System and method for controlling pulse width of a rectangular pulse waveform

Abstract

Systems and methods are described for controlling the pulse width of a rectangular pulse waveform. One of the methods includes generating a rectangular pulse waveform having multiple states, each of the multiple states including a series of rectangular pulses. The method includes modifying the pulse width of each of the multiple states to modify the rate at which a substrate is processed.

Description

[Technical Field]

[0001] The present embodiment relates to a system and method for controlling the pulse width of a rectangular pulse waveform. [Background technology]

[0002] In a plasma tool, a radio frequency (RF) generator is provided to generate a sinusoidal RF signal. The plasma tool has a matcher coupled to the RF generator to receive the sinusoidal RF signal. In response to receiving the sinusoidal RF signal from the RF generator, the matcher outputs the sinusoidal RF signal to a plasma chamber of the plasma tool. A semiconductor wafer disposed in the plasma chamber is processed by the plasma generated when the sinusoidal RF signal is received from the matcher. However, the sinusoidal RF signal generated by the RF generator does not enable various processes for fabricating semiconductor wafers to be achieved.

[0003] The discussion of the background art provided herein is intended to generally present the context for the present disclosure. The work of the presently named inventors, to the extent that that work is described in this background art section, as well as aspects of the description that may not otherwise be considered prior art at the time of filing, are not admitted expressly or impliedly as prior art to the present disclosure. Summary of the Invention

[0004]

[0009] Embodiments of the present disclosure provide a system, apparatus, method, and computer program for controlling the pulse width of a rectangular pulse waveform. It should be appreciated that the present embodiments can be implemented in numerous ways, such as a process, an apparatus, a system, a device, or a method, on a computer-readable medium. Several embodiments are described below.

[0005] In one embodiment, a method for adjusting the pulse width of a rectangular pulse waveform is described. The method includes generating a rectangular pulse waveform having a plurality of states and a second plurality of states, each of the plurality of states including a series of rectangular pulses. The method includes modifying the pulse width of each of the plurality of states to modify the rate at which a substrate is processed.

[0006] In one embodiment, a controller for adjusting the pulse width of a rectangular pulse waveform is described. The controller includes a processor that controls a pulse generator to generate a rectangular pulse waveform having a plurality of states, each of the plurality of states including a series of rectangular pulses. The processor controls the pulse generator to modify the pulse width of each of the plurality of states to modify a rate at which a substrate is processed. The controller includes a memory device coupled to the processor.

[0007] In one embodiment, a plasma system includes a low frequency (LF) radio frequency (RF) pulse generator, a high frequency (HF) RF signal generator, an HF filter coupled to the LF RF pulse generator, an impedance matching circuit coupled to the HF RF signal generator, and a plasma chamber coupled to the HF filter and the impedance matching circuit. The plasma system further includes a controller coupled to the LF RF pulse generator and the HF RF signal generator. The controller controls the LF RF pulse generator to generate a rectangular pulse waveform having multiple states, each of the multiple states including a series of rectangular pulses. The controller controls the LF RF pulse generator to modify the pulse width of each of the multiple states to modify the rate at which the substrate is processed.

[0008] Some advantages of the systems and methods described herein include controlling the pulse width of a rectangular pulse waveform to achieve uniformity across substrate features. The pulse width is controlled by increasing or decreasing the number of pulses in the rectangular pulse waveform. Furthermore, controlling the pulse width controls the rate at which the substrate is processed. Also, controlling the pulse width controls the selectivity associated with processing the substrate. Controlling the pulse width controls the rate at which bowing of the substrate increases.

[0009] Additional advantages of the systems and methods described herein include achieving a faster rate of processing substrates compared to that achieved using a sinusoidal RF signal. The rectangular pulse waveform achieves a power set point at a faster rate than the rate at which that power set point is achieved using a sinusoidal RF signal. By achieving a faster rate, substrates can be processed more quickly compared to those using a sinusoidal RF signal.

[0010] Other aspects will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

[0011] The embodiments may be best understood by referring to the following description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0012] [Figure 1A] FIG. 1 is an embodiment of a graph for illustrating a rectangular pulse waveform having a pulse width.

[0013] [Figure 1B] FIG. 2 is an embodiment of a graph for illustrating multiple states S1 and S0 of a rectangular pulse waveform, where state S0 has multiple pulses.

[0014] [Figure 2] FIG. 10 is an embodiment of a graph for illustrating variations in pulse width.

[0015] [Figure 3] FIG. 10 is an embodiment of a graph for illustrating variations in pulse width.

[0016] [Figure 4] FIG. 10 is an embodiment of a graph for illustrating variations in pulse width.

[0017] [Figure 5A] FIG. 1 is a diagram of one embodiment of a system to illustrate the use of a high frequency (HF) radio frequency (RF) signal generator to generate an RF signal, to be used in conjunction with a low frequency (LF) radio frequency (RF) pulse generator.

[0018] [Figure 5B] FIG. 1 is a diagram of one embodiment of a system to demonstrate the use of an HF RF signal generator with an LF RF pulse generator.

[0019] [Figure 6] FIG. 1 is a diagram of one embodiment of a system including a processor and an LF RF pulse generator.

[0020] [Figure 7A-1] FIG. 2 is an embodiment of a graph for illustrating a continuous waveform of an RF signal generated by an HF RF signal generator.

[0021] [Figure 7A-2] FIG. 1 is an embodiment of a graph for illustrating the envelope and phase of a rectangular pulse waveform.

[0022] [Figure 7B-1] 5C is an illustration of an embodiment of a graph for illustrating the envelope of a parameter of an RF signal generated by the HF RF signal generator of FIG. 5B.

[0023] [Figure 7B-2] FIG. 1 is a diagram of one embodiment of a graph for illustrating the change in phase of the envelope of a rectangular pulse waveform from phase 1 to phase 2.

[0024] [Figure 7B-3] FIG. 10 is a diagram of one embodiment of a graph to illustrate the change in phase of the envelope of a rectangular pulse waveform from phase 2 to phase 3.

[0025] [Figure 7B-4] FIG. 10 is a diagram of one embodiment of a graph to illustrate the change in phase of the envelope of a rectangular pulse waveform from phase 3 to phase 4.

[0026] [Figure 7B-5] FIG. 10 is a diagram of one embodiment of a graph to illustrate the change in phase of the envelope of a rectangular pulse waveform from phase 4 to phase 5.

[0027] [Figure 8] FIG. 1 is a diagram of an embodiment of a graph illustrating the change in etch rate (ER) of etching a substrate with a change in pulse width of a rectangular pulse waveform.

[0028] [Figure 9] FIG. 10 is an embodiment of a graph to illustrate the change in selectivity of etching a layer of a substrate with a change in pulse width of a rectangular pulse waveform.

[0029] [Figure 10] FIG. 10 is a diagram of an embodiment of a graph illustrating the change in the warpage growth rate of the wafer bow of a substrate with a change in the pulse width of a rectangular pulse waveform.

[0030] [Figure 11] FIG. 10 is a diagram showing that the chemical composition of plasma changes with the change in pulse width of a rectangular pulse waveform.

[0031] [Figure 12] FIG. 10 is a diagram of an embodiment of a graph to illustrate that the rate of transition between two states of an RF signal is greater than the rate of transition between two states of a rectangular pulse waveform. DETAILED DESCRIPTION OF THE INVENTION

[0032] The following embodiments describe systems and methods for controlling the pulse width of a rectangular pulse waveform. It will be apparent that the embodiments may be practiced without some or all of these specific details. In other instances, well-known operations have not been described in detail in order to not unnecessarily obscure the embodiments.

[0033] 1A is one embodiment of a graph 100 for illustrating a rectangular pulse waveform 102 having a pulse width 104. The graph 100 plots a parameter, such as power or voltage (V), of the rectangular pulse waveform 102 on the y-axis and time t on the x-axis, where time t is measured in seconds.

[0034] The rectangular pulse waveform 102 also has a sub-pulse width 110 and an inter-pulse width 112. As an example, the sub-pulse width 110 is the time interval, such as the average or median duration, between occurrences of each pulse of the rectangular pulse waveform 202. As an example, the inter-pulse width 112 is the time interval, such as the average or median duration, between two consecutive pulses of the rectangular pulse waveform 202 during a cycle of the clock signal.

[0035] An example of a rectangular pulse waveform described herein is a non-sinusoidal radio frequency (RF) signal having one or more pulses followed by a radio frequency (RF) voltage oscillation during a high state and no pulse during a low state. For illustrative purposes, during a high state, such as state S1 or the first state, of the rectangular pulse waveform, the rectangular pulse waveform has a series of a predetermined number of pulses, each of which is followed by a respective RF voltage oscillation. In illustrative examples, during the high state of the rectangular pulse waveform, the rectangular pulse waveform achieves a series of high amplitudes of a parameter a predetermined number of times, with each of the series of high amplitudes immediately followed by an RF voltage oscillation. In illustrative examples, the high amplitude includes the maximum amplitude of the rectangular pulse waveform. Also illustratively, the envelope, such as the amplitude, of the RF voltage oscillation is substantially smaller than the high amplitude. In illustrative examples, the high amplitude is at least 100% greater than the amplitude of the RF voltage oscillation. Also illustratively, each pulse of the rectangular pulse waveform is triangular-shaped and not sinusoidal. In the example, a rectangular pulse waveform gets its name from the substantially rectangular-shaped envelope that may surround each pulse of the rectangular pulse waveform. To further illustrate, rectangular pulse waveform 102 has a series of pulses 106A and 106B, with pulse 106A immediately followed by RF voltage oscillation 108A, and pulse 106B immediately followed by RF voltage oscillation 108B.

[0036] Continuing with the example, the RF voltage oscillation decreases over time from a higher amplitude to a lower amplitude. Further, in the example, the lower amplitude is output as the reduced amplitude. In the example, there is no pulse occurrence during a low state, such as state S0 or the second state, of the rectangular pulse waveform. Also, in the example, in the low state, the rectangular pulse waveform has a reduced amplitude or an amplitude less than the reduced amplitude. Furthermore, in the example, the amplitude of state S0 of the rectangular pulse waveform falls within a predetermined range, and the amplitude of the RF voltage oscillation preceding state S0 is outside the predetermined range.

[0037] A rectangular pulse waveform is relative to a sinusoidal RF signal in which the amplitude of the sinusoidal RF signal during each state of the sinusoidal RF signal is within a predetermined range. For example, the amplitude of a portion of the states of the sinusoidal RF signal is at least 100% less than or equal to the amplitude of the remaining portions of the states of the sinusoidal RF signal. As used herein, an example of amplitude is an envelope, such as a zero-to-peak amplitude or a peak-to-peak amplitude.

[0038] An example of a pulse width of a rectangular pulse waveform is the time interval, such as the statistical period, between each occurrence of one or more pulses, such as a series of pulses, of the rectangular pulse waveform and one or more RF voltage oscillations associated with the one or more pulses in state S1 of the rectangular pulse waveform. In this example, each of the one or more pulses precedes each of the RF voltage oscillations. For illustrative purposes, rectangular pulse waveform 102 has a pulse width 104 that includes the time interval between occurrences of pulses 106A and 106B and the time interval between occurrences of RF voltage oscillations 108A and 108B.

[0039] An example of an interpulse width of a rectangular pulse waveform is the time interval, such as a statistical period, between two consecutive pulses of a state of the rectangular pulse waveform. For illustrative purposes, the interpulse width is the time interval between when a first pulse of the rectangular pulse waveform is generated and when a second pulse of the rectangular pulse waveform is generated. In the illustrative example, the second pulse follows the first pulse, with no other pulses between the first and second pulses. Furthermore, in the illustrative example, both the first and second pulses are in the same state S1 of the rectangular pulse waveform. For further illustrative purposes, the interpulse width is the time interval between when the first pulse begins to transition from state S0 to state S1 and when the second pulse begins to transition from the RF voltage oscillation to state S1. In a further illustrative example, the RF voltage oscillation immediately follows the first pulse and precedes the second pulse. As another further example, the inter-pulse width is the time interval between the time when the first pulse begins to transition from the first plurality of RF voltage oscillations to the high amplitude of the rectangular pulse waveform state S1 and the time when the second pulse begins to transition from the second plurality of RF voltage oscillations to the high amplitude of the rectangular pulse waveform state S1. In a further example, the first plurality of RF voltage oscillations precedes the first pulse, and the second plurality of RF voltage oscillations immediately follows the first pulse and precedes the second pulse. An example of a statistical value is a mean value or a median value. For illustrative purposes, the statistical period is a mean time interval or a median time interval.

[0040] An example of a subpulse width is the time interval, such as a statistical period, during which each pulse of a rectangular pulse waveform is generated. For illustrative purposes, the subpulse width is the time interval between the time the pulse begins to transition from state S0 to state S1 and the time the pulse ends transitioning from state S1 to a plurality of RF voltage oscillations. In the illustrative example, the plurality of RF voltage oscillations immediately follows the pulse. As another illustrative example, the subpulse width is the time interval between the time the pulse begins to transition from a parameter amplitude of a first plurality of RF voltage oscillations to the high amplitude of state S1 and the time the pulse ends transitioning from the high amplitude of state S1 to a second plurality of RF voltage oscillations. In the illustrative example, the first plurality of RF voltage oscillations precede the pulse, and the second plurality of RF voltage oscillations immediately follow the pulse.

[0041] States S1 and S0 of the rectangular pulse waveform repeat during each cycle of the clock signal. For example, a first instance of state S1 and a first instance of state S0 occur during a first cycle of the clock signal, and a second instance of state S1 and a second instance of state S0 occur during a second cycle of the clock signal. The second cycle, in this example, is consecutive to the first cycle. For illustrative purposes, pulses 106A and 106B occur during cycle 1 of the clock signal, and pulses 114A and 114B of rectangular pulse waveform 102 occur during cycle 2 of the clock signal.

[0042] Note that the rectangular pulse waveforms described herein have a rate of transition from state S0 to state S1 that is greater than the rate of transition of the sinusoidal RF signal from state S0 to state S1. For example, rectangular pulse waveform 102 does not have a concave transition from state S0 to state S1. In this example, the concave transition has a concave envelope, such as a concave amplitude or an arc-shaped envelope. For illustration, the transition of rectangular pulse waveform 102 from state S0 to state S1 has an infinite slope, or a substantially infinite slope. For further illustration, pulse 106A achieves the amplitude of state S1 at the same time, or substantially the same time, that pulse 106A has the amplitude of state S0. As another illustration, the transition of pulse 106A from state S0 to state S1 has a linear slope. This is in comparison to the curved slope, such as the concave slope, of the transition of the sinusoidal RF signal from state S0 to state S1. As another example, a sinusoidal RF signal may have a large number of RF cycles, such as 8-12 cycles, to ramp up from state S0 to state S1 to achieve the power setpoint, and may take approximately 20 microseconds to achieve the power setpoint. In this example, the sinusoidal RF signal may have a large number of RF cycles, such as more than 20 RF cycles, to ramp down from state S1 to state S0. In this example, a large number of RF cycles in either the ramp up or ramp down would not allow for some operations to process a substrate.

[0043] Similarly, the rectangular pulse waveform has a rate of transition from state S1 to state S0 that is greater than the rate of transition of the sinusoidal RF signal from state S1 to state S0. For example, rectangular pulse waveform 102 does not have a transition from state S1 to state S0. For illustration, the transition of rectangular pulse waveform 102 from state S1 to state S0 has an infinite slope, or a substantially infinite slope. For further illustration, pulse 106B achieves the amplitude of state S1 at the same time, or substantially the same time, that pulse 106B has the amplitude of state S0. As another illustration, the transition of pulse 106B from state S1 to state S0 has a linear slope. This is in comparison to the curved slope, such as a concave slope, of the transition of the sinusoidal RF signal from state S1 to state S0.

[0044] The greater rate of transition allows a power setpoint received in a recipe signal, described below, to be achieved faster than by a generated sinusoidal RF signal. An example of a power setpoint includes a source power setpoint or a delivery power setpoint. For illustrative purposes, the delivered power is power provided by an RF generator, such as a low-frequency (LF) RF pulse generator, described below, or a high-frequency (HF) RF signal generator, also described below. An example of an LF is 400 kilohertz (kHz), and an example of an HF is 27 megahertz (MHz) or 60 MHz. Another example of an LF is 2 MHz, and another example of an HF is 27 MHz or 60 MHz. Yet another example of an LF is a frequency between 1 kHz and 800 kHz, inclusive. For illustrative purposes, an LF is a frequency of 10 kHz, or 100 kHz, or 400 kHz, or 800 kHz. The delivered power is the difference between the delivered power and the reflected power, which is the power reflected from the plasma chamber back to the RF generator.

[0045] It should be noted that state S0 of the sinusoidal RF signal includes a series of sine waves, and state S1 of the sinusoidal RF signal includes a series of sine waves. Furthermore, the amplitude of state S1 of the sinusoidal RF signal is greater than the amplitude of state S0 of the sinusoidal RF signal. For example, the amplitude of state S1 of the sinusoidal RF signal falls outside a preset range of the amplitude of state S0 of the sinusoidal RF signal.

[0046] In one embodiment, the terms RF voltage oscillation and RF oscillation are used interchangeably herein, for example, RF oscillation may be referred to herein as RF voltage oscillation.

[0047] In one embodiment, when the RF voltage oscillations are corrected, such as removed, they become flat. For example, the RF voltage oscillations are represented using horizontal lines. For illustrative purposes, the RF voltage oscillations may be referred to herein as flat portions.

[0048] 1B is an illustration of one embodiment of a graph 150 for illustrating states S1 and S0 of a rectangular pulse waveform 152, where state S0 has multiple pulses. Graph 150 plots a parameter of rectangular pulse waveform 152 on the y-axis and time t on the x-axis.

[0049] Graph 152 is similar to graph 100 (FIG. 1A), except that in graph 100, during state S0, rectangular pulse waveform 152 has multiple pulses, such as pulse 152A and pulse 152B, during state S0 of rectangular pulse waveform 152. Moreover, similar to state S1, each pulse during state S0 of rectangular pulse waveform 152 is followed by a respective RF oscillation, such as RF oscillation 154A and RF oscillation 154B. For example, pulse 152A is immediately followed by RF oscillation 154A, and pulse 152B is immediately followed by RF oscillation 154B. State S0 of rectangular pulse waveform 152 occurs during each cycle of the clock signal.

[0050] Like state S1 of rectangular pulse waveform 152, state S0 has an inter-pulse width and a sub-pulse width. For example, the inter-pulse width in state S0 is the time interval between the start of two consecutive pulses, such as pulses 152A and 152B, of rectangular pulse waveform 152. In this example, the sub-pulse width in state S0 is the time interval spanning the width of each pulse, such as pulse 152A or 152B, of rectangular pulse waveform 152.

[0051] The amplitude, such as the peak-to-peak amplitude or the zero-to-peak amplitude, of state S0 of the square pulse waveform 152 is less than the high amplitude of state S1 of the square pulse waveform 152. For example, the amplitude of state S0 of the square pulse waveform 152 is less than the amplitude of state S1 of the square pulse waveform 152 by at least 10%.

[0052] FIG. 2 is one embodiment of a graph 200 for illustrating a change, such as an increase, in pulse width. Graph 200 plots a parameter of a rectangular pulse waveform 202 versus time t. The parameter of rectangular pulse waveform 202 is plotted on the y-axis, and time t is plotted on the x-axis. As shown in graph 200, rectangular pulse waveform 202 has a pulse width 204 that is greater than pulse width 104 (FIG. 1A). For example, state S1 of rectangular pulse waveform 202 has four pulses, such as pulse 206A, pulse 206B, pulse 206C, and pulse 206D, and state S1 of rectangular pulse waveform 102 has two pulses, 106A and 106B (FIG. 1A). In this example, state S1 of rectangular pulse waveform 202 has a pulse width 204 that is twice the pulse width 104 (FIG. 1A). Additionally, rectangular pulse waveform 202 has state SO. In state S0, the rectangular pulse waveform 202 excludes the pulse but includes noise.

[0053] FIG. 3 is one embodiment of a graph 300 for illustrating a further change, such as an increase, in pulse width from pulse width 204 (FIG. 2). Graph 300 plots a parameter of a rectangular pulse waveform 302 versus time t. The parameter of rectangular pulse waveform 302 is plotted on the y-axis, and time t is plotted on the x-axis. As shown in graph 300, rectangular pulse waveform 302 has a pulse width 304 that is greater than pulse width 202. For example, state S1 of rectangular pulse waveform 302 has eight pulses, and state S1 of rectangular pulse waveform 202 has four pulses. In this example, state S1 of rectangular pulse waveform 302 has a pulse width 304 that is twice pulse width 204 (FIG. 2). Additionally, rectangular pulse waveform 302 has a state SO. In state SO, rectangular pulse waveform 302 excludes pulses but includes noise.

[0054] 4 is one embodiment of a graph 400 for illustrating a change, such as an increase, in pulse width compared to pulse width 304 (FIG. 3). Graph 400 plots a parameter of a rectangular pulse waveform 402 versus time t. The parameter of rectangular pulse waveform 402 is plotted on the y-axis, and time t is plotted on the x-axis. As shown in graph 400, rectangular pulse waveform 402 has a pulse width 404 that is greater than pulse width 304. For example, state S1 of rectangular pulse waveform 402 has a number of pulses greater than eight, and state S1 of rectangular pulse waveform 302 has eight pulses. In this example, state S1 of rectangular pulse waveform 402 has a pulse width 404 that is greater than pulse width 304.

[0055] Additionally, the rectangular pulse waveform 402 has a state SO, in which the rectangular pulse waveform 402 excludes the pulse but includes noise.

[0056] Note that each of the pulse widths 104, 204, 304, and 404 provides the same duty cycle. For example, the duty cycle of each of the rectangular pulse waveforms 102-402 is equal, such as 20 percent. For purposes of illustration, the duty cycle of a rectangular pulse waveform is the fraction of the period of a cycle of the clock signal during which the S1 state of the rectangular pulse waveform occurs.

[0057] In one embodiment, different duty cycles are provided by different pulse widths of different rectangular pulse waveforms.

[0058] FIG. 5A is a diagram of one embodiment of a system 500 to illustrate the use of an HF RF signal generator 502 to generate an RF signal 504 to be used with an LF RF pulse generator 506. The RF signal 504 is a continuous waveform. An example of a continuous waveform is a sinusoidal waveform that is not pulsed between states. For illustrative purposes, a continuous waveform has an envelope that does not transition from a high state to a low state or vice versa. For further illustrative purposes, the envelope of a continuous waveform is not a digitally pulsed signal. In the illustrative example, a continuous waveform is provided by the HF RF signal generator 502 rather than a multi-state sinusoidal RF signal due to the difference in the rate of transition between the multi-state sinusoidal RF signal and the rate of transition of the rectangular pulse waveform 538 generated by the LF RF pulse generator 506. In the illustrative example, the rate of transition between states of the multi-state sinusoidal RF signal is greater than the rate of transition between states of the rectangular pulse waveform 538. The system 500 includes an HF RF signal generator 502 , an impedance matching circuit (IMC) 508 , a plasma chamber 510 , an HF filter 512 , an LF RF pulse generator 506 , and a host computer 514 .

[0059] Examples of the host computer 514 include a desktop computer, a laptop computer, a tablet, a smartphone, and a controller. By way of example, the HF RF signal generator 502 has an operating high frequency of 27 megahertz (MHz) or 60 MHz. Also by way of example, the LF RF pulse generator 506 has an operating low frequency ranging from 10 kilohertz (kHz) to 800 kHz. For illustrative purposes, the low frequency is a baseline frequency of 400 kHz. For further illustrative purposes, the operating frequency of the LF RF pulse generator 506 is 400 kHz. An example of a baseline frequency is the fundamental frequency. By way of example, the HF filter 512 includes an inductor. By way of another example, the HF filter 512 is not an impedance matching circuit. By way of example, the HF filter 512 does not match the impedance of a load coupled to the output of the HF filter 512 with the impedance of a source coupled to the input of the HF filter 512. In the example, examples of a load coupled to the output of the HF filter 512 are the RF transmission line 516 and the plasma chamber 510. Further, in the illustrated example, examples of sources coupled to the input of HF filter 512 include RF cable 518 and LF RF pulse generator 506 .

[0060] Examples of the impedance matching circuit 508 include a matcher and an impedance matching network. For example, the impedance matching circuit 508 is a series of circuit components, such as a capacitor, an inductor, and a resistor. The circuit components are coupled to each other. For illustrative purposes, two of the circuit components are coupled to each other in series or parallel. The matcher matches the impedance of a load, such as the plasma chamber 510 and the RF transmission line 520, coupled to the output of the impedance matching circuit 508 with the impedance of a source coupled to the input of the impedance matching circuit 508. An example of a source coupled to the input of the impedance matching circuit 508 includes an RF cable 522 and an HF RF signal generator 502.

[0061] The plasma chamber 510 includes an upper electrode 524 and a substrate support 526. An example of the substrate support 526 includes an electrostatic chuck (ESC). The substrate support 526 includes a lower electrode. A substrate S, such as a semiconductor wafer, is placed on the upper surface of the substrate support 526 for processing in the plasma chamber 510.

[0062] The host computer 514 includes a processor 528 and a memory device 530. The processor 528 is coupled to the memory device 530. Examples of the processor 528 include an application specific integrated circuit (ASIC), a programmable logic device (PLD), and a central processing unit (CPU). Examples of the memory device 530 include a read only memory (ROM) and a random access memory (RAM).

[0063] The processor 528 is coupled to the input of the HF RF signal generator 502 via a transmission cable, which will be described below. The output of the HF RF signal generator 502 is coupled to the input of the impedance matching circuit 508 via an RF cable 522. The output of the impedance matching circuit 508 is coupled to the upper electrode 524 via an RF transmission line 522.

[0064] Additionally, processor 528 is coupled to an input of LF RF pulse generator 506 via a transfer cable 532. Examples of transfer cables include cables that allow serial transfer of data, parallel transfer of data, or transfer of data via a Universal Serial Bus (USB) protocol. An output of LF RF pulse generator 506 is coupled to an input of HF filter 512. An output of HF filter 512 is coupled to a lower electrode of substrate support 526 via RF transmission line 516.

[0065] Processor 528 generates recipe signal 534 and sends it to the input of LF RF pulse generator 506 via transfer cable 532. Recipe signal 534 includes information such as a predetermined number of pulses of rectangular pulse waveform 538 to be generated by LF RF pulse generator 506 during each cycle of a clock signal. As an example, processor 528 generates a clock signal and sends the clock signal to LF RF pulse generator 506 via transfer cable 534 and to HF RF signal generator 502. The predetermined number of pulses of rectangular pulse waveform 538 define pulse widths of states of rectangular pulse waveform 528. Furthermore, the information in recipe signal 534 includes statistical amplitudes of parameters of the predetermined number of pulses of rectangular pulse waveform 538 to be generated during each cycle of the clock signal. Examples of statistical amplitudes include mean amplitudes or median amplitudes. Furthermore, the information in recipe signal 534 includes statistical amplitudes of parameters of state S0 of rectangular pulse waveform 538. The information in recipe signal 534 also includes statistical pulse widths, such as pulse width 104 or 204 or 304 or 404 (FIGS. 1A, 2, 3, and 4), which are the time intervals between two consecutive pulses of a predetermined number of pulses in each cycle of the clock signal. Furthermore, the information in recipe signal 534 includes statistical sub-pulse widths, such as sub-pulse width 110 (FIG. 1A), of rectangular pulse waveform 538, and statistical inter-pulse widths, such as inter-pulse width 112 (FIG. 1A), of rectangular pulse waveform 538. Examples of rectangular pulse waveform 538 include rectangular pulse waveform 102 (FIG. 1A), rectangular pulse waveform 202 (FIG. 2), rectangular pulse waveform 302 (FIG. 3), and rectangular pulse waveform 402 (FIG. 4).

[0066] Additionally, the information in the recipe signal 534 includes a start time at which the first pulse of the rectangular pulse waveform 528 will be generated during each cycle of the clock signal. The first pulse is generated first in a series of pulses for the state of the rectangular pulse waveform 528. The start time or the number of pulses, or a combination thereof, for the state of the rectangular pulse waveform 528 provides a phase of the envelope of the multiple pulses for the state of the rectangular pulse waveform 528. For example, the start time at which the first pulse of the rectangular pulse waveform 528 will be generated is a phase, such as a time of transition, of the envelope from one parameter level to another. Also, in this example, the end time at which the last pulse in the series of pulses for the state of the rectangular pulse waveform 528 ends is another example of a phase of the envelope of the multiple pulses for the state of the rectangular pulse waveform 528. In this example, the end time at which the last pulse ends depends on the number of pulses in the series of pulses for the state of the rectangular pulse waveform 528.

[0067] The processor 528 also generates and sends a recipe signal 536 to the HF RF signal generator 502. The recipe signal 536 includes information on parameters of the RF signal 504 to be generated by the HF RF signal generator 502, such as a power level and a frequency level. An example of a frequency level is a fundamental frequency. An example of a power level is a peak-to-peak amplitude or a zero-to-peak amplitude. In one example, the recipe signal 506 includes a single value for the power level and a value for the frequency level. For illustrative purposes, the information in the recipe signal 536 indicates that the RF signal 506 is a continuous waveform having a single state. For further illustrative purposes, the information in the recipe signal 536 indicates that the RF signal 506 does not transition from a first state to a second state. In a further illustrative example, a first state of a multi-state sine wave signal has a power level that is different from a power level of a second state of the multi-state sine wave signal. In a further example, the rate of transition from the first state of the multi-state sine wave signal to the second state of the multi-state sine wave signal is less than the rate of transition from state S1 to state S0 of the rectangular pulse waveform 538, and the rate of transition from the second state of the multi-state sine wave signal is less than the rate of transition from state S0 to state S1 of the rectangular pulse waveform 538.

[0068] Upon receiving recipe signal 534, a processor in LF RF pulse generator 506 stores the information received in recipe signal 534 in a memory device of LF RF pulse generator 506. Similarly, upon receiving recipe signal 536, a processor in HF RF signal generator 502 stores the information received in recipe signal 536 in a memory device of HF RF signal generator 502.

[0069] Additionally, processor 528 generates a trigger signal and sends the trigger signal to HF RF signal generator 502 and to LF RF pulse generator 506 via transmission cable 532. An example of a trigger signal is a single pulse.

[0070] Upon receiving the trigger signal, a processor in LF RF pulse generator 506 accesses information received in recipe signal 534 from a memory device in LF RF pulse generator 506 and controls multiple signal components of LF RF pulse generator 506 to generate a rectangular pulse waveform 538 based on recipe signal 534. Examples of the signal components are provided below. LF RF pulse generator 506 sends rectangular pulse waveform 538 via RF cable 518 to an input of HF filter 512. HF filter 512 modifies the impedance of rectangular pulse waveform 538 to provide modified rectangular pulse waveform 540. As an example, modified rectangular pulse waveform 540 is similar in shape to or has the same shape as rectangular pulse waveform 538. For example, modified rectangular pulse waveform 540 has a series of pulses having a state S1 immediately followed by a state S0 with no pulse during each cycle of the clock signal. The HF filter 512 transmits the modified rectangular pulse waveform 540 via an RF transmission line 516 to the lower electrode of the substrate support 526 .

[0071] Similarly, upon receiving the trigger signal, the processor of the HF RF signal generator 502 accesses the information received in the recipe signal 536 from the memory device of the HF RF signal generator 502 and controls the RF power supply of the HF RF signal generator 502 to generate the RF signal 504 based on the recipe signal 536. The HF RF signal generator 502 transmits the RF signal 504 to an impedance matching circuit 508 via an RF cable 522. The impedance matching circuit 508 matches the impedance of a load coupled to the output of the impedance matching circuit 508 to the impedance of a source coupled to the input of the impedance matching circuit 508 to provide a modified RF signal 542. One example of the modified RF signal 542 is a continuous waveform that excludes more than a single state. For illustrative purposes, the modified RF signal 542 has a shape similar to or the same as the shape of the RF signal 504. The modified RF signal 542 is transmitted from the output of the impedance matching circuit 508 via an RF transmission line 520 to the upper electrode 524.

[0072] When one or more process gases are supplied to the plasma chamber 510 in addition to the modified RF signal 542 and the modified rectangular pulse waveform 540, a plasma is struck or maintained within the plasma chamber 510. Examples of the one or more process gases include an oxygen-containing gas, a fluorine-containing gas, and combinations thereof. The plasma is used to process the substrate S. Examples of processing the substrate S include depositing material on the substrate S, etching the substrate S, sputtering the substrate S, or cleaning the substrate S.

[0073] RF power is reflected from plasma chamber 510 through RF transmission line 516 to HF filter 512. HF filter 512 filters out high frequencies from the RF power and outputs a filtered signal. The filtered signal is provided from HF filter 512 to LF RF pulse generator 506 through RF cable 518. The filtered signal does not damage the components of LF RF pulse generator 506.

[0074] In one embodiment, in which the rectangular pulse waveform 152 ( FIG. 1B ) having multiple pulses in state S0 is to be generated by the LF RF pulse generator 506, another recipe signal (not shown) is generated by the processor 528. The information received in the other recipe signal (not shown) is the same as the information received in the recipe signal 534, except that the information in the other recipe signal (not shown) includes the statistical amplitude, such as the average amplitude or mean amplitude, of each pulse in state S0, a predetermined number of pulses in state S0, a subpulse width, such as the average subpulse width, of each pulse in state S0, and an interpulse width, such as the average interpulse width, between two consecutive pulses in state S0. Note that the statistical amplitude of state S0 is smaller than the statistical amplitude of state S1 of the rectangular pulse waveform 152. For example, the statistical amplitude of state S0 is at least 10% and at most 90% smaller than the statistical amplitude of state S1 of the rectangular pulse waveform 152.

[0075] 5B is a diagram of an embodiment of a system 550 to illustrate the use of an HF RF signal generator 502 used in conjunction with an LF RF pulse generator 506 to generate an RF signal 552. The RF signal 552 is a multi-state sinusoidal signal. System 550 is similar to system 500, except that in system 550, the HF RF signal generator 502 is coupled to the substrate support 526 through an impedance matching circuit 554, and the upper electrode 524 is coupled to ground potential.

[0076] An example of an impedance matching circuit is a network of circuit components, such as capacitors, inductors, or resistors, or a combination thereof. For illustrative purposes, the impedance matching circuit 554 includes an input I1, another input I2, an output O1, and a first branch circuit including a set of network components, such as capacitors and inductors, and a second branch circuit including a set of network components. The first branch circuit is coupled between the input I1 and the output O1, and the second branch circuit is coupled between the input I2 and the output O2.

[0077] The HF filter 512 is coupled to an input I1 of an impedance matching circuit 554 via an RF cable 560. The HF RF signal generator 502 is also coupled to an input I2 of the impedance matching circuit 554 via an RF cable 522. The output O1 of the impedance matching circuit 554 is coupled to the substrate support 526 via an RF transmission line 516.

[0078] Processor 528 generates and sends recipe signal 556 to HF RF signal generator 502. Recipe signal 556 includes information such as a duty cycle, multiple parameter levels, and a frequency level of the parameters of RF signal 552 to be generated by HF RF signal generator 502. In one example, recipe signal 556 includes multiple values ​​of the parameter levels, a first time of initiation of a transition from a first parameter level to a second parameter level, a second time of initiation of a transition from the second parameter level to the first parameter level, and a frequency level value. In this example, the period between the first time of initiation and the second time of initiation is the duty cycle of the envelope of the parameters of RF signal 552. For illustrative purposes, the information in recipe signal 556 indicates that RF signal 552 is a pulsed waveform having multiple states. To further illustrate, the information in recipe signal 556 indicates that RF signal 552 begins transitioning from a first state, such as a first parameter level, to a second state, such as a second parameter level, at a first time during startup, and that RF signal 552 begins transitioning from the second state to the first state at a second time during startup. In a further example, the first state of the multi-state sine wave signal has a first parameter level that is different from a second parameter level of the second state of the multi-state sine wave signal. In a further example, the first rate of transition from the first state of the multi-state sine wave signal to the second state of the multi-state sine wave signal is less than the rate of transition of rectangular pulse waveform 538 from state S1 to state S0, and the second rate of transition from the second state of the multi-state sine wave signal is less than the rate of transition of rectangular pulse waveform 538 from state S0 to state S1. Upon receiving recipe signal 556 , the processor of HF RF signal generator 502 stores the information received in recipe signal 556 in a memory device of HF RF signal generator 502 .

[0079] HF filter 512 transmits modified rectangular pulse waveform 540 via RF cable 560 to impedance matching circuit 554. Also, upon receiving the trigger signal, the processor of HF RF signal generator 502 accesses the information received in recipe signal 556 from a memory device of HF RF signal generator 502 and controls the RF power supply of HF RF signal generator 502 to generate RF signal 552 based on recipe signal 556. For example, RF signal 552 has the parameter levels received in recipe signal 556, a frequency level, and a duty cycle during each cycle of the clock signal.

[0080] An RF signal 552 is transmitted from the HF RF signal generator 502 through an RF cable 522 to an impedance matching circuit 554. The impedance matching circuit 554 matches the impedance of a load coupled to the output O1 of the impedance matching circuit 554 to the impedance of a source coupled to the inputs I1 and I2 of the impedance matching circuit 554 to output a modified signal 558 at the output O1 of the impedance matching circuit 554. Examples of sources coupled to the inputs I1 and I2 of the impedance matching circuit 554 include an RF cable 560, an HF filter 512, an RF cable 518, an LF RF pulse generator 506, an RF cable 522, and an HF RF signal generator 502. Examples of loads coupled to the output O1 of the impedance matching circuit 554 include an RF transmission line 516 and a plasma chamber 510. For illustrative purposes, a first branch of the impedance matching circuit 554 modifies the impedance of the modified rectangular pulse waveform 540 to output a modified rectangular pulse waveform at the output of the first branch, and a second branch modifies the impedance of the RF signal 552 to output a modified RF signal at the output of the second branch of the impedance matching circuit 554. In the illustrative example, the modified rectangular pulse waveform and the modified RF signal are combined, such as added, at output O1 to provide a modified signal 558. In the illustrative example, the first branch and the second branch are coupled to each other at output O1. The modified signal 558 is sent to the substrate support 526 via the RF transmission line 516. When one or more process gases are supplied to the plasma chamber 510 in addition to the modified signal 558, a plasma is struck or maintained within the plasma chamber 510.

[0081] In one embodiment, instead of coupling upper electrode 524 to ground potential, upper electrode 524 is floating in system 550. For example, upper electrode 524 is at a floating potential. By way of example, upper electrode 524 is not connected to ground potential or to a power source, such as HF RF signal generator 502.

[0082] 6 is an embodiment of a system 600 that includes a processor 528 and an LF RF pulse generator 506. The LF RF pulse generator 506 includes signal components 606 and a controller 608. The signal components 606 include a voltage and source regulator 610, a power storage 612, and a switch and converter system 614. As an example, the RF voltage oscillations described herein are noise due to one or more of the signal components 606.

[0083] An example of the voltage source and regulator 610 includes a combination of a voltage source, such as a direct current (DC) voltage source, and a voltage regulator, such as a variable resistor. The voltage source is coupled to the voltage regulator. An example of the switch and converter system 614 includes a combination of a switch, such as a solid-state switch, and a converter. An example of a solid-state switch is a transistor or a group of transistors. The solid-state switch is coupled to a converter. As an example, the converter includes a primary winding and a secondary winding. An example of the power storage device 612 includes a capacitor.

[0084] As one example, the controller 608 includes a processor 616 and a memory device 618. The processor 616 is coupled to the memory device 618. As another example, the controller 608 is an ASIC or a PLD.

[0085] The processor 616 is coupled to the processor 528 via the transfer cable 532. The processor 616 is coupled to the switches of the switch and converter system 614. The voltage regulator of the voltage source and regulator 610 is coupled to the power storage 612.

[0086] Additionally, a power storage device 612 is coupled to the converter, and a switch is coupled to the converter. For example, the power storage device 612 is coupled to a first end of a primary winding, and the switch is coupled to a second end of the primary winding. A secondary winding of the converter is coupled to the RF cable 518.

[0087] Upon receiving the information in the recipe signal 534 from the processor 528, the processor 616 stores the information in the memory device 618. The voltage supply generates a voltage signal and provides the voltage signal to the voltage regulator. The voltage regulator adjusts the voltage signal, such as maintaining the voltage signal to match a predetermined voltage signal, and outputs the adjusted voltage signal, which is sent to the power storage device 612. The power storage device 612 stores charge according to the adjusted voltage signal.

[0088] Furthermore, in response to receiving a trigger signal from processor 528 during cycle n of the clock signal, processor 616 accesses information received in recipe signal 534, such as the sub-pulse width, inter-pulse width, pulse width, start time, and predetermined number of pulses of rectangular pulse waveform 538, from the memory device of controller 306, generates an ON command signal, and sends the ON command signal to the switch at a start time, where n is a positive integer. When the ON command signal is received during cycle n of the clock signal, the switch is turned ON, and a switch current signal generated to discharge the charge stored in power storage 612 is supplied to the primary winding of the converter for a period of the sub-pulse width, such as sub-pulse width 110 (FIG. 1A). During cycle n of the clock signal, the secondary winding begins to convert the amount of voltage of the switch current signal to a different amount, such as increasing or decreasing, and output a voltage of the converted amount to generate a pulse, such as pulse 106A (FIG. 1A). The voltage of the converted amount is the voltage of the pulse.

[0089] During cycle n of the clock signal, at the end of the sub-pulse width period, processor 616 generates an OFF command signal and sends the OFF command signal to the switch. Also during cycle n, upon receiving the OFF command signal, the switch turns OFF and stops supplying the switch current signal to the primary winding. Also during cycle n, supply of the switch current signal stops, and the voltage applied by the switch current signal decreases, reducing the voltage across the primary winding. When the voltage across the primary winding decreases during cycle n, the converted voltage decreases, terminating the generation of a pulse having a sub-pulse width and outputting a reduced converted voltage. Also during cycle n, the reduced converted voltage is that of an RF voltage oscillation, such as RF voltage oscillation 108A (FIG. 1A), immediately following a pulse, such as pulse 106A (FIG. 1A).

[0090] Also, during cycle n of the clock signal, processor 616 controls the switch to be off until the end of an inter-pulse width period, such as inter-pulse width 112 (FIG. 1A). During cycle n of the clock signal, after the end of the inter-pulse width period, the processor of controller 306 controls the switch to be on again for a sub-pulse width period, such as sub-pulse width 110 (FIG. 1A), and further controls the switch to be off again at the end of the sub-pulse width period to complete the generation of successive pulses, such as pulse 106B (FIG. 1A). In this manner, multiple pulses of state S1 of square wave signal 538 and multiple RF voltage oscillations are generated during cycle n.

[0091] Moreover, after the switch is controlled to be turned off again at the end of the sub-pulse width period, the processor 616 controls the switch to remain off until the end of the period of cycle n of the clock signal. When the switch is off, an RF oscillation, such as RF oscillation 108B, occurs, followed by an additional RF oscillation, such as RF oscillation 116, of state S0 of a rectangular pulse waveform, such as rectangular pulse waveform 102. RF oscillation 116 transitions from a lower voltage, such as a negative voltage, to a higher voltage, such as a voltage closer to 0 volts, due to the discharge of capacitance in the substrate support 526 (FIG. 5A). The lower voltage is less than the higher voltage.

[0092] In a similar manner, the switches are controlled by processors 528 and 616 during each subsequent cycle of the clock signal, such as cycle (n+1), cycle (n+2), etc., to generate states S1 and S0 of the rectangular pulse waveform during each subsequent cycle of the clock signal. For example, upon receiving a clock signal indicating that cycle (n+1) of the clock signal has begun, processor 616 controls the switches to be on during cycle (n+1) to generate pulses such as pulses 114A and 114B.

[0093] To modify the pulse width, the information in recipe signal 534 is modified by processor 528 to increase or decrease a predetermined number of pulses. The information in recipe signal 534 is modified and outputs a modified recipe signal to processor 616. Upon receiving the modified recipe signal, processor 616 controls switch and converter system 614 to generate another rectangular pulse waveform, such as rectangular pulse waveform 202 (FIG. 2) or 302 (FIG. 3) or 402 (FIG. 4), based on the modified recipe signal in the same manner that rectangular pulse waveform 102 was generated based on recipe signal 534.

[0094] When the same duty cycle is to be maintained with an increase in the number of pulses of the rectangular pulse waveform 538 in each cycle of the clock signal, the processor 528 modifies the duration of each cycle of the clock signal. For example, to maintain the same duty cycle when the number of pulses of the rectangular pulse waveform 538 increases from two to four, the duration of each occurrence of the clock signal is increased by the same percentage as the percentage increase in the duration of the occurrence from two pulses to four pulses. For illustrative purposes, the duration of each occurrence of the clock signal increases by 100 percent when the number of pulses increases from two to four. In the example, the number of occurrences of pulses from two to four is a 100% increase.

[0095] In one embodiment in which a square pulse waveform 152 ( FIG. 1B ) is to be generated in which state S0 has multiple pulses, processor 528 sends another recipe signal (not shown) to processor 616 via transfer cable 532. Upon receiving the other recipe signal, processor 616 controls switches to be turned on and off to generate state S0 of square pulse waveform 152 in the same manner as state S1 of square pulse waveform 152 is generated, except that during state S0, the amplitude, such as peak-to-peak amplitude or zero-to-peak amplitude, of each pulse of state S0 of square pulse waveform 152 is less than the amplitude, such as high amplitude, of each pulse of state S1 of square pulse waveform 152.

[0096] 7A-1 is one embodiment of a graph 700 for illustrating a continuous waveform of RF signal 504 (FIG. 5A). Graph 700 plots a parameter of RF signal 504 versus time t. For example, an envelope 702 of RF signal 504 is plotted on the y-axis, and time t is plotted on the x-axis. The envelope 702, such as peak-to-peak amplitude or zero-to-peak amplitude, of graph 700 is constant or substantially constant.

[0097] 7A-2 is one embodiment of a graph 710 for illustrating the envelope 712 of the rectangular pulse waveform 538 (FIG. 6). The graph 710 plots the envelope 712 of the parameters of the rectangular pulse waveform 538 on the y-axis and time t on the x-axis. The envelope 712 encompasses multiple pulses of state S1 of the rectangular pulse waveform 538.

[0098] As shown, the envelope 712 is rectangular in shape during state S1. However, the statistical amplitude of the rectangular pulse waveform 538 during state S1 can be modified to achieve a rectangular envelope.

[0099] The envelope 712 has a variable pulse width. For example, the pulse width of state S1 of the envelope 712 can be modified by modifying the number of pulses in state S1 of the rectangular pulse waveform 538.

[0100] Also, envelope 712 has a phase 1. For example, during the first cycle of the clock signal, envelope 712 transitions from parameter level PR1 to parameter level PR2 at time t0 and transitions from parameter level PR2 back to parameter level PR1 at time t2. In this example, time t0 and time t2 are each an example of phase 1. Parameter level PR2 is greater than parameter level PR1, parameter level PR1 is a real number, and parameter level PR2 is a different real number. Note that envelope 712 remains at parameter level PR2 from time t0 to time t2 during the first cycle of the clock signal and remains at parameter level PR1 from time t2 to time t10. Time t0 is an example of a start time during the first cycle, and time t2 is an example of an end time during the first cycle. In a similar manner, pulsing, such as transitioning, between parameter levels PR1 and PR2 of envelope 712 repeats during each subsequent cycle, such as cycle 2, of the clock signal.

[0101] FIG. 7B-1 is one embodiment of a graph 720 for illustrating a parameter envelope 722 of an RF signal 724 generated by the HF RF signal generator 502 of FIG. 5B. The graph 720 plots the parameter level envelope 722 of the RF signal 724 on the y-axis and time t on the x-axis. The RF signal 724 is an example of an RF signal 552 (FIG. 5B). The HF RF signal generator 502 pulses the envelope 722 between a parameter level PRb and a parameter level −PRb, where PRb is a positive real number. The parameter level PRb is greater than a parameter level PRa, which is greater than the parameter level −PRb, where PRa is a positive real number. The HF RF signal generator 502 pulses between the parameter level PRb and the parameter level −PRb with level-to-level pulsing. Pulsing between parameter level PRb and parameter level -PRb is referred to as pulsing between parameter level PRa and parameter level PRb in zero-to-level pulsing.

[0102] During the first cycle of the clock signal, the RF signal 724 transitions starting at time t2 and continuing until time t3. The RF signal 724 transitions from parameter level PRa to parameter level PRb during the period between time t2 and time t3 and remains at parameter level PRb from time t3 to time t7. The RF signal 724 transitions starting at time t7 and continuing until time t8. The RF signal 724 transitions from parameter level PRb to parameter level PRa during the period between time t7 and time t8 during the first cycle of the clock signal and remains at parameter level PRa from time t8 to time t10. Similarly, the RF signal 724 transitions between parameter level PRa and parameter level PRb during each subsequent cycle of the clock signal, and during each subsequent cycle, the envelope 712 has a phase 1.

[0103] 7B-2 is one embodiment of a graph 730 for illustrating the change in phase of the envelope 712 of the rectangular pulse waveform 538 (FIG. 6) from Phase 1 to Phase 2. The graph 730 plots the envelope 712 of the parameter of the rectangular pulse waveform 538 on the y-axis and time t on the x-axis.

[0104] Envelope 712 has a phase 2 that is different from phase 1. For example, phase 2 lags phase 1. For illustration, during the first cycle of the clock signal, envelope 712 transitions from parameter level PR1 to parameter level PR2 at time t4 and transitions from parameter level PR2 back to parameter level PR1 at time t6. In this example, times t4 and t6 are each an example of phase 2. Also, time t4 is an example of a start time during the first cycle of the clock signal, and time t6 is an example of an end time during the first cycle. Note that envelope 712 remains at parameter level PR1 from time t0 to time t4, remains at parameter level PR2 from time t4 to time t6, and remains at parameter level PR1 from time t6 to time t10 during the first cycle of the clock signal. Similarly, pulsing, such as transitioning between parameter levels PR1 and PR2 of envelope 712, repeats during each subsequent cycle, such as cycle 2, of the clock signal, and during each subsequent cycle, envelope 712 has phase 2.

[0105] 7B-3 is one embodiment of a graph 740 for illustrating the change in phase of the envelope 712 of the rectangular pulse waveform 538 (FIG. 6) from phase 1 or phase 2 to phase 3. The graph 740 plots the envelope 712 of the parameter of the rectangular pulse waveform 538 on the y-axis and time t on the x-axis.

[0106] Envelope 712 has a phase 3 that is different from phase 1 and phase 2. For example, phase 3 lags phase 1 and leads phase 2. For illustration, during the first cycle of the clock signal, envelope 712 transitions from parameter level PR1 to parameter level PR2 at time t2 and transitions from parameter level PR2 back to parameter level PR1 at time t4. In this example, times t2 and t4 are each an example of phase 3. Also, time t2 is an example of a start time during the first cycle of the clock signal, and time t4 is an example of an end time during the first cycle. Note that envelope 712 remains at parameter level PR1 from time t0 to time t2, remains at parameter level PR2 from time t2 to time t4, and remains at parameter level PR1 from time t4 to time t10 during the first cycle of the clock signal. Similarly, pulsing, such as transitioning between parameter levels PR1 and PR2 of envelope 712, repeats during each subsequent cycle, such as cycle 2, of the clock signal, and during each subsequent cycle, envelope 712 has phase 3.

[0107] 7B-4 is one embodiment of a graph 740 for illustrating the change in phase of the envelope 712 of the rectangular pulse waveform 538 (FIG. 6) from phase 1 or phase 2 or phase 3 to phase 4. The graph 740 plots the envelope 712 of the parameter of the rectangular pulse waveform 538 on the y-axis and time t on the x-axis.

[0108] Envelope 712 has a phase 4 that is different from phase 1, phase 2, and phase 3. For example, phase 4 lags phase 1, phase 2, and phase 3. For illustration, during the first cycle of the clock signal, envelope 712 transitions from parameter level PR1 to parameter level PR2 at time t6 and transitions from parameter level PR2 back to parameter level PR1 at time t8. In this example, times t6 and t8 are each an example of phase 4. Also, time t6 is an example of a start time during the first cycle of the clock signal, and time t8 is an example of an end time during the first cycle. Note that envelope 712 remains at parameter level PR1 from time t0 to time t6, remains at parameter level PR2 from time t6 to time t8, and remains at parameter level PR1 from time t8 to time t10 during the first cycle of the clock signal. Similarly, pulsing, such as transitioning between parameter levels PR1 and PR2 of envelope 712, repeats during each subsequent cycle, such as cycle 2, of the clock signal, and during each subsequent cycle, envelope 712 has phase 4.

[0109] 7B-5 is one embodiment of a graph 750 for illustrating the change in phase of the envelope 712 of the rectangular pulse waveform 538 (FIG. 6) from phase 1 or phase 2 or phase 3 or phase 4 to phase 5. The graph 750 plots the envelope 712 of the parameter of the rectangular pulse waveform 538 on the y-axis and time t on the x-axis.

[0110] Envelope 712 has a phase 5 that is different from phase 1, phase 2, phase 3, and phase 4. For example, phase 5 lags phase 1, phase 2, phase 3, and phase 4. For illustration, during the first cycle of the clock signal, envelope 712 transitions from parameter level PR1 to parameter level PR2 at time t8 and transitions from parameter level PR2 back to parameter level PR1 at time t10. In this example, times t8 and t10 are each an example of phase 5. Also, time t8 is an example of a start time during the first cycle of the clock signal, and time t10 is an example of an end time during the first cycle. Note that envelope 712 remains at parameter level PR1 from time t0 to time t8 and remains at parameter level PR2 from time t8 to time t10 during the first cycle of the clock signal. Similarly, pulsing, such as transitioning between parameter levels PR1 and PR2 of envelope 712, repeats during each subsequent cycle, such as cycle 2, of the clock signal, and during each subsequent cycle, envelope 712 has phase 5.

[0111] Note that envelope 712 has phases 1 through 5 relative to the phase of envelope 720 (FIG. 7B-1). As an example, the period between time t2 and time t3 and the period between time t7 and time t8 are each an example of a phase of envelope 720.

[0112] 8 is one embodiment of a graph 800 for illustrating the variation of the etch rate (ER) of etching a substrate S with varying pulse width of a rectangular pulse waveform. Graph 800 plots etch rate on the y-axis and pulse width on the x-axis.

[0113] An example of a pulse width at point 802 on graph 800 is pulse width 104 (FIG. 1A), an example of a pulse width at point 804 on graph 800 is pulse width 204 (FIG. 2), and an example of a pulse width at point 806 is pulse width 404 (FIG. 4). As shown in graph 800, when there is a decrease in pulse width, there is an increase in etch rate.

[0114] 9 is one embodiment of a graph 900 for illustrating how selectivity for etching a layer of a substrate S varies with varying pulse width of a rectangular pulse waveform. Graph 900 plots selectivity on the y-axis and pulse width on the x-axis. As an example, selectivity is the ratio of the etch rate for etching a first layer of the substrate S to the etch rate for etching a second layer of the substrate S. The first layer will be etched at a greater rate compared to the second layer.

[0115] An example of a pulse width at point 902 on graph 900 is pulse width 104 (FIG. 1A), an example of a pulse width at point 904 on graph 900 is pulse width 204 (FIG. 2), and an example of a pulse width at point 906 is pulse width 404 (FIG. 4). As shown in graph 900, when there is an increase in pulse width, there is an increase in selectivity.

[0116] 10 is one embodiment of a graph 1000 for illustrating how the warpage growth rate of wafer bow of a substrate S varies with the pulse width of a rectangular pulse waveform. The graph 100 plots the warpage growth rate on the y-axis and the pulse width on the x-axis.

[0117] An example of a pulse width at point 1002 on graph 1000 is pulse width 104 (FIG. 1A), an example of a pulse width at point 1004 on graph 1000 is pulse width 204 (FIG. 2), and an example of a pulse width at point 1006 is pulse width 404 (FIG. 4). As shown in graph 1000, when there is an increase in pulse width, there is a decrease in the warpage growth rate.

[0118] 11 is a diagram illustrating the change in plasma electron temperature (Te) and plasma density in plasma chamber 510 (FIG. 5A) when the pulse width of a rectangular pulse waveform described herein is varied. For example, the pulse width is increased to increase the rate of change of electron temperature and increase the rate of change of plasma density. As another example, the pulse width is decreased to decrease the rate of change of electron temperature and decrease the rate of change of plasma density.

[0119] The changes in electron temperature and density modify the chemical composition of the plasma. As an example, decreasing the pulse width increases the density of reactants such as hydrogen, chlorine, fluorine, and bromine ions in the plasma and decreases the density of fluorocarbons (CFx) in the plasma. As another example, increasing the pulse width decreases the density of hydrogen, chlorine, fluorine, and bromine ions and increases the density of fluorocarbons. The chemical composition is modified to increase the uniformity of features produced within the substrate S.

[0120] Also, the pulse width of the square pulse waveform can be varied to increase the etch rate depending on the aspect ratio and etch depth, while the same gas chemistry is used while the pulse width is varied.

[0121] FIG. 12 is one embodiment of a graph 1200 for illustrating that the rate of transition between two states of an RF signal 1202 is greater than the rate of transition between two states of a rectangular pulse waveform, as described herein. Graph 1200 plots power versus time t of RF signal 1202. Power is plotted on the y-axis, and time t is plotted on the x-axis. RF signal 1202 transitions from state Sb to state Sa during a transition period TT(ba) and from state Sa to state Sb during a transition period TT(ab). Transition period TT(ab) is greater than the transition period of a transition from state S1 to state S0 of a rectangular pulse waveform, as described herein. As an example, the transition period of a transition from state S1 to state S0 of a rectangular pulse waveform, or transition period TT(ab), may be referred to herein as the ramp-down time. Furthermore, transition period TT(ba) is greater than the transition period of a transition from state S0 to state S1 of a rectangular pulse waveform, as described herein. As an example, the transition period, or transition period TT(ba), of the rectangular pulse waveform's transition from state S0 to state S1 may be referred to herein as the ramp-up time. The slower transition period associated with the RF signal 1202 creates a limitation that is eliminated by the use of rectangular pulsed waveforms described herein.

[0122] It should be noted that although the above embodiments are described with respect to rectangular pulse waveforms, in some embodiments the terms triangular pulse waveform, sawtooth pulse waveform, and rectangular pulse waveform are used interchangeably herein.

[0123] Generally, in various embodiments, a controller is defined as an electronic device having various integrated circuits, logic, memory, and / or software that receives instructions, issues instructions, controls operations, enables cleaning operations, enables endpoint measurements, etc. Integrated circuits include chips in the form of firmware that store program instructions, chips defined as digital signal processors (DSPs), ASICs, PLDs, and / or one or more microprocessors or microcontrollers that execute program instructions (e.g., software). Program instructions are instructions communicated to the controller in the form of various individual settings (or program files) that define parameters, factors, variables, etc. for performing a particular process on or for a semiconductor wafer or system. The program instructions, in some embodiments, are part of a recipe defined by a process engineer to accomplish one or more processing steps during the fabrication of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and / or dies of a wafer.

[0124] Without limitation, in various embodiments, exemplary systems to which the methods may be applied include a plasma etch chamber or module, a deposition chamber or module, a spin rinse chamber or module, a metal plating chamber or module, a cleaning chamber or module, a bevel edge etch chamber or module, a physical vapor deposition (PVD) chamber or module, a chemical vapor deposition (CVD) chamber or module, an atomic layer deposition (ALD) chamber or module, an atomic layer etch (ALE) chamber or module, an ion implantation chamber or module, a track chamber or module, and any other semiconductor processing system associated with or used in the fabrication and / or manufacturing of semiconductor wafers.

[0125] It is further noted that in some embodiments, the operations described above apply to several types of plasma chambers, such as plasma chambers including inductively coupled plasma (ICP) reactors, transformer coupled plasma chambers, plasma chambers including conductor tools, dielectric tools, electron cyclotron resonance (ECR) reactors, etc. For example, one or more RF generators are coupled to an inductor in an ICP reactor. Examples of inductor shapes include a solenoid, a dome-shaped coil, a flat-shaped coil, etc.

[0126] Some of the embodiments also relate to hardware units or apparatus for performing these operations. The apparatus is specially constructed for a special purpose computer. When defined as a special purpose computer, the computer is still capable of performing operations for its special purpose, while also performing other processes, program executions, or routines that are not part of its special purpose.

[0127] One or more embodiments may also be fabricated as computer-readable code on a non-transitory computer-readable medium. The non-transitory computer-readable medium is any data storage hardware unit, such as a memory device, that stores data, which is then 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. In some embodiments, the non-transitory computer-readable medium includes a computer-readable tangible medium that is distributed across network-coupled computer systems so that the computer-readable code is stored and executed in a distributed manner.

[0128] While the method operations above have been described in a particular order, it should be understood that in various embodiments, other housekeeping operations are performed between the operations, or the method operations are adjusted so that they occur at slightly different times or are distributed in a system that allows the method operations to occur at various intervals, or are performed in an order different from that described above.

[0129] Furthermore, it should be noted that in one embodiment, one or more features from any embodiment described above may be combined with one or more features of any other embodiment also described above without departing from the scope described in the various embodiments described in this disclosure.

[0130] Although the foregoing embodiments have been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. Accordingly, the present embodiments should be considered as illustrative rather than restrictive, and they should not be limited to the details given herein.

Claims

1. 1. A method for controlling the pulse width of a rectangular pulse waveform, comprising: generating the rectangular pulse waveform having a plurality of states, each of the plurality of states including a series of rectangular pulses; modifying the pulse width of each of the plurality of states to modify the rate at which the substrate is processed; A method comprising:

2. 10. The method of claim 1, wherein the rectangular pulse waveform is not a sine wave.

3. 2. The method of claim 1, wherein modifying the pulse width comprises increasing the number of the rectangular pulses to increase the period for which the rectangular pulses are applied.

4. 4. The method of claim 3, further comprising maintaining the same duty cycle while the number of rectangular pulses is increased.

5. 10. The method of claim 1, wherein the rectangular pulse waveform is supplied to a lower electrode of a plasma chamber through a high frequency filter, the method comprising: generating a sinusoidal continuous waveform; providing the sinusoidal continuous waveform to an impedance matching circuit coupled to an upper electrode of the plasma chamber; The method further comprises:

6. 6. The method of claim 5, wherein the impedance matching circuit does not receive a pulsed sinusoidal RF signal while the pulse width is being modified.

7. 2. The method of claim 1, wherein the series of rectangular pulses includes a first pulse and a second pulse.

8. 2. The method of claim 1, wherein a time of transition from one of a second plurality of states to one of a first plurality of states enables a power set point to be achieved at a first rate that is faster than a second rate, the second rate being of transition from a first state of a sinusoidal RF signal to a second state of the sinusoidal RF signal, wherein the power set point is achieved faster than achieving the power set point by applying the sinusoidal RF signal.

9. 10. The method of claim 1, wherein modifying the pulse width changes electron temperature and plasma density to modify a chemical composition of the plasma.

10. 10. The method of claim 9, wherein modifying the pulse width comprises: increasing the pulse width to increase the rate of change of the electron temperature and increase the rate of change of the plasma density; or Reducing the pulse width to decrease the rate of change of electron temperature and decrease the rate of change of plasma density. wherein the decrease in the pulse width increases a density of reactants and reduces a density of fluorocarbons (CFx), and the increase in the pulse width decreases the density of reactants and increases the density of fluorocarbons.

11. 10. The method of claim 1, Generating an RF signal that pulses between multiple parameter levels The method further comprises:

12. 12. The method of claim 11, providing the rectangular pulse waveform to a high frequency (HF) filter, the HF filter coupled to an impedance matching circuit, the impedance matching circuit coupled to a substrate support of a plasma chamber; supplying the RF signal to the impedance matching circuit, wherein the rectangular pulse waveform and the RF signal are supplied when an upper electrode of the plasma chamber is coupled to ground potential or is floating; The method further comprises:

13. 1. A controller for adjusting a pulse width of a rectangular pulse waveform, comprising: a processor configured to control a pulse generator to generate the rectangular pulse waveform having a plurality of states, each of the plurality of states comprising a series of rectangular pulses, the processor configured to control the pulse generator to modify the pulse width of each of the plurality of states to modify a rate at which substrates are processed; a memory device coupled to the processor; A controller comprising:

14. 14. The controller of claim 13, wherein the rectangular pulse waveform is not a sine wave.

15. 14. The controller of claim 13, wherein to modify the pulse width, the processor is configured to increase the number of square pulses to increase the period for which the square pulses are applied.

16. 16. The controller of claim 15, wherein the processor is configured to control the pulse generator to maintain the same duty cycle while the number of rectangular pulses increases.

17. 14. The controller of claim 13, wherein the rectangular pulse waveform is supplied to a lower electrode of a plasma chamber through a high frequency filter, and the processor is configured to control an RF signal generator to generate the sinusoidal continuous waveform to provide the sinusoidal continuous waveform to an impedance matching circuit coupled to an upper electrode of the plasma chamber.

18. 18. The controller of claim 17, wherein the impedance matching circuit does not receive a pulsed sinusoidal RF signal while the pulse width is being modified.

19. 1. A plasma system comprising: a low frequency (LF) radio frequency (RF) pulse generator; a high frequency (HF) RF signal generator; an HF filter coupled to the LF RF pulse generator; an impedance matching circuit coupled to the HF RF signal generator; a plasma chamber coupled to the HF filter and the impedance matching circuit; a controller coupled to the LF RF pulse generator and the HF RF signal generator; wherein the controller controlling the LF RF pulse generator to generate a rectangular pulse waveform having a plurality of states, each of the plurality of states comprising a series of rectangular pulses; controlling the LF RF pulse generator to modify the pulse width of each of the plurality of states to modify the rate at which substrates are processed; A plasma system configured to:

20. 20. The plasma system of claim 19, wherein the rectangular pulse waveform is not sinusoidal.

21. 21. The plasma system of claim 20, wherein to modify the pulse width, the controller is configured to increase the number of square pulses to increase the duration for which the square pulses are applied.

22. 22. The plasma system of claim 21, wherein the controller is configured to control the pulse generator to maintain the same duty cycle while the number of rectangular pulses increases.

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