for controlling the output, and a transmitting unit that transmits the signal to an AC power source that adjusts the output.

  In this case, you may comprise so that the alternating current power supply used as the starting point in order to perform the said adjustment process may have the said adjustment process means.

  The thin film forming apparatus may be provided with a control device provided with the adjusting means.

  When an arc discharge occurs in the target pair to which each of the AC power supplies is connected, an arc detection means for detecting the arc discharge, and when the arc discharge is detected by the arc detection means, It may have an output control means for controlling the output of each AC power source in order to cut off the output and simultaneously cut off the output to other target pairs.

  As is clear from the above description, the thin film forming method and thin film forming apparatus according to the present invention are connected to different AC power sources among a plurality of target pairs arranged in parallel, adjacent to each other, and via a floating capacitance. Therefore, it is possible to prevent an output potential difference from occurring between the targets that are coupled together, thereby maintaining a stable plasma state and effectively suppressing the occurrence of arc discharge and realizing a good thin film formation. There is an effect that can be done.

  FIG. 1 shows a basic configuration diagram of a thin film forming apparatus according to the present invention. In this thin film forming apparatus, a plurality of target pairs are arranged side by side to form a thin film on a substrate having a large area. The number of target pairs arranged side by side is determined according to the area of the substrate to be processed, but in FIG. 1, for convenience of explanation, the number of target pairs is two.

Referring to FIG. 1, reference numeral 1 denotes a vacuum chamber of a thin film forming apparatus according to the present invention. The vacuum chamber 1 maintains a predetermined degree of vacuum via a vacuum exhaust means 2 such as a rotary pump or a turbo molecular pump. A substrate transport means 3 such as a carrier is provided in the upper part of the vacuum chamber 1 and the substrate to be processed S is sequentially transported by intermittently driving a drive means (not shown). A sputtering gas such as Ar and a reactive gas such as O ₂ , H ₂ O, H ₂ , and N ₂ are introduced into the vacuum chamber 1 at a constant flow rate by the gas introduction means 4.

  A target pair T1 and a target pair T2 are arranged side by side in the vacuum chamber 1 so as to face the substrate S to be processed. An AC power supply E1 is connected to the target pair T1, and an AC power supply E2 is connected to the target pair T2. The AC power supply E1 and the AC power supply E2 are communicatively connected via a communication cable K.

  The two targets t11 and t12 constituting the target pair T1 and the two targets t21 and t22 constituting the T2 are alternately changed in polarity at a predetermined frequency via the AC power sources E1 and E2, and an AC voltage is output. The anode electrode and the cathode electrode are alternately switched. A glow discharge is generated between the anode electrode and the cathode electrode to form a plasma atmosphere P, and the target pair T1 and the target pair T2 are sputtered to form a thin film on the substrate S to be processed.

  FIG. 1 shows a case where the target t11 side of the target pair T1 is an anode electrode, the t12 side is a cathode electrode, the target t21 side of the target pair T2 is an anode electrode, and the t22 side is a cathode electrode. Further, the AC power supply E1 at this time The output waveform of the AC power supply E2 is shown under each AC power supply.

  The target t12 of the target pair T1 and the target t21 of the target pair T2 are coupled via a floating capacitance.

  FIG. 2 shows a basic circuit configuration diagram of the AC power supply E1 described in FIG. Although FIG. 2 illustrates the AC power supply E1, the AC power supply E2 has the same configuration.

  The AC power supply E1 includes a power supply unit 10 that can supply power and an oscillation unit 20 that alternately changes polarity at a predetermined frequency and outputs a voltage to the target pair T1.

  The power supply unit 10 includes a first CPU circuit 101 that controls the operation thereof, an input unit 102 to which a commercial AC power supply (three-phase AC200V) is input, and rectifies the input AC power to convert it into DC power. 6 diodes 103 that serve to output DC power to the oscillating unit 20 via the DC power lines 104a and 104b.

  The power supply unit 10 is connected to the switching transistor 105 provided between the DC power lines 104a and 104b and the first CPU circuit 101 so as to be communicable, and controls the on / off of the switching transistor 105. The driver circuit 106a and the first PMW control circuit 106b are provided. In this case, a detection circuit 107a and an AD conversion circuit 107b that have a current detection sensor and a voltage detection transformer and detect the current and voltage between the DC power lines 104a and 104b are provided, and the detection circuit 107a and the AD conversion circuit 107b are provided. Thus, the current and voltage signals are input to the CPU circuit 101.

  On the other hand, the oscillating unit 20 includes four CPUs 201 that are communicably connected to the first CPU circuit 101 and four oscillation switch circuits 202 provided between the DC power lines 104a and 104b. The second to fourth switching transistors 202a, 202b, 202c, and 202d are connected to the second CPU circuit 201 so as to be communicable, and the second switching transistors 202a, 202b, 202c, and 202d are controlled to turn on and off. A driver circuit 203a and a second PMW control circuit 203b are provided.

  The second driver circuit 203a and the second PMW control circuit 203b then turn on / off timing of the first and fourth switching transistors 202a and 202d and the second and third switching transistors 202b and 202c, for example. When the operation of each switching transistor 202a, 202b, 202c, 202d is controlled so as to be inverted, a sinusoidal AC power supply can be output via the AC power lines 204a, 204b from the oscillation switch circuit 202. In this case, a detection circuit 205a and an AD conversion circuit 205b for detecting an oscillation voltage and an oscillation current are provided, and the current and voltage signals are input to the second CPU circuit 201 via the detection circuit 205a and the conversion circuit 205b. It has become.

  The AC power lines 204a and 204b are connected to an output transformer 206 having a known structure, and an output cable k from the output transformer 206 is connected to the target pair T1. In this case, a detection circuit 207a and an AD conversion circuit 207b that have a current detection sensor and a voltage detection transformer and detect the output voltage and output current to the target pair T1 are provided, and the detection circuit 207a and the AD conversion circuit 207b are provided. The output voltage and output current signals are input to the second CPU circuit 201. Thereby, during sputtering, a constant voltage can be applied to the target pair T1 by alternately changing the polarity at a constant frequency via the AC power supply E1.

  The output from the detection circuit 207a is connected to a detection circuit 208a for detecting the output frequency and output phase of the output voltage and output current, and an output phase / output frequency control circuit connected to the detection circuit 208a so as to be communicable. The phase and frequency of the output voltage and output current are input to the second CPU circuit 201 via 208b. Thereby, the on / off of each switching transistor 202a, 202b, 202c, 202d of the oscillation switch circuit 202 is controlled by the second driver circuit 203a by the control signal from the second CPU circuit 201, and the output voltage and output current are controlled. Can be controlled so that their phases substantially coincide with each other.

  Then, the substrate to be processed is transferred to a position facing the target pair T1 by the substrate transfer means, and a predetermined sputtering gas is introduced through the gas introduction means. An AC voltage is applied to the target pair T1 via the AC power source E1, and each target constituting the target pair T1 is alternately switched between the anode electrode and the cathode electrode, and a glow discharge is generated between the anode electrode and the cathode electrode to generate a plasma atmosphere P Form. As a result, ions in the plasma atmosphere P are accelerated and collide with one target that has become the cathode electrode, and target atoms are scattered to form a thin film on the surface of the substrate to be processed.

  By the way, when a large arc energy is generated along with the abnormal discharge (arc discharge) generated for some reason during the glow discharge, splash or the like may occur, which may hinder good thin film formation.

  Accordingly, the oscillating unit 20 is provided with arc detecting means 209 for detecting a voltage drop in which the voltage drop time of the output voltage waveform to the target pair T1 is shorter than that during normal glow discharge. Further, when the arc detection means 209 detects the occurrence of arc discharge, a voltage drop output signal is output to the second CPU circuit 201 that is communicably connected, and the first CPU circuit that is communicable with the second CPU circuit 201. The output control means for controlling the operation of the switching transistor 105 by the first driver circuit 106a by the control signal from 101, controlling on / off of the first PMW control circuit 106b, and immediately shutting off the output to the target pair T1 Also provided.

  As a method of immediately shutting off the output to the target pair T1, the second driver circuit 203a uses the control signal from the second CPU circuit 201 so that the potential between the AC power lines 204a and 204b is the same. It is also possible to control the operation of each switching transistor 202a, 202b, 202c, 202d of the oscillation switch circuit 202 and immediately shut off the output to the target pair T1.

  By the way, when the arc discharge occurs in the target T1, as described above, the output of the AC power supply E1 connected to the target pair T1 is simply cut off and coupled to the target T1 via the floating capacitance. Since energy is supplied from the plasma generated in the target pair T2, the generated arc discharge is difficult to extinguish.

  Therefore, in order to suppress the influence of the target pair T2, the control signal received by the second CPU circuit 201 is transmitted to the CPU circuit of the oscillation unit of the adjacent AC power supply E2 via the communication cable K described in FIG. The output from the AC power supply E2 to the target pair T2 may be cut off by the same process.

  FIG. 3 shows an output waveform between the target t12 and the target t21 connected to the AC power supply E1 and the AC power supply E2 described in FIG. 1 before the output adjustment by the thin film forming method according to the present invention, and the output adjustment. This is shown after and after.

  FIG. 3A shows a waveform before output adjustment by the thin film forming method according to the present invention.

  In the case of FIG. 3A, the output potential difference between the target t12 and the target t21 increases as the peak-to-peak voltage Vpp. When an abnormal discharge occurs in this state, a large arc energy is generated, thereby causing a splash in which the target is melted and huge droplets are attached, thereby inhibiting good thin film formation.

  In the present embodiment, the AC power supply E1 and the AC power supply E2 output simultaneously, and the outputs of the AC power supplies E1 and E2 are the same. Therefore, the output phase is substantially inverted between the target t12 and the target t21.

FIG. 3 (b) shows a waveform after output adjustment by the thin film forming method according to the present invention.
The thin film forming method according to the present invention adjusts the output so as to converge the output potential difference between the AC power supply E1 and the AC power supply E2 in order to suppress the generation of large arc energy as described above. In the present embodiment, if the output phase between the targets is shifted by 180 degrees and the polarity is reversed, the waveforms of the AC power supply E1 and the AC power supply E2 overlap, and the output potential difference that causes arc discharge hardly occurs.

  For example, the output potential difference is converged by first transmitting the output current and output voltage signal of the AC power supply E2 to the CPU circuit 201 of the AC power supply E1 via the communication cable K described in FIG. Compare with output current and output voltage signal. When the output potential difference between the two exceeds a predetermined value, a control signal for converging the output potential difference is sent from the CPU circuit 201 of the AC power supply E1 via the communication cable K to the second oscillation unit of the AC power supply E2. Transmit to the CPU circuit. Based on the control signal received by the second CPU circuit, the operation of each switching transistor of the oscillation switch circuit is controlled via the output oscillation driver circuit and the PMW control circuit, and the output of the target pair T2 is adjusted. The output potential difference may be converged.

  The predetermined value may be within the range of the output potential difference that does not cause the abnormal discharge that causes the arc energy generation, and does not necessarily have to converge until the output potential difference becomes 0V. Specifically, it may be set at 10%, preferably 5%, of the 0-peak potential difference (or effective value) of each AC power source.

  In this embodiment, an example in which the output potential difference is converged by adjusting the output of the AC power supply E2 is shown. However, the present invention is not limited to this, and the output potential difference is converged by adjusting the output of the AC power supply E1. Alternatively, both the AC power supply E1 and the AC power supply E2 may be adjusted to converge the output potential difference.

  In addition, in FIG. 3, although the waveform shape of AC power supply E1 and E2 showed the sine wave, it is not limited to this, A square wave may be sufficient. Further, the same processing may be performed not only when the oscillation frequency of the AC power source is fixed but also when it is varied.

  4 and 5 are diagrams showing examples of specific embodiments of the sputtering apparatus according to the present invention. In any of the embodiments, the same reference numerals are assigned to those common to FIG.

  In FIG. 4, the target pairs T1, T2, T3, and T4 are arranged in parallel to face the target substrate S. The target pair T1 is connected to the AC power source E1, the target pair T2 is connected to the AC power source E2, the target pair T3 is connected to the AC power source E3, and the target pair T4 is connected to the AC power source E3. The AC power supplies E1 to E4 are connected via a communication cable K so as to be able to communicate. Each of the AC power supplies E1 to E4 has the same circuit configuration as the AC power supply E1 described in FIG.

    The AC power supply E1 compares the outputs between the target t12 and the target t21. If the output potential difference is equal to or greater than a predetermined value, the AC power supply E1 generates the control signal described with reference to FIG. Send to. Thereafter, the output between the target t22 and the target t31 and the output between the target t32 and the target t41 are sequentially compared. When the output potential difference is equal to or greater than a predetermined value, the control signal is generated and adjusted. This control signal may be transmitted to That is, starting from the AC power source E1 (master AC power source), the AC power sources E2 to E4 connected to the target pairs T2 to T4 from the target pair T1 connected to the AC power source E1 toward the outside in the parallel arrangement direction. The output may be adjusted sequentially.

  In FIG. 4, the adjustment processing is performed with the AC power supply E1 as a starting point. For example, after adjusting the output of the AC power supply E2, the output of the adjacent AC power supply E3 is adjusted using the AC power supply E2 as the master AC power supply. Alternatively, the AC power supply E4 may be adjusted using the adjusted AC power supply E3 as a master AC power supply.

  In this embodiment, the master AC power source is the AC power source E1, but is not limited to the master AC power source E1, and can be arbitrarily determined. For example, when the master AC power source is the AC power source E3, the adjacent AC power sources are two pairs of the AC power source E2 and the AC power source E4. After the adjustment processing of the AC power sources E2 and E3 is performed, the AC power source E1 is used. The adjustment process is performed.

  FIG. 5 is a modification of the embodiment of FIG. In FIG. 5, the same components as those in FIG. 4 are denoted by the same reference numerals.

  In the present embodiment, the control device U that is communicably connected to each AC power source E1 to E4 via the communication cable K is connected to a different AC power source instead of the master AC power source described in FIG. The outputs of the targets adjacent to each other are compared, and when the output potential difference is a predetermined value or more, a control signal is generated, and the control signal is transmitted to the AC power source to be adjusted.

Basic configuration diagram of thin film forming apparatus according to the present invention Basic circuit configuration diagram of AC power supply a) The figure which showed the waveform before adjustment by the thin film formation method concerning this invention, b) The figure which showed the waveform after adjustment by the thin film formation method concerning this invention The figure which shows one Embodiment of the thin film formation apparatus concerning this invention The figure which shows one Embodiment of the thin film formation apparatus concerning this invention (modification)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2 Vacuum exhaust means 3 Substrate conveyance means 4 Gas introduction means E1 AC power supply E2 AC power supply T1 Target pair T2 Target pair K Communication cable S Substrate

Claims (12)

A plurality of target pairs are arranged in parallel in a vacuum chamber so as to face the substrate to be processed, and an alternating voltage is output at alternating frequencies with a predetermined frequency via an alternating current power source connected to each target pair. Are alternately switched between an anode electrode and a cathode electrode, a glow discharge is generated between the anode electrode and the cathode electrode to form a plasma atmosphere, and each target pair is sputtered onto the substrate to be processed. A thin film forming method for forming a thin film,
Compare the outputs between adjacent targets connected to different AC power sources among the parallel target pairs, and adjust the output of the AC power source when the output potential difference exceeds a predetermined value A method of forming a thin film, characterized in that a potential difference is converged to the predetermined value or less.   2. The thin film forming method according to claim 1, wherein the output is adjusted by converging the output potential difference by inverting the polarity by shifting the output phase between the mutually adjacent targets by 180 degrees.   The adjustment of the output means that starting from any one AC power source, the output of each AC power source is sequentially adjusted from the target pair connected to the AC power source that is the starting point toward the outside in the parallel arrangement direction. The thin film forming method according to claim 1, wherein the thin film forming method is characterized.   Adjusting the output of the AC power source adjacent to the AC power source that is the starting point, and then adjusting the output of each AC power source adjacent to the outside in the juxtaposed direction sequentially with the adjusted AC power source as a further starting point. The thin film forming method according to claim 3.   5. The output adjustment is performed by generating a signal for controlling the output of the AC power source and transmitting the signal to the AC power source for adjusting the output. A method for forming a thin film according to 1.   6. The method of forming a thin film according to claim 5, wherein the signal is generated by an AC power source that is the starting point, and is transmitted from the AC power source that is the starting point to an AC power source that adjusts an output.   When an arc discharge occurs in any of the above target pairs, the output to the target pair where the arc discharge has occurred is cut off, and the output to the other target pair where no arc discharge has occurred is cut off at the same time. The thin film forming method according to claim 1, wherein: A thin film forming apparatus comprising a plurality of target pairs arranged in parallel to face a substrate to be processed disposed in a vacuum chamber, and an AC power source connected to each target pair,
Compare the outputs between adjacent targets connected to different AC power sources in the parallel target pairs, and adjust the output of the AC power source when the output potential difference exceeds a predetermined value. A thin film forming apparatus, comprising: adjustment processing means for converging at a predetermined value or less.   9. The adjustment processing means includes signal generation means for generating a signal for controlling the output of the AC power supply, and transmission means for transmitting this signal to the AC power supply for adjusting the output. The thin film forming apparatus described.   10. The thin film forming apparatus according to claim 8, wherein an AC power source that is a starting point for performing the adjustment processing includes the adjustment processing means.   10. The thin film forming apparatus according to claim 8, further comprising a control device including the adjustment processing unit.   When an arc discharge occurs in the target pair to which each of the AC power supplies is connected, an arc detection means for detecting the arc discharge, and when the arc discharge is detected by the arc detection means, The output control means for controlling the output of each AC power supply so as to shut off the output and simultaneously shut off the output to the other target pairs. The thin film forming apparatus described.

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