Methods and systems for controlling radiofrequency pulse-initiation power spike for plasma sheath stabilization

Abstract

To disclose a method for controlling plasma within a plasma processing chamber.SOLUTION: Multiple, sequential pulses of radiofrequency power are supplied to an electrode of a plasma processing chamber to control plasma within the plasma processing chamber. Each of the pulses of radiofrequency power includes a first duration over which a first radiofrequency power profile exists, immediately followed by a second duration over which a second radiofrequency power profile exists. The first radiofrequency power profile has greater radiofrequency power than that of the second radiofrequency power profile. The first duration is less than the second duration. And, the sequential pulses of radiofrequency power are separated from each other by a third duration. A radiofrequency signal generation system is provided to generate and control the multiple, sequential pulses of radiofrequency power.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] 1.Technical Field

[0002] The present disclosure relates to the fabrication of semiconductor devices. [Background technology]

[0003] 2. Background technology

[0004] In the fabrication of semiconductor devices such as integrated circuits, memory cells, and the like, a series of manufacturing operations are performed to define features on a semiconductor wafer (hereinafter "wafer"). The wafer contains integrated circuit devices in the form of multi-layer structures defined on a silicon substrate. At the substrate level, transistor devices with diffusion regions are formed. At the next level, interconnect metallization lines are patterned to electrically connect to the transistor devices and define the desired integrated circuit devices. Additionally, patterned conductive layers are insulated from other conductive layers by dielectric materials.

[0005] Many modern semiconductor chip fabrication processes involve the generation of a plasma that delivers ionic and / or radical components that are used to directly or indirectly affect changes on the surface of a substrate exposed to the plasma. For example, various plasma-based processes can be used to etch material from a substrate surface, deposit material onto a substrate surface, or modify material already present on the substrate surface. Plasmas are often generated by applying radio frequency (RF) power to a process gas in a controlled environment so that the process gas is energized and converted into the desired plasma. The characteristics of the plasma are affected by many process parameters, including, but not limited to, the material composition of the process gas, the flow rate of the process gas, the geometric features of the plasma generation region and surrounding structures, the temperature of the process gas and surrounding materials, the frequency of the applied RF power, the magnitude of the applied RF power, and the temporal manner in which the RF power is applied, among others. Therefore, it is important to understand, monitor, and / or control some of the process parameters that can affect the characteristics of the generated plasma, particularly with respect to the delivery of RF power to the plasma generation region. It is within this context that the present disclosure arises. Summary of the Invention

[0006] In an exemplary embodiment, a method for controlling a plasma in a plasma processing chamber is disclosed. The method includes supplying multiple consecutive pulses of RF power to an electrode of the plasma processing chamber. Each pulse of RF power includes a first duration during which a first RF power profile is present, followed immediately by a second duration during which a second RF power profile is present. The first RF power profile has a greater RF power than the second RF power profile. The first duration is shorter than the second duration. The consecutive pulses of RF power are separated from one another by a third duration.

[0007] In an exemplary embodiment, a controller is programmed to control a plasma in a plasma processing chamber. The controller includes program instructions stored in a computer memory that, when executed, direct the controller to supply multiple successive pulses of RF power to an electrode of the plasma processing chamber. Each pulse of RF power includes a first duration during which a first RF power profile is present, followed immediately by a second duration during which a second RF power profile is present. The first RF power profile has a greater RF power than the second RF power profile. The first duration is shorter than the second duration. The successive pulses of RF power are separated from one another by a third duration.

[0008] In an exemplary embodiment, an RF signal generating system is configured to control a plasma in a plasma processing chamber. The RF signal generating system includes an RF signal generator configured to generate an RF signal at or near a set frequency. The RF signal generating system also includes a first DC voltage source connected to a voltage input of the RF signal generator. The RF signal generating system also includes a second DC voltage source switchably connected to the voltage input of the RF signal generator. The RF signal generating system also includes a controller configured and connected to control each of the RF signal generator, the first DC voltage source, and the second DC voltage source. The voltages supplied to the voltage input of the RF signal generator by the first and second DC voltage sources control the amplitude of the RF signal generated by the RF signal generator.

[0009] In an exemplary embodiment, a method for controlling a plasma in a plasma processing chamber is disclosed. The method includes supplying multiple consecutive pulses of primary RF power to a primary electrode of the plasma processing chamber. Each of the pulses of primary RF power includes a first duration during which a first primary RF power profile is present, followed immediately by a second duration during which a second primary RF power profile is present. The first primary RF power profile has a greater RF power than the second primary RF power profile. The first duration is shorter than the second duration. The consecutive pulses of primary RF power are separated from each other by a third duration. The method also includes supplying multiple consecutive pulses of bias RF power to a bias electrode of the plasma processing chamber. Each of the pulses of bias RF power includes a fourth duration during which the first bias RF power profile is present, followed immediately by a fifth duration during which a second bias RF power profile is present. The first bias RF power profile has a greater RF power than the second bias RF power profile. The fourth duration is shorter than the fifth duration. Also, successive pulses of bias RF power are separated from one another by a sixth time duration.

[0010] Other aspects and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, which illustrate, by way of example, the invention. [Brief explanation of the drawings]

[0011] [Figure 1A] FIG. 1A is a side cross-sectional view of a plasma processing system for use in semiconductor wafer manufacturing, according to some embodiments.

[0012] [Figure 1B] FIG. 1B is a top view of the plasma processing system of FIG. 1A, according to some embodiments.

[0013] [Figure 2] FIG. 2 is a diagram illustrating an exemplary arrangement of a control system, according to some embodiments.

[0014] [Figure 3A] FIG. 3A illustrates a square RF power pulse profile that may be supplied by a bias RF signal generator to a bias electrode to generate a bias voltage, according to some embodiments.

[0015] [Figure 3B] FIG. 3B illustrates the square RF power pulse profile of FIG. 3A with an initial spike in RF power associated with the initial masking time of the bias RF signal generator, according to some embodiments.

[0016] [Figure 4] FIG. 4 is a diagram illustrating an RF power pulse profile including an RF pulse initiation power spike, according to some embodiments.

[0017] [Figure 5] FIG. 5 illustrates RF power pulse profiles representing dual-level RF power pulsing in which RF power is pulsed between a first set non-zero power level P1 and a set power level P2, and a first RF power profile p1 has a set power level P3, in accordance with some embodiments.

[0018] [Figure 6] FIG. 6 illustrates RF power pulse profiles in accordance with some embodiments, where RF power is pulsed between zero and a set power level P1, and a first RF power profile p1 exceeds the set power level P1, representing non-constant single-level RF power pulsing.

[0019] [Figure 7] FIG. 7 illustrates RF power pulse profiles in accordance with some embodiments, where RF power is pulsed between zero and a set power level P1, and a first RF power profile p1 exceeds the set power level P1, representing non-constant single-level RF power pulsing.

[0020] [Figure 8A] FIG. 8A illustrates the RF power pulse profile of FIG. 4 with frequency variation applied over the pulse duration, according to some embodiments.

[0021] [Figure 8B] FIG. 8B illustrates an exemplary frequency control function in which the frequency of the signal generated by the bias RF signal generator or the primary RF signal generator is substantially constant over time, according to some embodiments.

[0022] [Figure 8C] FIG. 8C illustrates an example frequency control function in which the frequency of a signal generated by a bias RF signal generator or a primary RF signal generator increases monotonically over time, according to some embodiments.

[0023] [Figure 8D] FIG. 8D illustrates an example frequency control function in which the frequency of a signal generated by a bias RF signal generator or a primary RF signal generator decreases monotonically over time, according to some embodiments.

[0024] [Figure 8E] FIG. 8E illustrates an example frequency control function in which the frequency of a signal generated by a bias RF signal generator or a primary RF signal generator varies nonlinearly over time, according to some embodiments.

[0025] [Figure 9] FIG. 9 illustrates an exemplary arrangement of an RF signal generation system implementing dual DC power supplies for RF pulse initiation power spike generation, according to some embodiments.

[0026] [Figure 10] FIG. 10 is a diagram of the voltage output by the first DC voltage source as a function of time to generate the RF power pulse profile of FIG. 4 according to some embodiments.

[0027] [Figure 11] FIG. 11 is a diagram of the voltage output by the second DC voltage source as a function of time to generate the RF power pulse profile of FIG. 4 according to some embodiments.

[0028] [Figure 12] FIG. 12 is a diagram of the sum of the voltages output by the first and second DC voltage sources as a function of time to generate the RF power pulse profile of FIG. 4 in accordance with some embodiments.

[0029] [Figure 13] FIG. 13 is a diagram of activation of an RF signal generator as a function of time to generate the RF power pulse profile of FIG. 4, according to some embodiments.

[0030] [Figure 14] FIG. 14 is a flowchart of a method for controlling a plasma in a plasma processing chamber, according to some embodiments.

[0031] [Figure 15] FIG. 15 is a flowchart of a method for controlling a plasma in a plasma processing chamber, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0032] In the following description, numerous specific details are set forth to provide an understanding of embodiments of the present disclosure. However, it will be apparent to one skilled in the art that embodiments of the present disclosure may be practiced without some or all of these specific details. In other instances, well-known process operations have not been described in detail in order to avoid unnecessarily obscuring the present disclosure.

[0033] FIG. 1A illustrates a vertical cross-sectional view of a plasma processing system 100 for use in semiconductor wafer manufacturing, according to some embodiments. FIG. 1B illustrates a top view of the plasma processing system of FIG. 1A, according to some embodiments. The vertical cross-sectional view of FIG. 1A is referenced as cross-section AA in FIG. 1B. In the semiconductor industry, semiconductor substrates can undergo fabrication operations in inductively coupled plasma (ICP) plasma processing chambers, such as plasma processing system 100. ICP processing chambers can also be referred to as transformer-coupled plasma (TCP) processing chambers. For ease of description herein, ICP processing chambers will be used to refer to both ICP and TCP processing chambers. It should be understood that plasma processing system 100 essentially represents any type of ICP processing chamber in which an RF signal is transmitted from a coil 101 located outside the processing chamber 103 to a process gas within the processing chamber 103 to generate a primary plasma 105 within a plasma processing volume 106 of the processing chamber 103, and the primary plasma 105 affects changes in the conditions of a substrate 107 held in exposure to components of the primary plasma 105. 1A shows a coil 101 from which an RF signal is transmitted into a plasma processing volume 106 to generate a primary plasma 105 within the plasma processing volume 106 upon exposure to a substrate 107. The coil 101 is also referred to as a primary electrode.

[0034] In some embodiments, the substrate 107 is a semiconductor wafer undergoing a fabrication procedure. However, it should be understood that in various embodiments, the substrate 107 can be essentially any type of substrate undergoing a plasma-based fabrication process. For example, in some embodiments, the term substrate 107 as used herein can refer to a substrate formed of sapphire, GaN, GaAs, or SiC, or other substrate materials, and can include glass panels / substrates, metal foils, metal sheets, polymeric materials, etc. Also, in various embodiments, the substrate 107 referred to herein can vary in form, shape, and / or size. For example, in some embodiments, the substrate 107 referred to herein can correspond to a 200 mm (millimeter) semiconductor wafer, a 300 mm semiconductor wafer, or a 450 mm semiconductor wafer. Also, in some embodiments, the substrate 107 referred to herein can correspond to a non-circular substrate, such as a rectangular substrate for a flat panel display, among other shapes.

[0035] The plasma processing volume 106 of the processing chamber 103 is formed within a surrounding structure 109, below an upper window structure 111, and above a substrate support structure 113. In some embodiments, the surrounding structure 109 is formed of a conductive material, such as a metal, that is mechanically and chemically compatible with the environment and materials present in the plasma processing volume 106 during operation of the plasma processing system 100. In these embodiments, the surrounding structure 109 can be electrically connected to a reference ground potential 115. The processing chamber 103 includes a door 151 that allows the substrate 107 to be inserted into and removed from the plasma processing volume 106.

[0036] The substrate support structure 113 is configured to safely support the substrate 107 for exposure to the primary plasma 105 generated in the plasma processing volume 106. In some embodiments, the substrate support structure 113 is an electrostatic chuck that includes one or more clamping electrodes 117 that can be powered by a clamping power supply 119 through an electrical connection 121. Power supplied to the one or more clamping electrodes 117 generates an electrostatic field for clamping the substrate 107 onto the substrate support structure 113. In various embodiments, the clamping power supply 119 can be configured to supply either RF power, direct current (DC) power, or a combination of both RF and DC power to the one or more clamping electrodes 117. In embodiments in which the clamping power supply 119 is configured to supply RF power, the clamping power supply 119 further includes an impedance matching circuit through which the RF power is transmitted to ensure that the RF power is not unacceptably reflected from the one or more clamping electrodes 117. In these embodiments, the impedance matching circuit in the clamping power supply 119 includes an arrangement of capacitors and / or inductors.

[0037] The substrate support structure 113 also applies a bias voltage (V bThe plasma processing volume 106 may include a bias electrode 123 to which RF bias power can be supplied to generate a bias voltage (V) . The RF power transmitted from the bias electrode 123 to the plasma processing volume 106 is referred to as bias RF power. In some embodiments, the bias RF power is generated by a bias RF signal generator 125, transmitted through an electrical connection 127 to an impedance matching circuit 129, and then transmitted from the impedance matching circuit 129 to the bias electrode 123 through a transmission rod 131. The transmission rod 131 is electrically isolated from the surrounding structure 109 of the processing chamber 103. The impedance matching circuit 129 includes an arrangement of capacitors and / or inductors configured to ensure that the impedance seen by the bias RF signal generator 125 at the transmission rod 131 is sufficiently close to the load impedance with which the bias RF signal generator 125 is designed to operate, so that the RF signal generated and transmitted by the bias RF signal generator 125 is transmitted to the plasma processing volume 106 efficiently, i.e., without unacceptable reflections.

[0038] The plasma processing system 100 operates by flowing one or more process gases from a process gas source 133 through an arrangement of fluid delivery structures 135 into a plasma processing volume 106 to affect changes in material or surface conditions on a substrate 107, and by applying RF power from a coil 101 to the one or more process gases, converting the one or more process gases into a primary plasma 105 upon exposure to the substrate 107. Spent process gases and other materials resulting from processing the substrate 107 are exhausted from the plasma processing volume 106 through one or more exhaust ports 147, as indicated by arrows 149. The coil 101 is disposed above an upper window structure 111. In the examples of FIGS. 1 and 2, the coil 101 is formed as a radial coil assembly, with the shaded portion of the coil 101 facing into the page and the unshaded portion of the coil 101 facing out of the page. FIG. 1B shows a top view of the exemplary coil 101 of FIG. 1A, in accordance with some embodiments of the present invention. It should be understood, however, that in other embodiments, the coil 101 can be of essentially any configuration suitable for transmitting RF power through the upper window structure 111 to the plasma processing volume 106. In various embodiments, the coil 101 can have any number of turns and any cross-sectional size and shape (circular, elliptical, rectangular, trapezoidal, etc.) as needed to provide the necessary transmission of the RF signal through the upper window structure 111 to the plasma processing volume 106. Also, in some embodiments, a return electrical connection 145 extends from the coil 101 to the matching circuit 141.

[0039] The RF power transmitted from coil 101 to plasma processing volume 106 is referred to as plasma primary RF power. The plasma primary RF power is generated by primary RF signal generator 137, transmitted through electrical connection 139 to impedance match circuit 141, and transmitted to coil 101 through electrical connection 143. Match circuit 141 includes an arrangement of capacitors and / or inductors configured to ensure that the impedance seen by primary RF signal generator 137 at coil 101 is sufficiently close to the load impedance with which primary RF signal generator 137 is designed to operate, so that the RF signal supplied by primary RF signal generator 137 to coil 101 is transmitted efficiently to plasma processing volume 106 without unacceptable reflections.

[0040] It should be understood that the coil 101 in Figures 1 and 2 is presented as an example. In some embodiments, the coil 101 can include multiple zones, each spanning a corresponding designated radial range above the upper window structure 111. In these embodiments, the RF power supplied to each zone of the coil 101 is independently controlled. It should also be understood that the number of turns of the exemplary coil 101 (near the center of the upper window structure 111) in Figures 1 and 2 is presented as an example. In various embodiments, the coil 101 can have any number of turns and any cross-sectional size and shape (circular, elliptical, rectangular, trapezoidal, etc.) as needed to provide the necessary transmission of the RF signal through the upper window structure 111 to the plasma processing volume 106.

[0041] The plasma processing system 100 has particular advantages in plasma process control in various plasma-based semiconductor fabrication applications, such as, for example, plasma etching. The plasma processing system 100 provides separate control of plasma density (ion flux / radical flux) and ion energy. Specifically, the plasma density can be controlled to some extent by the plasma primary RF power delivered from the coil 101 through the upper window structure 111 to the plasma processing volume 106. The ion energy can also be controlled by the bias voltage (V) generated at the substrate level by the bias RF power delivered from the bias electrode 123 to the plasma processing volume 106. b ) Separate control of plasma density (which is directly correlated to ion flux and radical flux) and ion energy is particularly useful in some semiconductor fabrication applications. For example, in patterning applications, where high plasma density is required to obtain the required etch rate and low ion energy is required to reduce damage to one or more materials present on the substrate, such as photoresist materials. It should be appreciated that in addition to patterning applications, many other plasma-based semiconductor fabrication applications can also benefit from separate control of plasma density and ion energy.

[0042] According to the plasma processing system 100, the plasma density can be increased by controlling the plasma primary RF power supplied to the coil 101, and the bias voltage (V b ) can be controlled. Also, the plasma primary RF power / frequency and the bias RF power / frequency may need to be controlled simultaneously and differently to achieve the desired results. For example, in some embodiments, to increase the plasma density in conjunction with low ion energy, the plasma primary RF power needs to be increased while the bias RF power needs to be decreased.

[0043] In some fabrication applications, a high density plasma is required at the substrate 107 level to obtain an increased ion flux and / or an increased radical flux near the substrate 107 and thus an increased interaction rate on the substrate 107, and at the same time, a low ion energy is required at the substrate 107 level to avoid damage to the material on the substrate 107 and / or to reduce the directionality of the ion flux incident on the substrate 107, i.e., to have a more isotropic ion flux at the substrate 107 level. In these fabrication applications, a bias voltage (V b ), the plasma density needs to be increased at the substrate 107 level without increasing the bias voltage (V). For example, in patterning applications, a photoresist material may be used to provide a protective coating over portions of the substrate 107 during etching operations. In this situation, a high bias voltage (V b ) can increase the ion energy to the point where ions incident on the photoresist material sputter the photoresist material from the substrate 107. And, since it is necessary for the photoresist material to remain throughout the etching process, a bias voltage (V) at the substrate 107 level is required to avoid sputtering of the photoresist material and premature loss of the photoresist material. b It is important to keep the voltage low, for example, below 200V (volts).

[0044] In some situations, the plasma primary RF power transmitted from the coil 101 through the upper dielectric window 111 to the plasma processing volume 106 does not provide sufficient plasma density to obtain the required etch rate and / or etch selectivity at the substrate 107 level. One reason for this is that the density of the primary plasma 105 generated by the plasma primary RF power transmitted from the coil 101 decreases with increasing distance from the coil 101. Therefore, as the distance between the coil 101 and the substrate support structure 113 increases, it becomes more difficult to obtain the required plasma density at the substrate 107 level. Also, the lower frequency of the bias RF power applied to the bias electrode 123 contributes less to the plasma density near the substrate 107, and the DC bias voltage (V b Additionally, it may not be possible to simply increase the plasma primary RF power supplied to the coil 101 beyond a specified maximum amount, such as about 3 kW (kilowatts), due to potential damage caused by overheating of the upper window structure 111. Also, decreasing the distance between the coil 101 and the substrate support structure 113 presents other challenges, as it may require costly redesign of the process chamber 103 and may cause problems with plasma uniformity at the substrate 107 level.

[0045] It is possible to increase the plasma density at the substrate 107 level without increasing the ion energy at the substrate 107 level. A specially controlled RF signal can be transmitted to the plasma processing volume 106 using the bias electrode 123 to generate an auxiliary plasma density 154 locally at the substrate 107 level. Also, in some embodiments, it is possible to generate an auxiliary plasma density 154 locally at the substrate 107 level without increasing the ion energy at the substrate 107 level. The bias RF power applied by the bias RF signal generator 125 at the substrate 107 level is controlled to generate the auxiliary plasma density 154 at the substrate 107 level, i.e., directly above the substrate 107. Generally, the bias voltage (V b) is inversely proportional to the frequency (f) of these RF signals (V b ∝1 / f). Bias RF power (P b ) is the bias voltage (V b ) and bias current (I b ), that is, (P b =V b *I b ), so the bias voltage (V b ) is lower, the bias current (I b ) at the same bias RF power (P b ) must be correspondingly higher to have a given bias RF power (P b ) to achieve higher plasma density, a lower bias voltage (V b ) and the corresponding higher bias current (I b ) and the bias voltage (V b ) is inversely proportional to the frequency (f) of the bias RF signal, so for a given bias RF power (P b ) for lower bias voltage (V b ), the frequency (f) of the bias RF signal can be increased. Thus, an increase in the auxiliary plasma density 154 generated at the substrate 107 level can be obtained while simultaneously increasing the bias voltage (V b To keep the RF power (f) low, a higher frequency (f) RF signal can be supplied to the bias electrode 123.

[0046] At the substrate 107 level, the effective plasma density is the sum of the plasma density generated by the plasma primary RF power and the plasma density generated by the RF signal supplied to the bias electrode 123. In some embodiments where a higher plasma density is required at the substrate 107 level without increasing the ion energy at the substrate 107 level, the RF power of the auxiliary plasma density 154 is supplied to the bias electrode 123 at a high frequency (e.g., about 27 MHz (megahertz) or higher) and a low bias voltage (V b) (e.g., less than about 200 V) to generate an auxiliary plasma density 154 at the substrate 107 level, and bias RF power is also supplied to the bias electrode 123 at a low frequency (e.g., less than about 15 MHz) to generate a bias voltage (V b ), plasma primary RF power is supplied to coil 101 to generate primary plasma 105 within plasma processing volume 106.

[0047] The plasma processing system 100 also includes a control system 153 configured and connected to control the operation of the plasma processing system 100. The control system 153 is configured and connected to control the process gas source 133 through connection 155. The control system 153 is configured and connected to control the primary RF signal generator 137 through connection 157. The control system 153 is configured and connected to control the impedance matching circuit 141 through connection 159. The control system 153 is configured and connected to control the bias RF signal generator 125 through connection 161. The control system 153 is configured and connected to control the impedance matching circuit 129 through connection 163. The control system 153 is configured and connected to control the clamp power supply 119 through connection 165. It should be understood that in various embodiments, any of the connections 155, 157, 159, 161, 163, and 165 can be either wired connections, wireless connections, optical connections, or combinations thereof. It should be understood that in various embodiments, control system 153 can be configured and connected to control essentially any aspect of plasma processing system 100 that lends itself to active control. It should also be understood that in various embodiments, control system 153 is connected to various metrology and sensors and other data acquisition devices located throughout plasma processing system 100 and configured to measure and monitor any parameters related to the operation of plasma processing system 100. It should also be understood that in various embodiments, data / signal connections between control system 153 and the various metrology and sensors and other data acquisition devices can be either wired connections, wireless connections, optical connections, or a combination thereof.

[0048] 2 shows an exemplary arrangement of a control system 153 according to some embodiments. In various embodiments, the control system 153 includes a processor 201, a storage hardware unit (HU) 203 (e.g., computer memory), an input HU 205, an output HU 207, an input / output (I / O) interface 209, an I / O interface 211, a network interface controller (NIC) 213, and a data communication bus 215. The processor 201, the storage HU 203, the input HU 205, the output HU 207, the I / O interface 209, the I / O interface 211, and the NIC 213 are in data communication with each other via the data communication bus 215. The input HU 205 is configured to receive data communication from several external devices, such as the process gas source 133, the primary RF signal generator 137, the impedance matching circuit 141, the bias RF signal generator 125, the impedance matching circuit 129, the clamp power supply 119, and / or any other devices within the plasma processing system 100. Examples of the input HU 205 include a data acquisition system, a data acquisition card, etc. The output HU 207 is configured to transmit data to several external devices, such as the process gas source 133, the primary RF signal generator 137, the impedance matching circuit 141, the bias RF signal generator 125, the impedance matching circuit 129, the clamp power supply 119, and / or any other device in the plasma processing system 100. One example of the output HU 207 is a device controller. Examples of the NIC 213 include a network interface card, a network adapter, etc. Each of the I / O interfaces 209 and 211 is defined to provide compatibility between different hardware units coupled to the I / O interface. For example, the I / O interface 209 can be defined to convert signals received from the input HU 205 to a format, amplitude, and / or speed compatible with the data communication bus 215. The I / O interface 211 can also be defined to convert signals received from the data communication bus 215 to a format, amplitude, and / or speed compatible with the output HU 207.While various operations are described herein as being performed by processor 201 of control system 153, it should be understood that in some embodiments, various operations may be performed by multiple processors of control system 153 and / or by multiple processors of multiple computing systems in data communication with control system 153. Also, in some embodiments, there is a user interface associated with control system 153. The user interface may include a display (e.g., a display screen and / or graphical software display of equipment and / or process conditions) and user input devices such as a pointing device, keyboard, touch screen, microphone, etc.

[0049] The control system 153 may be configured to execute a computer program including a series of instructions for controlling the operation of the process gas source 133, the primary RF signal generator 137, the impedance matching circuit 141, the bias RF signal generator 125, the impedance matching circuit 129, the clamp power supply 119, and / or any other controllable devices in the plasma processing system 100. Additionally, in some embodiments, a computer program stored in a memory device associated with the control system 153 may be used. Software for directing the operation of the control system 153 may be designed or configured in many different ways. The computer program for directing the operation of the control system 153 to directly operate the plasma processing system 100 may be written in any conventional computer-readable programming language (e.g., assembly language, C, C++, Pascal, Fortran, etc.). The compiled object code or script is executed by the processor 201 to perform the tasks identified in the program.

[0050] Broadly, the control system 153 is defined as electronic equipment having various integrated circuits, logic, memory, and / or software that receive instructions, issue instructions, and control operations. The integrated circuits may include chips in the form of firmware that store program instructions, digital signal processors (DSPs), chips defined as application-specific integrated circuits (ASICs), and / or one or more microprocessors, i.e., microcontrollers, that execute program instructions (e.g., software). The program instructions may be in the form of various individual settings (or program files) communicated to the control system 153 that define operational parameters for operating the plasma processing system 100 to perform a predetermined process on the substrate 107.

[0051] The chemical properties of the primary plasma 105 are highly electronegative, and the high bias voltage (V b In conductor etching applications where the bias voltage (V) is pulsed, it is very difficult to push out and stabilize the sheath of the plasma 105 when the bias RF signal generator 125 is turned on to supply RF power to the bias electrode 123. FIG. 3A shows the bias voltage (V) in accordance with some embodiments. b 3 shows a square RF power pulse profile 301 that may be supplied to the bias electrode 123 by the bias RF signal generator 125 to generate a pulse width (P1). The square RF power pulse profile 301 includes a series of pulses of RF power according to a set cycle duration d303. Each pulse of RF power has an essentially square shape. Each pulse of RF power varies from a power level of approximately zero to a power level P1. Each pulse of RF power has a pulse duration d301. The duration between successive RF power pulses is an inter-pulse duration d302. During each inter-pulse duration d302, the RF power varies from a power level of P1 to a lower power level (e.g., approximately zero power). The set cycle duration d303 is the sum of the pulse duration d301 and the inter-pulse duration d302.

[0052] The use of a square RF power pulse profile 301, as shown in FIG. 3A, presents a timing issue because the process of introducing RF energy into the plasma 105 starts slowly and takes time to complete. It is important to consider that there is a significant change in the impedance of the plasma processing volume 106 between the presence of the plasma 105 and the absence of the plasma 105, or between the presence of a plasma 105 sheath and the absence of a plasma 105 sheath. Furthermore, it is important to consider that there are heavy ions in the plasma 105 that must be pushed away from the bias electrode 123 to stabilize the plasma 105 sheath. Moving these heavy ions requires a significant amount of energy and time. At the start of the RF power pulse, the bias RF signal generator 125 and corresponding impedance match circuit 129 act as if they are pushing RF power into the plasma 105 sheath, because this is what they were doing at the end of the previous RF power pulse. However, at the beginning of each RF power pulse, the bias RF signal generator 125 and corresponding impedance matching circuit 129 are actually pushing RF power into a severely mismatched load. Therefore, at the beginning of the RF power pulse, not much RF power is pushed from the bias RF signal generator 125 and corresponding impedance matching circuit 129 into the plasma 105. Introducing RF power into the plasma 105 at the beginning of the RF power pulse is a slow process because RF energy initially enters the plasma 105 at a slow rate due to the impedance mismatch, and then, as the sheath of the plasma 105 begins to build, the bias RF signal generator 125 and corresponding impedance matching circuit 129 adjust their impedance to allow more RF energy to enter the plasma 105. Therefore, the process of introducing RF energy from the bias RF signal generator 125 and corresponding impedance matching circuit 129 into the plasma 105 during a square RF power pulse starts slowly and takes time to complete. For this reason, the chemistry of the primary plasma 105 is highly electronegative and the high bias voltage (Vb In certain applications, such as conductor etching applications where a pulsed RF power pulse profile 301 is used, a square RF power pulse profile 301 may not be possible. Instead, a high-amplitude, short-duration RF power spike at the beginning of each RF pulse is required to quickly establish and stabilize the plasma 105 sheath near the bias electrode 123. In some cases, without such a high-amplitude, short-duration RF power spike at the beginning of each RF pulse, the plasma 105 sheath will not stabilize over the RF power pulse duration d 301.

[0053] The bias RF signal generator 125 has an initial masking time when the bias RF signal generator 125 operates in open-loop control mode. During this initial masking time, there may be a naturally large initial spike of RF power depending on the cable configuration, the operating frequency of the bias RF signal generator 125, and the impedance seen by the bias RF signal generator 125. FIG. 3B shows the square RF power pulse profile 301 of FIG. 3A with the initial spike of RF power 303 associated with the initial masking time of the bias RF signal generator 125, according to some embodiments. More specifically, at the beginning of each square pulse of RF power, the bias RF signal generator 125 operating in open-loop control mode generates an initial spike of RF power 303. After the initial spike of RF power 303, the RF power settles to the power level P1 set for the RF power pulse profile 301. The magnitude and duration of the initial spike of RF power 303 depends on the cable configuration (between bias RF signal generator 125 and impedance match circuit 129, and between impedance match circuit 129 and bias electrode 123), the operating frequency of bias RF signal generator 125, the impedance seen by bias RF signal generator 125, and the chemistry of plasma 105. It should be understood that the initial spike of RF power 303 at the beginning of each RF power pulse is not controlled. Thus, while the initial spike of RF power 303 may be useful in accelerating the establishment and stabilization of a sheath in plasma 105 at the beginning of each RF power pulse, the initial spike of RF power 303 cannot be relied upon for that purpose.

[0054] In some embodiments, an attempt is made to maximize the initial spike of RF power 303 generated by the natural response of bias RF signal generator 125 operating in open-loop control mode. More specifically, an exemplary approach involves finding a specific cable length and / or a specific frequency setpoint for bias RF signal generator 125 that causes the impedance seen by bias RF signal generator 125 at the moment of the start of the RF power pulse to be where the RF power output is greatest, with bias RF signal generator 125 operating in natural open-loop control mode. For example, a specific cable configuration and setpoint frequency for bias RF signal generator 125 can be determined to maximize the initial spike of RF power 303. This approach can result in the initial spike of RF power 303 being several times higher than the actual power level (P1) setpoint of the RF power pulse, which can be up to twice the specified full-scale power of bias RF signal generator 125. Therefore, it should be understood that attempting to maximize the initial spike of RF power 303 with bias RF signal generator 125 operating in an open-loop control mode is dangerous and may even cause destruction of bias RF signal generator 125. Also, the optimal cable length and / or optimal setpoint frequency may vary from one process recipe for substrate 107 to another, and may even change with minor adjustments to process recipe parameters for several substrates 107. Therefore, it is important to develop a controlled approach for the initial spike of RF power at the beginning of each RF power pulse.

[0055] FIG. 4 illustrates an RF power pulse profile 401 including an RF pulse initiation power spike according to some embodiments. It should be understood that the RF power pulse profile 401 is equally applicable to the operation of the bias RF signal generator 125 and the primary RF signal generator 137. More specifically, the RF power pulse profile 401 can be used when the bias RF signal generator 125 is operating in pulsed mode. The RF power pulse profile 401 can also be used when the primary RF signal generator 137 is operating in pulsed mode. The RF power pulse profile 401 includes multiple consecutive pulses of RF power, such as 401A, 401B, and 401C, according to a set cycle duration d405. Each pulse of RF power, such as 401A, 401B, and 401C, includes a first duration d401 during which a first RF power profile p1 is present, followed immediately by a second duration d402 during which a second RF power profile p2 is present. The first RF power profile p1 has a greater RF power than the second RF power profile p2. In the example of FIG. 4, the first RF power profile p1 has an RF power level of P2, and the second RF power profile p2 has an RF power level of P1. The first duration d401 of the first RF power profile p1 is shorter than the second duration d402 of the second RF power profile p2. Each pulse of RF power 401A, 401B, 401C, etc., has a pulse duration d404 that is the sum of the first duration d401 of the first RF power profile p1 and the second duration d402 of the second RF power profile p2. Successive pulses of RF power 401A, 401B, 401C, etc., are separated from each other by a third duration d403, referred to as the inter-pulse duration d403. The set cycle duration d405 is the sum of the pulse duration d404 and the inter-pulse duration d403.

[0056] The first RF power profile p1 defines an RF pulse initiation power spike. The first RF power profile p1 allows the RF pulse initiation power spike to be controllable in terms of power and time. The power level P2 and duration d401 of the first RF power profile p1 are set to accelerate the establishment and stabilization of the plasma 105 sheath at the beginning of each RF power pulse 401A, 401B, 401C, etc. Therefore, it should be understood that the first RF power profile p1 is defined to put more RF energy into the plasma 105 at the beginning of its generation (when the plasma 105 sheath is first established). The RF power pulse profile 401 can be used in many different plasma processing operations for semiconductor device fabrication and is particularly useful for plasma-based etching of conductive materials and / or carbon-based hard mask materials on the substrate 107.

[0057] In the exemplary RF power pulse profile 401, the first RF power profile p1 is a substantially constant first RF power at a set power level P2, and the second RF power profile p2 is a substantially constant second RF power at a set power level P1, with the RF power being essentially zero during inter-pulse durations d403 between successive pulses 401A, 401B, 401C, etc. In some embodiments, when the bias RF signal generator 125 operates according to the RF power pulse profile 401, the impedance matching circuit 129 is optimized for the conditions present in the second RF power profile p2. In other embodiments, when the bias RF signal generator 125 operates according to the RF power pulse profile 401, the impedance matching circuit 129 is optimized for the conditions present in the first RF power profile p1. In some embodiments, when the primary RF signal generator 137 operates according to the RF power pulse profile 401, the impedance matching circuit 141 is optimized for the conditions present in the second RF power profile p2. In another embodiment, when the primary RF signal generator 137 operates according to the RF power pulse profile 401, the impedance matching circuit 141 is optimized for the conditions present during the first RF power profile p1.

[0058] In some embodiments, the sum of the first duration d401 of the first RF power profile p1, the second duration d402 of the second RF power profile p1, and the inter-pulse duration d403 is approximately 10 milliseconds or less. Or, in other words, in some embodiments, the set cycle duration d405 is approximately 10 milliseconds or less. In some embodiments, the sum of the first duration d401 of the first RF power profile p1 and the second duration d402 of the second RF power profile p1 is less than half the set cycle duration d405. Or, in other words, in some embodiments, the pulse duration d404 is less than half the set cycle duration d405. Or, in other words, in some embodiments, the sum of the first duration d401 of the first RF power profile p1 and the second duration d402 of the second RF power profile p1 is less than the inter-pulse duration d403. In some embodiments, the first duration d401 of the first RF power profile p1 is within a range ranging from about 10 microseconds to about 100 microseconds, or from about 20 microseconds to about 80 microseconds, or from about 40 microseconds to about 50 microseconds. In some embodiments, the first duration d401 of the first RF power profile p1 is between about 5% and about 25% of the sum of the first duration d401 of the first RF power profile p1 and the second duration d402 of the second RF power profile p2. In some embodiments, the first duration d401 of the first RF power profile p1 is between about 10% and about 15% of the sum of the first duration d401 of the first RF power profile p1 and the second duration d402 of the second RF power profile p2. In an exemplary embodiment, bias RF signal generator 125 operates to provide an RF pulse initiation power spike of about 1000 Watts for about 10 to about 100 microseconds at the beginning of each bias RF power pulse 401A, 401B, 401C, etc., and then provides a steady RF bias power level of about 500 W for the remainder of each bias RF power pulse 401A, 401B, 401C, etc.In an exemplary embodiment of the RF power pulse profile 401, the set power level P1 (of the second RF power profile p2) is 3000 watts (W), and the set power level P2 (of the first RF power profile p1) is in a range extending from approximately 5000 W to approximately 6000 W. In another exemplary embodiment of the RF power pulse profile 401, the set power level P1 (of the second RF power profile p2) is 500 watts (W), and the set power level P2 (of the first RF power profile p1) is in a range extending from approximately 1000 W to approximately 2000 W. As used herein, the term “approximately” refers to ±10%. It should be understood that the above values ​​for the set power levels P1 and P2 of the RF power pulse profile 401 are provided as examples. In other embodiments of the RF power pulse profile 401, the set power levels P1 and P2 are set as needed, such as to achieve a desired plasma control effect or other result.

[0059] The rail voltage supply for the bias RF signal generator 125 or the primary RF signal generator 137 primarily controls the absolute amount of maximum RF power that can be output. An additional amount of rail voltage can be provided to the bias RF signal generator 125 or the primary RF signal generator 137 at the beginning of the RF power pulses 401A, 401B, 401C, etc. to generate the RF pulse initiation power spike according to the first RF power profile p1. In some embodiments, the additional amount of rail voltage used to generate the RF pulse initiation power spike at the beginning of each RF power pulse 401A, 401B, 401C, etc. is provided by an additional voltage supply device (DC power supply) connected within the bias RF signal generator 125 or the primary RF signal generator 137, as the case may be. In some embodiments, the additional voltage supply device can be switchably connected to the rail voltage supply for the bias RF signal generator 125 or the primary RF signal generator 137 and provide temporal control of the rail voltage supply to conform to the first RF power profile p1.

[0060] In addition to having an additional voltage supply device, the output of an existing rail voltage supply for bias RF signal generator 125 or primary RF signal generator 137 can be increased during first RF power profile p1 to slightly boost power. However, the amount of power added by increasing the output of the existing rail voltage supply for bias RF signal generator 125 or primary RF signal generator 137 is less than what is needed and less than what is provided by the additional voltage supply device. Also, in some embodiments, during first RF power profile p1, power limits can be completely removed from bias RF signal generator 125 or primary RF signal generator 137, creating a "fire state" that allows the RF generator to frequency tune to reduce reflected power at maximum power output.

[0061] The RF power pulse profile 401 in Figure 4 represents single-level RF power pulsing, where RF power is pulsed between zero and a set power level P1, and a first RF power profile p1 has a set power level P2. Figure 5 shows an RF power pulse profile 501 representing dual-level RF power pulsing, where RF power is pulsed between a first set non-zero power level P1 and a set power level P2, and a first RF power profile p1 has a set power level P3, according to some embodiments. In the dual-level RF power pulsing of Figure 5, the RF power during a third duration (inter-pulse duration) d403 is at a substantially constant RF power level P1 that is greater than zero. In an exemplary embodiment of RF power pulse profile 501, the set power level P1 (for inter-pulse duration d403) is 500 W, the set power level P2 (for second RF power profile p2) is 3000 W, and the set power level P3 (for first RF power profile p1) is in a range extending from approximately 5000 W to approximately 6000 W. In an exemplary embodiment of RF power pulse profile 501, the set power level P1 (for inter-pulse duration d403) is 100 W, the set power level P2 (for second RF power profile p2) is 500 W, and the set power level P3 (for first RF power profile p1) is in a range extending from approximately 1000 W to approximately 2000 W. It should be understood that the above values ​​for the set power levels P1, P2, and P3 of RF power pulse profile 501 are provided as examples. In other embodiments of RF power pulse profile 501, the set power levels P1, P2, and P3 are set as needed, such as to achieve a desired plasma control effect or other result.

[0062] In RF power pulse profile 401 of FIG. 4, first RF power profile p1 has a substantially constant RF power level P2. However, in some embodiments, first RF power profile p1 may not be constant, i.e., may vary as a function of time. FIG. 6 illustrates RF power pulse profile 601, in which RF power is pulsed between zero and a set power level P1, and first RF power profile p1 exceeds the set power level P1, representing non-constant, single-level RF power pulsing, according to some embodiments. RF power pulse profile 601 is essentially the same as RF power pulse profile 401, except for first RF power profile p1. First RF power profile p1 of RF power pulse profile 601 initially jumps to power level P2 and then decreases from power level P2 to power level P1 over time. Specifically, the first RF power profile p1 of the RF power pulse profile 601 decreases over time from power level P2 to power level P1 in three steps, the first step spanning duration d601, the second step spanning duration d603, and the third step spanning duration d605.

[0063] Also, in some embodiments, the first RF power profile p1 can increase as a function of time. FIG. 7 illustrates an RF power pulse profile 701 in which RF power is pulsed between zero and a set power level P1, with the first RF power profile p1 exceeding the set power level P1, representing non-constant, single-level RF power pulsing, according to some embodiments. RF power pulse profile 701 is essentially the same as RF power pulse profile 401, except for the first RF power profile p1. The first RF power profile p1 of RF power pulse profile 701 increases in steps to reach power level P2. Specifically, the first RF power profile p1 of RF power pulse profile 701 increases from zero power level to power level P2 in two steps over time, with the first step spanning duration d701 and the second step spanning duration d703. It should be understood that the RF power pulse profiles 601 and 701 of FIGS. 6 and 7, respectively, are provided by way of example. In various embodiments, the first RF power profile p1, which defines the RF pulse initiation power spike, can be configured in a manner essentially required to most efficiently and / or quickly establish and stabilize the sheath of the plasma 105.

[0064] In some embodiments, the frequency of the signal generated by the bias RF signal generator 125 or the primary RF signal generator 137 is constant throughout the pulse duration d404. More specifically, in some embodiments, the frequency of the signal generated by the bias RF signal generator 125 or the primary RF signal generator 137 is the same during both the duration d401 of the first RF power profile p1, which corresponds to the RF pulse initiation power spike, and the duration d402 of the second RF power profile p2, which corresponds to a stable pulse power level. However, in some embodiments, the frequency of the signal generated by the bias RF signal generator 125 or the primary RF signal generator 137 varies during the pulse duration d404. In this manner, the frequency of the signal generated by the bias RF signal generator 125 or the primary RF signal generator 137 can be optimized for RF power delivery to the plasma 105. For example, it should be considered that the impedance of the plasma 105 during the first duration d401 of the first RF power profile p1 may be different from the impedance of the plasma 105 during the second duration d402 of the second RF power profile p2. With this in mind, the frequency of the signal generated by the bias RF signal generator 125 or the primary RF signal generator 137 can be controlled in a first manner during the first duration d401 of the first RF power profile p1 and in a second manner during the second duration d402 of the second RF power profile p2 to optimize RF power delivery to the plasma 105 throughout the pulse duration d404.

[0065] 8A illustrates the RF power pulse profile 401 of FIG. 4 with frequency variation applied over a pulse duration d404, according to some embodiments. In the example of FIG. 8A , the frequency of the signal generated by the bias RF signal generator 125 or the primary RF signal generator 137 during a first duration d401 of the first RF power profile p1 corresponds to a first frequency control function freq1{t}. Also, the frequency of the signal generated by the bias RF signal generator 125 or the primary RF signal generator 137 during a second duration d402 of the second RF power profile p2 corresponds to a second frequency control function freq2{t}. Each of the first frequency control function freq1{t} and the second frequency control function freq2{t} is essentially a specification of the frequency setpoint of the bias RF signal generator 125 or the primary RF signal generator 137 as a function of time. In some embodiments, the frequency of bias RF signal generator 125 or primary RF signal generator 137 can be changed / adjusted within a time period of about 1 microsecond or less. Thus, the frequency tuning resolution of each of first frequency control function freq1{t} and second frequency control function freq2{t} is about 1 microsecond or less.

[0066] The first frequency control function freq1{t} and the second frequency control function freq2{t} can be defined independently of each other and can be the same or different. In some embodiments, the first frequency control function freq1{t} and / or the second frequency control function freq2{t} can be linear functions with respect to time. FIG. 8B shows an example frequency control function 801(freq#{t}) in which the frequency of the signal generated by the bias RF signal generator 125 or the primary RF signal generator 137 is substantially constant over time, according to some embodiments. The frequency control function 801(freq#{t}) represents the first frequency control function freq1{t} and / or the second frequency control function freq2{t}.

[0067] 8C shows an exemplary frequency control function 803(freq#{t}) in which the frequency of the signal generated by bias RF signal generator 125 or primary RF signal generator 137 monotonically increases over time, according to some embodiments. Frequency control function 803(freq#{t}) represents a first frequency control function freq1{t} and / or a second frequency control function freq2{t}. In some embodiments, frequency control function 803(freq#{t}) is a linear function as shown in FIG. 8C. However, in other embodiments, frequency control function 803(freq#{t}) is a monotonically increasing nonlinear function.

[0068] 8D shows an exemplary frequency control function 805(freq#{t}) in which the frequency of the signal generated by bias RF signal generator 125 or primary RF signal generator 137 monotonically decreases over time, according to some embodiments. Frequency control function 805(freq#{t}) represents a first frequency control function freq1{t} and / or a second frequency control function freq2{t}. In some embodiments, frequency control function 805(freq#{t}) is a linear function as shown in FIG. 8D. However, in other embodiments, frequency control function 805(freq#{t}) is a monotonically decreasing nonlinear function.

[0069] 8E shows an example frequency control function 807(freq#{t}) in which the frequency of a signal generated by bias RF signal generator 125 or primary RF signal generator 137 varies nonlinearly over time, according to some embodiments. Frequency control function 807(freq#{t}) represents a first frequency control function freq1{t} and / or a second frequency control function freq2{t}. In some embodiments, frequency control function 807(freq#{t}) includes both a first portion in which the frequency increases over time and a second portion in which the frequency decreases over time.

[0070] A potential problem with current RF generators is that the DC rail voltage of the RF generator cannot be changed quickly enough to implement a first RF power profile p1 and transition to a second RF power profile p2 on the required timescale. In some embodiments, one way to control the DC rail voltage of the RF generator as needed to provide an RF pulse initiation power spike (corresponding to the first RF power profile p1) is to have two separately controllable DC power supplies within the RF generator.

[0071] In these embodiments, the first DC power supply operates to provide the necessary rail voltage for a duration d402 corresponding to a second RF power profile p2 following an RF pulse initiation power spike corresponding to a first RF power profile p1 to generate an RF signal. The second DC power supply also operates to provide an additional amount of rail voltage for a duration d401 of the RF pulse initiation power spike corresponding to the first RF power profile p1 to generate an RF signal. The additional amount of rail voltage provided by the second DC power supply is added to the baseline amount of rail voltage provided by the first DC power supply. The second DC power supply can be controlled over a timescale necessary to generate the RF pulse initiation power spike corresponding to the first RF power profile p1 and then transition to the second RF power profile p2 of the bulk of the RF power pulse in an appropriate time. The output of the second DC power supply is connected to a switching mechanism to control the transfer of the additional amount of rail voltage to the power rails of the RF generator. In some embodiments, a capacitor or equivalent electrical device is connected to the output of the second DC power supply to enable fast switching. Additionally, the first and second DC power sources are configured and connected to prevent power from being transferred to each other, such as with one or more diodes.

[0072] FIG. 9 shows an exemplary arrangement of an RF signal generation system 900 implementing dual DC power supplies for RF pulse initiation power spike generation, according to some embodiments. The RF signal generation system 900 of FIG. 9 can be used for the bias RF signal generator 125 and / or the primary RF signal generator 137. The RF signal generation system 900 includes an RF signal generator 901 configured to generate an RF signal at or near a set frequency. The RF signal generation system 900 also includes a first DC voltage source 903 connected to a voltage input 905 of the RF signal generator 901. In some embodiments, the first DC voltage source 903 is connected to the voltage input 905 through a diode 913. The diode 913 functions to protect the first DC voltage source 903 from power present at the voltage input 905 of the RF signal generator 901. The RF signal generation system 900 also includes a second DC voltage source 907 switchably connected to the voltage input 905 of the RF signal generator 901. In some embodiments, a switching device 911 is connected between the second DC voltage source 907 and the voltage input 905 of the RF signal generator 901. In some embodiments, a capacitor 915 or equivalent electrical device is connected between the output of the second DC voltage source 907 and a reference ground potential 917. The capacitor 915 or equivalent electrical device ensures that the output of the second DC voltage source 907 is charged to enable fast switching of the switching device 911.

[0073] The RF signal generating system 900 also includes a controller 909 configured and connected to control each of the RF signal generator 901, the first DC voltage source 903, the second DC voltage source 907, and the switching device 911. In some embodiments, the controller 909 is configured similarly to the control system 153. The switching device 911 is configured to control the electrical connection of the second DC voltage source 907 to the voltage input 905 of the RF signal generator 901 according to a control signal received from the controller 909. The voltages supplied to the voltage input 905 of the RF signal generator 901 by the first DC voltage source 903 and the second DC voltage source control the amplitude of the RF signal generated by the RF signal generator 901. The controller 909 is configured to execute program instructions stored in a computer memory, and when executed, the controller 909 directs the RF signal generator 901 to supply multiple sequential pulses of RF power to the electrodes (123 / 101) of the plasma processing system 100. Each pulse of RF power includes a first duration d401 during which a first RF power profile p1 is present, followed immediately by a second duration d402 during which a second RF power profile p2 is present. The first RF power profile p1 has a greater RF power than the second RF power profile p2. The first duration d401 is shorter than the second duration d402. Successive pulses of RF power are separated from one another by a third (interpulse) duration d403.

[0074] The first RF power profile p1 corresponds to connecting both the first DC voltage source 903 and the second DC voltage source 907 to the voltage input 905 of the RF signal generator 901. The second RF power profile p2 corresponds to connecting the first DC voltage source 903 to the voltage input 905 of the RF signal generator 901 without connecting the second DC voltage source 907 to the voltage input 905 of the RF signal generator 901. The controller 909 is configured to initiate a given pulse of RF power according to the first RF power profile p1 by directing activation of the RF signal generator 901 and by directing the switching device 911 to connect the second DC voltage source 907 to the voltage input 905 of the RF signal generator 901, with the first DC voltage source 903 being continuously connected to the voltage input 905 of the RF signal generator 901. The controller 909 is configured to transition from the first RF power profile p1 to the second RF power profile p2 by directing the switching device 911 to disconnect the second DC voltage source 907 from the voltage input 905 of the RF signal generator 901. The controller 909 is configured to terminate a given pulse of RF power by directing the deactivation of the RF signal generator 901.

[0075] 10, 11, and 12 collectively illustrate the voltage supplied to the voltage input 905 of the RF signal generator 901 as a function of time. FIG. 10 illustrates a diagram of the voltage output by the first DC voltage source 903 as a function of time to generate the RF power pulse profile 401 of FIG. 4 , according to some embodiments. The voltage output by the first DC voltage source 903 as a function of time is a substantially constant voltage V1. FIG. 11 illustrates a diagram of the voltage output by the second DC voltage source 907 as a function of time to generate the RF power pulse profile 401 of FIG. 4 , according to some embodiments. The voltage output by the second DC voltage source 907 as a function of time is pulsed between zero and a voltage ΔV, where ΔV = V2 - V1, where V2 is a voltage level corresponding to the generation of the first RF power profile p1. 12 shows a diagram of the sum of the voltages output by the first DC voltage source 903 and the second DC voltage source 907 as a function of time to generate the RF power pulse profile 401 of FIG. 4, according to some embodiments. The voltage diagram of FIG. 12 represents the voltage present at the voltage input 905 of the RF signal generator 901 as a function of time. FIG. 13 shows a diagram of the activation of the RF signal generator 901 as a function of time to generate the RF power pulse profile 401 of FIG. 4, according to some embodiments. The activation of the RF signal generator 901 follows the timing of the RF power pulse profile 401 of FIG. 4 with respect to RF power pulse generation. When the RF signal generator 901 is on, the RF signal generator 901 generates an RF signal according to the voltage present at the voltage input 905 of the RF signal generator 901. Thus, over pulse duration d404, RF signal generator 901 generates an RF signal according to voltage V2 during a first duration d401 of first RF power profile p1, and generates an RF signal according to voltage V1 during a second duration d402 of second RF power profile p2. Also, when RF signal generator 901 is off, no RF signal is generated by RF signal generator 901, regardless of the voltage present at voltage input 905 of RF signal generator 901.

[0076] FIG. 14 shows a flowchart of a method for controlling plasma in a plasma processing chamber, according to some embodiments. In some embodiments, a plasma is generated to cause etching of a conductive material and / or a carbon-based hard mask material on a substrate. The method includes operation 1401 for supplying multiple sequential pulses of RF power to an electrode of the plasma processing chamber. In some embodiments, the electrode is a bias electrode disposed within a substrate holder in the plasma processing chamber. In some embodiments, the electrode is a coil disposed outside a window of the plasma processing chamber. Each pulse of RF power includes a first duration during which a first RF power profile is present, followed immediately by a second duration during which a second RF power profile is present. The first RF power profile has a greater RF power than the second RF power profile. The first duration is shorter than the second duration. Additionally, the sequential pulses of RF power are separated from one another by a third duration. In some embodiments, the RF power during the third duration is essentially zero. In some embodiments, the RF power during the third duration is a substantially constant RF power level greater than zero.

[0077] In some embodiments, the sum of the first duration for which the first RF power profile is present, the second duration for which the second RF power profile is present, and the third duration separating consecutive pulses is about 10 milliseconds or less. In some embodiments, the sum of the first duration for which the first RF power profile is present and the second duration for which the second RF power profile is present is less than the third duration separating consecutive pulses. In some embodiments, the first duration for which the first RF power profile is present is within a range ranging from about 10 microseconds to about 100 microseconds, or from about 20 microseconds to about 80 microseconds, or from about 40 microseconds to about 50 microseconds. In some embodiments, the first duration for which the first RF power profile is present is about 5% to about 25% of the sum of the first duration and the second duration for which the second RF power profile is present. In some embodiments, the first duration during which the first RF power profile is present is about 10% to about 15% of the sum of the first duration and the second duration during which the second RF power profile is present.

[0078] In some embodiments, the first RF power profile is a substantially constant first RF power and the second RF power profile is a substantially constant second RF power. In some embodiments, the first RF power profile decreases from a first (initial) RF power and the second RF power profile is a substantially constant second RF power. In some embodiments, the first RF power profile increases toward the first RF power and the second RF power profile is a substantially constant second RF power.

[0079] In some embodiments, the method includes optional operation 1403 for generating an RF signal according to a first frequency control function for a first duration to generate a first RF power profile. Also, in some embodiments, the method includes optional operation 1405 for generating an RF signal according to a second frequency control function for a second duration to generate a second RF power profile. It should be understood that either or both of optional operations 1403 and 1405 can be implemented in any given embodiment. In some embodiments, the frequency tuning resolution of each of the first frequency control function and the second frequency control function is about 1 microsecond or less.

[0080] In some embodiments, the first frequency control function specifies a substantially constant frequency of the generated RF signal as a function of time. In some embodiments, the first frequency control function specifies a monotonically increasing frequency of the generated RF signal as a function of time. In some embodiments, the first frequency control function specifies a monotonically decreasing frequency of the generated RF signal as a function of time. In some embodiments, the first frequency control function specifies a non-linearly varying frequency of the generated RF signal as a function of time.

[0081] In some embodiments, the second frequency control function specifies a substantially constant frequency of the generated RF signal as a function of time. In some embodiments, the second frequency control function specifies a monotonically increasing frequency of the generated RF signal as a function of time. In some embodiments, the second frequency control function specifies a monotonically decreasing frequency of the generated RF signal as a function of time. In some embodiments, the second frequency control function specifies a non-linearly varying frequency of the generated RF signal as a function of time.

[0082] It should be appreciated that the systems and methods disclosed herein provide for the generation of an RF pulse onset power spike. It should also be appreciated that the systems and methods disclosed herein provide for precise control of the amplitude and duration of the RF pulse onset power spike. Thus, the RF pulse onset power spike generation methods and systems disclosed herein do not require attempting to use the open-loop response of an RF signal generator in conjunction with frequency searching and cable length adjustment to obtain an uncontrolled pulse onset spike.

[0083] Additionally, by having a way to boost the rail voltage and / or RF drive of an existing RF signal generator and / or by using the multi-level pulsing capability of an existing RF signal generator to create a "light-off condition," the methods and systems disclosed herein provide an additional degree of control over the RF pulse initiation power spike, which is particularly useful considering that the required amplitude and duration of the RF pulse initiation power spike may vary for each process recipe step. It should be understood that the methods and systems disclosed herein for generating a controlled RF pulse initiation power spike are particularly useful when the bias RF signal generator 125 and / or the primary RF signal generator 137 operate in a single-level pulsing mode. However, the methods and systems disclosed herein for generating a controlled RF pulse initiation power spike are also useful when the bias RF signal generator 125 and / or the primary RF signal generator 137 operate in a dual-level pulsing mode. Also, in general, the methods and systems disclosed herein for generating a controlled RF pulse initiation power spike are useful for the plasma striking stage of essentially any multiphase pulse generation mode of bias RF signal generator 125 and / or primary RF signal generator 137.

[0084] In some embodiments, the methods and systems disclosed herein for generating a controlled RF pulse onset power spike can be used for both the delivery of bias RF power to bias electrode 123 and the delivery of primary RF power to coil 101. However, it should be understood that the implementation of the method and system for generating a controlled RF pulse onset power spike for the delivery of bias RF power to bias electrode 123 is entirely independent from the implementation of the method and system for generating a controlled RF pulse onset power spike for the delivery of primary RF power to coil 101, and vice versa. The generation of a controlled RF pulse onset power spike is particularly useful when delivering a low-power pulse of primary RF power to coil 101.

[0085] FIG. 15 shows a flowchart of a method for controlling plasma in a plasma processing chamber, according to some embodiments. The method includes operation 1501 for supplying multiple consecutive pulses of primary RF power to a primary electrode of the plasma processing chamber. Each pulse of primary RF power includes a first duration during which a first primary RF power profile is present, followed immediately by a second duration during which a second primary RF power profile is present. The first primary RF power profile has a greater RF power than the second primary RF power profile. The first duration is shorter than the second duration. Additionally, the consecutive pulses of primary RF power are separated from one another by a third duration. In some embodiments, the primary RF power level is essentially zero during the third duration. In some embodiments, the primary RF power level is a substantially constant power level greater than zero during the third duration.

[0086] The method also includes operation 1503 for supplying multiple consecutive pulses of bias RF power to a bias electrode of the plasma processing chamber. Each pulse of bias RF power includes a fourth duration during which a first bias RF power profile is present, followed immediately by a fifth duration during which a second bias RF power profile is present. The first bias RF power profile has a greater RF power than the second bias RF power profile. The fourth duration is shorter than the fifth duration. The consecutive pulses of bias RF power are separated from one another by a sixth duration. In some embodiments, the bias RF power level is essentially zero during the sixth duration. In some embodiments, the bias RF power level is a substantially constant power level greater than zero during the sixth duration.

[0087] In some embodiments, the bias RF power pulse is delayed relative to the primary RF power pulse by a pulse delay amount ranging from about 2 microseconds to about 100 microseconds, or from about 2 microseconds to about 5 microseconds, or about 3 microseconds. In some embodiments, the pulse delay amount is set so that a given pulse of primary RF power can establish stable primary plasma conditions within the plasma processing chamber before the delivery of a subsequent pulse of bias RF power. Also, in the application of dual-level primary RF power pulses, bulk plasma impedance fluctuations and transitions between different primary RF power levels can be significant and may require a longer delay between the primary RF power pulse and the bias RF power pulse. This longer delay can be from about 50 microseconds to about 100 microseconds.

[0088] In some embodiments, the method includes optional operation 1505 for generating an RF signal according to a first frequency control function during a first duration to generate a first primary RF power profile. Also, in some embodiments, the method includes optional operation 1507 for generating an RF signal according to a second frequency control function during a second duration to generate a second RF power profile. It should be understood that either or both of optional operations 1505 and 1507 can be implemented in any given embodiment. Additionally, in some embodiments, the method includes optional operation 1509 for generating an RF signal according to a third frequency control function during a fourth duration to generate a first bias RF power profile. Also, in some embodiments, the method includes optional operation 1511 for generating an RF signal according to a fourth frequency control function during a fifth duration to generate a second bias RF power profile. It should be understood that either or both of optional operations 1509 and 1511 can be implemented in any given embodiment. In some embodiments, the frequency tuning resolution of each of the first frequency control function, the second frequency control function, the third frequency control function, and the fourth frequency control function is about 1 microsecond or less.

[0089] The various embodiments described herein can also be practiced using a variety of computer system configurations, including handheld hardware units, microprocessor systems, microprocessor-based or programmable consumer electronics, minicomputers, mainframe computers, and the like. The embodiments described herein can also be practiced in distributed computing environments where tasks are performed by remote processing hardware units linked through a network. It should be understood that the embodiments described herein can employ various computer-implemented operations involving data stored in computer systems. These operations require physical manipulation of physical quantities. Any of the operations described herein that form part of the embodiments are useful machine operations. The embodiments also relate to hardware units or apparatus for performing these operations. An apparatus may be specially constructed for a special-purpose computer. When defined as a special-purpose computer, the computer is operable for its dedicated purpose, while also performing other processes, program execution, or routines that are not part of its dedicated purpose. In some embodiments, operations may be processed by a general-purpose computer selectively activated or configured by one or more computer programs stored in a computer memory, cache, or obtained over a network. When data is obtained over a network, the data may be processed by other computers on the network (e.g., a cloud of computing resources).

[0090] Various embodiments described herein can be implemented through process control instructions instantiated as computer-readable code on a non-transitory computer-readable medium. A non-transitory computer-readable medium is any data storage hardware unit that can store data, which can then be read by a computer system. Examples of non-transitory computer-readable media include hard drives, network-attached storage (NAS), ROM, RAM, compact disc ROM (CD-ROM), CD-recordable (CD-R), CD-rewritable (CD-RW), magnetic tape, and other optical and non-optical data storage hardware units. A non-transitory computer-readable medium can include computer-readable tangible media distributed over network-coupled computer systems such that computer-readable code is stored and executed in a distributed manner.

[0091] Although the foregoing disclosure has been described in some detail for clarity of understanding, it will be apparent that certain changes and modifications can be practiced within the scope of the appended claims. For example, it should be understood that one or more features from any embodiment disclosed herein can be combined with one or more features of any other embodiment disclosed herein. Thus, the present embodiments should be considered illustrative rather than limiting, and the claims should not be limited to the details set forth herein, but may be modified within the scope and equivalents of the described embodiments.

[0092] The claims are as follows:

Claims

1. 1. A method for controlling a plasma in a plasma processing chamber, comprising: supplying a plurality of successive pulses of radio frequency power to an electrode of the plasma processing chamber, each of the successive pulses of radio frequency power including a first duration during which a first radio frequency power profile is present followed immediately by a second duration during which a second radio frequency power profile is present, the first radio frequency power profile having a greater radio frequency power than the second radio frequency power profile, the first duration being shorter than the second duration, and the successive pulses of radio frequency power being separated from one another by a third duration; A method comprising:

2. 10. The method of claim 1, The method, wherein the electrode is a bias electrode disposed in a substrate holder within the plasma processing chamber.

3. 10. The method of claim 1, The method, wherein the electrode is a coil positioned outside a window of the plasma processing chamber.

4. 10. The method of claim 1, The method, wherein the radio frequency power during the third time duration is essentially zero.

5. 10. The method of claim 1, The method, wherein the radio frequency power during the third duration is a substantially constant radio frequency power level greater than zero.

6. 10. The method of claim 1, The method, wherein the sum of the first duration, the second duration, and the third duration is less than or equal to about 10 milliseconds.

7. 10. The method of claim 1, The method, wherein the sum of the first duration and the second duration is less than or equal to the third duration.

8. 10. The method of claim 1, The method, wherein the first duration is in a range ranging from about 10 microseconds to about 100 microseconds, or in a range ranging from about 20 microseconds to about 80 microseconds, or in a range ranging from about 40 microseconds to about 50 microseconds.

9. 10. The method of claim 1, The method, wherein the first duration is about 5% to about 25% of the sum of the first duration and the second duration.

10. 10. The method of claim 1, The method, wherein the first duration is about 10% to about 15% of the sum of the first duration and the second duration.

11. 10. The method of claim 1, The method, wherein the plasma is generated to cause etching of a conductive material and / or a carbon-based hard mask material on a substrate.

12. 10. The method of claim 1, The method, wherein the first radio frequency power profile is a substantially constant first radio frequency power and the second radio frequency power profile is a substantially constant second radio frequency power.

13. 10. The method of claim 1, The method, wherein the first radio frequency power profile is a decreasing first radio frequency power and the second radio frequency power profile is a substantially constant second radio frequency power.

14. 10. The method of claim 1, The method, wherein the first radio frequency power profile increases toward a first radio frequency power and the second radio frequency power profile is a substantially constant second radio frequency power.

15. 10. The method of claim 1, generating a radio frequency signal according to a first frequency control function during the first duration to generate the first radio frequency power profile; generating a radio frequency signal according to a second frequency control function during the second duration to generate the second radio frequency power profile; The method further comprises:

16. 16. The method of claim 15, The method, wherein the frequency tuning resolution of each of the first frequency control function and the second frequency control function is about 1 microsecond or less.

17. 16. The method of claim 15, the first frequency control function specifies a substantially constant frequency of the generated radio frequency signal as a function of time; or the first frequency control function specifies a monotonically increasing frequency of the generated radio frequency signal as a function of time; or the first frequency control function specifies a monotonically decreasing frequency of the generated radio frequency signal as a function of time; or the first frequency control function specifies a nonlinearly varying frequency of the generated radio frequency signal as a function of time; the second frequency control function specifies a substantially constant frequency of the generated radio frequency signal as a function of time; or the second frequency control function specifies a monotonically increasing frequency of the generated radio frequency signal as a function of time; or the second frequency control function specifies a monotonically decreasing frequency of the generated radio frequency signal as a function of time; or the second frequency control function specifying a nonlinearly varying frequency of the generated radio frequency signal as a function of time. method.

18. 1. A controller programmed to control a plasma in a plasma processing chamber, comprising: and program instructions stored in a computer memory that, when executed, direct supplying a plurality of successive pulses of radio frequency power to an electrode of the plasma processing chamber, each of the successive pulses of radio frequency power including a first duration during which a first radio frequency power profile is present followed immediately by a second duration during which a second radio frequency power profile is present, the first radio frequency power profile having a greater radio frequency power than the second radio frequency power profile, the first duration being shorter than the second duration, and the successive pulses of radio frequency power being separated from one another by a third duration. Including the controller.

19. 20. The controller of claim 18, The electrode is a bias electrode disposed in a substrate holder within the plasma processing chamber.

20. 20. The controller of claim 18, The electrode is a coil positioned outside a window of the plasma processing chamber.

21. 20. The controller of claim 18, The radio frequency power during the third time duration is essentially zero.

22. 20. The controller of claim 18, The radio frequency power during the third duration is a substantially constant radio frequency power level greater than zero.

23. 1. A radio frequency signal generating system configured to control a plasma in a plasma processing chamber, comprising: a radio frequency signal generator configured to generate a radio frequency signal at or near a set frequency; a first DC voltage source connected to a voltage input of the radio frequency signal generator; a second DC voltage source switchably connected to the voltage input of the radio frequency signal generator; a controller configured and connected to control each of the radio frequency signal generator, the first DC voltage source, and the second DC voltage source, wherein voltages supplied by the first and second DC voltage sources to the voltage inputs of the radio frequency signal generator control the amplitude of the radio frequency signal generated by the radio frequency signal generator; A radio frequency signal generating system comprising:

24. 24. The radio frequency signal generating system of claim 23, The controller is configured to execute program instructions stored in a computer memory, which, when executed, causes the controller to direct the radio frequency signal generator to supply multiple successive pulses of radio frequency power to an electrode of the plasma processing chamber.

25. 25. A radio frequency signal generating system according to claim 24, comprising:

10. A radio frequency signal generating system comprising: a first pulse of radio frequency power having a first duration followed immediately by a second duration of a second radio frequency power profile, the first radio frequency power profile having a greater radio frequency power than the second radio frequency power profile; a first duration of a second duration of a second radio frequency power profile; a second duration of a first radio frequency power profile; a third duration of a second radio frequency power profile; and a third duration of a second radio frequency power profile.

26. 26. A radio frequency signal generating system according to claim 25, comprising:

1. A radio frequency signal generating system, wherein the first radio frequency power profile corresponds to connection of both the first and second DC voltage sources to the voltage input of the radio frequency signal generator, and the second radio frequency power profile corresponds to connection of the first DC voltage source to the voltage input of the radio frequency signal generator without connection of the second DC voltage source to the voltage input of the radio frequency signal generator.

27. 27. A radio frequency signal generating system according to claim 26, comprising: a switching device connected between the second DC voltage source and the voltage input of the radio frequency signal generator, the switching device configured to control the electrical connection of the second DC voltage source to the voltage input of the radio frequency signal generator according to a control signal received from the controller.

10. The radio frequency signal generating system according to claim 9, further comprising:

28. 28. A radio frequency signal generating system according to claim 27, comprising: the controller is configured to initiate a given pulse of radio frequency power according to the first radio frequency power profile by directing activation of the radio frequency signal generator and by directing the switching device to connect the second DC voltage source to the voltage input of the radio frequency signal generator, and the first DC voltage source is continuously connected to the voltage input of the radio frequency signal generator.

29. 29. A radio frequency signal generating system according to claim 28, comprising: the controller is configured to transition from the first radio frequency power profile to the second radio frequency power profile by instructing the switching device to disconnect the second DC voltage source from the voltage input of the radio frequency signal generator.

30. 30. The radio frequency signal generating system of claim 29, The radio frequency signal generating system, wherein the controller is configured to terminate a given pulse of the radio frequency power by directing deactivation of the radio frequency signal generator.

31. 1. A method for controlling a plasma in a plasma processing chamber, comprising: supplying a plurality of consecutive pulses of primary radio frequency power to a primary electrode of a plasma processing chamber, each pulse of primary radio frequency power including a first duration during which a first primary radio frequency power profile is present followed immediately by a second duration during which a second primary radio frequency power profile is present, the first primary radio frequency power profile having a greater radio frequency power than the second primary radio frequency power profile, the first duration being shorter than the second duration, and the consecutive pulses of primary radio frequency power being separated from one another by a third duration; supplying a plurality of consecutive pulses of bias radio frequency power to a bias electrode of the plasma processing chamber, each pulse of bias radio frequency power including a fourth duration during which a first bias radio frequency power profile is present followed immediately by a fifth duration during which a second bias radio frequency power profile is present, the first bias radio frequency power profile having a greater radio frequency power than the second bias radio frequency power profile, the fourth duration being shorter than the fifth duration, and the consecutive pulses of bias radio frequency power being separated from one another by a sixth duration; A method comprising:

32. 32. The method of claim 31 , wherein the pulse of the bias radio frequency power is delayed relative to the pulse of the primary radio frequency power by a pulse delay amount in a range ranging from about 2 microseconds to about 100 microseconds, or in a range ranging from about 2 microseconds to about 5 microseconds, or in a range of about 3 microseconds.

33. 33. The method of claim 32, The method, wherein the pulse delay amount is set to allow a given pulse of primary radio frequency power to establish a stable primary plasma condition within the plasma processing chamber before delivery of a subsequent pulse of bias radio frequency power.

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