JP2019528369A - Pulsed DC power supply - Google Patents

Abstract

A pulsed DC power supply is provided. The pulsed DC power supply is configured to supply unipolar pulsed DC power. The pulsed DC power supply includes a pulsing unit for alternately setting the nominal on-cycle DC voltage and the nominal off-cycle voltage during the off-cycle during the on-cycle of the unipolar pulse cycle of the pulsed DC power supply. A pulsed DC power source is configured to measure an off-cycle current during an off-cycle, and a zero-line determination unit configured to determine the presence of a zero-line condition of the measured off-cycle current including. The pulsing unit is configured to set a nominal on-cycle DC voltage upon determining the presence of a zero-line condition of the measured off-cycle current. [Selection] Figure 2

Description

  Embodiments relate to a pulsed DC power source for supplying unipolar pulsed DC power and a method of operation of such a pulsed DC power source. Further embodiments relate to deposition systems, such as sputter deposition systems, that include such pulsed DC power supplies.

  Pulsed DC sputtering is a physical vapor deposition process (PVD process) that has applications in the semiconductor and coating industries, for example. The abbreviation “DC” refers to direct current relative to alternating current. Pulsed DC sputtering is particularly effective in metal sputtering and dielectric coating and is often used in reactive sputtering. In reactive sputtering, a chemical reaction occurs in the plasma between the vaporized target material and an ionized gas such as oxygen, forming deposited molecules such as silicon oxide. In conventional DC sputtering (eg, reactive sputtering of aluminum, titanium, or silicon), the target may be charged and an arc may occur that significantly degrades the quality of the deposited film or layer.

  Arcing is reduced when the DC voltage applied to the target is pulsed. Arcing may be caused by charges accumulated in a dielectric layer formed during the deposition process. Thus, arcing may not be a problem at an early stage of the deposition process, but it may increase dramatically later and lead to poor coating application processes. The arc may degrade the quality of the deposited layer or film and may destabilize the application of power to the sputter target.

  In unipolar pulsed DC sputtering, sputtering occurs when the pulsed DC voltage is on during the on-cycle (duty cycle), i.e., a typical negative value of several hundred volts. Is done. During the subsequent off-cycle of the pulsed DC voltage, the target is discharged and, depending on the process, the substrate is also discharged. During the off-cycle, the voltage value can be zero or a positive value of tens of volts, often referred to as a reverse pulse. As the processing time elapses, for example, processing conditions such as the manner in which charge accumulates on the target may change, and pulsing of the DC voltage is usually not sufficient to prevent arcing. Thus, the pulsed DC voltage source may include an arc suppression circuit. The arc suppression circuit detects arc formation through changes in the target voltage and immediately initiates one or more special off periods, typically one or more reverse pulses, to suppress the arc. Once the arc is suppressed, normal pulse DC cycles resume.

  The on-cycle and off-cycle pulse frequencies and lengths are set by the operator at the pulsed DC voltage source. The setting of these processing parameters is based on the operator's experience. If the operator's experience in setting these process parameters properly is insufficient, or if the sputter process exhibits unexpected behavior or simply changes over time, it should be suppressed by an arc suppression circuit. There may be many arc formations, the on time at which sputtering occurs is too short, and the deposition rate of the sputter deposition process is adversely affected.

  Accordingly, there is a need for an improved DC voltage source, a method of operating a DC voltage source, and a deposition system that utilizes such a pulsed DC voltage source.

  In light of the above, devices and methods according to the independent claims are provided. Further details can be found in the dependent claims, the description and the drawings.

  According to one embodiment, a pulsed DC power supply is provided. The pulsed DC power supply may be configured to supply monopolar pulsed DC power. The pulsed DC power supply includes a pulsing unit for alternately setting the nominal on-cycle DC voltage and the nominal off-cycle voltage during the off-cycle during the on-cycle of the unipolar pulse cycle of the pulsed DC power supply. A pulsed DC power source is configured to measure an off-cycle current during an off-cycle, and a zero-line determination unit configured to determine the presence of a zero-line condition of the measured off-cycle current including. The pulsing unit is configured to set a nominal on-cycle DC voltage if it is determined that a zero-line condition of the measured off-cycle current is present.

  According to another embodiment, a pulsed DC power supply is provided. The pulsed DC power supply may be configured to supply monopolar pulsed DC power. The pulsed DC power supply is configured to set a nominal on-cycle DC voltage during the on-cycle of the unipolar pulse cycle of the pulsed DC power supply, and a nominal off-cycle voltage during the off-cycle of the unipolar pulse cycle of the pulsed DC power supply. Including a pulsing unit configured to set. The pulsed DC power source includes a measurement unit configured to measure at least one electrical quantity of the pulsed DC power source. The pulsed DC power source includes an evaluation unit configured to determine the presence of a predetermined condition from an evaluation of the measured value of at least one measured electrical quantity. The pulsing unit is configured to set a nominal on-cycle DC voltage once the presence of the predetermined condition is determined.

  In addition, a sputter deposition system is provided. The sputter deposition system includes a sputter target and a pulsed DC power source, according to embodiments described herein. A pulsed DC power source is connected to the sputter target.

  According to another embodiment, a method for operating a pulsed DC power supply is provided. A pulsed DC power supply may have some or all of the features according to the embodiments described herein. The pulsed DC power supply supplies monopolar pulsed DC power. The method includes setting a nominal on-cycle DC voltage for the first pulse cycle of the pulsed DC power source and outputting an on-cycle DC voltage and an on-cycle DC current with the pulsed DC power source. The method sets a nominal off-cycle DC voltage to trigger the off-cycle of the first pulse cycle and measures the off-cycle current of the off-cycle of the first pulse cycle with a pulsed DC power supply. Including. The method includes determining from the measurement of the off-cycle current that an off-cycle current zero line condition exists. The method includes setting a nominal on-cycle DC voltage for the second pulse cycle when it is determined that a zero-line condition for the off-cycle current of the first pulse cycle exists.

  The present disclosure is further directed to an apparatus for performing the disclosed method, which includes a portion of the apparatus for implementing each feature of the described method. These method features may be implemented using any combination of the two, using hardware components, using a computer programmed with appropriate software, or in any other manner. A further aspect is directed to a method in which the described pulsed DC power supply or sputter deposition system is operated, manufactured, or used. The method may include a portion of the method for performing any function of a pulsed DC power supply or sputter deposition system.

A more specific description can be obtained by referring to the embodiments so that the above features can be understood in detail. The accompanying drawings relate to embodiments and are described below.
The characteristics of a unipolar pulse DC voltage are shown. 2 illustrates a method of operating a pulsed DC power supply, according to embodiments described herein. 2 illustrates a method of operating a pulsed DC power supply, according to embodiments described herein. FIG. 3 illustrates a pulsed DC power source according to embodiments described herein. FIG. 1 illustrates a sputter deposition system in accordance with embodiments described herein. 2 illustrates a method of operating a pulsed DC power supply, according to embodiments described herein.

  Reference will now be made in detail to various exemplary embodiments, one or more examples of which are illustrated in each figure. Each example is provided by way of illustration only and is not meant as a limitation. For example, features illustrated and described as part of one embodiment may be used in other embodiments or used in conjunction with other embodiments, thereby providing further embodiments. The present disclosure is intended to include such modifications and variations.

  Within the following description of the drawings, the same reference numbers refer to the same or similar components. Generally, only the differences with respect to the individual embodiments are described. The illustrated structures are not necessarily drawn to scale or angles, and features may be emphasized so that the corresponding embodiments can be better understood.

FIG. 1 illustrates the characteristics of a unipolar pulsed DC voltage that can be applied to a sputter target in a sputter deposition process by a pulsed DC power supply. Time t is shown on the abscissa and voltage U is shown on the ordinate. Arbitrary units are used. The voltage exhibits a negative constant value during the on cycle (duty cycle) of FIG. ON period of the on cycle, i.e., the length of time that the on-cycle duration is expressed as T _on. The voltage exhibits a small positive constant value during the off cycle (reverse pulse) of FIG. Off period of off cycle, i.e., the length of time the off cycle persists, represented as T _off. One pulse consists of an on-cycle and an off-cycle, in other words, an on-pulse and a reverse pulse. A pulse is also referred to herein as a pulse cycle because of its repeating pattern. Pulse duration or pulse length, i.e., length of pulse duration _is represented as _{T pulse,} the sum of the _{T on} and _{T off.} The operating frequency or pulse frequency represented as F _pulse is the reciprocal of the pulse period.

The pulse frequency, on-cycle length (duty cycle period), and off-cycle length (reverse pulse period) can be set by the operator based on the operator's experience. For example, the operator can set the nominal pulse frequency, can set the on-cycle length, or the ratio between the on-cycle length and the off-cycle length, T _pulse , T _on , And T _off follow the mathematical relationship described above. When such a unipolar pulsed DC voltage is output from a pulsed DC voltage source and applied to the sputter target, sputtering can occur during the on-cycle, but the reverse pulse causes arcing due to discharge of the sputter target. cut back. However, if the operating parameters of the pulsed DC voltage source such as the pulse frequency and the reverse pulse period are not properly set, or if the sputtering process conditions change over time or show unexpected behavior, Arc formation can occur frequently. If arc formation occurs frequently, it is necessary to frequently use special means such as arc suppression by a special arc suppression circuit, which reduces efficiency and, in some cases, sputter deposition processing quality.

  In the embodiments described herein, the pulsed DC power source for supplying unipolar pulsed DC power is one or more during the current pulse cycle, in particular during the off cycle of the current pulse cycle. Based on the measurement of the amount of electricity, the condition for when to start the on-cycle of the next pulse cycle is determined. If the pulsed DC power supply supplies monopolar pulsed DC power for the sputter deposition process, the condition for when to start the on-cycle of the next pulse cycle is the charge removal condition, i.e. one or more sputter targets. The condition may indicate that the electric charge accumulated above is removed by the off-cycle voltage (reverse pulse voltage) of the off-cycle. After the charge removal condition is met, the next pulse cycle starts only with the on cycle. Unlike the situation shown in FIG. 1, the length of the off cycle, i.e., the off cycle period, may vary depending on the measurement of actual electrical quantities such as actual current and / or actual voltage. In FIG. 1, the length of the off-cycle varies only if the operator sets the nominal operating parameters, eg, the nominal operating frequency (and thus the nominal pulse length) or the off-cycle or on-cycle nominal length to be different. obtain.

  Thus, the pulsed DC power supply according to the embodiments described herein does not set the nominal on-cycle voltage and the nominal off-cycle voltage simply at a time predetermined by the operating parameters set by the operator, Can intelligently react to the actual processing situation that is perceived. Since the off-cycle of the current pulse cycle is maintained until a specific condition of the actual electrical quantity is met, particularly a charge removal condition indicating that charge has been removed from one or more sputter targets, the pulse DC The power supply can always ensure that all or at least sufficient charge is removed to reduce or even prevent arcing as the processing conditions of the sputter deposition process change.

  The charge removal condition can be the actual off-cycle current zero line condition measured by a pulsed DC power supply. This is because once the pulsed DC power supply has determined that the measured off-cycle current is zero or substantially close to zero, the on-cycle DC voltage is again turned on to initiate the on-cycle of the next pulse cycle. Means set. Without being bound by any particular theory, the existence (ie, implementation) of such an actual off-cycle current zero-line condition is believed to indicate that sufficient charge removal is taking place from the sputter target. ing.

Since the off cycle period varies from pulse cycle to pulse cycle depending on the actual amount of electricity measured by the pulsed DC power source, the sum of the nominal on cycle period _Ton and the variable off cycle period T _off is the nominal pulse frequency. It need not be equal to the nominal pulse period T _pulse , which is the reciprocal of F _pulse . According to some embodiments, the on-cycle period is adapted (first mechanism). The on-cycle period can be adapted such that the sum of the on-cycle period and the off-cycle period converges to a nominal pulse period, or at least on average equals or approaches the nominal pulse period. According to another embodiment, the pulse frequency and thus the pulse period is adapted instead (second mechanism). Both mechanisms can also be implemented together, tailored by specific conditions on when to apply the first mechanism and when to apply the second mechanism. The first mechanism (application of the on-cycle period) may be a default mechanism and may be used to fine tune the output of the pulsed DC power supply. In the second mechanism (application of the pulse frequency), for example, when some quality conditions cannot be satisfied by fine adjustment using the first mechanism, coarse adjustment can be performed without using it frequently. .

FIG. 2 shows the method of operation of the pulsed DC power supply. The time t is shown on the abscissa, and the nominal voltage U _nominal set by the pulsed DC power supply and the actual current I _actual measured by the pulsed DC power supply are shown schematically in arbitrary units on the ordinate. In FIG. 2, five pulse cycles are illustrated. During the on cycle of the pulse cycle, the nominal voltage is set to a constant on-cycle voltage, which is negative (eg, several hundred volts). During the off cycle of the pulse cycle (reverse pulse), the nominal voltage is set to a constant off-cycle voltage, which is positive and at least an order of magnitude less than the on cycle voltage (e.g., Tens of volts). Pulsed DC power supply, measuring the actual current _{I actual are} during at least each off cycle, pulsed DC power from the measured actual current _{I actual are} been determines that the zero line condition of the actual current _{I actual are} exist Only when it starts with an on cycle will it cause the next pulse cycle. This behavior can be seen in FIG. 2 for the five pulse cycles shown. Here, when it is determined from the measurement result that the actual current I _actual is zero or substantially zero, the nominal voltage U _nominal is set to a negative on-cycle voltage.

For example, as can be seen in the second pulse cycle shown in FIG. 2, the nominal voltage is not necessarily set to the on-cycle voltage at the end of the nominal pulse period, as in FIG. For the second pulse cycle, the nominal pulse period is indicated by a dashed arrow. This is because the actual pulse duration is longer for this second pulse cycle. The reason is that the actual current I _actual satisfies the zero line condition only after the nominal pulse period has ended. The pulsed DC power supply waits to cause an on cycle of the next third pulse cycle until it is determined that a zero line condition actually exists, regardless of the nominal pulse period.

In the embodiment shown in FIG. 2, the pulsed DC power supply determines the length of the off cycle of the second pulse cycle, ie, the off cycle period of the second pulse cycle. For the third pulse cycle, the pulsed DC power source may, for example, set the on-cycle period Ton to the difference between the nominal pulse period and the determined off-cycle period of the second pulse cycle. To be shorter. Conversely, as shown in the fourth and fifth pulse cycles of FIG. 2, the pulsed DC power supply may have a longer on-cycle period. In the fourth pulse cycle, the zero line condition of the _actual current I _actual is reached before the end of the nominal pulse period (shown again with a dashed arrow). By setting the on-cycle duration T _on the difference between the nominal pulse period and determined off-cycle period of the fourth pulse cycle, the on cycle period T _on is longer by between the fifth pulse cycle . The nominal pulse period T _pulse as well as the nominal pulse frequency F _pulse = 1 / T _pulse does not change during the pulse cycle shown in FIG. Only the on-cycle period is adapted to the variable off-cycle period (first mechanism).

  When a pulsed DC power supply is used to provide monopolar pulsed DC power for a sputter deposition process, sputtering occurs only during the on cycle (duty cycle). Therefore, the pulse DC power source that outputs the unipolar pulsed DC power shown in FIG. 2 can reduce the arc generation because the charge removal condition is reliably satisfied in the form of the zero line condition, and the given nominal pulse period can be reduced. Since the on-cycle period is maximized under the constraint of the above, the efficiency of the sputter deposition process can be increased. The duty factor is maximized without the need for operator intervention. It should be understood that the duty factor is a ratio between the on-cycle period and the nominal pulse period.

  FIG. 3 shows a further method of operation of the pulsed DC power supply. Three pulse cycles are shown, the first two pulse cycles being the same as in FIG. These further details are omitted. As shown in FIG. 2, the pulsed DC power supply determines the length of the off cycle of the second pulse cycle, that is, the off cycle period of the second pulse cycle. In contrast to the method of operation shown in FIG. 2, the nominal pulse frequency is decreased and the nominal pulse period is the third and subsequent pulse cycles until the nominal pulse frequency is changed again according to the second mechanism. Is set longer. In particular, the nominal pulse period may be set as the sum of the on-cycle period and the determined off-cycle period, as shown in FIG. The new setting of the nominal pulse frequency or nominal pulse period can be done automatically by the pulsed DC power supply, or it can be done after the operator receiving notification, for example through the display, approves.

In FIG. 3, the nominal pulse frequency decreases and the nominal pulse period T _pulse increases. The nominal operating frequency may be further increased and the nominal pulse period may be shorter. Illustratively, instead of applying the on-cycle period shown in FIG. 2, the nominal pulse period is set as the sum of the on-cycle period and off-cycle period of the fourth pulse in FIG. Imagine that the nominal pulse period of the fifth pulse is shorter. However, reducing the nominal pulse frequency is believed to be less risky about process stability of the sputter deposition process than increasing the nominal pulse frequency. However, for example, if a particular sputter deposition process is known to operate stably within a specific range of allowable nominal pulse frequencies, the nominal pulse frequency may be increased or decreased as long as it is within the allowable nominal pulse frequency range. You may let them.

  The second mechanism described in connection with FIG. 3 ensures a sufficient discharge of the sputter target by determining the zero line condition as a form of charge removal condition, so that the actual current is off during the off cycle. Allow enough time to meet the zero line condition.

  The first mechanism shown in FIG. 2 and the second mechanism shown in FIG. 3 can also be used together in a pulsed DC power supply. The first mechanism may be used as a default mechanism, and the second mechanism is used when certain operating parameter mismatch conditions are met. For example, if the use of the first mechanism leads to a situation where the on-cycle is unacceptably short, or in other words, the duty factor and thus the efficiency of the sputter deposition process is unacceptably low. If this is the case, this may indicate that the nominal pulse frequency was set too high. In that case, the pulsed DC power supply may switch to using the second mechanism automatically or semi-automatically with operator approval before returning to using the first mechanism as the default mechanism. .

  The pulsed DC power supply ensures sufficient charge removal from the sputter target automatically or semi-automatically based on the current measurement and evaluation if the measurement results meet certain conditions, and the on-cycle length (ie, Duty factor) is optimized and an appropriate nominal pulse frequency is set. Thus, the efficiency and stability of the sputter deposition process can be increased and arcing can be significantly reduced. Of course, the pulsed DC power supply may further include a dedicated arc suppression circuit that detects arc formation and weakens arc formation. Triggering one or more reverse pulses with a dedicated arc suppression circuit to suppress the detected arc may precede the normal unipolar pulse generation described herein.

  In accordance with the embodiments described herein, a pulsed DC power supply is provided. The pulsed DC power supply is configured to supply unipolar pulsed DC power. The supply of monopolar pulsed DC power can be one of the operating modes of the pulsed DC power supply. The pulsed DC power supply may be capable of still other modes of operation, such as a bipolar pulsed DC power mode. The pulsed DC power supply can be a voltage controlled pulsed DC power supply. The pulsed DC power supply can be configured to drive a unipolar pulsed DC sputter deposition process. The pulsed DC power source may be connectable to a sputter deposition system, particularly one or more sputter targets.

  The pulsed DC power source includes a pulsing unit. The pulsed DC power supply may include a DC voltage source as a separate component. Alternatively, the pulsing unit may include a DC voltage source. The pulsing unit and the DC voltage source may be integral with each other. The pulsing unit may be configured to form a DC voltage output with a DC voltage source so as to form a monopolar pulsed DC voltage. The actual unipolar pulsed DC voltage at the output of the pulsed DC power supply may depend on the electrical characteristics of the system to which the pulsed DC power supply is connected. For pulsed DC power supplies, the system to which the pulsed DC power supply is connected appears to be a time-dependent complex impedance. Such a system may be a sputter deposition system, but may be a test device that mimics the characteristics of the deposition system.

  The pulsing unit is configured to set a nominal on-cycle DC voltage and to set a nominal off-cycle DC voltage. The nominal amount is an operating parameter set for the pulsed DC power supply by the pulsed DC power supply or the operator. The pulsing unit can alternately set the nominal on-cycle voltage and the nominal off-cycle voltage. A nominal on-cycle DC voltage is set during the on-cycle. The on-cycle continues from the moment the nominal on-cycle DC voltage is set at the moment the subsequent nominal off-cycle DC voltage is set. The length of the on-cycle time is called the on-cycle period. A nominal off-cycle DC voltage is set during the off-cycle. The off-cycle continues from the moment the nominal off-cycle DC voltage is set at the moment when the subsequent nominal on-cycle DC voltage is set. The length of time of the off cycle is called the off cycle period. The off cycle may be referred to as a reverse pulse, and the off cycle period may be referred to as a reverse pulse length or off time. Thus, the nominal unipolar pulsed DC voltage has a square wave pattern, but the actual unipolar pulsed DC voltage can be disturbed by the back-action of the system to which the pulsed DC power supply is coupled.

  One on cycle and one off cycle immediately following it form a monopolar pulse cycle. This is simply called a pulse cycle. The length of time of the pulse cycle is called the pulse period. The reciprocal of the pulse period is called the pulse frequency. The nominal pulse frequency is also called the operating frequency of the pulsed DC power supply. The pulsing unit may be configured to alternately set the nominal on-cycle DC voltage and the nominal off-cycle voltage during the off-cycle during the on-cycle of the unipolar pulse cycle of the pulsed DC power supply.

  The nominal on-cycle DC voltage may be set to a value in the range of −100V to −1000V, eg, −100V to −200V. The nominal off-cycle DC voltage may be set to a value in the range of a positive voltage from zero volts to the nominal on-cycle DC voltage, eg, 100V to 1000V, with sign inversion. The nominal off-cycle DC voltage may be in the range of 0V to 100V, such as 0 to 20V or 5 to 20V. The absolute value of the nominal off-cycle DC voltage may be at least 5 times, at least 10 times, or at least 20 times less than the absolute value of the nominal on-cycle DC voltage. The nominal pulse frequency (operating frequency) may have a value in the range of 100 Hz to 200 KHz, in particular in the range of 100 kHz to 100 KHz, for example 1 kHz to 100 kHz. Accordingly, the nominal pulse period, which is the reciprocal thereof, may have a value in the range of 10,000 μs to 5 μs, more specifically, 10,000 μs to 10 μs, for example, 1000 μs to 10 μs.

  The pulsed DC power source includes a current measurement unit. The current measurement unit may be configured to measure the actual current at least during the off cycle, and possibly further during the on cycle. The actual current during the off cycle is called the off cycle current. The current measurement unit is configured to measure off-cycle current during the off-cycle. The current measurement unit can be an analog device having an analog output. Alternatively, the current measurement unit may include an analog to digital converter that converts the analog measurement value to a corresponding digital value. Thus, the current measurement unit outputs a digital value and is therefore considered a digital device.

  The current measuring unit may be a current probe, in particular a DC current probe, or may include such a current probe. The current probe may include one or more hall sensors. The current probe can generate an analog measurement. The current probe may generate a probe voltage that is proportional to the measured current, in particular the measured off-cycle current. The current measurement unit may include an analog to digital converter configured to sample and digitize analog measurements that represent probe voltage or off-cycle current.

  The pulsed DC power supply includes a zero line determination unit. The current measurement unit may be configured to pass a measurement value, such as an analog value or a digital value, to the zero line determination unit. If the analog value is passed to the zero line determination unit, i.e., if the current measurement unit is an analog device, the zero line determination unit may include an analog-to-digital converter that converts the received analog measurement value to a corresponding digital value. . The zero line determination unit is configured to determine the presence of a zero line condition of the measured off cycle current. A zero line condition exists if the off-cycle current is zero, or at least substantially zero, or within a predetermined range. The predetermined range may include a current value of zero, but alternatively may be excluded if, for example, some bias is applied.

  If the current value is within the zero line condition range (eg, between -0.1A and 0.1A), the off-cycle current can be said to be substantially zero. The off-cycle current can be represented by a measured value such as the probe voltage of the current probe, and since the probe voltage is proportional to the measured off-cycle current, these values are zero or substantially zero In this case, it can be determined that the zero line condition exists. In this context, substantially zero means that the measured value representing the off-cycle current value is within a certain range and the off-cycle current value represented by the measured value is within the zero line condition range. For example, if the probe voltage of the current probe is k times the measured off-cycle current and k is a proportionality constant, when the probe voltage is in the range of −k * 0.1V to k * 0.1V, It is determined that a zero line condition exists.

  The zero line determination unit may be configured to analyze measured off-cycle current measurements, eg, sampled and digitized measurements of current probes. The zero line determination unit may be configured to determine when the probe voltage from the current probe is zero, or at least substantially zero. If the other measurement value representing the probe voltage or off-cycle current is found to be zero or at least substantially zero, the zero line determination unit determines that a zero line condition for the measured off-cycle current exists. judge. The zero line determination unit can generate a signal, eg, a digital signal, indicating the presence of a zero line condition. This digital signal may be as small as 1 bit (eg, logic 1). The signal can be supplied to a pulsing unit.

  The pulsing unit is configured to set a nominal on-cycle DC voltage if it is determined that a zero-line condition of the measured off-cycle current is present. This means that the next pulse cycle starting with an on cycle can be triggered when the presence of a zero line condition is detected. The pulsing unit may set a nominal on-cycle DC voltage when receiving a signal from the zero-line determination unit indicating the presence of a measured off-cycle current zero-line condition. The zero line determination unit may be a sub-component of the pulsing unit or another component.

  FIG. 4 shows a pulsed DC power supply 100 to illustrate the embodiments described herein. The pulsed DC power supply 100 is configured to supply unipolar pulsed DC power, for example, for sputter deposition processing. The pulsed DC power source 100 includes a pulse unit 110, a current measurement unit 120, and a zero line determination unit 130. To illustrate the respective functions, the pulsing unit 110 is shown with a schematic graph of nominal pulse DC voltage, the current measurement unit 120 is shown with a schematic graph of actual current, and the zero line determination unit 130 is It is shown with a schematic graph of trigger points indicating the presence of a zero line condition. The pulsed DC power source 100, as well as the pulsing unit 110, the current measurement unit 120, and the zero line determination unit 130 may be configured as in the embodiments described herein.

  The pulsed DC power supply may be configured to determine the off-cycle off-cycle period from the time difference between setting the off-cycle nominal off-cycle voltage and determining the presence of a zero line condition. The pulsed DC power supply may be configured to determine the on-cycle period of the on-cycle from or as the time difference between the nominal pulse period and the determined off-cycle period. The nominal pulse period is the reciprocal of the nominal pulse frequency of the pulsed DC power source. The determination can be made by a pulsing unit. The pulsing unit may be configured to maintain a nominal on-cycle DC voltage for a determined on-cycle period, at least for a pulse cycle subsequent to the pulse cycle for which the determination of the on-cycle period was made. The first mechanism described in connection with FIG. 2 illustrates how on-cycle period determination and adaptation can be made from pulse cycle to pulse cycle.

  The pulsed DC power supply determines the time difference between the setting of the nominal on-cycle DC voltage for the first pulse cycle and the setting of the nominal on-cycle DC voltage for the subsequent second pulse cycle once the presence of the zero line condition is determined. From which the actual pulse duration of the first pulse cycle can be determined. The determination can be made by a pulsing unit. The pulsing unit may be configured to set the nominal operating frequency of the pulsed DC power supply to correspond to the determined actual pulse duration inverse of the first pulse cycle.

The pulsing unit may be configured to set the nominal operating frequency in this way when the inverse of the determined actual pulse duration of the first pulse is within the allowable nominal operating frequency. The range of allowable nominal operating frequencies may depend on the particular sputter deposition process in which the pulsed DC power supply supplies monopolar pulsed DC power. The range of allowable nominal operating frequencies may comprise, for example, frequencies within ± 20 kHz or ± 10 kHz of the initial nominal operating frequency selected and set by the operator. Since lowering the operating frequency is considered safer with respect to the stability of the sputter deposition process than increasing the operating frequency, the allowable nominal operating frequency range is the initial nominal operation selected and set by the operator. It can be selected asymmetrically around the frequency. For example, the range of permissible nominal operating _frequency, resulting there from F 0 -20kHz at _{F 0} + 5kHz, _F 0 is the initial nominal operating frequency.

  Alternatively, the pulsing unit sets the nominal operating frequency to the determined actual pulse period of the first pulse only if the inverse of the determined actual pulse period of the first pulse is lower than the current nominal operating frequency. May be configured to set the reciprocal of. That is, the pulsing unit can only automatically reduce the nominal operating frequency. Increasing the operating frequency requires operator approval. The second mechanism described in connection with FIG. 3 is an example of how the nominal operating frequency (nominal pulse frequency) can be set to different values.

  The pulsed DC power supply can be configured to adapt the on-cycle duration of the pulse cycle or adjust the nominal pulse frequency (nominal operating frequency) based on the length of the off-cycle of the preceding pulse cycle, The decision to apply the cycle period or adjust the nominal pulse frequency depends on one or more specific conditions, referred to herein as operating parameter mismatch conditions.

  The pulsed DC power supply may be configured to determine the off-cycle off-cycle period from the time difference between setting the off-cycle nominal off-cycle voltage and determining the presence of a zero line condition. The pulsed DC power supply is configured to perform the following evaluation and corresponding operations. If there is no operating parameter mismatch condition that depends on the determined off cycle period, the pulsed DC power supply determines the on cycle period of the on cycle from the difference between the pulse period and the off cycle period. The pulse period is the inverse of the nominal pulse frequency of the pulsed DC power source. The pulsed unit of the pulsed DC power supply then maintains a nominal on-cycle DC voltage for the determined on-cycle period. If an operating parameter mismatch condition exists, the pulsed DC power supply automatically changes the nominal operating frequency or notifies an operator who may approve or reject the change in the nominal operating frequency. The nominal operating frequency can be varied in the manner described herein.

  The adjustment of the on-cycle period may be a default operation, and the adjustment of the nominal operating frequency can only be made if an operating parameter mismatch condition exists (ie, is met). One operating parameter mismatch condition may be to drop the duty factor below a threshold duty factor. The threshold duty factor may be selected from 0.8 to 0.95, such as 0.8 or 0.85. If adjustment of the on-cycle period for subsequent pulse cycles results in a duty factor that is less than the threshold duty factor, the pulsed DC power supply may perform an evaluation. In this case, i.e. when the operating parameter mismatch condition is determined, the nominal pulse frequency is changed, otherwise the on-cycle period is adjusted. Other operating parameter mismatch conditions may alternatively or additionally be specified to adjust when the on-cycle period adjustment is used and when the nominal operating frequency adjustment is used.

  The pulsed DC power supply may include an operator interface. The operator interface may include at least one input device (eg, keyboard, mouse, touch screen, etc.) and at least one output device (eg, display or touch screen). The output device outputs a notification or warning to the operator and may be configured to request operator input via the input device in some cases. The output device may be configured to output the status of the pulsed DC power source. The status of the pulsed DC power supply includes currently set nominal operating parameters such as nominal operating frequency, nominal on-cycle voltage, nominal off-cycle voltage, etc., and in some cases, such as off-cycle period, on-cycle period, etc. Contains instantaneous or time averaged values of variables. Time averaging can be beneficial because instantaneous changes in variables can be too fast for the operator to confirm. The pulsed DC power supply may include, for example, memory for currently set nominal operating parameters and application conditions such as operation mismatch conditions, charge removal conditions, and the like. The pulsed DC power supply may be configured to allow an operator to change these conditions and / or change nominal operating parameters, for example via an input device. The memory can also store a log file of the monitored sputter deposition process, for example, for analysis.

  According to a further embodiment, a sputter deposition system is provided. The sputter deposition system includes a sputter target and a pulsed DC power source, according to embodiments described herein. A pulsed DC power source is connected to the sputter target to supply monopolar pulsed DC power to the sputter target.

  FIG. 5 shows a sputter deposition system 500 for purposes of illustration. Sputter deposition system 500 includes a sputter target 510 connected to a pulsed DC power supply 210 and a sputter target 520 connected to a pulsed DC power supply 220. Sputter targets 510, 520 may be rotating sputter targets, as indicated by axis A and the arrows drawn in sputter target 510. Sputtered material from sputter target 510 and sputter target 520 can be deposited on substrate 10.

  The sputter deposition system may include N sputter targets and N corresponding pulsed DC power supplies, where N may be in the range of 1 to 30, for example 1 to 24 or 2 to 24. The N pulse DC power sources may be integrated into a single pulse DC power system that supplies all N sputter targets. The sputter target can act as a cathode during the sputter deposition process. The sputter deposition system can include one or more anodes, eg, anode bars, that can be disposed between the sputter targets. Alternatively, the sputter chamber may form an anode, eg, an electrically grounded sputter chamber. Each pulsed DC power source can be connected to a sputter target and an anode that closes the electrical circuit.

  According to a further embodiment, a method for operating a pulsed DC power supply is provided. The features of the method may be performed automatically by a pulsed DC power supply and are described herein, in particular, a measurement unit such as a current probe, an evaluation unit such as a zero line condition determination unit, and a pulsed unit. May be executed by a unit that has been Some method features may be performed semi-automatically after input by the operator. The pulsed DC power supply supplies monopolar pulsed DC power in at least one of the operating modes of the pulsed DC power supply. A pulsed DC power source may be connected to the sputter target of the sputter deposition system.

  FIG. 6 shows a method 600 of operating a pulsed DC power source. The method includes setting a nominal on-cycle DC voltage for the first pulse cycle, indicated by reference symbol 610. The method may include outputting an actual on-cycle DC voltage and an actual on-cycle DC current with a pulsed DC power supply. The method includes setting a nominal off-cycle DC voltage to trigger the off-cycle of the first pulse cycle, indicated by reference symbol 620, and measuring the off-cycle current, indicated by reference symbol 630. . The off cycle current is the actual off cycle current of the off cycle of the first pulse cycle. The method includes determining the presence of a zero line condition of off-cycle current from measurement, ie, from measurement of off-cycle current, as indicated by reference symbol 640. The method includes setting a nominal on-cycle DC voltage for the second pulse cycle when it is determined that a zero line condition exists, as indicated by reference numeral 650.

  Setting the nominal on-cycle DC voltage for the first pulse cycle may be performed by a pulsed unit of the pulsed DC power source. If the pulsing unit does not include an internal DC voltage source, the output of the on-cycle DC voltage and the on-cycle DC current can be performed by the pulsing unit, optionally in conjunction with the output from the external DC voltage source. The setting of the nominal off-cycle DC voltage can be done by a pulsing unit. The measurement of the off-cycle current of the off-cycle of the first pulse cycle can be performed by a measuring unit. The determination of the presence of the zero line condition can be made by a zero line determination unit. Setting the nominal on-cycle DC voltage for the second pulse cycle may be performed by the pulsing unit.

  The method may include determining an off cycle period from the time difference between setting the nominal off cycle DC voltage and the moment of determination of the presence of a zero line condition. The method may include determining an on cycle period from a difference between the nominal pulse period and the determined off cycle period. The nominal pulse period is the reciprocal of the nominal operating frequency of the pulsed DC power supply. These determinations can be made by a zero line determination unit or a pulsing unit. The method can include maintaining a nominal on-cycle DC voltage of the second pulse cycle for a determined on-cycle period. The method may include setting a nominal off-cycle DC voltage to trigger the off-cycle of the second pulse cycle when the determined on-cycle period ends.

  This method calculates the actual pulse duration of the first pulse cycle from the time difference between setting the nominal on-cycle DC voltage for the first pulse cycle and setting the nominal on-cycle DC voltage for the second pulse cycle. Determining. The method may include setting the nominal operating frequency to correspond to the reciprocal of the determined actual pulse duration of the first pulse cycle.

  The method may include determining an off cycle period from a time difference between setting a nominal off cycle DC voltage and determining the presence of a zero line condition. This method determines the on-cycle period from the difference between the nominal pulse period and the determined off-cycle period, in the absence of operating parameter mismatch conditions that depend on the determined off-cycle period. Maintaining the nominal on-cycle DC voltage of the second pulse cycle during the cycle period and further changing the nominal operating frequency if an operating parameter mismatch condition exists.

  If the provisional duty factor is greater than or equal to the threshold duty factor, the operating parameter mismatch condition may not exist, i.e., may be absent or not met. The provisional duty factor is the difference between the nominal pulse period and the determined off-cycle period divided by the nominal pulse period. If the provisional duty factor is less than the threshold duty factor, an operating parameter mismatch condition exists. If the nominal operating frequency is changed, the nominal operating frequency can be maintained for subsequent pulse cycles until changed again.

  The method includes setting an on-cycle DC voltage for the on-cycle of the current pulse cycle and setting an off-cycle DC voltage for the current pulse cycle if the presence of a zero line condition is determined. Measuring the off-cycle current of the off-cycle current of the current pulse cycle and determining the presence of a zero-line condition of the off-cycle current of the current pulse cycle. If the presence of the zero line condition is determined, the next pulse cycle becomes the current pulse cycle and the feature can be repeated.

  As a further example, a pulsed DC power supply is provided. The pulsed DC power supply is configured to output unipolar pulsed DC power. The pulsed DC power supply is configured to stop the off cycle of the pulse cycle based on the measurement of at least one electrical quantity of the pulsed DC power supply. Stopping can include starting an on-cycle period of a subsequent pulse cycle. The pulsed DC power supply may be configured to adjust the off cycle period of the pulse cycle based on the measurement of at least one electrical quantity of the pulsed DC power supply. The pulsed DC power supply can be configured to adjust the off cycle period of every pulse cycle. The off-cycle period can be adjusted from pulse cycle to pulse cycle. The length of the off cycle can vary based on the measurement of at least one electrical quantity.

  The pulsed DC power supply may include a measurement unit that measures at least one electrical quantity of the pulsed DC power supply. At least one electrical quantity can be measured at the output of the pulsed DC power source. The at least one electrical quantity can be at least one quantity selected from the group consisting of voltage, current, and their time derivatives. The pulsed DC power supply may include an evaluation unit configured to evaluate the measurement value of the measurement unit and determine the presence of a charge removal condition. The pulsed DC power supply may include a pulsing unit for setting a nominal on-cycle DC voltage during the on-cycle of the pulse cycle and for setting a nominal off-cycle voltage during the off-cycle of the pulse cycle. The pulsing unit may be configured to set a nominal on-cycle DC voltage once it is determined that a charge removal condition exists.

  The at least one electrical quantity may be a current, in particular at least an off-cycle current. The measurement unit may include a current probe that measures current at least during an off-cycle as described herein. The charge removal condition can be the zero line condition described herein.

  The charge removal condition may alternatively be different from the zero line condition. For example, the charge removal condition may be a reverse pulse zero energy condition. This means that the pulsed DC power supply can be configured to determine if the energy left in the system that supplies the unipolar pulsed DC power is zero or substantially zero. . The reverse pulse zero energy condition can be determined by integrating the product of voltage and current over time. If this integral is zero or substantially zero, it can be determined that a zero energy condition exists. The measurement unit may include a voltage measurement device and a current measurement device. The evaluation unit may be configured to evaluate the voltage measurement from the voltage measurement device, evaluate the current measurement from the current measurement device, and determine the presence of a zero energy condition.

  The pulsed DC power supply may be further configured to adjust the on-cycle period of the pulse cycle based on the off-cycle period of the preceding pulse cycle. The pulsed DC power supply may be configured to adjust the nominal pulse frequency of the pulsed DC power supply based on the off cycle period of the pulse cycle. A pulsed DC power supply relates to an embodiment that includes an on-cycle period, a nominal pulse frequency, or a mechanism that adjusts both the on-cycle period and the nominal pulse frequency based on the specific conditions described herein. All other features described herein may be included or indicated.

  According to a further embodiment, a method for operating such a pulsed DC power supply is provided. The method includes stopping the off cycle of the unipolar pulse cycle based on the measurement of at least one electrical quantity of the pulsed DC power source. Stopping the off cycle may include stopping the off cycle when it is determined that the charge removal condition is satisfied. Achieving charge removal conditions depends on the measurement of at least one electrical quantity. The charge removal conditions can be as described above.

This method may include performing some or all of the functions of the pulsed DC power source described herein. Further, a method of operating a sputter deposition system is provided, which may include performing some or all of the functions of the sputter deposition system described herein. A further aspect is directed to using a pulsed DC power source to provide monopolar pulsed DC power, such as to a sputter target of the sputter deposition system described herein. This use may include automatic determination of the length of the off-cycle (ie, off-cycle period) of the unipolar pulse cycle of the nominal voltage, as described above.
A further aspect is directed to a method of sputtering a substrate using the sputter deposition system described herein.

  The terms and expressions used herein are used as descriptive terms, and are not limiting terms, and any equivalents of the features shown and described in the use of such terms and expressions or their equivalents are used. There is no intention to exclude some. While the above description is directed to embodiments, other and further embodiments can be devised without departing from the scope, which is defined by the appended claims.

Claims (15)

A pulsed DC power supply (100) for supplying monopolar pulsed DC power comprising:
A pulsing unit (110) for alternately setting a nominal on-cycle DC voltage during an on-cycle and a nominal off-cycle voltage during an off-cycle of a unipolar pulse cycle of the pulsed DC power supply;
A current measurement unit (120) configured to measure off-cycle current during the off-cycle, and a zero-line determination unit (200) configured to determine the presence of a zero-line condition of the measured off-cycle current 130)
A pulsed DC power supply, wherein the pulsed unit is configured to set the nominal on-cycle DC voltage when the presence of the zero-line condition of the measured off-cycle current is determined. The pulsed DC power supply is configured to determine an off cycle period of the off cycle from a time difference between setting the nominal off cycle voltage of the off cycle and determining the presence of the zero line condition; A pulsed DC power supply is configured to determine an on-cycle period of an on-cycle from a time difference between a nominal pulse period and the determined off-cycle period, wherein the nominal pulse period is a nominal pulse of the pulsed DC power supply The pulsed DC power supply of claim 1, wherein the pulsed DC power source is a reciprocal of frequency and the pulsed unit is configured to maintain the nominal on-cycle DC voltage during the determined on-cycle period. If the pulsed DC power source is determined to have the zero line condition, setting the nominal on-cycle DC voltage for a first pulse cycle and setting the nominal on-cycle DC voltage for a subsequent second pulse cycle; Is configured to determine an actual pulse duration of the first pulse cycle, and the pulsed DC power source is a reciprocal of the determined actual pulse duration of the first pulse cycle. The pulsed DC power supply of claim 1, configured to set a nominal operating frequency of the pulsed DC power supply to accommodate. The pulsing unit determines an off cycle period of the off cycle from a time difference between setting the nominal off cycle voltage of the off cycle and determining the presence of the zero line condition;
In the absence of an operating parameter mismatch condition that depends on the determined off-cycle period, an on-cycle on-state is determined from the time difference between the nominal pulse period, which is the inverse of the nominal operating frequency of the pulsed DC power supply, and the off-cycle period. Configured to determine a cycle period, to maintain the nominal on-cycle DC voltage during the determined on-cycle period, and to change the nominal operating frequency if the operating parameter mismatch condition exists. The pulse DC power supply according to claim 1.   A current probe for measuring the off-cycle current and outputting a corresponding measurement value representing the off-cycle current; an analog-to-digital converter for converting the measurement value representing the off-cycle current into a digital value; 5. The pulsed DC power source according to claim 1, comprising at least one of the following:   The zero line condition is determined to be present by the zero line determination unit when the measured value representing the measured off-cycle current is zero or within a predetermined range. The pulse DC power source according to any one of 5. A pulsed DC power supply for supplying monopolar pulsed DC power,
It is configured to set a nominal on-cycle DC voltage during the on-cycle of the unipolar pulse cycle of the pulsed DC power supply, and sets a nominal off-cycle voltage during the off-cycle of the unipolar pulse cycle of the pulsed DC power supply. Pulsed unit, configured as
A measurement unit configured to measure at least one electrical quantity of the pulsed DC power source, and configured to determine the presence of a predetermined condition from an evaluation of the measured value of the measured at least one electrical quantity A pulsed DC power supply comprising an evaluation unit, wherein the pulsed unit is configured to set the nominal on-cycle DC voltage when the presence of the predetermined condition is determined. (A) the measured at least one electrical quantity includes a voltage and a current, and the predetermined condition is a zero energy condition, or (b) the measured at least one electrical quantity is an off-cycle current The predetermined condition is a zero line condition of the measured off-cycle current,
The pulse DC power supply according to claim 7. A sputter deposition system (500) comprising:
A sputter target (510, 520), and a pulsed DC power source (100, 210, 220) according to any one of claims 1 to 8.
A sputter deposition system, wherein the pulsed DC power source is connected to the sputter target for supplying monopolar pulsed DC power to the sputter target. A method (600) of operating a pulsed DC power supply for supplying monopolar pulsed DC power comprising:
Setting 610 a nominal on-cycle DC voltage for a first pulse cycle of the pulsed DC power supply, and outputting an on-cycle DC voltage and an on-cycle DC current by the pulsed DC power supply;
Setting (620) a nominal off-cycle DC voltage to trigger an off-cycle of the first pulse cycle;
Measuring (630) off-cycle current with the pulsed DC power source;
Determining (640) the presence of a zero line condition of the off-cycle current from the measurement;
Setting (650) a nominal on-cycle DC voltage for a second pulse cycle when it is determined that the zero line condition exists. Determining an off-cycle period from the time difference between setting the nominal off-cycle DC voltage and determining the presence of the zero line condition;
Determining an on-cycle period from the difference between a nominal pulse period and the off-cycle period, wherein the nominal pulse period is the inverse of the nominal operating frequency of the pulsed DC power supply. And
11. The method of claim 10, comprising maintaining the nominal on-cycle DC voltage of the second pulse cycle during the determined on-cycle period. From the time difference between setting the nominal on-cycle DC voltage for the first pulse cycle and setting the nominal on-cycle DC voltage for the second pulse cycle, the actual pulse duration of the first pulse cycle And determining
11. A method according to claim 10, comprising setting a nominal operating frequency to correspond to the reciprocal of the determined actual pulse duration. Determining an off cycle period from the time difference between setting the nominal off cycle DC voltage of the off cycle and determining the presence of the zero line condition;
If there is no operating parameter mismatch condition that depends on the determined off-cycle period, the difference between the nominal pulse period, which is the reciprocal of the nominal operating frequency of the pulsed DC power supply, and the determined off-cycle period is Determining a cycle period and maintaining the nominal on-cycle DC voltage of the second pulse cycle for a time corresponding to the determined on-cycle period;
11. The method of claim 10, comprising changing the nominal operating frequency if the operating parameter mismatch condition exists.   If the provisional duty factor is greater than or equal to a threshold duty factor, the operating parameter mismatch condition does not exist and the provisional duty factor is divided by the nominal pulse period and the determined off-cycle period The method of claim 13, wherein the operating parameter mismatch condition exists if the temporary duty factor is less than the threshold duty factor.   Measuring the off-cycle current with the pulsed DC power source includes generating a measurement value representative of the off-cycle current, and determining the presence of the zero-line condition of the off-cycle current. 15. The method according to any one of claims 10 to 14, comprising evaluating whether is zero or within a predetermined range.

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