Plasma system and method for using a square pulse signal

Abstract

A system for processing a substrate using a square wave signal is described. The system includes a first pulse generator generating a first square wave signal at a first frequency. The system further includes a first filter filtering a second frequency from interference with the first square wave signal to provide a first filter output signal. The first filter provides the first filter output signal to an electrode of a plasma chamber via a first transmission line. The system includes a second pulse generator generating a second square wave signal at a third frequency. The system also includes a second filter filtering the second frequency from interference with the second square wave signal to provide a second filter output signal. The second filter provides the second filter output signal to an edge ring of the plasma chamber via a second transmission line.

Description

[Technical field]

[0001] The present embodiment relates to a system and method for using a square pulse signal. [Background technology]

[0002] Generally, a capacitively coupled parallel plate plasma etching apparatus includes a chamber in which a pair of parallel plate electrodes, such as an upper electrode and a lower electrode, are disposed. A radio frequency (RF) signal is applied to at least one of the electrodes to form an electric field between the electrodes while a process gas is supplied into the chamber. The process gas is conditioned into a plasma by the RF signal, thereby performing plasma etching on a predetermined layer disposed on a semiconductor wafer. However, an etching rate for etching the predetermined layer may not be achieved.

[0003] The background description provided herein is intended to provide a general overview of the contents of the present disclosure. Work by the currently named inventors within the scope of what is described in this Background section, as well as aspects of the description that may not otherwise be regarded as prior art at the time of filing, are not admitted, expressly or impliedly, as prior art against the present disclosure. Summary of the Invention

[0004] The embodiments of the present disclosure provide a system, an apparatus, a method, and a computer program for using a square pulse signal. It should be understood that the embodiments can be implemented in various ways, such as a process, an apparatus, a system, a device, or a method on a computer-readable medium. Some embodiments are described below.

[0005] In one embodiment, a system for processing a substrate using a square pulse signal is described. The system includes a first pulse generator that generates a first square wave signal at a first frequency. The system further includes a first filter that receives the first square wave signal and filters a second frequency from interference with the first square wave signal to provide a first filter output signal. The first filter provides the first filter output signal to an electrode disposed in the plasma chamber via a first radio frequency (RF) transmission line. The system includes a second pulse generator that generates a second square wave signal at a third frequency. The system also includes a second filter that receives the second square wave signal and filters the second frequency from interference with the second square wave signal to provide a second filter output signal. The second filter provides the second filter output signal to an edge ring disposed in the plasma chamber via a second RF transmission line.

[0006] In one embodiment, a system for processing a substrate using a square pulse signal is described. The system includes a first pulse generator that generates a first square wave signal at a first frequency. The system further includes a first filter that receives the first square wave signal and filters a second frequency from interference with the first square wave signal to provide a first filter output signal. The system includes an RF generator that generates an RF signal. The system also includes an impedance matching circuit that receives the RF signal and outputs a modified signal based on the RF signal. The system includes an RF transmission line coupled to the first filter and the impedance matching circuit and that receives the first filter output signal and the modified signal. The RF transmission line combines the first filter output signal and the modified signal to output a combined signal. The combined signal is provided to a lower electrode disposed within the plasma chamber.

[0007] In one embodiment, a method for processing a substrate using a square pulse signal is described. The method includes generating a first square wave signal at a first frequency and filtering a second frequency from interference with the first square wave signal to output a first filter output signal. The method further includes generating a second square wave signal at a third frequency and filtering the second frequency from interference with the second square wave signal to output a second filter output signal. The method includes providing the first filter output signal to an electrode of a plasma chamber and providing the second filter output signal to an edge ring of the plasma chamber.

[0008] Some advantages of the systems and methods described herein for using square pulse signals include increasing the processing speed of semiconductor substrates such as wafers. Instead of RF signals, square pulse signals are used to etch semiconductor substrates. By using square pulse signals, the number of ions with large amounts of ion energy is increased compared to the number of ions generated using RF signals. Thus, the processing speed is increased.

[0009] Further advantages of the systems and methods described herein for using square pulse signals include achieving uniformity across the entire top surface of a semiconductor substrate. A first square wave signal is provided to an electrode of a plasma chamber, and a second square wave signal is provided to an edge ring of the plasma chamber. One or more parameter characteristics, such as frequency, phase, and magnitude of a parameter of the second square wave signal are adjusted until the parameter is within a predetermined range from the parameter of the first square wave signal to achieve uniformity. Further advantages of the systems and methods described herein for using square pulse signals include adjusting the parameters of the first square wave signal and the parameters of the second square wave signal to achieve a predetermined processing speed.

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

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

[0012] [Figure 1] FIG. 1 is a diagram of one embodiment of a system for generating a square wave.

[0013] [Figure 2A] FIG. 2A is a diagram of an embodiment of another system illustrating the generation of a square wave for processing a substrate.

[0014] [Figure 2B] FIG. 2B is a diagram of one embodiment of a system that is similar to the system of FIG. 2A, except that in the system of FIG. 2B, the high frequency (HF) filter is located in the filter housing and the HF radio frequency (RF) match is located in the matching housing.

[0015] [Figure 3A] FIG. 3A shows one embodiment of a graph illustrating a square wave signal generated by a LF RF pulse generator.

[0016] [Figure 3B] FIG. 3B shows an embodiment of a graph illustrating another square wave signal generated by another LF RF pulse generator.

[0017] [Figure 3C] FIG. 3C is an illustration of an embodiment of a graph illustrating an RF signal generated by an HF RF generator.

[0018] [Figure 3D] FIG. 3D shows one embodiment of a graph illustrating a clock signal.

[0019] [Figure 4A] FIG. 4A is a diagram illustrating one embodiment of an inductor that illustrates an HF filter.

[0020] [Figure 4B] FIG. 4B is a diagram illustrating one embodiment of a parallel circuit illustrating the HF filter.

[0021] [Diagram 5] FIG. 5 is a flow chart illustrating one embodiment of a method for achieving uniformity across the surface of a substrate.

[0022] [Figure 6A] FIG. 6A is an illustration of one embodiment of a graph illustrating a plot of voltage of an RF signal generated by a 400 kilohertz (kHz) RF generator versus time.

[0023] [Figure 6B] FIG. 6B is an illustration of one embodiment of a graph illustrating a plot of the envelope of a number of ions of a plasma generated when the 400 kHz RF generator illustrated with reference to FIG. 6A is used.

[0024] [Figure 7A] FIG. 7A is an illustration of one embodiment of a graph illustrating a plot of the voltage of a square wave signal output from a sensor as a parameter signal.

[0025] [Figure 7B] FIG. 7B is an illustration of one embodiment of a graph illustrating a plot of the envelope of a number of ions of a plasma generated when a LF RF pulse generator is used to generate the square wave signal illustrated with reference to FIG. 7A.

[0026] [Figure 8] FIG. 8 is a diagram of one embodiment of a LF RF pulse generator.

[0027] [Figure 9A] FIG. 9A is an illustration of one embodiment of a graph illustrating contact etch rate for a square wave signal and a sinusoidal RF signal.

[0028] [Figure 9B] FIG. 9B is an illustration of one embodiment of a graph illustrating contact critical dimension (CD) growth rates for square wave and sinusoidal RF signals. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] The following embodiments describe systems and methods for using square pulse signals. 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 so as not to unnecessarily obscure the embodiments.

[0030] 1 is a diagram of one embodiment of a system 100 for generating a square wave. System 100 includes a low frequency (LF) radio frequency (RF) pulse generator 102, another LF RF pulse generator 114, a high frequency (HF) filter 106, another HF filter 118, a plasma chamber 112, a host computer 128, an HF RF generator (RFG) 138, and an HF RF match 140.

[0031] An example of a pulse generator is a square pulse generator that periodically generates high voltage nanosecond pulses. In one embodiment, the pulse generator is a nanosecond pulser. An example of a nanosecond pulser is described in U.S. Patent Application Publication No. 2015 / 0130525.

[0032] Examples of low frequencies include frequencies in the range of 10 kilohertz (kHz) to 800 kHz. Illustratively, the low frequency is a baseline frequency of 400 kHz. Illustratively, the operating frequency of LF RF pulse generator 102 or 114 is 400 kHz. Illustratively, the operating frequency of LF RF pulse generator 102 is the same as the operating frequency of LF RF pulse generator 114. Illustratively, both LF RF pulse generators 102 and 114 operate at a baseline frequency of 400 kHz. Illustratively, the operating frequency of LF RF pulse generator 102 is different from the operating frequency of LF RF pulse generator 114. Illustratively, the LF RF pulse generator 102 operates at a baseline frequency of 100 kHz and the LF RF pulse generator 114 operates at a baseline frequency of 400 kHz.

[0033] Examples of high frequencies include frequencies in the range of 13 megahertz (MHz) to 120 MHz. For example, the high frequency is a baseline frequency of 13.56 MHz, or 27 MHz, or 40 MHz, or 60 MHz, or 100 MHz. By way of example, the operating frequency of the HF RF generator 138 is 60 MHz. The high frequency is greater than the low frequency. For example, the low frequency is 400 kHz and the high frequency is 60 MHz. As another example, the low frequency is 100 kHz and the high frequency is 60 MHz.

[0034] Examples of the host computer 128 include a desktop computer, a laptop computer, a tablet, a smartphone, and a controller. The host computer 128 includes a processor 142 and a memory device 144. By way of example, the processor 142 can be an application specific integrated circuit (ASIC), a central processing unit (CPU), a field programmable gate array (FPGA), a programmable logic device (PLD), an integrated controller, or a microcontroller. Examples of the memory device 144 include a read only memory (ROM) and a random access memory (RAM). By way of example, the memory device 144 is a flash memory or a redundant array of independent disks (RAID). The processor 142 is coupled to the memory device 144.

[0035] An example of a matcher is an impedance matching circuit or an impedance matching network. For example, a matcher is a series of circuit components such as a capacitor, an inductor, and a resistor. The circuit components are coupled to each other. For example, two of the circuit components are coupled to each other in series or parallel.

[0036] The plasma chamber 112 includes a substrate support 136, such as an electrostatic chuck (ESC). The plasma chamber 112 further includes an upper electrode 146 located above the substrate support 136 and forming a gap 148 between the upper electrode 146 and the substrate support 136. The upper electrode 146 faces the substrate support 136. A lower electrode 158 embedded within the substrate support 136 is made of a metal, such as aluminum or an aluminum alloy. The substrate support 136 is made of a metal and a ceramic, such as aluminum oxide (Al2O3). The upper electrode 146 is fabricated from a metal.

[0037] The plasma chamber 112 also includes an edge ring 122, such as a variable edge sheath (TES) ring, surrounding the substrate support 136. By way of example, the edge ring 122 is fabricated from a conductive material, such as silicon, boron-doped single crystal silicon, silicon carbide, a silicon alloy, or a combination thereof. It is noted that the edge ring 122 has an annular body, such as a circular body, a ring-shaped body, or a dish-shaped body. By way of example, the edge ring 122 has an inner radius and an outer radius, the inner radius being greater than the radius of the substrate support 136. One example of the plasma chamber 112 is a capacitively coupled plasma (CCP) chamber.

[0038] The system 100 further includes a sensor 154 coupled to a point PT1 on the RF rod of the RF transmission line RFT1. Examples of the sensor 154 include a voltage sensor and a power sensor. The system 100 also includes a sensor 156 coupled to a point PT2 on the RF rod of the RF transmission line RFT2. Examples of the sensor 156 include a voltage sensor and a power sensor.

[0039] The sensors 154 and 156 are coupled to the processor 142. For example, the sensor 154 is coupled to the processor 142 via a first transmission cable, and the sensor 156 is coupled to the processor 142 via a second transmission cable.

[0040] The processor 142 is coupled to the LF RF pulse generator 102 via a transmission cable TC1. The processor 128 is also coupled to the LF RF pulse generator 114 via another transmission cable TC2. The processor 142 is coupled to the HF RF generator 138 via a transmission cable TC3. Examples of transmission cables include cables that allow serial transmission of data, or cables that allow parallel transmission of data, or cables that allow transmission of data using the Universal Serial Bus (USB) protocol.

[0041] An output O102 of the LF RF pulse generator 102 is coupled to an input I106 of the HF filter 106 via an RF cable RFC1, and an output O106 of the HF filter 106 is coupled to the lower electrode 158 via an RF transmission line RFT1. For example, there is no impedance matching circuit between the LF RF pulse generator 102 and the lower electrode 158. By way of example, the impedance matching circuit includes a network of circuit components such as capacitors and inductors. By way of further example, the impedance matching circuit includes a number of branch circuits and a number of series circuits. The impedance matching circuit matches the impedance of a load coupled to the output of the impedance matching circuit with the impedance of a source coupled to the input of the impedance matching circuit. The impedance is matched to modify the impedance of a signal received by the impedance matching circuit, which outputs a modified signal.

[0042] Similarly, an output O114 of the LF RF pulse generator 114 is coupled to an input I118 of the HF filter 118 via RF cable RFC2, and an output O118 of the HF filter 118 is coupled to the edge ring 122 via RF transmission line RFT2. For example, there is no impedance matching circuit between the LF RF pulse generator 114 and the edge ring 122. Also, an output O138 of the HF RF generator 138 is coupled to an input I140 of the HF RF matcher 140 via RF cable RFC3, and an output O140 of the HF RF matcher 140 is coupled to the upper electrode 146 via RF transmission line RFT3.

[0043] An example of an RF cable includes a coaxial cable having a center conductor surrounded by an RF cover. As an example, each of the RF cables RFC1 and RFC2 is capable of transmitting a square wave signal having a voltage ranging from 100 volts to 20 kilovolts (kV). An example of an RF transmission line includes an RF rod surrounded by an RF tunnel with an insulator between the RF rod and the RF tunnel. The RF tunnel is sometimes referred to herein as an RF ground. The RF rod, the RF ground, and the insulator are components of an RF transmission line. Another example of an RF transmission line includes a combination of one or more RF straps, an RF rod, and an RF ground. In this example, the one or more RF straps are coupled to the RF rod. Also, in this example, the RF rod is surrounded by an RF ground.

[0044] The processor 142 generates a command signal 160 having parameters and transmits the command signal 160 to the LF RF pulse generator 102 via the transmission cable TC1. Examples of parameters used herein include voltage and power. The parameters have characteristics such as magnitude, frequency, and phase. Examples of the magnitude of the parameter include peak-to-peak magnitude and zero-to-peak magnitude. Upon receiving the parameters from the processor 142, the LF RF pulse generator 102 stores the parameters in one or more memory devices of the LF RF pulse generator 102.

[0045] Processor 142 also transmits a synchronization signal 166 via transmission cable TC1 to LF RF pulse generator 102 and also transmits a synchronization signal 166 via transmission cable TC2 to LF RF pulse generator 114. One example of a synchronization signal 166 is a signal having a single digital or trigger pulse.

[0046] Upon receiving the synchronization signal 166, the LF RF pulse generator 102 generates the square wave signal 104 based on the parameters and provides the square wave signal 104 at the output O102. The square wave signal 104 increases the directivity and number of ions of the plasma toward the central region of the substrate S compared to a non-square wave signal. As the directivity and number of ions increases, the central region is processed at a faster rate. For example, the central region is etched at a faster rate, or material is deposited on the central region at a faster rate, or the central region is cleaned at a faster rate.

[0047] The square wave signal 104 is transferred to the input I 106 via the RF cable RFC1. The HF filter 106 filters, e.g., reduces or removes, high frequencies to reduce or prevent the high frequencies from interfering with the low frequencies of the square wave signal 104 to output the signal 108 at the output O 106. Thus, the HF RF filter 106 protects the LF RF pulse generator 102 from adverse effects or damage due to the high frequencies. By way of example, the high frequencies are received by the HF filter 106 from the upper electrode 146 via the gap 148, the electrode 158, and the RF transmission line RFT1. One example of the filter output signal 108 is a square wave signal. By way of example, the filter output signal 108 has the same or similar shape as the square wave signal 104. The filter output signal 108 is transferred to the lower electrode 158 via the RF transmission line RFT1.

[0048] In a similar manner, processor 142 generates command signals 162 having the parameters and transmits command signals 162 over transmission cable TC2 to LF RF pulse generator 114. Upon receiving the parameters from processor 142, LF RF pulse generator 114 stores the parameters in one or more memory devices of LF RF generator 114.

[0049] Upon receiving the synchronization signal 166, the LF RF pulse generator 114 generates the square wave signal 116 based on the parameters and provides the square wave signal 116 at the output O114. The square wave signal 116 increases the directivity and number of ions of the plasma toward the edge region of the substrate S compared to a non-square wave signal. As the directivity and number of ions increases, the edge region is etched at a higher etch rate. It should be noted that the central region of the substrate S does not include the edge region and vice versa. For example, the edge region is a portion of the central region. As another example, the edge region is located around or on the periphery of the central region.

[0050] As an example, the square wave signal described herein includes main pulses, each having a width in the range of 10 nanoseconds (ns) to 500 ns and a rise time of approximately 50 ns. By way of example, each main pulse of the square wave signal has a rise time in the range of 40 ns to 60 ns.

[0051] The square wave signal 116 is transferred to the input I 118 via the RF cable RFC2. The HF filter 118 filters, e.g., reduces or removes, high frequencies to reduce or prevent the high frequencies from interfering with the low frequencies of the square wave signal 116 to output a signal 120 at the output O 118. As an example, the high frequencies are received by the HF filter 118 from the top electrode 146 via the gap 148, the edge ring 122, and the RF transmission line RFT2. The filter output signal 120 is transferred to the edge ring 122 via the RF transmission line RFT2. An example of the filter output signal 120 is a square wave signal. Illustratively, the filter output signal 120 has the same or similar shape as the shape of the square wave signal 116.

[0052] Additionally, the processor 142 generates a command signal 164 including the parameters and transmits the command signal 164 to the HF RF generator 138 via the transmission cable TC3. Upon receiving the parameters, the HF RF generator 138 stores the parameters in one or more memory devices of the HF RF generator 138. The processor 142 also transmits a synchronization signal 166 to the HF RF generator 138 via the transmission cable TC3.

[0053] Upon receiving the synchronization signal 166, the HF RF generator 138 generates the RF signal 150 based on the parameters and provides the RF signal 150 at the output O138. The RF signal 150 is transferred to the input I140 via the RF cable RFC3. The HF RF matcher 140 matches the impedance of the load coupled to the output O140 with the impedance of the source coupled to the input I140 to modify the impedance of the RF signal 150. An example of a source coupled to the input I140 includes the RF cable RFC3 and the HF RF generator 138. An example of a load coupled to the output O140 includes the RF transmission line RFT3 and the plasma chamber 112. The impedance of the RF signal 150 is modified to output a modified RF signal 152 at the output O140. The modified RF signal 152 is transferred to the upper electrode 146 via the RF transmission line RFT3.

[0054] When one or more process gases are provided to the gap 148 in addition to the filter output signals 108 and 120 and the modified RF signal 152, a plasma is generated or maintained in the gap 148 to process the substrate S. Examples of processing the substrate S include etching the substrate S, or depositing one or more material layers on the substrate S, or cleaning the substrate S, or sputtering the substrate S. Examples of the one or more process gases include an oxygen-containing gas, a fluorine-containing gas, and combinations thereof. Examples of the substrate S include a semiconductor wafer and a substrate stack. Illustratively, the substrate stack includes one or more layers, such as a metal layer and an oxide layer. The substrate stack further includes a substrate layer on which one or more layers are fabricated to form one or more integrated circuits on the substrate layer.

[0055] While the substrate S is being processed, the sensor 154 measures a parameter of the filter output signal 108 at the point PT1 and generates the parameter signal 130. For example, the parameter of the parameter signal 130 is the same as the parameter of the filter output signal 108. Illustratively, the frequency of the parameter signal 130 is the same as the frequency of the filter output signal 108, the phase of the parameter signal 130 is the same as the phase of the filter output signal 108, and the magnitude of the parameter signal 130 is the same as the magnitude of the filter output signal 108.

[0056] The parameter signal 130 is transmitted from the sensor 154 to the processor 142. The processor 142 determines whether a parameter of the parameter signal 130 is within a predetermined range from a predetermined parameter. For example, the processor 142 applies a Fourier transform to the parameter signal 130 to determine a frequency band. The processor 142 further calculates a statistic, such as a moving average or a moving median, from the frequency of the band to determine the frequency of the parameter signal 130. In this example, the processor 142 determines whether the frequency of the parameter signal 130 is within a predetermined frequency range from a predetermined frequency. Furthermore, in this example, the processor 142 determines whether the phase of the parameter signal 130 is within a predetermined phase range from a predetermined phase. In this example, the processor 142 determines the phase of the parameter signal 130 by determining the time when the magnitude of the parameter signal 130 is at a predetermined parameter value. Also, in this example, the processor 114 determines the magnitude of the parameter signal 130 and determines whether the magnitude is within a predetermined magnitude range from a predetermined magnitude.

[0057] Upon determining that the parameters of the parameter signal 130 are within a predetermined range from the predetermined parameters, the processor 142 determines not to modify the parameters of the square wave signal 104 generated by the LF RF pulse generator 102. For example, in response to determining that the frequency of the parameter signal 130 is within a predetermined frequency range from a predetermined frequency, the phase of the parameter signal 130 is within a predetermined phase range from a predetermined phase, and the magnitude of the parameter signal 130 is within a predetermined magnitude range from a predetermined magnitude, the processor 142 determines not to change the parameters of the square wave signal 104. Illustratively, the processor 142 does not generate an additional command signal that is different from the command signal 160. For example, the processor 142 does not generate an additional command signal that includes parameters that are different from the parameters included in the command signal 160. Thus, the LF RF pulse generator 102 continues to generate and transmit the square wave signal 104.

[0058] Meanwhile, in response to determining that a parameter of the parameter signal 130 is not within a predetermined range from a predetermined parameter, the processor 142 determines to modify a parameter of the square wave signal 104. For example, in response to determining that the frequency of the parameter signal 130 is not within a predetermined frequency range from a predetermined frequency, or that the phase of the parameter signal 130 is not within a predetermined phase range from a predetermined phase, or that the magnitude of the parameter signal 130 is not within a predetermined magnitude range from a predetermined magnitude, the processor 142 determines to change a parameter of the square wave signal 104.

[0059] Illustratively, processor 142 generates an additional command signal including parameters different from the parameters included in command signal 160. Illustratively, in response to determining that the frequency of parameter signal 130 is not within a predetermined frequency range from a predetermined frequency, processor 114 determines to modify the frequency of square wave signal 104. Illustratively, in response to determining that the phase of parameter signal 130 is not within a predetermined phase range from a predetermined phase, processor 114 determines to modify the phase of square wave signal 104. Illustratively, in response to determining that the magnitude of parameter signal 130 is not within a predetermined magnitude range from a predetermined magnitude, processor 142 determines to modify the magnitude of square wave signal 104.

[0060] Upon receiving an additional command signal from the processor 142 regarding the modification of the square wave signal 104, the LF RF pulse generator 102 generates an additional square wave signal based on a different parameter. In this manner, the processor 142 continues to control the LF RF pulse generator 102 until the parameter of the parameter signal received from the sensor 154 is within a predetermined range from the predetermined parameter. When the parameter signal received from the sensor 154 is within a predetermined range from the predetermined parameter, a predetermined rate of processing the central region of the substrate S is achieved. For example, the central region of the substrate S is etched or material is deposited on the substrate S at a predetermined rate.

[0061] Additionally, while substrate S is being processed, sensor 156 measures a parameter of filter output signal 120 at point PT2 and generates parameter signal 132. By way of example, the parameter of parameter signal 132 is the same as the parameter of filter output signal 120. By way of example, the frequency of parameter signal 132 is the same as the frequency of filter output signal 120, the phase of parameter signal 132 is the same as the phase of filter output signal 120, and the magnitude of parameter signal 132 is the same as the magnitude of filter output signal 120.

[0062] The parameter signal 132 is transmitted from the sensor 156 to the processor 142. The processor 142 determines whether a parameter of the parameter signal 132 is within a predetermined range from a predetermined parameter. For example, the processor 142 applies a Fourier transform to the parameter signal 132 to determine a frequency band. In this example, the processor 142 further calculates a statistic, such as a moving average or a moving median, from the frequency of the band to determine the frequency of the parameter signal 132. Also, in this example, the processor 142 determines whether the frequency of the parameter signal 132 is within a predetermined frequency range from a predetermined frequency. Furthermore, in this example, the processor 142 determines whether the phase of the parameter signal 132 is within a predetermined phase range from a predetermined phase. In this example, the processor 142 determines the phase of the parameter signal 132 by determining the time when the magnitude of the parameter signal 132 is at a predetermined parameter value. Also, in this example, the processor 142 determines the magnitude of the parameter signal 132 and determines whether the magnitude is within a predetermined magnitude range from a predetermined magnitude.

[0063] Upon determining that the parameters of parameter signal 132 are within a predetermined range from the predetermined parameters, processor 142 determines not to modify the parameters of square wave signal 116 generated by LF RF pulse generator 114. For example, in response to determining that the frequency of parameter signal 132 is within a predetermined frequency range from a predetermined frequency, the phase of parameter signal 132 is within a predetermined phase range from a predetermined phase, and the magnitude of parameter signal 132 is within a predetermined magnitude range from a predetermined magnitude, processor 142 determines not to change the parameters of parameter signal 132. Illustratively, processor 142 does not generate a further command signal that is different from command signal 162. For example, processor 142 does not generate a further command signal that includes parameters that are different from the parameters included in command signal 162. Thus, LF RF pulse generator 114 continues to generate and transmit square wave signal 116.

[0064] On the other hand, in response to determining that the parameter of parameter signal 132 is not within a predetermined range from the predetermined parameter, processor 142 determines to modify a parameter of square wave signal 116 generated by LF RF pulse generator 114. For example, in response to determining that the frequency of parameter signal 132 is not within a predetermined frequency range from a predetermined frequency, or that the phase of parameter signal 132 is not within a predetermined phase range from a predetermined phase, or that the magnitude of parameter signal 132 is not within a predetermined magnitude range from a predetermined magnitude, processor 142 determines to change the parameter of square wave signal 116.

[0065] Illustratively, processor 142 generates an additional command signal including parameters different from the parameters included in command signal 162. Illustratively, in response to determining that the frequency of parameter signal 132 is not within a predetermined frequency range from a predetermined frequency, processor 142 determines to modify the frequency of square wave signal 116. Illustratively, in response to determining that the phase of parameter signal 132 is not within a predetermined phase range from a predetermined phase, processor 142 determines to modify the phase of square wave signal 116. Illustratively, in response to determining that the magnitude of parameter signal 132 is not within a predetermined magnitude range from a predetermined magnitude, processor 142 determines to modify the magnitude of square wave signal 116.

[0066] Upon receiving further instructions from processor 142 regarding modifications to square wave signal 116, LF RF pulse generator 114 generates additional square wave signals based on different parameters. In this manner, processor 142 continues to control LF RF pulse generator 114 until the parameter of the parameter signal received from sensor 156 is within a predetermined range of the predetermined parameter. When the parameter signal received from sensor 156 is within a predetermined range of the predetermined parameter, a predetermined rate of processing substrate S is achieved.

[0067] In one embodiment, the sensor 154 is coupled to any point on the RF transmission line RFT1 between the output O106 and the bottom electrode 158. For example, the sensor 154 is coupled to the output O106 or to an internal point on the RF rod of the RF transmission line RFT1. The internal point is located within an enclosure, such as a housing of the plasma chamber 112. As an example, the housing of the plasma chamber 112 includes a top wall TW of the plasma chamber 112, a bottom wall BW of the plasma chamber 112, and a side wall SW of the plasma chamber 112. The side wall SW is attached to the top wall TW at one end of the side wall SW and to the bottom wall BW at the other end of the side wall SW.

[0068] Similarly, in one embodiment, the sensor 156 is coupled to any point on the RF transmission line RFT2 between the output O 118 and the edge electrode 122. For example, the sensor 156 is coupled to the output O 118 or to an internal point on the RF rod of the RF transmission line RFT2, the internal point being located within the enclosure of the plasma chamber 112.

[0069] In one embodiment, the terms matcher, impedance matching circuit, and impedance matching network are used interchangeably herein.

[0070] In one embodiment, instead of being coupled to RF transmission line RFT3, the top electrode 146 is coupled to a reference potential, such as ground or a negative voltage.

[0071] In one embodiment, the square wave signal may be referred to herein as a square pulse signal, or a square waveform, or a square RF waveform, for example, a square or substantially square shape is formed between two successive main pulses of the square wave signal.

[0072] 2A is a diagram of one embodiment of a system 200 illustrating the generation of a square wave for processing a substrate S. System 200 is similar to system 100, except that in system 200, upper electrode 146 is coupled to a reference potential and lower electrode 158 is coupled to an HF RF generator 138 via an HF RF match 140.

[0073] The system 200 includes a host computer 128, an LF RF pulse generator 102, an HF RF generator 138, an LF RF pulse generator 114, a filter and matcher 215, an HF filter 118, and sensors 154 and 156. The filter and matcher 215 includes an HF filter 106 and an HF RF matcher 140. For example, the filter and matcher 215 is a housing that surrounds the HF filter 106 and the HF RF matcher 140. Illustratively, the electrical circuit components of the HF filter 106 and the HF RF matcher 140 are enclosed by the housing of the filter and matcher 215. As an example, the housing of the filter and matcher 215 is fabricated from a metal such as aluminum or an aluminum alloy.

[0074] RF cable RFC1 extends through port 216 of filter and matcher 215 and couples to input I106. RF cable RFC3 also extends through port 218 of filter and matcher 215 and couples to input I140. RF transmission line RFT1 also extends through port 220 of filter and matcher 215 and couples to output O106. RF connection 210 extends through port 222 of filter and matcher 215 and couples to output O140. By way of example, the ports are openings.

[0075] An output O140 of the HF RF matcher 140 is coupled to a point PT3 on the RF rod of the RF transmission line RFT1 via an RF connection 210. One example of the RF connection 210 includes an RF strap. Another example of the RF connection 210 includes two or more RF straps coupled together. Another example of the RF connection 210 includes a combination of one or more RF straps and an RF transmission line. Illustratively, a first RF strap of the RF connection 210 is coupled to the output O140 and a first end of the RF rod of the RF transmission line. In this illustrative example, a second RF strap of the RF connection 210 is coupled to a second end of the RF rod and to a point PT3.

[0076] Point PT3 is also coupled to output O106 of HF filter 106. Sensor 154 is coupled to point PT4 on the RF rod of RF transmission line RFT1. Point PT4 is located between point PT3 and bottom electrode 158.

[0077] In operation, the HF RF matcher 140 matches the impedance of a load coupled to the output O140 with the impedance of a source coupled to the input I140. An example of a load coupled to the output O140 includes the RF connection 210, a portion of the RF transmission line RFT1 between point PT3 and the lower electrode 158, and the plasma chamber 112. The impedance is matched to output a modified RF signal 213 at the output O140.

[0078] The modified RF signal 213 is transferred from output O140 to point PT4 via RF connection 210. The filter output signal 108 is combined, e.g., summed or added, with the modified RF signal 213 at point PT4 to output a combined signal 212 at point PT4. For example, the magnitude of the filter output signal 108 is added to the magnitude of the modified RF signal 213 at point PT4. The combined signal 212 is transferred from point PT4 to the bottom electrode 158 via a portion of the RF rod of the RF transmission line RFT1 between point PT3 and the bottom electrode 158.

[0079] When the combined signal 212 is provided to the bottom electrode 158, the filtered output signal 120 is provided to the edge ring 122, and one or more process gases are provided to the gap 148 to process the substrate S, the sensor 154 measures a parameter of the combined signal 212 at the point PT4 and generates a parameter signal 214. For example, the parameter of the parameter signal 214 is the same as the parameter of the combined signal 212. Illustratively, the frequency of the parameter signal 214 is the same as the frequency of the combined signal 212, the phase of the parameter signal 214 is the same as the phase of the combined signal 212, and the magnitude of the parameter signal 214 is the same as the magnitude of the combined signal 212. As another example, both the combined signal 212 and the parameter signal 214 are square wave signals. The parameter signal 214 is transmitted from the sensor 154 to the processor 142.

[0080] The processor 142 determines whether the parameter of the parameter signal 214 is within a predetermined range from a predetermined parameter. For example, the processor 142 applies a Fourier transform to the parameter signal 214 to determine a frequency band. The processor 142 further calculates a statistic, such as a moving average or a moving median, from the frequency of the band to determine the frequency of the parameter signal 214. In this example, the processor 142 determines whether the frequency of the parameter signal 214 is within a predetermined frequency range from a predetermined frequency. Furthermore, in this example, the processor 142 determines whether the phase of the parameter signal 214 is within a predetermined phase range from a predetermined phase. In this example, the processor 142 determines the phase of the parameter signal 214 by determining the time at which the magnitude of the parameter signal 214 becomes a predetermined parameter value. Also, in this example, the processor 142 determines the magnitude of the parameter signal 214 and determines whether the magnitude is within a predetermined magnitude range from a predetermined magnitude.

[0081] Upon determining that the parameters of parameter signal 214 are within a predetermined range from the predetermined parameters, processor 142 determines not to modify the parameters of square wave signal 104 generated by LF RF pulse generator 102, or the parameters of RF signal 150 generated by HF RF generator 138, or both parameters. For example, in response to determining that the frequency of parameter signal 214 is within a predetermined frequency range from a predetermined frequency, the phase of parameter signal 214 is within a predetermined phase range from a predetermined phase, and the magnitude of parameter signal 214 is within a predetermined magnitude range from a predetermined magnitude, processor 142 determines not to change the parameters of square wave signal 104 and not to change the parameters of RF signal 150. Illustratively, processor 142 does not generate an additional command signal that is different from command signal 160 and does not generate a next command signal that is different from command signal 164. For example, processor 142 does not generate a next command signal that includes parameters that are different from the parameters included in command signal 164. Thus, the LF RF pulse generator 102 continues to generate and transmit the square wave signal 104 , and the HF RF generator 138 continues to generate and transmit the RF signal 150 .

[0082] On the other hand, in response to determining that the parameter of parameter signal 214 is not within a predetermined range from the predetermined parameter, processor 142 determines to modify the parameter of square wave signal 102, the parameter of RF signal 150, or both parameters. For example, in response to determining that the frequency of parameter signal 214 is not within a predetermined frequency range from a predetermined frequency, or the phase of parameter signal 214 is not within a predetermined phase range from a predetermined phase, or the magnitude of parameter signal 214 is not within a predetermined magnitude range from a predetermined magnitude, processor 142 determines to change the parameter of square wave signal 102, the parameter of RF signal 150, or both parameters.

[0083] To illustrate, the processor 142 generates an additional command signal, or a next command signal, or a combination thereof. In this example, the next command signal includes a different parameter than the parameter included in the command signal 164. To further illustrate, in response to determining that the frequency of the parameter signal 214 is not within a predetermined frequency range from a predetermined frequency, the processor 142 determines to change the frequency of the square wave signal 104, or the frequency of the RF signal 150, or a combination thereof. Also, in response to determining that the phase of the parameter signal 214 is not within a predetermined phase range from a predetermined phase, the processor 114 determines to change the phase of the square wave signal 104, or the phase of the RF signal 150, or a combination thereof. Furthermore, in response to determining that the magnitude of the parameter signal 210 is not within a predetermined magnitude range from a predetermined magnitude, the processor 142 determines to change the magnitude of the square wave signal 104, or the magnitude of the RF signal 150, or a combination thereof.

[0084] Upon receiving the next command signal from processor 142 for a change in RF signal 150, HF RF generator 138 generates the next RF signal based on the different parameter. In this manner, processor 142 continues to control LF RF pulse generator 102, or HF RF generator 138, or both LF RF pulse generator 102 and HF RF generator 138, until the parameter of the parameter signal received from sensor 154 is within a predetermined range of the predetermined parameter.

[0085] In one embodiment, the RF connection 210 is located within the filter and matcher 215. In this embodiment, the point PT3 is located within the filter and matcher 215 or is co-located with the location of the port 220. For example, the connection point PT3 between the RF connection 210 and the RF rod of the RF transmission line RFT1 is surrounded by the port 220.

[0086] 2B is a diagram of one embodiment of a system 250. System 250 is similar to system 200, except that in system 250, HF filter 106 is located in a filter housing 252 and HF RF matcher 140 is located in a matcher housing 254. By way of example, each housing 252 and 254 is fabricated from a metal, such as aluminum or an aluminum alloy. Note that host computer 128 is not shown in system 250 so as not to clutter FIG. 2B.

[0087] RF cable RFC1 extends through port 256 of filter housing 252 and couples to input I106. RF transmission line RFT1 also extends through port 258 of filter housing 252 and couples to output O106. Similarly, RF cable RFC2 extends through port 260 of matcher housing 254 and couples to input I140. RF connection 210 also extends through port 262 of matcher housing 254 and couples to output O140. The functionality of system 250 is the same as that described above with reference to system 200.

[0088] 3A is one embodiment of a graph 300 illustrating the square wave signal 104 generated by the LF RF pulse generator 102 (FIG. 1). The graph 300 includes parameters of the square wave signal 104 versus time t. The parameters of the square wave signal 104 are plotted on the y-axis and time t is plotted on the x-axis.

[0089] The square wave signal 104 has a peak-to-peak amplitude 302, which is the amplitude between a maximum value 304 of the square wave signal 104 and a minimum value 308 of the square wave signal 104. The peak-to-peak amplitude 302 is the difference between the maximum value 304 and the minimum value 308. As an example, the peak-to-peak amplitude 302 is in the range of 8 kilovolts (kV) to 10 kV.

[0090] During each cycle of the clock signal, a main pulse occurs in the square wave signal 104. For example, during a first cycle, such as cycle 1, of the clock signal, a main pulse 310A occurs. During a second cycle, such as cycle 2 of the clock signal, in this example, another main pulse 310B occurs.

[0091] It should be noted that during each cycle of the clock signal, the main pulse of the square wave signal 104 is followed by a small variation in voltage. For example, during the first cycle, the main pulse 310A is followed by a small variation in voltage 306. During the second cycle, the main pulse 310B is followed by a small variation in voltage 314. An example of each small variation is a small deformation, or a small waveform, or a sinusoidal waveform, or a sinusoidal RF waveform. The small variation in voltage may be referred to herein as a voltage variation. As another example, during each cycle of the clock signal, the peak-to-peak amplitude of the voltage variation of the square wave signal 104 is less than the peak-to-peak amplitude of the main pulse of the square wave signal 104.

[0092] It is further noted that each voltage variation of the square wave signal 104 has a similar shape, such as a sinusoidal shape. For example, each voltage variation of the square wave signal 104 is a sinusoidal waveform. Also, by way of example, each main pulse of the square wave signal 104 has an approximately triangular or sawtooth shape. By way of example, the main pulse 310A has a triangular shape with a deformation in which two sides of the triangle form local peaks. By way of further example, the main pulse 310A has a local peak 311A ​​and a local peak 311B formed by its first side, and a local peak 311C formed by its second side. The local peaks of the main pulse of the square wave signal 104 have a lower amplitude than the maximum value 304 of the square wave signal 104.

[0093] Furthermore, each main pulse of square wave signal 104 during a cycle of the clock signal has a maximum value that is substantially greater than the maximum value of the voltage fluctuation occurring during the cycle. For example, main pulse 310A has a maximum value that is 7 to 10 times greater than maximum value 316 of voltage fluctuation 306.

[0094] The square wave signal 104 includes a number of square waves, each occurring during a corresponding cycle of the clock signal. For example, a square wave of the square wave signal 104 includes a main pulse and a small voltage variation following the main pulse.

[0095] In one embodiment, the frequency of the square wave signal 104 is a statistical value, such as a moving average or moving median, of the frequencies of the voltage fluctuations and main pulses of the square wave signal 104. For example, the frequency of the square wave signal 104 is a moving average of the frequencies of the voltage fluctuations 306 and 314 and the main pulses 310A and 310B.

[0096] In one embodiment, the phase of the square wave signal 104 during a cycle of the clock signal is the time when the main pulse of the square wave signal 104 has a predetermined magnitude. For example, the phase of the square wave signal 104 during cycle 1 is the time t 312A when the main pulse 310A during cycle 1 has a maximum magnitude, such as a maximum value. As another example, the phase of the square wave signal 104 during cycle 1 is the time when the magnitude of the square wave signal 104 is zero.

[0097] In one embodiment, the phase of the square wave signal 104 is a statistical value, such as a moving average or a moving median, of all phases of the square wave signal 104 during a predetermined number of cycles of the clock signal. For example, the phase of the square wave signal 104 over cycles 1 and 2 is a moving average of times t312B and t312C where the main pulses 310A and 310B have the same magnitude, such as zero. The times t312B and t312C are normalized to calculate the moving average. To illustrate, the time interval between the start time of cycle 1 and time t312B matches the time interval between the start time of cycle 2 and time 312C, normalizing the times t312B and t312C.

[0098] In one embodiment, the magnitude of the square wave signal 104 is the peak-to-peak amplitude 302 of the square wave signal 104 .

[0099] It is further noted that in one embodiment, the maximum value 304 is a statistical value, such as a moving average or moving median, generated based on the maximum values ​​of the main pulse of the square wave signal 104 during a predetermined number of cycles of the clock signal. For example, the maximum value 304 is the average of the maximum values ​​of the main pulses 310A and 310B. In this example, the maximum value 304 changes to the average of the maximum value of the main pulse 310B and the maximum value of the main pulse of the square wave signal 104 during cycle 3 of the clock signal. It is noted that cycle 2 of the clock signal is consecutive to cycle 1 of the clock signal, and cycle 3 of the clock signal is consecutive to cycle 2.

[0100] Similarly, in this embodiment, the minimum value 308 is a statistical value, such as a moving average or a moving median, generated based on the minimum values ​​of the square wave signal 104 over a predetermined number of cycles. For example, the minimum value 308 is an average of the minimum values ​​of the voltage fluctuation 306 and the main pulse 310A. As another example, the minimum value 308 is an average of the minimum values ​​of the voltage fluctuation 314 and the main pulse 310B.

[0101] 3B is one embodiment of a graph 320 illustrating the square wave signal 116 generated by the LF RF pulse generator 114 (FIG. 1). The graph 320 includes parameters of the square wave signal 116 versus time t. The parameters of the square wave signal 116 are plotted on the y-axis and time t is plotted on the x-axis.

[0102] The square wave signal 116 has a peak-to-peak amplitude 322, which is the amplitude between a maximum value 324 of the square wave signal 116 and a minimum value 326 of the square wave signal 116. The peak-to-peak amplitude 322 is the difference between the maximum value 324 and the minimum value 326. As an example, the peak-to-peak amplitude 322 is in the range of 7 kV to 10 kV.

[0103] During each cycle of the clock signal, a main pulse occurs in the square wave signal 116. For example, during the first cycle, a main pulse 328A occurs, and during the second cycle, another main pulse 328B occurs.

[0104] It should be noted that during each cycle of the clock signal, the main pulse is followed by multiple voltage fluctuations of the square wave signal 116. For example, during a first cycle, the voltage fluctuation 330 of the square wave signal 116 immediately follows the main pulse 328A of the square wave signal 116. During a second cycle, the multiple voltage fluctuations 334 of the square wave signal 116 immediately follow the main pulse 328B of the square wave signal 116. As another example, during each cycle of the clock signal, the peak-to-peak amplitude of the voltage fluctuations of the square wave signal 116 is less than the peak-to-peak amplitude of the main pulse of the square wave signal 116.

[0105] It is further noted that each voltage variation of the square wave signal 116 has a similar shape, such as a sinusoidal shape. For example, each voltage variation of the square wave signal 116 is a sinusoidal waveform. Also, each main pulse of the square wave signal 116 has an approximately triangular shape or a sawtooth shape. By way of example, the main pulse 328A has a triangular shape with a deformation in which two sides of the triangle form local peaks. By way of further example, the main pulse 328A has a local peak 329A and a local peak 329B formed by its first side, and a local peak 329C formed by its second side. The local peaks of the main pulse of the square wave signal 116 have an amplitude lower than the maximum value 324 of the square wave signal 116.

[0106] Furthermore, each main pulse of square wave signal 116 during a cycle of the clock signal has a maximum value that is substantially greater than the maximum value of the voltage fluctuation occurring during the cycle. For example, main pulse 328A has a maximum value that is 7 to 10 times greater than maximum value 336 of voltage fluctuation 330.

[0107] In one embodiment, the frequency of the square wave signal 116 is a statistical value, such as a moving average or moving median, of the frequencies of the voltage fluctuations and main pulses of the square wave signal 116. For example, the frequency of the square wave signal 116 is a moving average of the frequencies of the voltage fluctuations 330 and 334 and the main pulses 328A and 328B.

[0108] In one embodiment, the phase of the square wave signal 116 during a cycle of the clock signal is the time when the main pulse during that cycle has a predetermined magnitude. For example, the phase of the square wave signal 116 during cycle 1 is the time t 332A when the main pulse 328A during cycle 1 has a maximum magnitude, such as a maximum value. As another example, the phase of the square wave signal 116 during cycle 1 is the time when the magnitude of the square wave signal 116 is zero.

[0109] In one embodiment, the phase of the square wave signal 116 is a statistical value, such as a moving average or a moving median, of all phases during a predetermined number of cycles of the clock signal. For example, the phase of the square wave signal 116 over cycles 1 and 2 is a moving average of times t332B and t332C where the main pulses 328A and 328B have the same magnitude, such as zero. The times t332B and t332C are normalized to calculate the moving average. To illustrate, the time interval between the start time of cycle 1 and time t332B matches the time interval between the start time of cycle 2 and time 332C, normalizing the times t332B and t332C.

[0110] In one embodiment, the magnitude of the square wave signal 116 is the peak-to-peak amplitude 322 of the square wave signal 116 .

[0111] It is further noted that in one embodiment, maximum value 324 is a statistical value, such as a moving average or moving median, generated from the maximum values ​​of the main pulse of square wave signal 116 during a predetermined number of cycles of the clock signal. For example, maximum value 324 is the average of the maximum values ​​of main pulses 328A and 328B. In this example, maximum value 324 changes to the average of the maximum value of main pulse 328B and the maximum value of the main pulse of square wave signal 116 during cycle 3.

[0112] Similarly, in this embodiment, minimum 326 is a statistical value, such as a moving average or moving median, generated from the minimum values ​​of square wave signal 116 over a predetermined number of cycles. For example, minimum 326 is an average of the minimum values ​​of voltage fluctuation 330 and main pulse 328A. As another example, minimum 326 is an average of the minimum values ​​of voltage fluctuation 334 and main pulse 328B.

[0113] 3C is an illustration of an embodiment of a graph 340 illustrating an RF signal 342 generated by HF RF generator 138 (FIG. 1). RF signal 342 is an example of RF signal 150 (FIG. 1). Graph 340 includes parameters of RF signal 150 versus time t. The parameters of RF signal 342 are plotted on the y-axis and time t is plotted on the x-axis.

[0114] The RF signal 342 has a peak-to-peak amplitude 342, which is the amplitude between a maximum value 344 of the RF signal 342 and a minimum value 346 of the RF signal 342. The peak-to-peak amplitude 342 is the difference between the maximum value 344 and the minimum value 346.

[0115] Note that during each cycle of the clock signal, there are multiple sinusoidal waveforms of the RF signal 342. For example, there is not a low peak-to-peak voltage waveform and a high peak-to-peak voltage main pulse during each cycle. As another example, each sinusoidal waveform of the RF signal 342 has a similar shape, such as a sine wave shape.

[0116] It is further noted that in one embodiment, maximum value 344 is a statistical value, such as a moving average or moving median, generated from the maximum values ​​of RF signal 342 over a predetermined number of cycles of the clock signal. For example, maximum value 344 is the average of the maximum values ​​of the sinusoidal waveform of RF signal 342 during cycle 1. In this example, maximum value 344 changes to the average of the maximum values ​​of the sinusoidal waveform of RF signal 342 during cycle 2, and then changes to the average of the maximum values ​​of the sinusoidal waveform of RF signal 342 during cycle 3.

[0117] Similarly, in this embodiment, minimum value 346 is a statistical value, such as a moving average or moving median, generated from the minimum values ​​of RF signal 342 over a predetermined number of cycles. For example, minimum value 346 is the average of the minimum values ​​of the sinusoidal waveform of RF signal 342 during cycle 1. As another example, minimum value 346 is the average of the minimum values ​​of the sinusoidal waveform of RF signal 342 during cycle 2.

[0118] 3D is one embodiment of a graph 350 illustrating a clock signal 352. Graph 350 plots the logic levels of clock signal 352 on the y-axis and time t on the x-axis. Time t includes times t0, t2, t3, t4, t5, t6, etc., in chronological order of occurrence. Clock signal 352 transitions periodically between logic level 1 and logic level 0. For example, during cycle 1 of clock signal 352, clock signal 352 transitions from logic level 0 to logic level 1 at time t0 and transitions from logic level 1 to logic level 0 at time t1. During cycle 2 of clock signal 352, clock signal 352 transitions from logic level 0 to logic level 1 at time t2 and transitions from logic level 1 to logic level 0 at time t3.

[0119] A clock signal 352 is generated by the processor 142 and provided to the LF RF pulse generators 102 and 114 (FIG. 1) and the HF RF generator 138 (FIG. 1). The generators 102, 114, and 138 operate synchronously with the clock cycles of the clock signal 352.

[0120] In one embodiment, the controller of the LF RF pulse generator generates the clock signal 352 and provides the clock signal to the other generators. For example, the controller of the LF RF pulse generator 102 generates the clock signal 352 and transmits the clock signal 352 to the LF RF pulse generator 114 and the HF RF pulse generator 138 via one or more transmission cables.

[0121] In one embodiment, a controller including a digital signal processor of the HF RF generator 138 generates the clock signal. The controller of the HF RF generator 138 provides the clock signal 352 to the LF RF pulse generators 102 and 114 via one or more transmission cables.

[0122] 4A is an embodiment of an inductor 400 that is an example of an HF filter 106 or 118 (FIG. 1). Inductor 400 has one end 402 and another end 404. End 402 is an example of an input I106 or I118 (FIG. 1), and end 404 is an example of an input output O106 or O118 (FIG. 1).

[0123] 4B is an embodiment of a parallel circuit 406, which is an example of the HF filter 106 or 118 (FIG. 1). The parallel circuit 406 includes an inductor 408 and a capacitor 410. The inductor 408 is coupled in parallel with the capacitor 410. The parallel circuit 406 has one end 412 and another end 414. The end 412 is an example of the input I106 or I118 (FIG. 1), and the end 414 is an example of the input output O106 or O118 (FIG. 1).

[0124] In one embodiment, the HF filter 106 or 118 includes one or more inductors and one or more capacitors coupled in parallel with the one or more capacitors.

[0125] 5 is a flow chart illustrating one embodiment of a method 500 for achieving uniformity across a surface of a substrate S (FIG. 1). The method 500 includes an operation 502. In operation 502, the processor 142 receives parameter signals 130 and 132 (FIG. 1) from sensors 154 and 156 (FIG. 1) or parameter signals 214 and 132 from sensors 154 and 156 (FIG. 2A).

[0126] The method includes an operation 504 of frequency alignment. For example, in operation 504, processor 142 determines whether the frequency of parameter signal 132 is within a predetermined range from the frequency of parameter signal 130. Illustratively, processor 142 determines whether the frequency of parameter signal 132 is within ±2 percent or ±5 percent from the frequency of parameter signal 130. In this example, upon determining that the frequency of parameter signal 132 is within the predetermined range from the frequency of parameter signal 130, processor 142 does not modify the frequency of square wave signal 104 and the frequency of square wave signal 116 (FIG. 1).

[0127] Meanwhile, in this example, in response to determining that the frequency of parameter signal 132 is not within the predetermined range from the frequency of parameter signal 130, processor 142 modifies the frequency of square wave signal 104, or the frequency of square wave signal 116, or a combination thereof. In this example, the frequency of square wave signal 104, or the frequency of square wave signal 116, or a combination thereof is modified until the frequency of the parameter signal received from sensor 156 is within the predetermined range from the frequency of the parameter signal received from sensor 154. Illustratively, upon determining that the frequency of parameter signal 132 is not within the predetermined range from the frequency of parameter signal 130, processor 142 sends a command signal to LF RF pulse generator 102 or 114 to adjust (e.g., slightly modify) the operating frequency of the LF RF pulse generator. In this example, the operating frequency of the LF RF pulse generator is slightly modified from 400 kHz to 400 kHz ±5%. In this example, upon receiving the adjusted operating frequency, the LF RF generator generates a square wave signal having the adjusted operating frequency.

[0128] As another example, in operation 504, processor 142 determines whether the frequency of parameter signal 132 is within a predetermined range from the frequency of parameter signal 214. In this example, upon determining that the frequency of parameter signal 132 is within the predetermined range from the frequency of parameter signal 214, processor 142 does not modify the frequency of square wave signal 104, the frequency of RF signal 150, and the frequency of square wave signal 116 (FIG. 2A). On the other hand, in this example, in response to determining that the frequency of parameter signal 132 is not within the predetermined range from the frequency of parameter signal 214, processor 142 modifies the frequency of square wave signal 104, or the frequency of RF signal 150, or the frequency of square wave signal 116, or a combination of two or more thereof. In this example, the frequency of square wave signal 104, or the frequency of RF signal 150, or the frequency of square wave signal 116, or a combination of two or more thereof, is modified until the frequency of the parameter signal received from sensor 156 is within the predetermined range from the frequency of the parameter signal received from sensor 154. Illustratively, upon determining that the frequency of parameter signal 132 is not within a predetermined range from the frequency of parameter signal 214, processor 142 sends a command signal to generator 102 or 114 or 138 to adjust (e.g., slightly modify or modify to within a predetermined range) the operating frequency of the generator. In this example, the operating frequency of LF RF pulse generator 102 or 114 is slightly modified from 400 kHz to 400 kHz ±5%, or the operating frequency of HF RF generator 138 is slightly modified from 60 MHz to 60 MHz ±5%. In this example, upon receiving the adjusted operating frequency, the generator generates a signal having the adjusted operating frequency.

[0129] Method 500 further includes an operation 506 of phase matching. For example, in operation 506, processor 142 determines whether the phase of parameter signal 132 is within a predetermined range from the phase of parameter signal 130 (FIG. 1). Illustratively, processor 142 determines whether the phase of parameter signal 132 is within ±2 percent or ±5 percent from the phase of parameter signal 130. In this example, upon determining that the phase of parameter signal 132 is within the predetermined range from the phase of parameter signal 130, processor 142 does not modify the phase of square wave signal 104 and the phase of square wave signal 116 (FIG. 1). On the other hand, in this example, in response to determining that the phase of parameter signal 132 is not within the predetermined range from the phase of parameter signal 130, processor 142 modifies the phase of square wave signal 104, or the phase of square wave signal 116, or a combination thereof. In this example, the phase of square wave signal 104, or the phase of square wave signal 116, or a combination thereof, is modified until the phase of the parameter signal received from sensor 156 is within a predetermined range of the phase of the parameter signal received from sensor 154.

[0130] As an example of correcting the phase, the processor 142 generates an alternative synchronization signal different from the synchronization signal 166 (FIG. 1) and transmits the alternative synchronization signal to the LF RF pulse generator 114 via the transmission cable TC2. The alternative synchronization signal is transmitted to the LF RF pulse generator 114 in place of the synchronization signal 166, and modifies the phase of the parameter signal received from the sensor 156 to be within a predetermined range from the phase of the parameter signal received from the sensor 154, within a predetermined period of time from the time the synchronization signal 166 was transmitted to the LF RF pulse generator 102. An example of the predetermined period of time is a predetermined number of time units (e.g., microseconds or milliseconds) from the time the synchronization signal 166 was transmitted to the LF RF pulse generator 102. Upon receiving the alternative synchronization signal, the LF RF pulse generator 114 generates a square wave signal. In this manner, the LF RF pulse generator 114 generates the square wave signal until the phase of the parameter signal received from the sensor 156 is within a predetermined range from the phase of the parameter signal received from the sensor 154. As another example, instead of being transmitted to LF RF pulse generator 114 via transmission cable TC2, the other synchronization signal is transmitted from processor 142 to LF RF pulse generator 102 via transmission cable TC1. In this example, synchronization signal 166 is transmitted to LF RF pulse generator 114. Continuing with this example, upon receiving the other synchronization signal, LF RF pulse generator 102 generates a square wave signal. Thus, in this example, LF RF pulse generator 102 generates the square wave signal until the phase of the parameter signal received from sensor 156 is within a predetermined range of the phase of the parameter signal received from sensor 154.

[0131] As another example, in operation 506, processor 142 determines whether the phase of parameter signal 132 is within a predetermined range from the phase of parameter signal 214 (FIG. 2A). In this example, upon determining that the phase of parameter signal 132 is within the predetermined range from the phase of parameter signal 214, processor 142 does not modify the phase of square wave signal 104, the phase of RF signal 150, and the phase of square wave signal 116 (FIG. 2A). On the other hand, in this example, in response to determining that the phase of parameter signal 132 is not within the predetermined range from the phase of parameter signal 214, processor 142 modifies the phase of square wave signal 104, or the phase of RF signal 150, or the phase of square wave signal 116, or a combination of two or more thereof. In this example, the phase of square wave signal 104, or the phase of RF signal 150, or the phase of square wave signal 116, or a combination of two or more thereof, is modified until the phase of the parameter signal received from sensor 156 is within a predetermined range of the phase of the parameter signal received from sensor 154.

[0132] As an example of correcting the phase, the processor 142 generates another synchronization signal different from the synchronization signal 166 and transmits the other synchronization signal to the HF RF generator 138 via the transmission cable TC3. The other synchronization signal is transmitted to the HF RF generator 138 instead of the synchronization signal 166, and is transmitted within a predetermined period from the time the synchronization signal 166 is transmitted to the LF RF pulse generators 102 and 114 to change the phase of the parameter signal received from the sensor 156 to be within a predetermined range from the phase of the parameter signal received from the sensor 154. Upon receiving the other synchronization signal, the HF RF generator 138 generates an RF signal. In this manner, the HF RF generator 138 generates an RF signal until the phase of the parameter signal received from the sensor 156 is within a predetermined range from the phase of the parameter signal received from the sensor 154. As another example, instead of transmitting the other synchronization signal to the HF RF generator 138 via the transmission cable TC3, the other synchronization signal is transmitted from the processor 142 to the LF RF pulse generator 102 via the transmission cable TC1 or to the LF RF pulse generator 114 via the transmission cable TC2.

[0133] Method 500 further includes an operation 508 of set point matching. For example, processor 142 determines from a magnitude, such as a peak-to-peak amplitude or a zero-to-peak amplitude, of a parameter of parameter signals 132 and 130 (FIG. 1) whether LF RF pulse generator 102 or LF RF pulse generator 114 is operating at a predetermined set point. Illustratively, processor 142 determines whether the magnitude of the parameter of parameter signal 132 is within a predetermined range from the magnitude of the parameter of parameter signal 130. In this example, the predetermined range is ±5 percent or ±3 percent. Continuing with this example, in response to determining that the magnitude of the parameter of parameter signal 132 is not within the predetermined range from the magnitude of the parameter of parameter signal 130, processor 142 modifies (e.g., increases or decreases) the magnitude of the parameter of square wave signal 116 (FIG. 1) to provide a modified magnitude and transmits the modified magnitude to LF RF pulse generator 114 via transfer cable TC2. In this example, upon receiving the modified magnitude, LF RF pulse generator 114 generates a square wave signal having the modified magnitude. Thus, in this example, LF RF pulse generator 114 continues to modify the magnitude of the square wave signal generated by LF RF pulse generator 114 until the parameter magnitude of the parameter signal received from sensor 156 is within a predetermined range of the parameter magnitude of the parameter signal received from sensor 154. Meanwhile, in this example, in response to determining that the parameter magnitude of parameter signal 132 is within a predetermined range of the parameter magnitude of parameter signal 130, processor 142 determines that LF RF pulse generator 102 is operating at a predetermined set point and that LF RF pulse generator 114 is operating at a predetermined set point. As one example, the predetermined operating set point of LF RF pulse generator 102 is equal to the predetermined operating set point of LF RF pulse generator 114. As another example, the predetermined operating set point of LF RF pulse generator 102 is different from the predetermined operating set point of LF RF pulse generator 114.

[0134] As another example, instead of modifying the parameter magnitude of square wave signal 116, processor 142 modifies the parameter magnitude of square wave signal 104 until the parameter magnitude of the parameter signal received from sensor 156 is within a predetermined range from the parameter magnitude of the parameter signal received from sensor 154. Illustratively, processor 142 determines whether the parameter magnitude of parameter signal 132 is within a predetermined range from the parameter magnitude of parameter signal 130. In this example, the predetermined range is ±5 percent or ±3 percent. Continuing with this example, in response to determining that the parameter magnitude of parameter signal 132 is not within the predetermined range from the parameter magnitude of parameter signal 130, processor 142 modifies (e.g., increases or decreases) the parameter magnitude of square wave signal 104 (FIG. 1) to provide a modified magnitude and transmits the modified magnitude to LF RF pulse generator 102 via transfer cable TC1. In this example, upon receiving the modified magnitude, LF RF pulse generator 102 generates a square wave signal having the modified magnitude. Thus, in this example, LF RF pulse generator 102 continues to modify the magnitude of the square wave signal generated by LF RF pulse generator 102 until the magnitude of the parameter of the parameter signal received from sensor 156 is within a predetermined range of the magnitude of the parameter of the parameter signal received from sensor 154.

[0135] As yet another example, processor 142 determines from the parameter magnitudes of parameter signals 132 and 214 (FIG. 2A) whether LF RF pulse generator 102 is operating at a predetermined set point, or LF RF pulse generator 114 is operating at a predetermined set point, or HF RF generator 138 is operating at a predetermined set point. Illustratively, processor 142 determines whether the parameter magnitude of parameter signal 132 is within a predetermined range from the parameter magnitude of parameter signal 214. In this example, the predetermined range is ±5 percent or ±3 percent. Continuing with this example, in response to determining that the parameter magnitude of parameter signal 132 is not within a predetermined range from the parameter magnitude of parameter signal 214, processor 142 modifies (e.g., increases or decreases) the parameter magnitude of square wave signal 116 (FIG. 1) to provide a modified magnitude and transmits the modified magnitude to LF RF pulse generator 114 via transfer cable TC2. Upon receiving the modified magnitude, LF RF pulse generator 114 generates a square wave signal having the modified magnitude. In this manner, LF RF pulse generator 114 continues to modify the magnitude of the square wave signal generated by LF RF pulse generator 114 until the magnitude of the parameter of the parameter signal received from sensor 156 is within a predetermined range of the magnitude of the parameter of the parameter signal received from sensor 154.

[0136] As another example, instead of modifying the parameter magnitude of square wave signal 116, processor 142 modifies the parameter magnitude of square wave signal 104 or the parameter magnitude of RF signal 150 until the parameter magnitude of the parameter signal received from sensor 156 is within a predetermined range from the parameter magnitude of the parameter signal received from sensor 154. Illustratively, processor 142 determines whether the parameter magnitude of parameter signal 132 is within a predetermined range from the parameter magnitude of parameter signal 214. In this example, the predetermined range is ±5 percent or ±3 percent. Continuing with this example further, in response to determining that the parameter magnitude of parameter signal 132 is not within a predetermined range from the parameter magnitude of parameter signal 214, processor 142 modifies (e.g., increases or decreases) the parameter magnitude of RF signal 150 (FIG. 2A) to provide a modified magnitude and transmits the modified magnitude to HF RF generator 138 via transmission cable TC3. Upon receiving the modified magnitude, HF RF generator 138 generates an RF signal having the modified magnitude. In this manner, HF RF generator 138 continues to modify the magnitude of the RF signal generated by HF RF generator 138 until the magnitude of the parameter of the parameter signal received from sensor 156 is within a predetermined range of the magnitude of the parameter of the parameter signal received from sensor 154. Meanwhile, in response to determining that the magnitude of the parameter of parameter signal 132 is within a predetermined range of the magnitude of the parameter of parameter signal 214, processor 142 determines that LF RF pulse generator 102 is operating at a predetermined set point, LF RF pulse generator 114 is operating at a predetermined set point, and HF RF generator 138 is operating at a predetermined set point.

[0137] In one embodiment, operations 504, 506, and 508 are performed in a different order than that shown in Figure 5. For example, operation 506 is performed before operation 504. As another example, portions 506 and 508 are performed before operation 504. As yet another example, operation 508 is performed first, operation 506 is performed second, and operation 502 is performed third.

[0138] 6A is an illustration of one embodiment of a graph 600 illustrating a plot 602 of the voltage of an RF signal generated by a 400 kHz RF generator versus time t. Voltage is plotted on the y-axis and time t is plotted on the x-axis. The RF signal generated by the 400 kHz RF generator is not a square wave signal. Rather, the RF signal generated by the 400 kHz RF generator is a sinusoidal signal. The voltage of the RF signal generated by the 400 kHz RF generator transitions periodically between a maximum amplitude V3 and a minimum amplitude −V3.

[0139] The magnitude V3 is greater than the voltage magnitude V2 of the RF signal, which is greater than the magnitude V1 of the RF signal, which is greater than zero, which is greater than the magnitude -V1 of the RF signal, which is greater than the magnitude -V2 of the RF signal, which is greater than the magnitude -V3.

[0140] FIG. 6B is an illustration of one embodiment of a graph 610 illustrating a plot 612 of the envelope of the number of ions of a plasma generated when the 400 kHz RF generator illustrated with reference to FIG. 6A is used. The envelope of the plot 612 shows the maximum number of ions of the plasma at a particular energy. The number of ions is plotted on the y-axis, and ion energy and electron volts (eV) are plotted on the x-axis. As shown, the ions are distributed over a range from ion energy E1 to ion energy E2. For example, there is a large number of ions of the plasma having ion energy E1, and there is a large number of ions of the plasma having ion energy E2. There is also a significant amount of ions of the plasma having energies between ion energies E1 and E2.

[0141] FIG. 7A is a diagram of an embodiment of a graph 700 illustrating a plot of the voltage of a square wave signal 702 output from a sensor as a parameter signal. For example, the square wave signal 702 is output by the sensor 154 or 156 (FIG. 1). To illustrate, the square wave signal 702 is an example of the parameter signal 130 or 132 (FIG. 1). To further illustrate, the square wave signal 702 is an example of the parameter signal 214 (FIG. 2A). In the graph 700, voltage is plotted on the y-axis and time t is plotted on the x-axis. During each cycle of the clock signal 352 (FIG. 3D), the square wave signal 702 has multiple voltage fluctuations and a main pulse. The voltage of the square wave signal 702 has a peak-to-peak amplitude ranging from a maximum of 0 volts to a minimum of −V3 volts.

[0142] FIG. 7B is an illustration of one embodiment of a graph 710 illustrating a plot 712 of the envelope of the number of ions of the plasma generated when a LF RF pulse generator generating the square wave signal illustrated with reference to FIG. 7A is used. In the graph 710, the number of ions is plotted on the y-axis and the ion energy is plotted on the x-axis. As shown, the ions are distributed over a range from E1 to E2 electron volts. However, it should be noted that there is a large number of ions of the plasma having high ion energies. For example, the large number of ions of the plasma have ion energies of Ea, Eb, Ec, and E2. The ion energies Ea-Ec are greater than the ion energy E1 but less than the ion energy E2. Due to the large number of ions, the processing speed of the substrate S with the one or more square wave signals is increased compared to the processing speed of the substrate S with one or more LF RF signals or a combination of LF RF signals and HF RF signals.

[0143] FIG. 8 is a diagram of an embodiment of a LF RF pulse generator 800. The LF RF pulse generator 800 is an example of the LF RF pulse generator 102 or 114 (FIGS. 1, 2A, and 2B). The LF RF pulse generator 800 includes a controller 820, a voltage source and regulator 802, a driver 826, a switch and transformer system 804, and a power storage device 808. An example of the voltage source and regulator 802 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 connected to the voltage regulator. An example of the switch and transformer system 804 includes a combination of a switch and a transformer, such as a solid-state switch. An example of a solid-state switch is a transistor or a group of transistors. The solid-state switch is coupled to a transformer. As an example, the transformer includes a primary winding and a secondary winding. An example of the power storage device 808 includes a capacitor. One example of a driver 826 is one or more transistors coupled together.

[0144] An example of the controller 820 includes a processor and a memory device. The processor of the controller 820 is coupled to the memory device of the controller 820. As another example, the controller 820 is an ASIC or a PLD.

[0145] The processor 142 is coupled to the controller 820 via a transfer cable 818. The transfer cable 818 is an example of a transfer cable TC1 or TC2 (FIG. 1). The controller 820 is coupled to the switches of the switch and transformer system 804 and is also coupled to a driver 826. The driver 826 is coupled to a voltage regulator of the voltage source and regulator 802. The voltage regulator of the voltage source and regulator 802 is coupled to the power storage device 808.

[0146] Further, the power storage device 808 is coupled to the transformer, and the switch is coupled to the transformer. For example, the power storage device 808 is coupled to a first end of the primary winding, and the switch is coupled to a second end of the primary winding. A first end of a secondary winding of the transformer is coupled to a conductor 810 of the RF cable 812, and a second end of the secondary winding of the transformer is coupled to an RF cover 814 of the RF cable 812. The RF cable 812 is an example of the RF cable RFC1 or RFC2 (FIGS. 1 & 2A).

[0147] The voltage supply generates a voltage signal. The processor 142 controls the voltage regulator via the driver 826 to modify (e.g., increase or decrease) the voltage of the voltage signal and output the modified voltage signal. A charge based on the modified voltage of the modified voltage signal is stored in the power storage device 808. The controller 820 controls the switch to switch between an on state and an off state. In the off state, the switch is open, and in the on state, the switch is closed. When the switch is open, it prohibits the energy of the charge stored in the power storage device 808 from passing to the transformer. When the switch is closed, it allows the energy to pass to the transformer. During the on state of the switch, the energy of the charge stored in the power storage device 808 is discharged to the primary winding of the transformer. The charge stored in the power storage device 808 may not be substantially discharged during each on state, which allows for a higher pulse repetition frequency. For example, 5% to 50% of the charge stored in the power storage device 808 is discharged in one switch cycle. As yet another example, in one switch cycle, 1% to 5% of the charge stored in the power storage device 808 is discharged. As an example, during a switch cycle, the switch is turned on once and off once.

[0148] The voltage provided by the charge in the power storage device 808 is transformed (e.g., increased or decreased) from the primary winding of the transformer to the secondary winding of the transformer to output the transformed voltage across the secondary winding of the transformer. The transformed voltage is the voltage of a square wave signal 816 provided from the transformer to the conductor 810. The square wave signal 816 is an example of a square wave signal 104 or 116 (FIGS. 1 & 2A).

[0149] The processor 142 generates and sends a frequency command signal to the processor of the controller 820 to generate the square wave signal 814. For example, the frequency command signal includes a first frequency for opening and closing the switch to generate a main pulse of the square wave signal 816 within each cycle of the clock signal 352. The frequency command signal further includes instructions for the switch to open and close at the first frequency only once during each cycle of the clock signal 352. In this example, the command signal further includes a second frequency for opening and closing the switch to generate a voltage variation of the square wave signal 816 within each cycle of the clock signal 352. Further, in this example, upon receiving the first and second frequencies, the processor of the controller 820 stores the first and second frequencies in a memory device of the controller 820. In response to receiving a trigger signal 822 from the processor 142 via the transfer cable 818, the processor of the controller 820 generates and transmits a first current signal based on a first frequency to the switch during each cycle of the clock signal 352, and generates and transmits a second current signal based on a second frequency to the switch. Also, in this example, the switch opens and closes according to the first and second frequencies during each cycle of the clock signal 352 to output a square wave signal. Illustratively, the switch opens and closes only once according to the first frequency, allowing the LF RF pulse generator 800 to generate a single main pulse during each cycle of the clock signal 352. In this example, the switch opens and closes according to the second frequency during each cycle of the clock signal 352, allowing the LF RF pulse generator 800 to generate multiple voltage fluctuations during the cycle. The trigger signal 822 is an example of a synchronization signal 166 (FIG. 1) or other synchronization signal described herein.

[0150] The processor 142 also generates and sends another synchronization signal to the controller 820 to change the phase of the square wave signal 816. Upon receiving the other synchronization signal, the processor in the controller 820 controls the switch to be off for a predetermined amount of time and on after a predetermined amount of time, changing the phase of the square wave signal 816.

[0151] Further, the processor 142 generates and transmits a magnitude command signal to the controller 820 to modify the magnitude of the square wave signal 816. For example, the magnitude command signal includes a peak-to-peak amplitude of the square wave signal 816 output from the LF RF pulse generator 800. In this example, the controller 820 stores the peak-to-peak amplitude in a memory device of the controller 820. Based on the correspondence between the peak-to-peak amplitude of the voltage regulator and the predetermined resistance, the processor of the controller 826 generates a command signal to achieve the predetermined resistance. The processor of the controller 826 transmits the command signal to the driver 826. Further, in this example, upon receiving the command signal, the driver 826 generates a current signal to modify the resistance of the voltage regulator to the predetermined resistance. The predetermined resistance corresponds to a modified voltage for charging the power storage device 808. For example, if the voltage regulator has a predetermined resistance, the voltage regulator outputs the modified voltage. The driver 826 transmits the current signal to the voltage regulator. Upon receiving the current signal, the resistance of the voltage regulator is modified to achieve the predetermined resistance. The amount of voltage provided from the voltage supply through the voltage regulator to the power storage device 808 is modified based on the predetermined resistance. The amount of voltage is modified to achieve the peak-to-peak amplitude of the square wave signal 816 parameter.

[0152] 9A shows one embodiment of a graph 900 illustrating a comparison of contact hole etch rates between an RF signal and a square wave signal. For this comparison, the maximum ion energies generated based on the RF signal and the square wave signal are matched. Graph 900 plots contact hole etch rate on the y-axis and etch depth on the x-axis. The contact hole etch rate is measured in nanometers per minute (nm / min) and the etch depth is measured in nanometers.

[0153] In graph 900, the contact hole etch rate for the square wave signal is greater than the contact hole etch rate for the RF signal. The contact hole etch rate for the square wave signal is shown in FIG. 9A as a circle, and the contact hole etch rate for the RF signal is shown in FIG. 9A as a circle with a cross ("X") in it. Higher etch rates are achieved using high energy plasma ions, such as plasma ions having ion energies Ea-E2 (FIG. 7B). The higher etch rates facilitate achieving greater etch depths compared to those achieved using an RF signal.

[0154] 9B shows one embodiment of a graph 910 illustrating critical dimension (CD) growth rate of a contact hole as a function of etch depth. Graph 910 plots CD growth rate on the y-axis and etch depth on the x-axis.

[0155] In graph 910, the CD growth rate achieved using the square wave signal (FIG. 8) is lower compared to the CD growth rate achieved using the RF signal. The CD growth rate for the square wave signal is shown in FIG. 9B as a circle, and the CD growth rate for the RF signal is shown in FIG. 9B as a circle with a cross ("X") in it. The lower CD growth rate is a result of the narrower angular distribution of ions in the high energy ion beam produced by the square wave signal.

[0156] It should be noted that while the above embodiments are described with reference to square wave signals, in some embodiments the terms triangular wave signals, sawtooth signals, and square wave signals are used interchangeably herein.

[0157] The embodiments described herein may be practiced with a variety of computer system configurations including hand-held hardware units, microprocessor systems, microprocessor-based or programmable consumer electronics, minicomputers, mainframe computers, etc. The embodiments may also be practiced in distributed computing environments where tasks are performed by remote processing hardware units that are linked through a network.

[0158] In some embodiments, the controller is part of a system that may be part of the examples described above. Such systems include semiconductor processing equipment, including one or more processing tools, one or more chambers, one or more processing platforms, and / or specific processing components (wafer pedestals, gas flow systems, etc.). These systems are integrated with electronics for controlling pre-, during, and post-processing operations of semiconductor wafers or substrates. Such electronics may be referred to as a "controller" and may control various components or subparts of one or more systems. The controller is programmed to control any of the processes disclosed herein depending on the processing requirements and / or type of system. Such processes include delivery of process gases, temperature settings (e.g., heating and / or cooling), pressure settings, vacuum settings, power settings, RF generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, position and motion settings, wafer loading and unloading from tools and other transfer tools coupled or interlocked with the system, and / or wafer loading and unloading from load locks.

[0159] Broadly, in various embodiments, a controller is defined as an electronic device having various integrated circuits, logic, memory, and / or software that receive instructions, issue instructions, control operations, enable cleaning operations, enable endpoint measurements, etc. Integrated circuits include chips in the form of firmware that store program instructions, digital signal processors (DSPs), chips defined as ASICs, PLDs, and / or one or more microprocessors, i.e., 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, coefficients, variables, etc. for performing a particular process on or for a semiconductor wafer or in a system. Program instructions, in some embodiments, are part of a recipe defined by a process engineer to accomplish one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and / or one or more processing steps in the fabrication of a wafer die.

[0160] The controller, in some embodiments, is part of a computer that is integrated or coupled with the system or otherwise networked to the system, or is coupled to such a computer, or a combination thereof. For example, the controller is in the "cloud" and is all or part of a fab host computer system. This allows remote access of wafer processing. The computer allows remote access to the system to monitor the current progress of a fabrication operation, review the history of past fabrication operations, review trends or performance criteria from multiple fabrication operations, change parameters of a current process, set up processing steps following the current process, or initiate a new process.

[0161] In some embodiments, a remote computer (e.g., a server) provides the process recipe to the system over a network. Such a network includes a local network or the Internet. The remote computer includes a user interface that allows for entry or programming of parameters and / or settings, which are then communicated from the remote computer to the system. In some examples, the controller receives instructions in the form of data, which specifies parameters, coefficients, and / or variables of each of the processing steps to be performed during one or more operations. It should be understood that the parameters, coefficients, and / or variables are specific to the type of process to be performed and the type of tool the controller is configured to interface with or control. Thus, as described above, the controller is distributed, for example, by including one or more individual controllers that are networked together and cooperate toward a common purpose (such as the processes and controls described herein). Examples of distributed controllers for such purposes include one or more integrated circuits on the chamber that communicate with one or more integrated circuits that are remotely located (e.g., at the platform level or as part of a remote computer) and coupled to control the process in the chamber.

[0162] In various embodiments, exemplary systems to which the methods may be applied include, but are not limited to, 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 tracking chamber or module, and any other semiconductor processing system associated with or used in the fabrication and / or manufacturing of semiconductor wafers.

[0163] It is further noted that in some embodiments, the above operations apply to several types of plasma chambers, such as plasma chambers including inductively coupled plasma (ICP) reactors, transformer coupled plasma chambers, conductor tools, dielectric tools, plasma chambers including 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 coil, a flat coil, etc.

[0164] As described above, depending on the process step or steps being performed by the tool, the host computer communicates with one or more other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, nearby tools, tools located throughout the factory, a main computer, another controller, or tools used for material transport to and from tool locations and / or load ports within the semiconductor manufacturing factory.

[0165] With the above embodiments in mind, it should be understood that some of the embodiments employ various computer-implemented operations involving data stored in computer systems. These operations are operations that physically manipulate physical quantities. Any of the operations described herein that form part of the embodiments are useful machine operations.

[0166] Some of the embodiments also relate to hardware units or devices for performing these operations. The device is specially constructed for a special purpose computer. When defined as a special purpose computer, the computer is operable for its dedicated purpose while performing other processes, program execution or routines that are not part of its dedicated purpose.

[0167] In some embodiments, the operations may be processed by a computer selectively activated or configured by one or more computer programs stored in a computer memory, cache, or obtained over a computer network. If data is obtained over a computer network, the data may be processed by other computers on the computer network (e.g., a cloud of computational resources).

[0168] One or more embodiments may also be fabricated as computer readable code on a non-transitory computer readable medium. A non-transitory computer readable medium is any data storage hardware unit (e.g., memory device, etc.) 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 disk ROM (CD-ROM), CD recordable (CD-R), CD rewriteable (CD-RW), magnetic tape, and other optical and non-optical data storage hardware units. In some embodiments, a non-transitory computer readable medium includes a computer readable tangible medium distributed over a network-coupled computer system such that the computer readable code is stored and executed in a distributed manner.

[0169] Although 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 each operation, or each method operation is coordinated to occur at slightly different times, or distributed across a system that allows each method operation to occur at various intervals, or performed in an order different than that described above.

[0170] It should further be noted that in one embodiment, one or more features of 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.

[0171] Although the foregoing embodiments have 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. Thus, the present embodiments should be considered as illustrative and not restrictive, and the embodiments should not be limited to the details set forth herein.

Claims

1. A system for processing a substrate using a square wave signal, comprising: a first pulse generator configured to generate a first square wave signal having a first frequency; a first filter configured to receive the first square wave signal and filter a second frequency from interference with the first square wave signal to provide a first filtered output signal, the first filter being further configured to provide the first filtered output signal to an electrode disposed within a plasma chamber via a first radio frequency (RF) transmission line; a second pulse generator configured to generate a second square wave signal having a third frequency; a second filter configured to receive the second square wave signal and filter the second frequency from interference with the second square wave signal to provide a second filtered output signal, the second filter being further configured to provide the second filtered output signal to an edge ring disposed within the plasma chamber via a second RF transmission line; and a system comprising the same.

2. The system according to claim 1, further comprising the plasma chamber including the electrode and the edge ring.

3. The system according to claim 1, wherein the first filtered output signal is a square wave signal and the second filtered output signal is a square wave signal.

4. The system according to claim 1, wherein the first frequency is equal to the third frequency and the second frequency is greater than the first and third frequencies.

5. The system according to claim 1, further comprising a host computer coupled to the first pulse generator, the host computer being configured to: receive a parameter signal related to an output of the first filter; determine whether a frequency of the parameter signal is within a predetermined frequency range from a predetermined frequency; and in response to a determination that the frequency of the parameter signal is not within the predetermined frequency range from the predetermined frequency, modify the first frequency of the first square wave signal, the first frequency of the first square wave signal being modified until the frequency of the parameter signal is within the predetermined frequency range from the predetermined frequency.

6. The method according to claim 5, further comprising: determining whether a frequency of a second parameter signal related to an output of the second filter is within a second predetermined frequency range from a second predetermined frequency; and in response to a determination that the frequency of the second parameter signal is not within the second predetermined frequency range from the second predetermined frequency, modifying the third frequency of the second square wave signal, the third frequency of the second square wave signal being modified until the frequency of the second parameter signal is within the second predetermined frequency range from the second predetermined frequency.

7. The system according to claim 1, further comprising a host computer coupled to the first pulse generator, the host computer being configured to: receive a parameter signal related to an output of the first filter; determine whether a frequency of the parameter signal is within a predetermined frequency range from a predetermined frequency; and in response to a determination that the frequency of the parameter signal is not within the predetermined frequency range from the predetermined frequency, modify the first frequency of the first square wave signal, the first frequency of the first square wave signal being modified until the frequency of the parameter signal is within the predetermined frequency range from the predetermined frequency.

8. The method according to claim 7, further comprising: determining whether a frequency of a second parameter signal related to an output of the second filter is within a second predetermined frequency range from a second predetermined frequency; and in response to a determination that the frequency of the second parameter signal is not within the second predetermined frequency range from the second predetermined frequency, modifying the third frequency of the second square wave signal, the third frequency of the second square wave signal being modified until the frequency of the second parameter signal is within the second predetermined frequency range from the second predetermined frequency.

9. The system according to claim 1, further comprising a host computer coupled to the first pulse generator, the host computer being configured to: receive a parameter signal related to an output of the first filter; determine whether a frequency of the parameter signal is within a predetermined frequency range from a predetermined frequency; and in response to a determination that the frequency of the parameter signal is not within the predetermined frequency range from the predetermined frequency, modify the first frequency of the first square wave signal, the first frequency of the first square wave signal being modified until the frequency of the parameter signal is within the predetermined frequency range from the predetermined frequency.

10. The method according to claim 9, further comprising: determining whether a frequency of a second parameter signal related to an output of the second filter is within a second predetermined frequency range from a second predetermined frequency; and in response to a determination that the frequency of the second parameter signal is not within the second predetermined frequency range from the second predetermined frequency, modifying the third frequency of the second square wave signal, the third frequency of the second square wave signal being modified until the frequency of the second parameter signal is within the second predetermined frequency range from the second predetermined frequency. Determine whether the phase of the parameter signal is within a predetermined phase range from a predetermined phase, In response to a determination that the phase of the parameter signal is not within the predetermined phase range from the predetermined phase, correct the phase of the first square wave signal, and the phase of the first square wave signal is corrected until the phase of the parameter signal is within the predetermined phase range from the predetermined phase. A second operation, and Determine whether the magnitude of the parameter signal is within a predetermined range from a predetermined magnitude, In response to a determination that the magnitude of the parameter signal is not within the predetermined range from the predetermined magnitude, correct the magnitude of the first square wave signal, and the magnitude of the first square wave signal is corrected until the magnitude of the parameter signal is within the predetermined range from the predetermined magnitude. A third operation Perform one or more of a plurality of operations including A host computer configured to Further comprising a system.

6. The system according to claim 1, wherein A host computer coupled to the second pulse generator, the host computer Receives a parameter signal related to the output of the second filter, Determine whether the frequency of the parameter signal is within a predetermined frequency range from a predetermined frequency, In response to a determination that the frequency of the parameter signal is not within the predetermined frequency range from the predetermined frequency, correct the third frequency of the second square wave signal, and the third frequency of the second square wave signal is corrected until the frequency of the parameter signal is within the predetermined frequency range from the predetermined frequency. A first operation, Determine whether the phase of the parameter signal is within a predetermined phase range from a predetermined phase, In response to a determination that the phase of the parameter signal is not within the predetermined phase range from the predetermined phase, correct the phase of the second square wave signal, and the phase of the second square wave signal is corrected until the phase of the parameter signal is within the predetermined phase range from the predetermined phase. A second operation, and Determine whether the magnitude of the parameter signal is within a predetermined range from a predetermined magnitude, In response to a determination that the magnitude of the parameter signal is not within the predetermined range from the predetermined magnitude, the magnitude of the second square wave signal is modified, and the magnitude of the second square wave signal is modified until the magnitude of the parameter signal is within the predetermined range from the predetermined magnitude. A third operation Performing one or more of a plurality of operations including A host computer configured to Further comprising a system.

7. The system according to claim 1, wherein A host computer coupled to the first pulse generator and the second pulse generator, the host computer comprising: Receiving a first parameter signal related to the output of the first filter, Receiving a second parameter signal related to the output of the second filter, Determining the frequency of the first parameter signal, Determining the frequency of the second parameter signal, Determining whether the frequency of the second parameter signal is within a predetermined frequency range from the frequency of the first parameter signal, When it is determined that the frequency of the second parameter signal is not within the predetermined frequency range from the frequency of the first parameter signal, the first frequency of the first square wave signal or the third frequency of the second square wave signal is modified, and the first frequency or the third frequency is modified until the frequency of the second parameter signal is within the predetermined frequency range from the frequency of the first parameter signal. A host computer configured to Further comprising a system.

8. The system according to claim 1, wherein A host computer coupled to the first pulse generator and the second pulse generator, the host computer comprising: Receiving a first parameter signal related to the output of the first filter, Receiving a second parameter signal related to the output of the second filter, Determining the phase of the first parameter signal, Determining the phase of the second parameter signal, Determining whether the phase of the second parameter signal is within a predetermined phase range from the phase of the first parameter signal, When it is determined that the phase of the second parameter signal is not within the predetermined phase range from the phase of the first parameter signal, the phase of the first square wave signal or the phase of the second square wave signal is corrected, and the phase of the first square wave signal or the phase of the second square wave signal is corrected until the phase of the second parameter signal is within the predetermined phase range from the phase of the first parameter signal. A host computer configured as A system further comprising.

9. The system according to claim 1, A host computer coupled to the first pulse generator and the second pulse generator, the host computer comprising: Receiving a first parameter signal related to the output of the first filter, Receiving a second parameter signal related to the output of the second filter, Determining the magnitude of the first parameter signal, Determining the magnitude of the second parameter signal, Determining whether the magnitude of the second parameter signal is within a predetermined magnitude range from the magnitude of the first parameter signal, In response to a determination that the magnitude of the second parameter signal is not within the predetermined magnitude range from the magnitude of the first parameter signal, changing the magnitude of the second square wave signal, and the magnitude of the second square wave signal is changed until the magnitude of the second parameter signal is within the predetermined magnitude range from the magnitude of the first parameter signal. A host computer configured as A system further comprising.

10. A system for processing a substrate using square wave signals, A first pulse generator configured to generate a first square wave signal of a first frequency, A first filter configured to receive the first square wave signal and filter a second frequency from interference with the first square wave signal to provide a first filter output signal, An RF generator configured to generate a radio frequency (RF) signal, An impedance matching circuit configured to receive the RF signal and output a correction signal based on the RF signal, An RF transmission line coupled to the first filter and the impedance matching circuit and receiving the first filter output signal and the correction signal, wherein the RF transmission line combines the first filter output signal and the correction signal to output a combined signal, and the combined signal is configured to be provided to a lower electrode disposed in a plasma chamber, and an RF transmission line comprising a system. **Claim 11** The system according to claim 10, further comprising the plasma chamber including the lower electrode. **Claim 12** The system according to claim 10, wherein the first filter and the impedance matching circuit are located in the same housing. **Claim 13** The system according to claim 10, wherein the first filter is located in a first housing and the impedance matching circuit is located in a second housing. **Claim 14** The system according to claim 10, a host computer coupled to the first pulse generator and the RF generator, the host computer receiving a parameter signal related to the output of the first filter, determining whether the frequency of the parameter signal is within a predetermined frequency range from a predetermined frequency, in response to a determination that the frequency of the parameter signal is not within the predetermined frequency range from the predetermined frequency, correcting the first frequency of the first square wave signal or the second frequency of the RF signal, and the first frequency of the first square wave signal or the second frequency of the RF signal is corrected until the frequency of the parameter signal is within the predetermined frequency range from the predetermined frequency a first operation, determining whether the phase of the parameter signal is within a predetermined phase range from a predetermined phase, in response to a determination that the phase of the parameter signal is not within the predetermined phase range from the predetermined phase, correcting the phase of the first square wave signal or the phase of the RF signal, and the phase of the first square wave signal or the phase of the RF signal is corrected until the phase of the parameter signal is within the predetermined phase range from the predetermined phase a second operation, and determining whether the magnitude of the parameter signal is within a predetermined range from a predetermined magnitude, In response to a determination that the magnitude of the parameter signal is not within the predetermined range from the predetermined magnitude, the magnitude of the first square wave signal or the magnitude of the RF signal is modified, and the magnitude of the first square wave signal or the magnitude of the RF signal is modified until the magnitude of the parameter signal is within the predetermined range from the predetermined magnitude. A third operation Performing one or more of a plurality of operations including A host computer configured to A system further comprising.

15. The system according to claim 10, A second pulse generator configured to generate a second square wave signal having a third frequency, A second filter coupled to the second pulse generator, the second filter being configured to receive the second square wave and filter the third frequency from interference with the second square wave signal to output a second filter output signal, the second filter output signal being provided to an edge ring disposed within the plasma chamber. A second filter configured to A system further comprising.

16. The system according to claim 15, The system, wherein the third frequency is equal to the first frequency.

17. The system according to claim 15, The system, wherein the first filter output signal is a square wave signal and the second filter output signal is a square wave signal.

18. The system according to claim 15, The system, wherein the second pulse generator is configured to be coupled to the edge ring via the second filter without using an impedance matching circuit between the second pulse generator and the edge ring.

19. The system according to claim 15, The host computer Receives a parameter signal related to the output of the second filter, Determines whether the frequency of the parameter signal is within a predetermined frequency range from a predetermined frequency, In response to a determination that the frequency of the parameter signal is not within the predetermined frequency range from the predetermined frequency, the third frequency of the second square wave signal is modified, and the third frequency is modified until the frequency of the parameter signal is within the predetermined frequency range from the predetermined frequency. A first operation, Determine whether the phase of the parameter signal is within a predetermined phase range from a predetermined phase, In response to a determination that the phase of the parameter signal is not within the predetermined phase range from the predetermined phase, correct the phase of the second square wave signal, and the phase of the second square wave signal is corrected until the phase of the parameter signal is within the predetermined phase range from the predetermined phase A second operation, and Determine whether the magnitude of the parameter signal is within a predetermined range from a predetermined magnitude, In response to a determination that the magnitude of the parameter signal is not within the predetermined range from the predetermined magnitude, correct the magnitude of the second square wave signal, and the magnitude of the second square wave signal is corrected until the magnitude of the parameter signal is within the predetermined range from the predetermined magnitude A third operation Perform one or more of a plurality of operations including A system configured as

20. The system according to claim 15, wherein A host computer coupled to the first pulse generator and the second pulse generator, the host computer Receives a first parameter signal related to the output of the first filter, Receives a second parameter signal related to the output of the second filter, Determine the frequency of the first parameter signal, Determine the frequency of the second parameter signal, Determine whether the frequency of the second parameter signal is within a predetermined frequency range from the frequency of the first parameter signal, When it is determined that the frequency of the second parameter signal is not within the predetermined frequency range from the frequency of the first parameter signal, correct the first frequency of the first square wave signal, or the second frequency of the RF signal, or the third frequency of the second square wave signal, and the first frequency, or the second frequency, or the third frequency is corrected until the frequency of the second parameter signal is within the predetermined frequency range from the frequency of the first parameter signal A host computer configured as A system further comprising

21. The system according to claim 15, wherein A host computer coupled to the first pulse generator and the second pulse generator, the host computer Receive a first parameter signal related to the output of the first filter, Receive a second parameter signal related to the output of the second filter, Determine the phase of the first parameter signal, Determine the phase of the second parameter signal, Determine whether the phase of the second parameter signal is within a predetermined phase range from the phase of the first parameter signal, When it is determined that the phase of the second parameter signal is not within the predetermined phase range from the phase of the first parameter signal, correct the phase of the first square wave signal, or the phase of the RF signal, or the phase of the second square wave signal, and the phase of the first square wave signal, or the phase of the RF signal, or the phase of the second square wave signal is corrected until the phase of the second parameter signal is within the predetermined phase range from the phase of the first parameter signal A host computer configured as A system further comprising.

22. The system according to claim 15, wherein A host computer coupled to the first pulse generator and the second pulse generator, the host computer comprising Receive a first parameter signal related to the output of the first filter, Receive a second parameter signal related to the output of the second filter, Determine the magnitude of the first parameter signal, Determine the magnitude of the second parameter signal, Determine whether the magnitude of the second parameter signal is within a predetermined magnitude range from the magnitude of the first parameter signal, In response to the determination that the magnitude of the second parameter signal is not within the predetermined magnitude range from the magnitude of the first parameter signal, change the magnitude of the first square wave signal, or the magnitude of the RF signal, or the magnitude of the second square wave signal, The magnitude of the first square wave signal, or the magnitude of the RF signal, or the magnitude of the second square wave signal is changed until the magnitude of the second parameter signal is within the predetermined magnitude range from the magnitude of the first parameter signal A host computer configured as A system further comprising.

23. The system according to claim 10, wherein The first filter is coupled to the first pulse generator via an RF cable, and the first filter is configured to be coupled to the plasma chamber via an RF transmission line without using an impedance matching circuit between the first filter and the plasma chamber. A system.

24. The system according to claim 10, wherein the first pulse generator is configured to be coupled to the plasma chamber via the first filter without using an impedance matching circuit between the first pulse generator and the plasma chamber. A system.

25. The system according to claim 10, wherein the RF signal has a second frequency greater than the first frequency, the RF signal is a sine wave signal, and the first square wave signal includes a plurality of voltage fluctuations and a main pulse. A system.

26. A method for processing a substrate using a square wave signal, generating a first square wave signal of a first frequency; filtering a second frequency from interference with the first square wave signal to provide a first filter output signal; generating a second square wave signal of a third frequency; filtering the second frequency from interference with the second square wave signal to provide a second filter output signal; providing the first filter output signal to an electrode of a plasma chamber; providing the second filter output signal to an edge ring of the plasma chamber and including. A method.

27. The method according to claim 26, wherein the first filter output signal is a square wave signal and the second filter output signal is a square wave signal. A method.

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