JP6329543B2 - Method for controlling a switched-mode ion energy distribution system - Google Patents

Description

(Related applications and priority)
This application is a continuation-in-part of US Patent Application No. 13 / 193,299 (filed on July 28, 2011), and US Non-Provisional Patent Application No. 12 / 870,837 (filed on April 29, 2010). ) Part continuation application. The details of applications 13 / 193,299, 12 / 870,837 are hereby incorporated by reference in their entirety for all purposes.

(Technical field)
The present invention generally relates to plasma processing. In particular, but not exclusively, the present invention relates to methods and apparatus for plasma assisted etching, deposition, and / or other plasma assisted processes.

  Many types of semiconductor devices are processed using plasma-based etching techniques. If what is etched is a conductor, a negative voltage is applied to the conductive substrate relative to ground to produce a substantially uniform negative voltage across the surface of the substrate conductor, and the negative voltage is The positive ions that attract positively charged ions toward the conductor so that they affect the conductor have substantially the same energy.

  However, if the substrate is dielectric, the invariant voltage is not effective for applying a voltage across the surface of the substrate. However, an AC voltage (eg, high frequency) can be applied to the conductive plate (or chuck) such that the AC field induces a voltage on the surface of the substrate. During the positive AC half cycle, the substrate attracts light electrons compared to the mass of positive ions. Thus, many electrons will be attracted to the surface of the substrate during the positive cycle portion. As a result, the surface of the substrate will be negatively charged, causing ions to be attracted towards the negatively charged surface. Also, when the ions collide with the surface of the substrate, the collision removes material from the surface of the substrate, ie, results in etching.

  In many cases, it is desirable to have a narrow ion energy distribution, but applying a sinusoidal waveform to the substrate induces a wide distribution of ion energy, which results in the desired etch profile. Limit the ability of the plasma process. Known techniques for achieving narrow ion energy distribution are expensive, inefficient, difficult to control, and can adversely affect plasma density. As a result, these known techniques have not been adopted for commercial use. Therefore, there is a need for systems and methods that overcome the shortcomings of current technology and provide other new and innovative features.

  Illustrative embodiments of the invention shown in the drawings are summarized below. These and other embodiments are fully described in the Detailed Description section. It should be understood, however, that the intention is not to limit the invention to the form described in the disclosure or the detailed description. Those skilled in the art may recognize that there are numerous modifications, equivalents, and alternative constructions that fall within the spirit and scope of the invention as defined in the claims.

  According to one embodiment, the present invention may be characterized as an apparatus for providing a modified periodic voltage function to an electrical node, the electrical node configured to couple to a substrate support of a plasma processing chamber. The The apparatus can include a power supply, an ionic current compensation component, and a controller. The power supply can provide a periodic voltage function to the electrical node, the periodic voltage function having a pulse and a portion between pulses. The ion current compensation component can provide ion current compensation to modify the slope of the portion between the pulses and thus form a modified periodic voltage function. The controller communicates with the switch mode power supply and the ion current compensation component to provide a defined ion energy distribution function for the ions that reach the surface of the substrate when provided to the electrical node. Can be configured to identify a value of.

According to another embodiment, the present invention may be described as a method for providing a modified periodic voltage function to an electrical node, the electrical node configured to be electrically coupled to a substrate support of a plasma processing chamber. Is done. The method may include providing an ion current compensation I _C into an electrical node. The method further comprises providing a periodic voltage function to the electrical node, periodic voltage function is modified by ion current compensation I _C to form a periodic voltage function that has been modified, that May be included. The method may also include providing a modified periodic voltage function to the electrical node, the modified periodic voltage function having a pulse and a portion between pulses. The method may also include accessing the effective capacity value C ₁ which represents a capacity of at least the substrate supporting unit. At the same time, the method can include determining the slope dV ₀ / dt of the portion between pulses of the modified periodic voltage function. Finally, the method is to identify the value of the ion current compensation Ic that will result in a defined ion energy distribution function of the ions that reach the surface of the substrate, the identification being the effective capacity C ₁ And the slope dV ₀ / dt of the portion between the pulses.

  According to yet another embodiment, the present invention may be characterized as a method that includes applying, sampling, estimating, and adjusting. As an example, the method may include applying a modified periodic voltage function to the electrical node, the modified periodic voltage function comprising a periodic voltage function modified by ion current compensation. The electrical node can be configured to couple to a substrate support that is coupled to a substrate in the plasma processing chamber. The method may also include sampling at least one cycle of the modified periodic voltage function to generate voltage data points. The method can further include estimating a value of a first ion energy of ions that reach the surface of the substrate, wherein the estimating can be based on voltage data points. Finally, the method can include adjusting the modified periodic voltage function until the first ion energy is equal to the defined ion energy.

  Another aspect of the present disclosure can be characterized as a method that includes providing, sampling, calculating, comparing, and adjusting operations. First, the method can provide a modified periodic voltage function to an electrical node, the electrical node configured to couple to a substrate support of a plasma processing chamber. The method also samples at least two voltages from the modified periodic voltage function at the first time and the second time. Thus, the method can calculate the slope of at least two voltages as dV / dt. The method can also compare the slope to a reference slope that is known to correspond to the ion energy distribution function width. Finally, the method can adjust the modified periodic voltage function so that the slope approaches the reference slope.

Another aspect of the present disclosure, characterized as a non-transitory tangible computer-readable storage medium encoded with processor readable instructions for performing the method of identifying a defined ionic current compensation I _C Can be done. The method may include sampling the modified periodic voltage function given ion current compensation I _C having a first value. The method may further include sampling the modified periodic voltage function given ion current compensation I _C having a second value. Further, the method may include accessing the effective capacity value C ₁ of the plasma processing chamber. The method may further include determining a slope dV ₀ / dt of the modified periodic voltage function based on the first and second samplings. Finally, the method may include calculating a third value of ion current compensation I _C that makes the following equation true:

These and other embodiments are described in further detail herein.
For example, the present invention provides the following.
(Item 1)
An apparatus for providing a modified periodic voltage function to an electrical node, wherein the electrical node is configured to couple to a substrate support of a plasma processing chamber, the apparatus comprising:
A power supply for providing a periodic voltage function to the electrical node, wherein the periodic voltage function comprises a pulse and a portion between the pulses;
An ionic current compensation component that modifies the slope of the portion between the pulses by providing ionic current compensation and thus forms a modified periodic voltage function;
A controller in communication with the switch mode power supply and the ion current compensation component;
With
The controller is configured to identify a value of the ion current compensation that, when provided to the electrical node, will result in a defined ion energy distribution function of ions that reach the surface of the substrate. ,apparatus.
(Item 2)
The apparatus according to item 1, wherein the power supply unit is a switch mode power supply unit.
(Item 3)
The apparatus of claim 2, wherein the switch mode power supply includes one or more switching components.
(Item 4)
The system of claim 1, wherein the controller samples two or more voltages from the modified periodic voltage function and calculates a slope dV ₀ / dt of the two or more voltages .
(Item 5)
Item 5. The slope dV ₀ / dt is calculated based on two or more voltages sampled from a portion of the modified periodic voltage function between pulses of the modified periodic voltage function. System.
(Item 6)
The controller is configured to adjust the switch mode power supply voltage a first time to establish an average ion energy of a first set of ions that reach the surface of the substrate. The system described in.
(Item 7)
The controller is configured to adjust the switch mode power supply voltage a second time to establish an average ion energy of a second set of ions that reach the surface of the substrate. The system described in.
(Item 8)
The switch mode power supply is configured to adjust a voltage step of the modified periodic voltage function to establish the average ion energy of the first set of ions reaching the surface of the substrate. 6. The system according to item 5, being configured.
(Item 9)
The switch mode power supply is configured to adjust a peak-to-peak voltage of the modified periodic voltage function to establish the average ion energy of the first set of ions reaching the surface of the substrate. 6. The system according to item 5, wherein the system is configured.
(Item 10)
Switching of the one or more switching components is timed to affect the slope of the portion of the modified periodic voltage function between the pulses of the modified periodic voltage function. The system according to item 5.
(Item 11)
The apparatus of claim 1, wherein the controller adjusts the amplitude of the ion current compensation until the defined ion energy distribution function of ions arriving at the surface of the substrate is achieved.
(Item 12)
A method of providing a modified periodic voltage function to an electrical node, wherein the electrical node is configured to be electrically coupled to a substrate support of a plasma processing chamber, the method comprising:
Providing a ion current compensation I _C to the electrical node,
The method comprising: providing a periodic voltage function to the electrical node, the periodic voltage function is modified by the ion current compensation I _C, to form the modified periodic voltage function, and that,
Providing the modified periodic voltage function to the electrical node, the modified periodic voltage function comprising a pulse and a portion between the pulses;
Accessing at least an effective capacitance value C ₁ representing the capacitance of the substrate support ;
Determining a slope dV ₀ / dt of the portion between the pulses of the modified periodic voltage function ;
Identifying a value of the ion current compensation Ic that would result in a defined ion energy distribution function of ions reaching the surface of the substrate, the identifying comprising identifying the effective capacitance C ₁ and the Is a function of the slope dV ₀ / dt of the portion between pulses ;
Including a method.
(Item 13)
13. The method of item 12, wherein the defined ion energy distribution is a narrow ion energy distribution.
(Item 14)
The value of the ion current compensation Ic that will result in the defined ion energy distribution function of ions reaching the surface of the substrate is a value that satisfies the function f as follows:
(Equation 11)


13. The method according to item 12.
(Item 15)
Setting the ion current compensation Ic to a first value;
Determining the sign of the function f;
Increasing the ion current compensation Ic if the sign of the function f is positive, and decreasing the ion current compensation Ic if the sign of the function f is negative;
The method according to item 14, further comprising:
(Item 16)
13. The method of item 12, wherein the identifying comprises sampling the voltage of the portion between the pulses of the modified periodic voltage function at two or more times.
(Item 17)
17. The method of item 16, wherein the identifying includes calculating the slope dV ₀ / dt from the voltages sampled at the two or more times .
(Item 18)
The identifying includes calculating the slope dV ₀ / dt for two or more cycles of the modified periodic voltage function , each of the two or more cycles comprising the ion current compensation 18. A method according to item 17, associated with different values of Ic.
(Item 19)
The identifying includes sampling a voltage of the portion between the pulses of the modified periodic voltage function during a first cycle and a second cycle, and at least from these sampled voltages The method according to item 16, comprising calculating the slope dV ₀ / dt.
(Item 20)
13. A method according to item 12, wherein the ion current compensation Ic is linearly related to an ion current I _I across a plasma sheath of plasma formed in the plasma processing chamber .
(Item 21)
The ion current compensation Ic is linearly related to the ion current I _I according to the following equation:
(Equation 12)


C ₁ is the effective volume of the plasma _{chamber, C stray} is the cumulative stray capacitance of the plasma chamber, the method of claim 10.
(Item 22)
The effective capacitance C ₁ varies in time, The method of claim 21.
(Item 23)
Item 22. The method according to Item 21, wherein the ion current compensation Ic varies with time.
(Item 24)
13. The method of item 12, further comprising providing the modified periodic voltage function to the electrical node such that ions reach the surface of the substrate with a first ion energy.
(Item 25)
25. A method according to item 24, wherein the modified periodic voltage function comprises a first voltage step corresponding to the first ion energy.
(Item 26)
26. The method of item 25, further comprising: providing the modified periodic voltage function with a second value of the ion current compensation Ic to the electrical node to expand the ion energy distribution function.
(Item 27)
26. The method of item 25, wherein the first voltage step and the second voltage step are provided in adjacent cycles of the modified periodic voltage function.
(Item 28)
25. A method according to item 24, wherein the providing has a negligible effect on the density of the plasma.
(Item 29)
Applying a modified periodic voltage function to an electrical node, the modified periodic voltage function comprising a periodic voltage function modified by ion current compensation, wherein the electrical node comprises a plasma processing chamber Configured to couple to a substrate support coupled to an inner substrate; and
Sampling at least one cycle of the modified periodic voltage function to generate voltage data points;
Estimating a value of a first ion energy of ions reaching the surface of the substrate, wherein the estimating is based on the voltage data points;
Adjusting the modified periodic voltage function until the first ion energy is equal to a defined ion energy;
Including a method.
(Item 30)
30. The method of item 29, further comprising sampling at least one cycle of the modified periodic voltage function after each voltage increment of the adjustment to estimate the value of the first ion energy.
(Item 31)
30. The method of item 29, wherein the estimating is a function of ion current.
(Item 32)
32. A method according to item 31, wherein the ion current is a function of the ion current compensation.
(Item 33)
The following equation is used in estimating the value of the first ion energy:
(Equation 13)


ΔV is the voltage step of each cycle of the modified periodic voltage function, C ₁ is the effective capacity of the chamber, C _sheath is the sheath capacity of the plasma sheath, and C _sheath is the ion 33. A method according to item 32, which depends on current.
(Item 34)
34. The method of item 33, wherein the adjusting includes adjusting the step voltage ΔV of the modified periodic voltage function until the first ion energy is equal to the defined ion energy. .
(Item 35)
30. The method according to item 29, further comprising changing a first value of the ion current compensation to a second value and expanding a width of the distribution of the ion energy.
(Item 36)
30. The method of item 29, wherein the adjusting includes adjusting a bias supply voltage until the first ion energy is equal to the defined ion energy.
(Item 37)
Providing a modified periodic voltage function to an electrical node, wherein the electrical node is configured to couple to a substrate support of a plasma processing chamber;
Sampling at least two voltages from the modified periodic voltage function at a first time and a second time;
Calculating the slope of the at least two voltages as dV / dt;
Comparing the slope to a reference slope known to correspond to the ion energy distribution function width;
Adjusting the modified periodic voltage function such that the slope approaches the reference slope;
Including a method.
(Item 38)
The first time occurs during a first cycle of the modified periodic voltage function and the second time occurs during a second cycle of the modified periodic voltage function; 38. The method according to item 37.
(Item 39)
38. The method of item 37, wherein the first and second times occur during the same cycle of the modified periodic voltage function.
(Item 40)
38. The method of item 37, wherein the sampling is performed at a sampling rate of at least 400 kHz.
(Item 41)
A non-transitory tangible computer-readable storage medium encoded with processor readable instructions for performing a method for identifying a defined ionic current compensation I _C, the method comprising:
And sampling said ion current compensation I modified periodic voltage function given _C having a first value,
And sampling said ion current compensation I modified periodic voltage function given _C having a second value,
Accessing the effective capacity value C ₁ of the plasma processing chamber ;
Determining a slope dV ₀ / dt of the modified periodic voltage function based on the first and second samplings ;
Calculating a third value of the ion current compensation I _C that makes the following equation true:
(Equation 14)


A non-transitory tangible computer-readable storage medium.
(Item 42)
42. A non-transitory tangible computer readable storage medium according to item 41, further comprising calculating a sheath voltage across a plasma sheath of plasma in the plasma processing chamber.

  Various objects and advantages and a more complete understanding of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings in which like or similar elements are represented by the same reference numerals throughout the several views. It will be clear and readily understood by reference to the detailed description and appended claims.

FIG. 1 illustrates a block diagram of a plasma processing system according to one implementation of the present invention. FIG. 2 is a block diagram depicting an exemplary embodiment of the switch mode power system depicted in FIG. FIG. 3 is a schematic diagram of components that can be utilized to implement the switch mode bias supply described with reference to FIG. FIG. 4 is a timing diagram depicting two drive signal waveforms. FIG. 5 is a single mode graphical representation of operating a switch mode bias supply that provides an ion energy distribution that is concentrated at a particular ion energy. FIG. 6 is a graph depicting a bimodal mode of operation in which two distinct peaks in the ion energy distribution are generated. Figures 7A and 7B are graphs depicting actual direct ion energy measurements made in a plasma. FIG. 8 is a block diagram depicting another embodiment of the present invention. FIG. 9A is a graph depicting an exemplary periodic voltage function modulated by a sinusoidal modulation function. FIG. 9B is an exploded view of a portion of the periodic voltage function depicted in FIG. 9A. FIG. 9C depicts the resulting distribution of ion energy resulting from a sinusoidal modulation of the periodic voltage function based on a time average. FIG. 9D depicts the actual direct ion energy measurements made in a time-averaged IEDF plasma that results when the periodic voltage function is modulated by a sinusoidal modulation function. FIG. 10A depicts that the periodic voltage function is modulated by a sawtooth modulation function. FIG. 10B is an exploded view of a portion of the periodic voltage function depicted in FIG. 10A. FIG. 10C is a graph depicting the resulting distribution of ion energy based on the time average resulting from the sinusoidal modulation of the periodic voltage function in FIGS. 10A and 10B. FIG. 11 is a graph showing the IEDF function in the right column and the modulation function associated with the left column. FIG. 12 is a block diagram depicting an embodiment in which an ion current compensation component compensates for ion current in a plasma chamber. FIG. 13 is a schematic diagram depicting exemplary ion current compensation components. FIG. 14 is a graph depicting an exemplary voltage at node Vo depicted in FIG. 15A-15C are voltage waveforms that appear on the surface of the substrate or wafer in response to the compensation current. FIG. 16 is an exemplary embodiment of a current source that may be implemented to implement the current source described with reference to FIG. 17A and 17B are block diagrams depicting other embodiments of the present invention. FIG. 18 is a block diagram depicting yet another embodiment of the present invention. FIG. 19 is a block diagram depicting yet another embodiment of the present invention. FIG. 20 is a block diagram input parameter and control output that may be utilized in connection with the embodiment described with reference to FIGS. 1-19. FIG. 21 is a block diagram depicting yet another embodiment of the present invention. FIG. 22 is a block diagram depicting yet another embodiment of the present invention. FIG. 23 is a block diagram depicting yet another embodiment of the present invention. FIG. 24 is a block diagram depicting yet another embodiment of the present invention. FIG. 25 is a block diagram depicting yet another embodiment of the present invention. FIG. 26 is a block diagram depicting yet another embodiment of the present invention. FIG. 27 is a block diagram depicting yet another embodiment of the present invention. FIG. 28 illustrates a method according to an embodiment of the present disclosure. FIG. 29 illustrates another method according to certain embodiments of the present disclosure. FIG. 30 illustrates one embodiment of a method for controlling the ion energy distribution of ions that affect the surface of the substrate. FIG. 31 illustrates a method for setting IEDF and ion energy. FIG. 32 illustrates two modified periodic voltage function waveforms delivered to a substrate support, according to one embodiment of the present disclosure. FIG. 33 illustrates ion current waveforms that can indicate plasma source instability or changes in plasma density. FIG. 34 illustrates an ion current I _I of a modified periodic voltage function waveform having an aperiodic shape. FIG. 35 illustrates a modified periodic voltage function waveform that can indicate a fault in the bias supply. FIG. 36 illustrates a modified periodic voltage function waveform that can show dynamic changes in system capacity. FIG. 37 illustrates a modified periodic voltage function waveform that may show a change in plasma density. FIG. 38 illustrates ion current sampling for different process runs where ion current drift can indicate system drift. FIG. 39 illustrates ion current sampling for different process parameters. FIG. 40 illustrates two bias waveforms that were monitored without plasma in the chamber. FIG. 41 illustrates two bias waveforms that can be used to validate the plasma process. FIG. 42 illustrates several power supply voltage and ion energy plots showing the relationship between power supply voltage and ion energy. FIG. 43 illustrates one embodiment of a method for controlling the ion energy distribution of ions affecting the surface of a substrate. FIG. 44 illustrates various waveforms at different points in the system disclosed herein. FIG. 45 illustrates the effect of producing a final gradual change of the ionic current compensation Ic to match the ionic current I _I. FIG. 46 illustrates the selection of ion energy. FIG. 47 illustrates the selection and expansion of the ion energy distribution function width. FIG. 48 illustrates one pattern of power supply voltage V _PS that can be used to achieve more than one ion energy level, with each ion energy level having a narrow IEDF width. FIG. 49 illustrates another pattern of power supply voltage V _PS that can be used to achieve more than one ion energy level, with each ion energy level having a narrow IEDF width. FIG. 50 illustrates one combination of power supply voltage V _PS and ion current compensation I _C that can be used to generate a defined IEDF.

  An exemplary embodiment of a plasma processing system is generally shown in FIG. As depicted, the plasma power supply 102 is coupled to the plasma processing chamber 104 and the switch mode power supply 106 is coupled within the chamber 104 to a support 108 on which the substrate 110 is placed. The Also shown is a controller 112 that is coupled to the switch mode power supply 106.

  In this exemplary embodiment, the plasma processing chamber 104 may be realized by a chamber of substantially conventional structure (eg, including a vacuum enclosure that is evacuated by a pump or pumps (not shown)). . Also, as will be appreciated by those skilled in the art, the plasma excitation in the chamber 104 can be from any one of a variety of sources, such as, for example, a helicon type plasma source, and the various sources can be within the reactor. Including a magnetic coil and antenna for igniting and sustaining the plasma 114, a gas inlet may be provided to introduce gas into the chamber 104.

  As depicted, the exemplary plasma chamber 104 is arranged to perform plasma assisted etching of the material utilizing energetic ion bombardment and other plasma processing (eg, plasma deposition and plasma assisted ion implantation) of the substrate 110. And composed. The plasma power supply 102 in this embodiment is configured to chamber 104 via a matching circuit (not shown) at one or more frequencies (eg, 13.56 MHz) to ignite and sustain the plasma 114. Configured to apply power (e.g., RF power). The present invention is not limited to any particular type of plasma power supply 102 or source for coupling power to the chamber 104, and various frequencies and power levels are capacitively or inductively coupled to the plasma 114. It should be understood that these can be combined.

  As depicted, a dielectric substrate 110 to be processed (eg, a semiconductor wafer) is at least partially supported by a support 108 that may include a portion of a conventional wafer chuck (eg, for semiconductor wafer processing). Is done. The support 108 has an insulating layer between the support 108 and the substrate 110, and the substrate 110 may be formed to be capacitively coupled to the platform, but may float at a different voltage than the support 108. .

  As described above, when the substrate 110 and the support portion 108 are conductors, an invariable voltage can be applied to the support portion 108, and the voltage applied to the support portion 108 as a result of electrical conduction through the substrate 110. Is also applied to the surface of the substrate 110.

  However, if the substrate 110 is dielectric, application of a constant voltage to the support 108 is not effective to apply a voltage across the surface of the substrate 110 being processed. As a result, the exemplary switch mode power supply 106 attracts ions to collide with the substrate 110 in the plasma 114 so as to perform a controlled etching and / or deposition and / or other plasma assisted process of the substrate 110. It is configured to be controlled to provide a voltage on the surface of the substrate 110 that is possible.

  Further, as further discussed herein, embodiments of the switch mode power supply 106 include power applied by the plasma power supply 102 (to the plasma 114) and the substrate 110 by the switch mode power supply 106. It is configured to operate such that there is very little interaction with the applied power. The power applied by the switch mode power supply 106 can be controlled to allow control of ion energy without substantially affecting the density of the plasma 114, for example.

  Further, many embodiments of the exemplary switch mode power supply 106 depicted in FIG. 1 are implemented with relatively inexpensive components that can be controlled by a relatively simple control algorithm. Also, compared to prior art approaches, many embodiments of the switch mode power supply 106 are much more efficient. That is, it reduces energy costs and expensive materials associated with removing excess thermal energy.

  One known technique for applying a voltage to a dielectric substrate utilizes a high power linear amplifier along with a complex control scheme for applying power to the substrate support that induces a voltage at the surface of the substrate. To do. However, this technology has not been adopted by commercial entities because it has been found to be not cost effective or well manageable. In particular, the utilized linear amplifiers are typically large, very expensive, inefficient, and difficult to control. Furthermore, linear amplifiers essentially require AC coupling (eg, blocking capacitors) and auxiliary functions such as chucking, which auxiliary functions such as chucking are achieved by a parallel power supply circuit. The circuit, along with the chuck, compromises the AC spectral purity of the system relative to the source.

  Another technique that has been considered is to apply high frequency power to the substrate (eg, by one or more linear amplifiers). However, it has been found that this technique adversely affects the plasma density because the high frequency power applied to the substrate affects the plasma density.

  In some embodiments, the switch mode power supply 106 depicted in FIG. 1 may be implemented with buck, boost, and / or buck-boost power technologies. In these embodiments, the switch mode power supply 106 may be controlled to apply a variable level of pulsed power and induce a potential on the surface of the substrate 110.

  In other embodiments, the switch mode power supply 106 is implemented with other more advanced switch mode power and control techniques. Referring now to FIG. 2, for example, the switch mode power supply described with reference to FIG. 1 applies power to the substrate 110 and produces one or more desired energies of ions that impact the substrate 110. Implemented by a switch mode bias supply 206 that is utilized to provide. Also shown is a controller 212 coupled to the ion energy control component 220, the arc detection component 222, and both the switch mode bias supply 206 and the waveform memory 224.

  The illustrated arrangement of these components is logical. Thus, the components can be combined or further separated in actual implementations, and the components can be connected in various ways without changing the basic operation of the system. In some embodiments, a controller 212, which can be implemented, for example, by hardware, software, firmware, or a combination thereof, can be utilized to control both the power supply 202 and the switch mode bias supply 206. However, in an alternative embodiment, the power supply 202 and the switch mode bias supply 206 are implemented by completely separated functional units. As a further example, the controller 212, waveform memory 224, ion energy control portion 220, and switch mode bias supply 206 can be integrated into a single component (eg, residing in a common housing) or individual. It can be distributed among the components.

  The switch mode bias supply 206 in this embodiment generally applies a voltage to the support 208 in a controllable manner to provide a desired (or defined) distribution of the energy of ions impinging on the surface of the substrate. Configured to apply. More specifically, the switch mode bias supply 206 provides a desired (or defined) distribution of ion energy by applying one or more specific waveforms to the substrate at specific power levels. Configured. Even more specifically, in response to an input from the ion energy control portion 220, the switch mode bias supply 206 provides a specific ion energy by applying a specific power level, within the waveform memory 224. One or more voltage waveforms defined by the waveform data are used to apply a particular power level. As a result, one or more specific ion bombardment energies can be selected by the ion control portion to perform a controlled etch (or other form of plasma processing) of the substrate.

  As depicted, switch mode power supply 206 is adapted to switch power to support 208 of substrate 210 in response to drive signals from corresponding drive components 228 ', 228' '. It includes switch components 226 ′, 226 ″ (eg, high power field effect transistors). Also, the drive signals 230 ′, 230 ″ generated by the drive components 228 ′, 228 ″ are controlled by the controller 212 based on the timing defined by the contents of the waveform memory 224. For example, the controller 212 in many embodiments is adapted to interpret the contents of the waveform memory and generate the drive control signals 232 ′, 232 ″, which are switched components 226. Used by drive components 228 ', 228 "to control drive signals 230', 230" to '226'. Two switch components 226 ', 226' ', which can be arranged in a half-bridge configuration, are depicted for illustrative purposes, but it will be appreciated that fewer or additional switch components may be used in various architectures (e.g., It is envisioned that it may be implemented within an H-bridge configuration.

  In many modes of operation, the controller 212 (eg, using waveform data) modulates the timing of the drive control signals 232 ′, 232 ″ to provide the desired waveform at the support 208 of the substrate 210. In addition, the switch mode bias supply 206 is adapted to supply power to the substrate 210 based on the ion energy control signal 234, which can be a DC signal or a time-varying waveform. Thus, this embodiment controls the timing signal to the switching component and by controlling the power (controlled by the ion energy control component 220) applied by the switching component 226 ′, 226 ″. Allows control of ion distribution energy.

  In addition, the controller 212 in this embodiment is configured to perform an arc management function in response to an arc in the plasma chamber 204 detected by the arc detection component 222. In some embodiments, once an arc is detected, the controller 212 may control the drive control signal 232 ′, such that the waveform applied at the output 236 of the switch mode bias supply 206 extinguishes the arc in the plasma 214. Change 232 ″. In other embodiments, the controller 212 may interrupt the arc by simply interrupting the application of the drive control signals 232 ′, 232 ″ so that application of power at the output 236 of the switch mode bias supply 206 is interrupted. Turn off.

  Reference is now made to FIG. 3, which is a schematic illustration of components that can be utilized to implement the switch mode bias supply 206 described with reference to FIG. As shown, the switching components T1 and T2 in this embodiment are arranged in a half-bridge (also referred to as totem pole) topology. Collectively, R2, R3, C1, and C2 represent plasma loads, C10 is the effective capacity (also referred to herein as series capacity or chuck capacity), and C3 is on the surface of the substrate. Any physical capacitor to prevent DC current from the induced voltage or the electrostatic chuck (not shown) voltage from flowing through the circuit. C10 includes a series capacity (also referred to as a chuck capacity) of the substrate support and the electrostatic chuck (or E chuck), and other capacity inherent to the application of bias such as insulation and the substrate, and hence is referred to as an effective capacity. Is done. As depicted, L1 is the stray inductance (eg, the natural inductance of the conductor that powers the load). Also, in this embodiment, there are three inputs: Vbus, V2, and V4.

  V2 and V4 represent drive signals (eg, drive signals 230 ′, 230 ″ output by drive components 228 ′, 228 ″ described with reference to FIG. 2), and in this embodiment, V2 and V4 can be timed so that the closure of T1 and T2 can be modulated and control the shape of the voltage output at Vout applied to the substrate support (eg, the pulse Length and / or mutual delay). In many implementations, the transistors used to implement the switching components T1 and T2 are not ideal switches, and therefore transistor-specific characteristics are considered in order to reach the desired waveform. In many modes of operation, simply changing the timing of V2 and V4 allows the application of the desired waveform at Vout.

  For example, the switches T1, T2 can be operated so that the voltage at the surface of the substrate 110, 210 is generally negative and the periodic voltage pulse approaches and / or slightly exceeds the positive voltage reference. The value of the voltage at the surface of the substrate 110, 210 defines the energy of the ions, which can be characterized in terms of the ion energy distribution function (IEDF). To provide the desired voltage at the surface of the substrate 110, 210, the pulse at Vout attracts enough electrons to the surface of the substrate 110, 210 to achieve a desired voltage and corresponding ion energy, generally rectangular. And may have a width long enough to induce a short positive voltage at the surface of the substrate 110, 210.

  Periodic voltage pulses approaching and / or slightly exceeding the positive voltage reference may have a minimum time limited by the switching capability of the switches T1, T2. As long as the voltage does not accumulate to a level that damages the switch, the generally negative portion of the voltage can be extended. At the same time, the length of the negative part of the voltage should exceed the ion transition time.

  Vbus in this embodiment defines the amplitude of the pulse measured at Vout, which defines the voltage at the surface of the substrate and consequently the ion energy. Again, referring briefly to FIG. 2, the Vbus can be coupled to an ion energy control portion, which is realized by a DC power supply adapted to apply a DC signal or time-varying waveform to the Vbus. Can be done.

  The pulse width, pulse shape, and / or the mutual delay of the two signals V2, V4 is modulated to reach the desired waveform at Vout (also referred to herein as a modified periodic voltage function). In addition, the voltage applied to Vbus can affect the characteristics of the pulse. In other words, the voltage Vbus can affect the pulse width, the pulse shape, and / or the relative phase of the signals V2, V4. Referring briefly to FIG. 4, for example, as depicted in FIG. 4, two drive signal waveforms (as V2 and V4) that can be applied to T1 and T2 to generate a periodic voltage function at Vout. A timing diagram depicting is shown. In order to modulate the shape of the pulse at Vout (eg, to achieve a minimum pulse time at Vout but to reach the peak value of the pulse), the timing of the two gate drive signals V2, V4 is controlled. Can be done.

  For example, the time that each pulse is applied at Vout is short compared to the time T between pulses, but induces a positive voltage at the surface of the substrate 110, 210, causing electrons on the substrate 110, 210 surface. Two gate drive signals V2, V4 can be applied to the switching components T1, T2 so that they can be long enough to attract. Furthermore, it has been found that by changing the gate voltage level between pulses, the slope of the voltage applied to Vout between pulses can be controlled (eg, substantially between the pulses at the surface of the substrate). To achieve constant voltage). In some modes of operation, the repetition rate of the gate pulse is about 400 kHz, but this rate can of course vary from application to application.

  Although not required, in practice, a waveform that can be used to generate a desired (or defined) ion energy distribution can be defined based on modeling and refinement of the actual implementation, and the waveform can be defined (e.g., Can be stored as a series of voltage levels (in the waveform memory portion described with reference to FIG. 1). In addition, in many implementations, the waveform can be generated directly (eg, without feedback from Vout). Thus, undesirable aspects of the feedback control system are avoided (eg, settling time).

  Referring again to FIG. 3, Vbus can be modulated to control the energy of the ions, while the stored waveform controls the gate drive signals V2, V4 to achieve the desired pulse amplitude at Vout. Can be used to minimize the pulse width. Again, this is done according to the specific characteristics of the transistor that can be modeled or implemented and established experimentally. Referring to FIG. 5, a graph depicting, for example, Vbus vs. time, voltage at the surface of the substrate 110, 210 vs. time, and corresponding ion energy distribution is shown.

  The graph of FIG. 5 depicts a single mode of operating the switch mode bias supply 106, 206 resulting in an ion energy distribution that is concentrated at a particular ion energy. As depicted, to provide a single concentration of ion energy in this example, the voltage applied to Vbus remains constant while the voltages applied to V2 and V4 are shown in FIG. Controlled to generate pulses at the output of the switch mode bias supplies 106, 206, resulting in corresponding ion energy distributions (eg, using the drive signals depicted in FIG. 3).

  As depicted in FIG. 5, the potential at the surface of the substrate 110, 210 is generally negative and strikes the surface of the substrate 110, 210 and attracts ions to etch. Periodic short pulses (by applying a pulse to Vout) applied to the substrates 110, 210 have a scale defined by the potential applied to Vbus, which is the potential of the substrates 110, 210. A short time change (eg, near positive or weakly positive potential), and the short time change in potential generally achieves a negative potential along the surface of the substrate 110, 210. Attracts electrons to the surface. As depicted in FIG. 5, a constant voltage applied to Vbus results in a single concentrated ion flux at a particular ion energy. Thus, a specific ion bombardment energy can be selected by simply setting Vbus to a specific potential. In other modes of operation, two or more separate concentrations of ion energy may be generated (see, eg, FIG. 49).

One skilled in the art will recognize that the power supply need not be limited to a switch mode power supply, and therefore, the power supply output can also be controlled to achieve some ion energy. Will. Therefore, the power supply output, whether in switch mode or otherwise, is also referred to as power supply voltage V _PS when considered without being combined with ion current compensation or ion current. it can.

  Referring now to FIG. 6, a graph depicting a bimodal mode of operation is shown, for example, where two distinct peaks are generated in the ion energy distribution. As shown, in this mode of operation, the substrate experiences two different levels of voltage and periodic pulses, resulting in two separate concentrations of ion energy. As depicted, to provide two different ion energy concentrations, the voltage applied at Vbus alternates between the two levels, each level defining the energy level of the two ion energy concentrations.

  Although FIG. 6 depicts the two voltages at the substrates 110, 210 to alternate after each pulse (eg, FIG. 48), this is not necessary. In other modes of operation, for example, the voltage applied to V2 and V4 is such that the voltage induced at the surface of the substrate is changed from the first voltage to the second after two or more pulses (eg, FIG. 49). It is switched (eg, using the drive signal depicted in FIG. 3) for the voltage applied to Vout to alternate with the voltage (and vice versa).

  In the prior art, a combination of two waveforms (generated by a waveform generator) is applied to a linear amplifier and a combination of two or more amplified waveforms is applied to a substrate to provide multiple ion energy. Has been tried. However, this approach is much more complex than the approach described with reference to FIG. 6 and therefore requires expensive linear amplifiers and waveform generators.

  Referring now to FIGS. 7A and 7B, depict actual direct ion energy measurements made in the plasma, corresponding to single energy adjustment and dual level adjustment of the DC voltage applied to Vbus, respectively. A graph is shown. As depicted in FIG. 7A, the ion energy distribution is concentrated to about 80 eV in response to a constant application of voltage to Vbus (eg, as depicted in FIG. 5). Also in FIG. 7B, two distinct concentrations of ion energy are present at about 85 eV and 115 eV in response to the dual level adjustment of Vbus (eg, as depicted in FIG. 6).

  Referring now to FIG. 8, a block diagram depicting another embodiment of the present invention is shown. As depicted, switch mode power supply 806 is coupled to substrate support 808 via controller 812, ion energy control component 820, and arc detection component 822. The controller 812, switch mode supply 806, and ion energy control component 820 collectively provide a desired (or defined) ion energy distribution at the surface of the substrate 810 based on a time average. Operate to provide power to the substrate support 808.

  For example, referring briefly to FIG. 9A, a periodic voltage function with a frequency of about 400 kHz is shown, which is modulated by a sinusoidal modulation function of about 5 kHz over multiple cycles of the periodic voltage function. . FIG. 9B is an exploded view of the portion of the periodic voltage function circled in FIG. 9A, and FIG. 9C results from the ion energy based on the time average resulting from the sinusoidal modulation of the periodic voltage function. Describe the distribution. FIG. 9D also depicts the actual direct ion energy measurements made in the plasma of the resulting time average IEDF when the periodic voltage function is modulated by a sinusoidal modulation function. As further discussed herein, achieving a desired (or defined) ion energy distribution based on a time average is accomplished by simply changing the modulation function applied to the periodic voltage. obtain.

  As another example, referring to FIGS. 10A and 10B, a 400 kHz periodic voltage function is based on a time average to achieve a distribution of ion energy depicted in FIG. 10C at about 5 kHz sawtooth modulation. Modulated by function. As depicted, the periodic voltage function utilized in connection with FIG. 10 is the same as in FIG. 9, but the periodic voltage function in FIG. 10 is a sawtooth wave instead of a sinusoidal function. Modulated by function.

  It should be appreciated that the ion energy distribution function depicted in FIGS. 9C and 10C does not represent the instantaneous distribution of ion energy at the surface of the substrate 810, but instead represents the time average of ion energy. Referring to FIG. 9C, for example, at a particular time instant, the distribution of ion energy would be a subset of the depicted distribution of ion energy that exists over the course of one cycle of the modulation function.

  It should also be appreciated that the modulation function need not be a fixed function or a fixed frequency. For example, in some cases, a periodic voltage function is modulated by one or more cycles of a particular modulation function, resulting in a particular time average ion energy distribution, and then one or more cycles of another modulation function It may be desirable to modulate the periodic voltage function resulting in another time-averaged ion energy distribution. Changes to such a modulation function (which modulates the periodic voltage function) can be beneficial in many cases. For example, if a specific ion energy distribution is required to etch a specific geometric structure or to etch through a specific material, a first modulation function is used, then subsequently Different modulation functions can be used to produce different etching geometries or to etch through different materials.

  Similarly, the periodic voltage function (eg, the 400 kHz component in FIGS. 9A, 9B, 10A, and 10B, and Vout in FIG. 4) need not be strictly fixed (eg, the shape and frequency of the periodic voltage function). However, in general, the frequency is established by the elapsed time of the ions in the chamber so that the ions in the chamber are affected by the voltage applied to the substrate 810.

  Referring back to FIG. 8, the controller 812 provides the drive control signals 832 ′ and 832 ″ to the switch mode supply unit 806 so that the switch mode supply unit 806 generates a periodic voltage function. The switch mode supply 806 can be implemented by the components depicted in FIG. 3 (eg, to create the periodic voltage function depicted in FIG. 4), although other switching architectures can be utilized. Of course, recalled.

  In general, the ion energy control component 820 functions to apply a modulation function to a periodic voltage function (generated by the controller 812 in connection with the switch mode power supply 806). As shown in FIG. 8, the ion energy control component 820 includes a custom IEDF portion 850, an IEDF function memory 848, a user interface 846, and a modulation controller 840 that communicates with the power component 844. It should be appreciated that the depiction of these components is actually intended to convey functional components that may be provided by common or separate components.

  Modulation controller 840 in this embodiment generally controls power component 844 (and thus its output 834) based on data defining a modulation function, which is generated by switch mode supply 806. A modulation function 834 (based on a control signal 842 from the modulation controller 840) applied to the periodic voltage function. The user interface 846 in this embodiment allows the user to select a predetermined IEDF function that is stored in the IEDF function memory 848 or to define a custom IEDF in connection with the custom IEDF component 850. Configured to be.

  In many implementations, the power component 844 is a DC power supply that applies a modulation function (eg, a variable DC voltage) to a switch mode power supply (eg, Vbus of the switch mode power supply depicted in FIG. 3). (Eg, DC switch mode power supply or linear amplifier). In these implementations, the modulation controller 840 controls the voltage level output by the power component 844 such that the power component 844 applies a voltage that matches the modulation function.

  In some implementations, IEDF function memory 848 includes a plurality of data sets corresponding to each of a plurality of IEDF distribution functions, and user interface 846 allows a user to select a desired (or defined) IEDF function. Make it possible to do. For example, referring to FIG. 11, an exemplary IEDF function that may be available for a user to select is shown in the right column. The left column also depicts the associated modulation function that the modulation controller 840 will apply to the periodic voltage function in conjunction with the power component 844, resulting in a corresponding IEDF function. It should be appreciated that the IEDF function depicted in FIG. 11 is exemplary only, and other IEDF functions may be available for selection.

  Custom IEDF component 850 generally functions to allow a user to define a desired (or defined) ion energy distribution function via user interface 846. For example, in some implementations, the custom IEDF component 850 allows the user to establish values for specific parameters that define the distribution of ion energy.

  For example, the custom IEDF component 850 can be used with respect to the relative levels of flux (eg, with respect to the percentage of flux at high levels (IF-high), intermediate levels (IF-mid), and low levels (IF-low)). In conjunction with a function that defines an IEDF between different energy levels, an IEDF function may be defined. In many cases, only IF-high, IF-low, and IEDF functions between these levels are sufficient to define the IEDF function. As a specific example, a user may request 1200 eV at a 20% contribution level (contribution to the overall IEDF) and 700 eV at a 30% contribution level, along with a sinusoidal IEDF between these two levels.

  Custom IEDF portion 850 may also allow the user to create a table with a list of one or more (eg, multiple) energy levels and the corresponding percentage contribution of each energy level to IEDF. Is recalled. Also, in a further alternative embodiment, custom IEDF component 850 presents a graphical tool associated with user interface 846 that allows the user to draw a desired (or defined) IEDF. It is recalled that this allows the user to graphically generate the desired (or defined) IEDF.

  In addition, the IEDF function memory 848 and the custom IEDF component 850 also allow the user to select a predetermined IEDF function and then generate a custom IEDF function that is derived from the predetermined IEDF function. It is recalled that they can interact to allow the function to be modified.

  Once the IEDF function is defined, the modulation controller 840 provides data defining the desired (or defined) IEDF function and the power component 844 provides a modulation function corresponding to the desired (or defined) IEDF. Thus, the power component 844 is converted into a control signal 842 for controlling. For example, the control signal 842 controls the power component 844 such that the power component 844 outputs a voltage defined by the modulation function.

  Referring now to FIG. 12, a block diagram of an embodiment in which the ion current compensation component 1260 compensates for ion current in the plasma chamber 1204 is depicted. Applicants have found that at high energy levels, the high level of ion current in the chamber affects the voltage at the surface of the substrate, and as a result, the ion energy distribution is also affected. For example, referring briefly to FIGS. 15A-15C, voltage waveforms as they appear on the surface of the substrate 1210 or wafer and their relationship to the IEDF are shown.

More specifically, FIG. 15A depicts a periodic voltage function at the surface of the substrate 1210 when the ionic current I _I is equal to the compensation current Ic, and FIG. 15B illustrates that the ionic current I _I FIG. 15C depicts the voltage waveform at the surface of the substrate 1210 when the ion current is less than the compensation current Ic.

When I _I = Ic, depicted in FIG. 15A, the spread of ion energy 1470 is depicted in FIG. 15B, the uniform spread of ion energy 1472 when I _I > Ic, or depicted in FIG. 15C. Compared with the uniform spread 1474 of ion energy when I _I <Ic, it is relatively narrow. Accordingly, the ion current compensation component 1260 allows a narrow spread of ion energy (eg, by compensating for the effects of ion current) when the ion current is high, and the width of the uniform ion energy spread 1572, 1574. Is controllable (eg, where it is desirable to have a spread of ion energy).

As depicted in FIG. 15B, without ion current compensation (if I _I > Ic), the voltage at the surface of the substrate between the positive portions of the periodic voltage function is progressively less negative with a smaller absolute value. Value, creating a wider spread 1572 of ion energy. Similarly, when ion current compensation is utilized to raise the level of compensation current to a level above the ion current (I _I <Ic), as depicted in FIG. 15C, the voltage at the surface of the substrate is During the positive part of the periodic voltage function, progressively more absolute negative values and a wider spread 1574 of uniform ion energy is created.

  Referring back to FIG. 12, the ion current compensation component 1260 can optionally be implemented as a separate appendage that can be added to the switch mode power supply 1206 and the controller 1212. In other embodiments (eg, as depicted in FIG. 13), the ionic current compensation component 1260 may be connected to the common housing 1366 with other components described herein (eg, switch mode power supplies). 106, 206, 806, 1206 and ion energy control 220, 820 components). In this embodiment, the periodic voltage function provided to the plasma chamber 1204 comprises a periodic voltage function that is modified by ion current compensation from the ion current compensation component 1260, so that the modified periodic voltage function It can be called. The controller 1212 can sample the voltage at different times at the electrical node where the output of the switch mode power supply 1206 and the output of the ionic current compensation 1260 merge.

An exemplary ion current comprising a current source 1364 coupled to the output 1336 of the switch mode supply and a current controller 1362 coupled to both the current source 1364 and the output 1336, as depicted in FIG. A compensation component 1360 is shown. Also depicted in FIG. 13 is a plasma chamber 1304, in which there are capacitive elements C ₁ , C ₂ , and ion current I _I. As depicted, C ₁ may include insulation, substrate, substrate support, and electrostatic chuck, including, but not limited to, the intrinsic capacity of components associated with chamber 1304 (effective capacity herein). also referred) represents, C ₂ represents the sheath capacitance and stray capacitance. In this embodiment, the periodic voltage function provided to the plasma chamber 1304 and measurable at V _{0 comprises} a periodic voltage function that is modified by the ion current compensation Ic, so the modified periodic voltage function. Can be called.

A sheath (also referred to herein as a plasma sheath) is a layer of plasma that is near the substrate surface, and possibly near the walls of the plasma processing chamber, that has a high density of positive ions, and thus an overall excess of positive charge. Accompany. The surface with which the sheath is in contact typically has an overwhelming number of negative charges. The sheath is caused by a velocity of electrons that is faster than the positive ions, thus causing the majority of the electrons to reach the substrate surface or wall, thus leaving the sheath deprived of electrons. The sheath thickness λ _sheath is a function of plasma properties such as plasma density and plasma temperature.

Since C ₁ in this embodiment is the inherent (also referred to herein as effective) capacity of the component associated with chamber 1304, it is the accessible capacity that is added to gain control of the process. Note that there is no. For example, some prior art approaches that utilize linear amplifiers couple bias power to the substrate with a blocking capacitor, and then use the monitoring voltage of the blocking capacitor as feedback to control the linear amplifier. While a capacitor may couple the switch mode power supply to the substrate support in many of the embodiments disclosed herein, feedback control using a blocking capacitor is, in some embodiments of the invention, It is unnecessary to do so because it is not required.

  With reference to FIG. 13, simultaneously refer to FIG. 14, which is a graph depicting an exemplary voltage (eg, a modified periodic voltage function) at Vo depicted in FIG. 13. In operation, the current controller 1362 monitors the voltage at Vo and the ionic current is calculated over the interval t (depicted in FIG. 14) as follows.

Either or both of the ionic current I _I and the specific capacity C ₁ (also referred to as effective capacity) can change over time. Since C ₁ is substantially a constant for a given tool and is measurable, only Vo needs to be monitored to allow continuous control of the compensation current. As described above, to obtain a more monoenergetic distribution of ion energy (eg, as depicted in FIG. 15A), the current controller is such that Ic is substantially the same as I _I (or In the alternative, the current source 1364 is controlled as related to Equation 2). In this way, the narrow spread of ion energy can be maintained even when the ion current reaches a level that affects the voltage at the surface of the substrate. In addition, if desired, the spread of ion energy can be controlled as depicted in FIGS. 15B and 15C such that additional ion energy is realized at the surface of the substrate.

Also depicted in FIG. 13 is a feedback line 1370 that may be utilized in connection with controlling ion energy distribution. For example, the value of ΔV depicted in FIG. 14 (also referred to herein as a voltage step or third portion 1406) indicates the instantaneous ion energy and as part of a feedback control loop, many embodiments Can be used. In one embodiment, the voltage step ΔV is related to ion energy according to Equation 4. In other embodiments, the peak-to-peak voltage V _PP can be related to the instantaneous ion energy. Alternatively, the difference between the peak-to-peak voltage V _PP and the product of the slope dV ₀ / dt of the fourth portion 1408 and time t can be related to the instantaneous ion energy (eg, V _PP − dV ₀ / dt · t).

  Referring now to FIG. 16, there is shown an exemplary embodiment of a current source 1664 that can be implemented to implement the current source 1364 described with reference to FIG. In this embodiment, the controllable negative DC voltage source functions as a current source in connection with the series inductor L2, but those skilled in the art will recognize, in light of this specification, that the current source may be other components and / or It will be understood that it can be realized by configuration.

FIG. 43 illustrates one embodiment of a method for controlling the ion energy distribution of ions affecting the surface of a substrate. The method 4300 begins by applying a modified periodic voltage function 4302 (see modified periodic voltage function 4402 in FIG. 44) to a substrate support that supports a substrate in a plasma processing chamber. The modified periodic voltage function includes at least two “knobs” such as ion current compensation I _C (see I _C 4404 in FIG. 44) and power supply voltage V _PS (see power supply voltage 4406 in FIG. 44). Can be controlled via. An exemplary component for generating the power supply voltage is the switch mode power supply 106 of FIG. To help explain the power supply voltage V _PS , this is illustrated herein as measured without coupling to ionic current and ionic current compensation. The modified periodic voltage function is then sampled at the first and second values of ion current compensation I _C 4304. At least two samples of the modified periodic voltage function of the voltage is obtained for each value of the ion current compensation I _C. Sampling 4304 is performed to allow calculation 4306 (or determination) of ionic current I _I and sheath capacitance C _sheath 4306. Such a determination would produce a narrow (eg, minimum) ion energy distribution function (IEDF) width when applied to the substrate support (or when applied to the substrate support). It may involve finding the I _C. The calculation 4306 also optionally determines a voltage step ΔV (also known as the third part of the modified periodic voltage function 1406) based on a sampling 4304 of the waveform of the modified periodic voltage function. Can also include. The voltage step ΔV can be related to the ion energy of the ions that reach the surface of the substrate. When first finding the ion current I _I , the voltage step ΔV can be ignored. Details of sampling 4304 and calculation 4306 are provided in the discussion of FIG. 30 below.

Once the ionic current I _I and the sheath capacity C _sheath are known, the method 4300 may move to the method 3100 of FIG. 31, which involves setting and monitoring the ion energy and shape (eg, width) of the IEDF. . For example, FIG. 46 illustrates how a change in power supply voltage can result in a change in ion energy. In particular, the magnitude of the illustrated power supply voltage is reduced, resulting in a reduction in the magnitude of ion energy. In addition, FIG. 47, considering the narrow IEDF4714, illustrates that can enlarge the IEDF by adjusting the ionic current compensation _{I C.} Alternatively or in parallel, the method 4300 is described with reference to FIGS. 32-41 that utilize other aspects of the waveform of the ionic current I _I , sheath capacitance C _sheath , and the modified periodic voltage function. As described above, various measurement methods can be performed.

In addition to setting the ion energy and / or IEDF width, the method 4300 may adjust the modified periodic voltage function 4308 to maintain the ion energy and IEDF width. In particular, adjustment of ion current compensation I _C provided by the ion current compensation component and adjustment of power supply voltage may be performed 4308. In some embodiments, the power supply voltage may be controlled by the power supply bus voltage V _bus (eg, the bus voltage V _{bus of} FIG. 3). Ion current compensation I _C controls the IEDF width, the power supply unit voltage controls the ion energy.

After these adjustments 4308, the modified periodic voltage function can be resampled 4304, and the calculation of ion current I _I , sheath capacitance C _sheath , and voltage step ΔV can be performed 4306 again. If the ionic current I _I or voltage step ΔV is other than a defined value (or an alternative desired value), the ionic current compensation I _C and / or power supply voltage can be adjusted 4308. A loop of sampling 4304, calculation 4306, and adjustment 4308 may occur to maintain ion energy eV and / or IEDF width.

FIG. 30 illustrates another embodiment of a method for controlling the ion energy distribution of ions that affect the surface of the substrate. In some embodiments, as discussed above, it may be desirable to achieve a narrow IEDF width (eg, a minimum IEDF width or about 6% full width at half maximum in the alternative). Thus, the method 3000 can provide a modified periodic voltage function to the chamber and substrate support such that a constant substrate voltage, and thus a sheath voltage, is present at the surface of the substrate. This in turn accelerates the ions across the sheath with a substantially constant voltage, thus allowing the ions to affect the substrate with substantially the same ion energy, which in turn provides a narrow IEDF width. For example, in FIG. 45, it can be seen that adjusting the ionic current compensation I _C can cause the substrate voltage V _sub between pulses to have a constant or substantially constant voltage, thus narrowing the IEDF.

Such a modified periodic voltage function does not assume any stray capacitance and is achieved when the ion current compensation I _C is equal to the ion current I _I (of the periodic voltage function (V ₀ ) of FIG. 45). See last 5 cycles). In an alternative where the _stray capacitance C _strain is considered, the ionic current compensation I _C is related to the ionic current I _I according to Equation 2.

In the formula, C ₁ is an effective capacity (for example, a specific capacity described with reference to FIGS. 3 and 13). Effective capacity C ₁ may be either be time varying, or constant. For purposes of this disclosure, a narrow IEDF width can exist either when I _I = I _C , or alternatively when Equation 2 is satisfied. FIGS. 45-50 specifically use I _I = I _C , but these equations are only simplifications of Equation 2, and therefore Equation 2 is used in FIGS. 45-50. It should be understood that an equation can be substituted. The stray capacitance C _strain is the cumulative volume of the plasma chamber as seen by the power supply. There are eight cycles illustrated in FIG.

The method 3000 may include a modified periodic voltage function (eg, the modified periodic voltage function depicted in FIG. 14 or the modified FIG. 44) to the substrate support 3002 (eg, the substrate support 108 of FIG. 1). Application of the periodic voltage function 4402). The voltage of the modified periodic voltage function can be sampled more than once 3004, from which a slope dV ₀ / dt for at least a portion of the modified periodic voltage function cycle can be calculated 3006 ( For example, the slope of the portion or the fourth portion 1408 during the pulse). At some point before decision 3010, access to previously determined values (eg, from memory or from user input) of effective capacity C ₁ (eg, specific capacity C _{1 in} FIG. 13 and specific capacity C _{10 in} FIG. 3). Can be 3008. Based on the slope dV ₀ / dt, effective capacity C ₁ , and ion current compensation I _C , the function f (Equation 3) can be evaluated for each value of the ion current compensation I _C as follows.

If the function f is true, the ion current compensation I _C is equal to the ion current I _I , or alternatively, Equation 2 is true and a narrow IEDF width is achieved 3010 (see, eg, FIG. 45). If the function f is not true, until the function f is true, it is possible to further adjust the ionic current compensation I _C 3012. Another way of looking at this, until matching the ion current I _I (or, in alternative to satisfy the relationship of Equation 2) can modulate ion current compensation I _C, narrow IEDF width is present at that time Will. Such adjustment to ion current compensation Ic and the narrowing that results from IEDF can be seen in FIG. The ionic current I _I and the corresponding ionic current compensation Ic can be stored (eg, in a memory) at a storage operation 3014. The ionic current I _C can be time-varying, similar to the effective capacity C ₁ .

When equation 3 is satisfied, the ionic current I _I is known (either because I _C = I _I or because equation 2 is true). Thus, the method 3000 allows remote and non-invasive measurement of the ionic current I _{I in} real time without affecting the plasma. This leads to several new metrics such as those that will be described with reference to FIGS. 32-41 (eg, remote monitoring of plasma density and remote failure detection of the plasma source).

While adjusting the compensation current I _C 3012, the ion energy is likely to be wider than the delta function, and the ion energy will be similar to that of either FIG. 15B, 15 C, or 44. However, once the compensation current _{I C} that satisfies the equation 2 is found, IEDF is, as illustrated in the right portion of FIG. 15A or FIG. 45, narrowing IEDF width (e.g., minimum IEDF width) emerge as having I will. This is because when I _C = I _I (or alternatively, when Equation 2 is true), the voltage between pulses of the modified periodic voltage function is substantially constant sheath or substrate voltage. Therefore, it is for causing ion energy. In FIG. 46, the substrate voltage 4608 includes pulses during the constant voltage portion. Since these pulses have a very short duration, their impact on ion energy and IEDF is negligible, and thus the substrate voltage 4608 is referred to as substantially constant.

The following provides further details about each of the method steps illustrated in FIG. In one embodiment, the modified periodic voltage function can have a waveform such as that illustrated in FIG. 14 and includes a first portion (eg, first portion 1402), a second portion (eg, 1404), a third portion (eg, third portion 1406), and a fourth portion (eg, fourth portion 1408), where the third portion has a voltage step ΔV. And the fourth portion can have a slope dV ₀ / dt. The slope dV ₀ / dt can be positive, negative, or zero. The modified periodic voltage function 1400 also has a pulse comprising a first portion 1402, a second portion 1404, and a third portion 1406, and a portion between pulses (fourth portion 1408). Can be expressed as a thing.

The modified periodic voltage function can be measured as V ₀ in FIG. 3 and can appear as a modified periodic voltage function 4402 in FIG. A modified periodic voltage function 4402 is generated by combining a power supply voltage 4406 (known as a periodic voltage function) with ion current compensation 4404. The power supply voltage 4406 is largely responsible for generating and shaping pulses of the modified periodic voltage function 4402, and the ionic current compensation 4404 is mostly a straight slope. It is involved in generating and shaping the part between pulses, which is the voltage. Increasing the ion current compensation Ic causes a decrease in the magnitude of the slope of the portion between pulses, as seen in FIG. Decreasing the magnitude of the power supply voltage 4606 causes a reduction in the magnitude of the amplitude of the pulse and peak-to-peak voltage of the modified periodic voltage function 4602, as seen in FIG.

  When the power supply unit is a switch mode power supply unit, the switching diagram 4410 of the first switch T1 and the second switch T2 can be applied. For example, the first switch T1 can be implemented as the switch T1 in FIG. 3, and the second switch T2 can be implemented as the second switch T2 in FIG. The two switches have the same switching time but are illustrated as being 180 ° out of phase. In other embodiments, the switch may have a slight phase offset such as that illustrated in FIG. When the first switch T1 is on, since the power supply has a negative bus voltage, the power supply voltage is drawn to the maximum scale, which is the negative value of FIG. The second switch T2 is turned off during this period so that the power supply voltage 4406 is isolated from ground. When the switch reverses, the power supply voltage 4406 approaches ground and passes slightly. In the illustrated embodiment, there are two pulse widths, but this is not required. In other embodiments, the pulse width may be the same for all cycles. In other embodiments, the pulse width can be varied or modulated in time.

A modified periodic voltage function is applied to the substrate support 3002 and the modified periodic voltage function is finally reached before it reaches the substrate support (eg, between the switch mode power supply and the effective capacity). 3004 can be sampled as V _{0 at the} point of access. An unmodified periodic voltage function (or power supply voltage of FIG. 44) can be supplied from a power supply such as switch mode power supply 1206 of FIG. The ion current compensation 4404 of FIG. 44 can be supplied from a current source such as the ion current compensation component 1260 of FIG. 12 or 1360 of FIG.

A portion or all of the modified periodic voltage function can be sampled 3004. For example, a fourth portion (eg, the fourth portion 1408) can be sampled. Sampling 3004 can be performed between the power supply unit and the substrate support unit. For example, in FIG. 1, the sampling 3004 can be performed between the switch mode power supply unit 106 and the support unit 108. In FIG. 3, the sampling 3004 can be performed between the inductor L1 and the specific capacitance C10. In one embodiment, sampling 3004 can be performed at V ₀ between capacitance C3 and specific capacitance C10. Sampling 3004 is typically performed on the left side of specific capacity C10 in FIG. 3 because specific capacity C10 and the elements representing plasma (R2, R3, C1, and C2) are not accessible for real-time measurement. Is called. The specific capacitance C10 is typically not measured during processing, but is typically a known constant and can therefore be set during manufacturing. At the same time, in some cases, the specific capacity C10 may vary over time.

In some embodiments, only two samples of a modified periodic voltage function are required, while in other embodiments hundreds, thousands, or tens of thousands of samples are modified periods. For each cycle of the dynamic voltage function. For example, the sampling rate can be greater than 400 kHz. These sampling rates allow for a more accurate and detailed monitoring of the modified periodic voltage function and its shape. Similarly, more detailed monitoring of the periodic voltage function allows for a more accurate comparison of waveforms between cycles, between different process conditions, between different processes, between different chambers, between different sources, etc. For example, at these sampling rates, the first, second, third, and fourth portions 1402, 1404, 1406, 1408 of the periodic voltage function illustrated in FIG. It may not be possible with conventional sampling rates. In some embodiments, a higher sampling rate allows for a resolution of voltage step ΔV and slope dV ₀ / dt that is not possible with the prior art. In some embodiments, a portion of the modified periodic voltage function can be sampled while other portions are not sampled.

The slope dV ₀ / dt calculation 3006 may be based on a plurality of V ₀ measurements obtained during time t (eg, fourth portion 1408). For example, a linear fit can be performed to fit the line to the V ₀ value, and the slope of the line results in a slope dV _o / dt. In another case, the time t (e.g., a fourth portion 1408) of Figure 14 can be V ₀ value at the beginning and end is resolved, these using a slope of the line obtained as dV o / _dt A line can be fitted between two points. These are just two of the many ways in which the slope dV _o / dt of the part between pulses can be calculated.

The decision 3010 may be part of an iterative loop that is used to adjust the IEDF to a narrow width (eg, minimum width, or alternatively 6% full width at half maximum). Equation 3 applies only if the ion current compensation Ic is equal to the ion current I _I (or alternatively is related to I _I according to equation 2), which is a constant substrate voltage, and therefore constant and substantially singular. Occurs only when there is a large ion energy (narrow IEDF width). A constant substrate voltage 4608 (V _sub ) can be seen in FIG. Thus, either ion current I _I or alternatively ion current compensation Ic can be used in Equation 3.

Alternatively, two values along the fourth portion 1408 (also referred to as the portion between the pulses) can be sampled for the first cycle and the second cycle, respectively, The slope can be determined for each cycle. From these two slopes, the ionic current compensation Ic expected to make equation 3 true for the third unmeasured slope can be determined. Therefore, it is possible to estimate the ion current I _I that is predicted to correspond to the narrow IEDF width. These are only two of the many ways in which the narrow IEDF width can be determined, and the corresponding ion current compensation Ic and / or the corresponding ion current I _I can be found.

  Adjustment 3012 to ion current compensation Ic can involve either increasing or decreasing ion current compensation Ic, and there is no limit on the step size for each adjustment. In some embodiments, the sign of function f in Equation 3 can be used to determine whether to increase or decrease ion current compensation. If the sign is negative, the ion current compensation Ic can be decreased, while the positive sign can indicate the need to increase the ion current compensation Ic.

Once the ion current I (in or alternative are related to it according to equation 2) equal to the _I ion current compensation Ic is identified, the method 3000 may further set point operation (see FIG. 31) or remote chamber and a source monitoring operation (See FIGS. 32-34). Further set point operations can include setting ion energy (see also FIG. 46) and ion energy distribution or IEDF width (see also FIG. 47). Source and chamber monitoring can include monitoring plasma density, source supply anomalies, plasma arcing, and the like.

Further, the method 3000 can optionally return to sampling 3004 to update the ionic current compensation Ic continuously (or alternatively, periodically). For example, sampling 3004, calculation 3006, decision 3010, and adjustment 3012 can be performed periodically taking into account current ion current compensation Ic to ensure that Equation 3 continues to be satisfied. At the same time, if the ion current compensation Ic that satisfies Equation 3 is updated, the ion current I _I can also be updated, and the updated value can be stored 3014.

The method 3000 can find and set the ion current compensation Ic to be equal to the ion current I _I or, alternatively, satisfy Equation 2, but is required to achieve a narrow IEDF width. the value of the ion current compensation Ic is (before that in or alternative) without setting the ion current I _C to that value can be determined. For example, the first ion current compensation Ic ₁ is applied for the first cycle, the first slope dV ₀₁ / dt of the voltage between pulses is measured, and the second ion current compensation Ic for the second cycle By applying ₂ and measuring the second slope dV ₀₂ / dt of the voltage between pulses, a third ion current compensation Ic ₃ associated with the third ion current compensation Ic ₃ is expected to be true. The slope dV ₀₃ / dt can be determined. The third ion current compensation Ic ₃ may be one that would result in a narrow IEDF width when applied. Thus, only a single adjustment of ion current compensation can be used to satisfy Equation 3 and thus determine the ion current compensation Ic corresponding to the ion current I _I. Then, the method 3000, the ion current I _C, without even be set to a value that is required to achieve a narrow IEDF width, be moved to the method described in FIGS. 31 and / or Figure 32-41 Can do. Such an embodiment may be implemented to increase the adjustment rate.

  FIG. 31 illustrates a method for setting the IEDF width and ion energy. The method originates from the method 3000 illustrated in FIG. 30 and includes a left path 3100 (also referred to as an IEDF branch) or a right path 3101 (ion energy branch), with IEDF width and ion energy settings, respectively. (Also referred to as). The ion energy eV is proportional to the voltage step ΔV or the third portion 1406 of the modified periodic voltage function 1400 of FIG. The relationship between ion energy eV and voltage step ΔV can be expressed as Equation 4.

Where C ₁ is the effective capacity (eg, chuck capacity, specific capacity C 10 of FIG. 3 or specific capacity C 1 of FIG. 13), and C ₂ is the sheath capacity (eg, sheath capacity C 4 of FIG. 3, or This is the sheath capacity C2) of FIG. Sheath capacitance C ₂ may include a stray capacitance depends on the ion current I _I. The voltage step ΔV can be measured as a change in voltage between the second portion 1404 and the fourth portion 1408 of the modified periodic voltage function 1400. By controlling and monitoring the voltage step ΔV (which is a function of the power supply voltage or bus voltage such as the bus voltage V _{bus in} FIG. 3), the ion energy eV can be controlled and grasped.

  At the same time, the IEDF width can be estimated according to Equation 5.

Where I is I _I when C is C _series and I _C when C is C _effective . Time t is the time between pulses, V _PP is the peak-to-peak voltage, and ΔV is the voltage step.

In addition, the sheath capacitance C ₂ can be used in various calculation and monitoring operations. For example, the Debye _sheath distance λ _sheath can be estimated as follows.

  Where ε is the vacuum dielectric constant and A is the area of the substrate (or alternatively the surface area of the substrate support). For some high voltage applications, Equation 6 is expressed as Equation 7.

In addition, the electric field in the sheath can be estimated as a function of the sheath capacitance C ₂ , the sheath distance λ _shear , and the ion energy eV. Sheath capacitance C _2, along with the ion current I _I, from Equation 8 (alone saturation current I _sat against ionized plasma is linearly is related to the compensation current I _C in), to determine the plasma density n _e Can also be used.

Using the sheath capacitance C ₂ and the saturation current I _sat , the effective mass of ions at the substrate surface can be calculated. The plasma density n _e , the electric field in the sheath, the ion energy eV, the effective mass of the ions, and the DC potential V _{DC of the} substrate are typically monitored only via indirect means in the art. It is a plasma parameter. The present disclosure allows for direct measurement of these parameters and thus allows more accurate monitoring of plasma properties in real time.

As seen in Equation 4, the sheath capacitance C ₂ is also as illustrated in ion energy branch 3101 in FIG. 31, can also be used to monitor and control the ion energy eV. The ion energy branch 3101 begins 3102 by receiving a user selection of ion energy. The ion energy branch 3101 may then set 3104 an initial power supply voltage for the switch mode power supply that provides the periodic voltage function. At some point prior to the periodic voltage sampling operation 3108, ion current may also be accessed 3106 (eg, accessed from memory). A periodic voltage can be sampled 3108 and a measurement of a third portion of the modified periodic voltage function can be measured 3110. The ion energy I _I can be calculated 3112 from a voltage step ΔV (also referred to as a third portion (eg, third portion 1406)) of the modified periodic voltage function. The ion energy branch 3101 can then determine if the ion energy is equal to the defined ion energy 3114, if so, the ion energy is at the desired set point and the ion energy branch 3101 ends. can do. If the ion energy is not equal to the defined ion energy, the ion energy branch 3101 can adjust the power supply voltage 3116 and again sample the periodic voltage 3108. The ion energy branch 3101 can then cycle through the sampling 3108, measurement 3110, calculation 3112, decision 3114, and setting 3116 until the ion energy is equal to the defined ion energy.

  A method for monitoring and controlling the IEDF width is illustrated by the IEDF branch 3100 of FIG. IEDF branch 3100 includes receiving 3150 a user selection of IEDF width and sampling 3152 of current IEDF width. Decision 3154 then determines whether the defined IEDF width is equal to the current IEDF width, and if decision 3152 is satisfied, the IEDF width is as desired (or defined) and the IEDF branch 3100 is Can be terminated. However, if the current IEDF width is not equal to the defined IEDF width, the ion current compensation Ic can be adjusted 3156. This determination 3154 and adjustment 3156 can be continued in a cyclic fashion until the current IEDF width is equal to the defined IEDF width.

  In some embodiments, the IEDF branch 3100 can also be implemented to ensure a desired IEDF shape. Various IEDF shapes can be generated, each of which can be associated with a different ion energy and IEDF width. For example, the first IEDF shape can be a delta function, while the second IEDF shape can be a square function. Other IEDF shapes can be cup-shaped. Examples of various IEDF shapes can be seen in FIG.

Using knowledge of ion current I _I and voltage step ΔV, equation 4 can be solved for ion energy eV. The voltage step ΔV can be controlled by changing the power supply voltage, and changing the power supply voltage changes the voltage step ΔV. A larger power supply voltage causes an increase in voltage step ΔV, and a decrease in power supply voltage causes a decrease in voltage step ΔV. In other words, increasing the power supply voltage results in greater ion energy eV.

  Further, since the system and method operate on a continuously changing feedback loop, it is desirable (or defined) despite plasma changes due to variations or intentional adjustments to the plasma source or chamber conditions. Ion energy and IEDF width can be maintained.

30-41 are described with respect to a single ion energy, those skilled in the art will be able to generate and monitor the desired (or defined) IEDF width (or IEDF shape) and ion energy. It will be further appreciated that the method can be used to produce and monitor more than one ion energy, each having its own IEDF width (or IEDF shape). For example, by providing a first power supply voltage V _PS in first, third, and fifth cycles, and a second power supply voltage in second, fourth, and sixth cycles, Two different narrow ion energies can be achieved for ions arriving at the surface (eg, FIG. 42A). Using three different power supply voltages results in three different ion energies (eg, FIG. 42B). By varying the time at which each of the plurality of power supply voltages is applied or the number of cycles in which each power supply voltage level is applied, the ion flux of different ion energies can be controlled (e.g., FIG. 42C).

  The above discussion describes the periodic voltage function provided by the power supply to control the ion energy and the IEDF width and / or IEDF shape of the ions that reach the surface of the substrate during plasma processing. Fig. 2 shows how a combination with ion current compensation provided by the element can be used.

  Some of the controls described thus far include (1) a fixed waveform (the continuous cycle of the waveform is the same), (2) at least two parts proportional to ion energy and IEDF (eg, illustrated in FIG. 14). Using several combinations of waveforms having third and fourth portions 1406 and 1408), and (3) a high sampling rate (eg, 125 MHz) that allows accurate monitoring of the different features of the waveform Enabled by. For example, if a prior art such as a linear amplifier transmits a waveform to the substrate that resembles a modified periodic voltage function, undesirable variations between cycles may characterize ion energy or IEDF width (or IEDF shape). Making it difficult to use these prior art waveforms.

  If a linear amplifier is used to bias the substrate support, the waveform is not consistent from cycle to cycle, so waveform features (eg, slope of the portion between pulses) are typically useful The need to sample at a high rate is not recognized. Such useful information, as found in this disclosure and related disclosures, does not occur when fixed waveforms are used.

  The fixed waveforms and high sampling rates disclosed herein further allow for more accurate statistical observation. With this increased accuracy, the operating and processing characteristics of the plasma source and the plasma in the chamber can be monitored through monitoring various characteristics of the modified periodic voltage function. For example, a modified periodic voltage function measurement allows remote monitoring of sheath volume and ion current and can be monitored without knowledge of chamber processes or other chamber details. Some examples follow, and only a few of the many methods that can be used with the systems and methods described so far for non-invasive monitoring and fault detection of sources and chambers. Illustrate.

As an example of monitoring, referring to FIG. 14, the DC offset of waveform 1400 may represent the health of the plasma source (hereinafter referred to as “source”). In another example, the slope of the top portion 1404 (second portion) of the pulse of the modified periodic voltage function can be related to the attenuation effect in the source. The standard deviation of the slope of the top portion 1404 from horizontal (shown as having a slope equal to 0) is another way to monitor the health of the source based on certain aspects of the waveform 1400. Another aspect involves measuring the standard deviation of the V ₀ sampled along the fourth portion 1408 of the modified periodic voltage function and relating the standard deviation to the chamber resonance. For example, if this standard deviation is monitored between successive pulses and the standard deviation increases over time, this may indicate that there is resonance in the chamber, eg, in the electrostatic chuck. Resonance can be a sign of poor electrical connection to or in the chamber, or a sign of additional unwanted inductance or capacity.

FIG. 32 illustrates two modified periodic voltage function waveforms delivered to a substrate support, according to one embodiment of the present disclosure. When compared, the two modified periodic voltage functions can be used for chamber alignment or in-situ or fault detection. For example, one of the two modified periodic voltage functions can be a reference waveform and the second function can be obtained from a plasma processing chamber during calibration. The difference between the two modified periodic voltage functions (eg, the difference in peak-to-peak voltage V _PP ) can be used to calibrate the plasma processing chamber. Alternatively, the second modified periodic voltage function can be compared to a reference waveform during processing, and any difference in waveform characteristics (eg, shift) can indicate a fault (eg, The slope difference of the fourth portion 3202 of the modified periodic voltage function).

FIG. 33 illustrates ion current waveforms that can indicate plasma source instability or changes in plasma density. To identify faults and anomalies in the system, variations in ion current I _I such as that illustrated in FIG. 33 can be analyzed. For example, the periodic variation in FIG. 33 may indicate low frequency instability in the plasma source (eg, plasma power supply 102). Such variations in ion current I _I can also indicate a periodic change in plasma density. This indication and the possible failure or anomaly it may indicate is only one of many ways in which remote monitoring of the ionic current I _I can be used particularly advantageously.

FIG. 34 illustrates an ion current I _I of a modified periodic voltage function waveform having an aperiodic shape. This embodiment of the ionic current I _I can exhibit non-periodic variations such as plasma source instability or changes in plasma density. Such fluctuations may also indicate various plasma instabilities such as arcing, parasitic plasma formation, or plasma density drift.

  FIG. 35 illustrates a modified periodic voltage function waveform that can indicate a failure in the bias supply. The uppermost portion of the third illustrated cycle (also referred to as the second portion) exhibits anomalous behavior that may indicate resonance in a bias supply (eg, power supply 1206 in FIG. 12). This resonance can be an indication of a failure in the bias supply. Further analysis of the resonance may identify characteristics that help identify faults in the power system.

  FIG. 36 illustrates a modified periodic voltage function waveform that can show a dynamic (or non-linear) change in system capacity. For example, stray capacitance that is nonlinearly dependent on voltage can provide such a modified periodic voltage function. In another example, plasma breakdown or failure in the chuck can also result in such a modified periodic voltage function. In each of the three illustrated cycles, the non-linearity in the fourth portion 3602 of each cycle can indicate a dynamic change in system capacity. For example, because other components of the system capacity are largely fixed, non-linearity can indicate a change in sheath capacity.

FIG. 37 illustrates a modified periodic voltage function waveform that may indicate a change in plasma density. The modified periodic voltage function shown shows a monotonic shift of the slope dV ₀ / dt that can indicate a change in plasma density. These monotonic shifts can provide a direct indication of predictive events such as process etch endpoints. In other embodiments, these monotonic shifts may indicate a process failure if no predictive event is present.

  FIG. 38 illustrates ion current sampling for different process runs, and ion current drift can indicate system drift. Each data point can represent an ion current for a given run, and the tolerance limit is a user-defined or automatic limit that defines the tolerance ion current. Ion current drift, which gradually pushes the ion current above acceptable limits, may indicate that substrate damage may occur. This type of monitoring can also be combined with any number of other conventional monitors, such as optical emission thickness measurements. In addition to monitoring ion current drift, these conventional types of monitors can enhance existing monitoring and statistical control.

  FIG. 39 illustrates ion current sampling for different process parameters. In this illustration, the ionic current can be used as a figure of merit to distinguish different processes and different process characteristics. Such data can be used in the development of plasma recipes and processes. For example, eleven process conditions that yield eleven illustrated ion current data points can be tested, and the process that yields the preferred ion current is selected as an ideal process or, alternatively, as a preferred process. be able to. For example, the lowest ion current can be selected as an ideal process, and then using the ion current associated with the preferred process as a metric to determine whether the process is being performed using the preferred process conditions Can do. This figure of merit can be used in addition to, or as an alternative to, similar conventional metric characteristics such as percentage, selectivity, and profile angle, to name a few non-limiting examples.

  FIG. 40 illustrates two modified periodic voltage functions monitored without plasma in the chamber. These two modified periodic voltage functions can be compared and used to characterize the plasma chamber. In an embodiment, the first modified periodic voltage function may be a reference waveform, while the second modified periodic voltage function may be a currently monitored waveform. These waveforms can be obtained without plasma in the processing chamber, for example after chamber cleaning or preventive maintenance, so the second waveform is for the release of the chamber to production (or back to production). Prior to that, it can be used to provide verification of the electrical state of the chamber.

  FIG. 41 illustrates two modified periodic voltage functions that can be used to validate the plasma process. The first modified periodic voltage function can be a reference waveform, while the second modified periodic voltage function can be a waveform that is currently being monitored. The currently monitored waveform can be compared to a reference waveform, and any difference may indicate parasitic and / or non-parasitic impedance problems that are otherwise not detectable using conventional monitoring methods. . For example, a resonance seen on the waveform of FIG. 35 can be detected, which can represent a resonance in the power supply.

Monitoring any of the metrics illustrated in FIGS. 32-41 while the method 3000 is cycled to update the ion current compensation Ic, ion current I _I , and / or sheath capacitance C _sheath Can do. For example, after each ion current I _I sample is obtained in FIG. 38, the method 3000 can return to sampling 3004 to determine an updated ion current I _I. In another example, correction of ion current I _I , ion energy eV, or IEDF width may be desired as a result of the monitoring operation. Corresponding corrections can be made and method 3000 can return to sampling 3004 to find a new ion current compensation Ic that satisfies Equation 3.

  A person skilled in the art does not require any particular or illustrated operating order, or any of the methods illustrated in or suggested by the figures, as illustrated in FIGS. 30, 31, and 43. It will be appreciated that the order is not limited. For example, the metric (FIGS. 32-41) can be monitored before, during, or after setting and monitoring the IEDF width and / or ion energy eV.

FIG. 44 illustrates various waveforms at different points in the system disclosed herein. Illustrated switching pattern 4410, power supply voltage V _PS 4406 (also referred to herein as a periodic voltage function), ion current compensation Ic 4404, modified periodic voltage function for switching components of the switch mode power supply Considering 4402 and the substrate voltage V _sub 4412, the IEDF has the illustrated width 4414 (which may not be drawn to scale) or the IEDF shape 4414. This width is wider than what this disclosure refers to as “narrow width”. As shown, the substrate voltage V _sub 4412 is not constant when the ion current compensation Ic 4404 is greater than the ion current I _I. The IEDF width 4414 is proportional to the voltage difference of the slope portion between the pulses of the substrate voltage V _sub 4412.

Considering this non-narrow IEDF width 4414, the method disclosed herein is such that the ionic current compensation Ic is adjusted until I _C = I _I (or alternatively related according to Equation 2). Request. FIG. 45 illustrates the effect of producing a final incremental change in ion current compensation Ic to match the ion current I _I. When I _C = I _I , the substrate voltage V _sub 4512 becomes substantially constant, and the IEDF width 4514 decreases from a non-narrow width.

Once the narrow IEDF is achieved, the ion energy can be adjusted to a desired or defined value, as illustrated in FIG. Here, the magnitude of the power supply voltage (or alternatively the switch mode power supply bus voltage V _bus ) is reduced (eg, the maximum negative amplitude of the pulse of the power supply voltage 4606 is reduced). As a result, ΔV ₁ decreases to ΔV ₂ so that the peak-to-peak voltage decreases from V _PP1 to V _PP2 . As a result, the magnitude of the substantially constant substrate voltage V _sub 4608 is reduced, thus reducing the magnitude of the ion energy from 4615 to 4614 while maintaining a narrow IEDF width.

Whether or not the ion energy is adjusted, the IEDF width can be increased after the narrow IEDF width is achieved as shown in FIG. Here, I _C can be adjusted to take into account I _I = I _C (or, in the alternative, the equation 2 that yields the relationship between I _I and I _C ), and thus modified periodic The slope of the part between the pulses of the voltage function 4702 is changed. As a result of unequal ion current compensation Ic and ion current I _I , the substrate voltage moves from substantially constant to non-constant. A further result is that the IEDF width 4714 extends from a narrow IEDF 4714 to a non-narrow IEDF 4702. The more I _C is adjusted away from I _I , the greater the IEDF 4714 width.

  FIG. 48 illustrates one pattern of power supply voltages that can be used to achieve more than one ion energy level, with each ion energy level having a narrow IEDF 4814 width. The magnitude of the power supply voltage 4806 alternates with each cycle. This results in alternating ΔV and peak-to-peak voltages for each cycle of the modified periodic voltage function 4802. The substrate voltage 4812 in turn has two substantially constant voltages that alternate between pulses of the substrate voltage. This results in two different ion energies, each having a narrow IEDF 4814 width.

FIG. 49 illustrates another pattern of power supply voltages that can be used to achieve more than one ion energy level, with each ion energy level having a narrow IEDF 4914 width. Here, the power supply voltage 4906 alternates between two different magnitudes, but does so once for the two previous cycles. As shown, the average ion energy is the same as when V _PS 4906 is alternated from cycle to cycle. This shows only one example of how various other patterns of V _PS 4906 can be used to achieve the same ion energy.

FIG. 50 illustrates one combination of power supply voltage V _PS 5006 and ion current compensation I _C 5004 that can be used to generate a defined IEDF 5014. Here, alternating power supply voltages 5006 result in two different ion energies. In addition, the IEDF 5014 width of each ion energy can be expanded by adjusting the ion current compensation 5004 away from the ion current I _I. If the ion energy is close enough as in the illustrated embodiment, IEDF 5014 of both ion energies will overlap, resulting in one large IEDF 5014. While other embodiments are possible, this embodiment uses a combination of adjustments to V _PS 5006 and I _C 5004 to achieve a defined ion energy and a defined IEDF 5014. Is intended to show what can be done.

  Referring now to FIGS. 17A and 17B, a block diagram depicting another embodiment of the present invention is shown. As shown, the substrate support 1708 in these embodiments includes an electrostatic chuck 1782 and the electrostatic chuck supply 1780 is utilized to apply power to the electrostatic chuck 1782. In some variations, as depicted in FIG. 17A, the electrostatic chuck supply 1780 is positioned to apply power directly to the substrate support 1708; in other variations, the electrostatic chuck supply 1780 The 1780 is positioned to apply power in conjunction with the switch mode power supply. Note that serial chucking can be done by a separate supply or by the use of a controller, resulting in a net DC chucking function. This DC coupled (eg, no blocking capacitor) series chucking function can minimize undesired interference with other RF sources.

  In FIG. 18, the plasma power supply 1884 that generally functions to generate plasma density is also configured to drive the substrate support 1808 along with the switch mode power supply 1806 and the electrostatic chuck supply 1880. A block diagram depicting yet another embodiment of the present invention is shown. In this implementation, each of plasma power supply 1884, electrostatic chuck supply 1880, and switch mode power supply 1806 can reside in separate assemblies or two of supplies 1806, 1880, 1884. One or more can be constructed to reside in the same physical assembly. Advantageously, the embodiment depicted in FIG. 18 electrically grounds the top electrode 1886 (eg, showerhead) to obtain electrical symmetry and reduced damage levels due to fewer arcing events. Enable.

  Referring to FIG. 19, a block diagram depicting yet another embodiment of the present invention is shown. As depicted, the switch mode power supply 1906 in this embodiment does not require an additional plasma power supply (eg, without the plasma power supplies 102, 202, 1202, 1702, 1884), Power is applied to the substrate support and chamber 1904 to bias the substrate and ignite (and sustain) the plasma. For example, the switch mode power supply 1806 can be operated with a duty cycle that is sufficient to ignite and sustain the plasma while providing a bias to the substrate support.

  Referring now to FIG. 20, a block diagram of the control portion input parameters and control output that may be utilized in connection with the embodiment described with reference to FIGS. 1-19 is depicted. The depiction of the control portion is intended to provide a simplified depiction of exemplary control inputs and outputs that may be utilized in connection with the embodiments discussed herein. That is, it is not intended to be a hardware schematic. In an actual implementation, the depicted control portion may be distributed among several individual components that may be realized by hardware, software, firmware, or a combination thereof.

  Referring to the embodiments previously discussed herein, the controller depicted in FIG. 20 is the controller 112, described with reference to FIG. 1, the controller 212, described with reference to FIG. Energy control 220 component, described with reference to FIG. 8, controller 812 and ion energy control portion 820, described with reference to FIG. 12, ion current compensation component 1260, described with reference to FIG. Current controller 1362, depicted in FIG. 16, Icc control, depicted in FIGS. 17A and 17B, controllers 1712A, 1712B, and controllers 1812, 1912, respectively, depicted in FIGS. 18 and 19, respectively. One or more functionalities may be provided.

  As shown, parameters that can be utilized as inputs to the control portion include dVo / dt and ΔV, which are described in more detail with reference to FIGS. As discussed, dVo / dt is utilized in conjunction with the ion energy distribution spread input ΔE and as described with reference to FIGS. 12, 13, 14, 15A-C, and FIG. 16, ion energy distribution. A control signal Icc that controls the width of the spread may be provided. In addition, the ion energy control input (Ei) is utilized in connection with optional feedback ΔV and, as will be described in more detail with reference to FIGS. Can affect the depicted Vbus), resulting in the desired (defined) ion energy distribution. Another parameter that may be utilized in connection with many electrostatic chucking embodiments is a DC offset input that provides electrostatic force and holds the wafer to the chuck for efficient thermal control.

FIG. 21 illustrates a plasma processing system 2100 according to an embodiment of the present disclosure. System 2100 includes a plasma processing chamber 2102 that encloses plasma 2104 to etch an upper surface 2118 of substrate 2106 (and other plasma processes). The plasma is generated by a plasma source 2112 powered by a plasma power supply 2122 (eg, in situ, remotely, or projected). The plasma sheath voltage V _sheath measured between the plasma 2104 and the top surface 2118 of the substrate 2106 accelerates ions from the plasma 2104 across the plasma sheath 2115 and causes the accelerated ions to move to the substrate 2106 (or photoresist). The upper surface 2118 of a portion of the substrate 2106 that is not protected by the substrate 2106, and the substrate 2106 is etched. Plasma 2104 is at a plasma potential V ₃ with respect to ground (eg, plasma processing chamber 2102 wall). The substrate 2106 has a bottom surface 2120, and the bottom surface 2120 supports the support 2108 via an electrostatic chuck 2111 and a chucking potential V _chuck between the top surface 2121 of the electrostatic chuck 2111 and the substrate 2106. Is held electrostatically. The substrate 2106 is dielectric and thus may have a first potential V _{1 on} the top surface 2118 and a second potential V _{2 on} the bottom surface 2120. The top surface of the electrostatic chuck 2121 is in contact with the bottom surface 2120 of the substrate, thus, these two surfaces 2120,2121 are identical potential _{V 2.} The first potential V ₁ , chucking potential V _chuck , and second potential V ₂ are generated by the switch mode power supply unit 2130 and provided to the electrostatic chuck 2111 via the first conductor 2124. Controlled via AC waveform with DC bias or offset. Optionally, the AC waveform is provided via first conductor 2124 and the DC waveform is provided via optional second conductor 2125. The AC and DC outputs of the switch mode power supply 2130 can similarly be controlled via a controller 2132 that is configured to control various aspects of the switch mode power supply 2130.

Ion energy and ion energy distribution is a first function of the potential V _1. The switch mode power supply 2130 provides an AC waveform that is tuned to provide a desired first potential V ₁ that is known to produce a desired (or defined) ion energy and ion energy distribution. . The AC waveform is RF and can have non-sinusoidal waveforms such as those illustrated in FIGS. 5, 6, 11, 14, 15a, 15b, and 15c. First potential V ₁ was, be proportional to the change in voltage ΔV illustrated in Figure 14. The first potential V ₁ is also equal to the plasma voltage V ₃ minus the plasma sheath voltage V _shear . However, the plasma voltage _{V 3} is often the plasma sheath voltage _{V sheath} (e.g., 50 V-2000V) compared to a small (e.g., less than 20V), so the first potential _{V 1} and plasma sheath voltage _{V sheath} Can be treated as being approximately equal and equal for implementation purposes. Therefore, since the plasma sheath voltage V _sheath affects the ion energy, the first potential V ₁ is proportional to the ion energy distribution. By maintaining a constant first potential V ₁ , the plasma sheath voltage V _shear is constant, so that substantially all ions are accelerated through the same energy, and thus narrow ion energy. Distribution is achieved. Plasma voltage V ₃ arises from energy applied to plasma 2104 via plasma source 2112.

The first potential V _{1 at} the upper surface 2118 of the substrate 2106 is formed through a combination of capacitive charging from the electrostatic chuck 2111 and charge accumulation from electrons and ions passing through the sheath 2115. The AC waveform from the switch mode power supply 2130 shows the effects of ion and electron movement through the sheath 2115 and the upper surface 2118 of the substrate 2106 so that the first potential V ₁ remains substantially constant. The resulting charge accumulation is adjusted to offset.

The chucking force that holds the substrate 2106 on the electrostatic chuck 2111 is a function of the chucking potential V _chuck . The switch mode power supply unit 2130 provides a DC bias, that is, a DC offset, to the AC waveform so that the second potential V ₂ is at a potential different from the first potential V ₁ . This potential difference generates a chucking voltage V _chuck . The chucking voltage V _chuck can be measured from the top surface 2221 of the electrostatic chuck 2111 to a reference layer inside the substrate 2106, which includes any elevation inside the substrate except the bottom surface 2120 of the substrate 2106. (The exact location of the reference layer in the substrate 2106 may vary). Therefore, chucking is controlled by the second electric potential V _2, proportional thereto.

In some embodiments, the second electric potential _{V 2} is modified by the AC waveform is equal to the DC offset of the switch mode power supply unit 2130 (in other words, an AC waveform with a DC offset, DC offset, the AC waveform Exceeding the peak-to-peak voltage). The DC offset may be substantially larger than the AC waveform so that the DC component of the switch mode power supply 2130 output dominates the second potential V2 and the AC component can be excluded or ignored.

The potential in the substrate 2106 varies between the first and second potentials V ₁ and V ₂ . Regardless chucking voltage _{V chuck} polarity, Coulomb attraction between the substrate 2106 and the electrostatic chuck 2111 is present, the chucking voltage _{V chuck} is positive or negative _(e.g., V 1> _{V 2} or _V 1 < V ₂ ).

The switch mode power supply unit 2130 can monitor various voltages together with the controller 2132 deterministically and without a sensor. In particular, ion energy (eg, average energy and ion energy distribution) is deterministically monitored based on AC waveform parameters (eg, slope and stage). For example, the plasma voltage V ₃ , ion energy, and ion energy distribution are proportional to the parameters of the AC waveform produced by the switch mode power supply 2130. In particular, the ΔV (eg, see FIG. 14) of the falling edge of the AC waveform is proportional to the first potential V ₁ and hence the ion energy. By maintaining the first potential V ₁ constant, the ion energy distribution is maintained in a narrow region.

The first potential V ₁ cannot be measured directly, and the correlation between the switch mode power supply output and the first voltage V ₁ is based on the capacitance of the substrate 2106 and the processing parameters. The proportionality constant between ΔV and the first potential V ₁ can be determined empirically after a short processing time. For example, if the AC waveform falling edge ΔV is 50V and the proportionality constant is experimentally found to be 2 for a given substrate and process, the first potential V1 is 100V Can be expected. The proportionality between the step voltage ΔV and the first potential V ₁ (hence the ion energy eV) is represented by Equation 4. Thus, along with the ion energy and ion energy distribution, the first potential V ₁ is determined based on the knowledge of the AC waveform of the switch mode power supply without any sensors inside the plasma processing chamber 2102. be able to. In addition, the switch mode power supply unit 2130, together with the controller 2132, determines whether or not chucking has occurred (for example, whether or not the substrate 2106 is held by the electrostatic chuck 2111 via the chucking potential V _chuck ). Can be monitored.

Dechucking is performed by eliminating or reducing the chucking potential V _chuck . This can be done by setting equal the second potential V ₂ to the first potential V _1. In other words, the DC offset and AC waveform can be adjusted to bring the chucking voltage V _chuck close to 0V. Compared to conventional dechucking methods, the system 2100 achieves faster dechucking and therefore more throughput because both DC offset and AC waveform can be adjusted to achieve dechucking. To do. Also, when DC and AC power supplies are in the switch mode power supply 2130, their circuits are more integrated, closer together, and controlled via a single controller 2132 (typical of DC and AC power supplies). The output can be changed at a higher speed compared to a parallel array. The rate of dechucking enabled by the embodiments disclosed herein also allows dechucking after the plasma 2104 is extinguished or at least after power from the plasma source 2112 is turned off.

  The plasma source 2112 can take a variety of forms. For example, in one embodiment, the plasma source 2112 includes an electrode inside the plasma processing chamber 2102 that establishes an RF field within the chamber 2102 that both ignites and sustains the plasma 2104. In another embodiment, the plasma source 2112 remotely generates an ionized electromagnetic field, projects or extends the ionized electromagnetic field into the processing chamber 2102, and uses the ionized electromagnetic field to ignite and sustain the plasma 2104 in the plasma processing chamber. Including a remotely projected plasma source. Further, the remotely projected plasma source also includes a field transfer portion (eg, a conductive tube) through which the ionized electromagnetic field passes on its way to the plasma processing chamber 2102, while the ionized electromagnetic field is attenuated and the plasma processing chamber The field strength in 2102 is only a tenth, or a hundredth, or a thousandth, or even a fraction of the field strength when the field is first generated in a remotely projected plasma source It becomes. The plasma source 2112 is not drawn to scale.

  Switch mode power supply 2130 can float and is therefore biased at any DC offset by a DC power supply (not shown) connected in series between ground and switch mode power supply 2130. be able to. The switch mode power supply unit 2130 is connected to the AC and DC power supplies inside the switch mode power supply unit 2130 (see, for example, FIGS. An AC waveform with a DC offset can be provided either via a DC power supply external to the mode power supply 2130 (see, eg, FIGS. 24 and 27). In some embodiments, the switch mode power supply 2130 can be coupled in series to a floating DC power source that is grounded and coupled in series between the switch mode power supply 2130 and the electrostatic chuck 2111.

  The controller 2132 can control the AC and DC outputs of the switch mode power supply when the switch mode power supply 2130 includes both AC and DC power. When the switch mode power supply unit 2130 is connected in series with the DC power supply, the controller 2132 can control only the AC output of the switch mode power supply unit 2130. In an alternative embodiment, the controller 2130 can control both the DC power supply coupled to the switch mode power supply 2130 and the switch mode power supply 2130. One skilled in the art will recognize that although a single controller 2132 is illustrated, other controllers can also be implemented to control the AC waveform and DC offset provided to the electrostatic chuck 2111. .

The electrostatic chuck 2111 is dielectric (eg, ceramic) and therefore can substantially block the passage of DC voltage, or it is a semiconductive material such as a doped ceramic. be able to. In either case, the electrostatic chuck 2111 capacitively couples a voltage to the upper surface 2118 (usually dielectric) of the substrate 2106 to form a _first voltage V1 on the upper surface 2121 of the electrostatic chuck 2111. It can have a _second voltage V2.

  The shape and size of the plasma 2104 are not necessarily drawn to scale. For example, the edge of the plasma 2104 can be defined by a certain plasma density, in which case the illustrated plasma 2104 is not drawn taking into account any particular plasma density. Similarly, at least some plasma densities fill the entire plasma processing chamber 2102 regardless of the shape of the plasma 2104 shown. The illustrated plasma 2104 shape is primarily intended to show a sheath 2115 having a plasma density substantially less than the plasma 2104.

FIG. 22 illustrates another embodiment of a plasma processing system 2200. In the illustrated embodiment, the switch mode power supply 2230 includes a DC power source 2234 and an AC power source 2236 connected in series. The controller 2232 is configured to control the AC waveform with the DC offset output of the switch mode power supply 2230 by controlling both the AC power supply 2236 waveform and the DC power supply 2234 bias or offset. This embodiment also includes an electrostatic chuck 2211 having a grid or mesh electrode 2210 embedded within the chuck 2211. Switch mode power supply 2230 provides both AC and DC bias to grid electrode 2210. A DC bias with an AC component that is substantially less than the DC bias and thus negligible establishes a third potential V ₄ on the grid electrode 2210. When the third potential V ₄ is different from the potential at the reference layer anywhere in the substrate 2206 (except the bottom surface 2220 of the substrate 2206), the chucking potential V _chuck and the Coulomb chucking force are established, The substrate 2206 is held on the electrostatic chuck 2211. The reference layer is a virtual plane parallel to the grid electrode 2210. The AC waveform is capacitively coupled from the grid electrode 2210 through a portion of the electrostatic chuck 2211 and through the substrate 2206 to control the _first potential V ₁ on the upper surface 2218 of the substrate 2206. Since the plasma potential V ₃ is negligible with respect to the plasma sheath voltage V _shear , the first potential V ₁ and the plasma sheath voltage V _shear are approximately equal and are considered equal for practical purposes. Thus, the first potential V ₁ is equal to the potential used to accelerate ions through the sheath 2215.

In certain embodiments, the electrostatic chuck 2211 can be doped so as to be sufficiently conductive through the body of the chuck 2211 such that significant potential differences are negligible, so that the grid or mesh electrode 2210 is substantially It may be a second potential V ₂ equal to the voltage.

Grid electrode 2210 is embedded in electrostatic chuck 2211, parallel to substrate 2206, biased by switch mode power supply 2230, and any conductive planar device configured to establish a chucking potential V _chuck. Can be. Although the grid electrode 2210 is illustrated as being embedded in the lower portion of the electrostatic chuck 2211, the grid electrode 2210 can be located closer or further from the substrate 2206. The grid electrode 2210 need not also have a grid pattern. In some embodiments, the grid electrode 2210 can be a solid electrode or have a non-solid structure with a non-grid shape (eg, a checkerboard pattern). In certain embodiments, the electrostatic chuck 2211 is a ceramic or other dielectric, and therefore the third potential V ₄ on the grid electrode 2210 is the first potential V on the upper surface 2221 of the electrostatic chuck 2211. Not equal to ₁ . In another embodiment, the electrostatic chuck 2211 is a slightly conductive, doped ceramic, so the third potential V ₄ on the grid electrode 2210 is on the upper surface 2221 of the electrostatic chuck 2211. the second may be equal to the potential _{V 2.}

  Switch mode power supply 2230 generates an AC output that can be non-sinusoidal. In the switch mode power supply unit 2230, the DC power source 2234 is AC conductive and the AC power source 2236 is DC conductive, so that the DC and AC sources 2234 and 2236 can be operated in series. An exemplary AC power supply that is not DC conductive is a linear amplifier that can be damaged if a DC voltage or current is provided. The use of AC conductive and DC conductive power supplies reduces the number of components used in the switch mode power supply 2230. For example, if the DC power source 2234 provides AC blocking, an AC bypass or DC blocking component (eg, a capacitor) may need to be arranged in parallel with the DC power source 2234. If the AC power source 2236 provides DC blocking, a DC bypass or AC blocking component (eg, an inductor) may need to be arranged in parallel with the AC power source 2236.

  In this embodiment, the AC power source 2238 generally provides a voltage bias in a controllable manner to provide a desired (defined) ion energy distribution for ions striking the top surface 2218 of the substrate 2206. It is configured to apply to the electrostatic chuck 2211. More specifically, the AC power source 2236 is configured to provide a desired (defined) ion energy distribution by applying one or more specific waveforms at specific power levels to the grid electrode 2210. . Also more specifically, the AC power source 2236 applies a specific power level, provides a specific ion energy, and is defined by one or more waveform data stored in a waveform memory (not shown). A voltage waveform is used to apply a specific power level. As a result, one or more specific ion strike energies may be selected to perform a controlled etch of the substrate 2206 (or other plasma assisted process). In one embodiment, the AC power source 2236 can utilize a switched mode configuration (see, eg, FIGS. 25-27). The switch mode power supply 2230, in particular the AC power source 2236, can produce an AC waveform as described in various embodiments of the present disclosure.

One skilled in the art will recognize that the grid electrode 2210 is not necessary and that other embodiments can be implemented without the grid electrode 2210. _Those skilled in the art will also recognize that the grid electrode 2210 is just one example of a number of devices that can be used to establish a chucking potential V _chuck .

FIG. 23 illustrates another embodiment of a plasma processing system 2300. The illustrated embodiment includes a switch mode power supply 2330 for providing an AC waveform and a DC bias to the electrostatic chuck 2311. Switch mode power supply 2330 includes a DC power supply 2334 and an AC power supply 2336, both of which can be grounded. The AC power source 2336 generates an AC waveform that is provided to the first grid or mesh electrode 2310 embedded in the electrostatic chuck 2311 via the first conductor 2324. The AC power source 2336 establishes a potential V ₄ on the first grid or mesh electrode 2310. The DC power source 2334 generates a DC bias that is provided to the second grid or mesh electrode 2312 embedded in the electrostatic chuck 2311 via the second conductor 2325. A DC power source 2334 establishes a potential V ₅ on the second grid or mesh electrode 2312. Potential _{V 4} and _{V 5} are each, via the AC and DC power 2336,2334 can be independently controlled. However, the first and second grid or mesh electrodes 2310, 2312 can also be capacitively coupled and / or between the grid or mesh electrodes 2310, 2312 via a portion of the electrostatic chuck 2311. DC coupling may exist. If either AC or DC coupling is present, the potentials V ₄ and V ₅ can be coupled. Those skilled in the art will recognize that the first and second grid electrodes 2310, 2312 may be arranged throughout the electrostatic chuck 2311, including arranging the first grid electrode 2310 closer to the substrate 2306 than the second grid electrode 2312. It will be appreciated that they can be arranged in various locations.

  FIG. 24 illustrates another embodiment of a plasma processing system 2400. In this embodiment, the switch mode power supply unit 2430 provides an AC waveform to the electrostatic chuck 2411 and the output of the switch mode power supply unit 2430 is offset by a DC bias provided by the DC power supply unit 2434. The AC waveform of switch mode power supply 2430 has a waveform selected by controller 2435 to cause substrate 2406 to strike ions from plasma 2404 having a narrow ion energy distribution. The AC waveform may be a non-sinusoidal wave (eg, a square wave or a pulse) and may be generated via the AC power supply 2436 of the switch mode power supply 2430. Chucking is controlled via a DC offset from a DC power supply 2434 controlled by the controller 2433. The DC power supply 2434 may be coupled in series between the ground and the switch mode power supply 2430. Switch mode power supply 2430 is floating such that its DC bias can be set by DC power supply 2434.

  One skilled in the art will recognize that although the illustrated embodiment shows two independent controllers 2433, 2435, they can be combined in a single functional unit, device, or system, such as optional controller 2432. I will. In addition, controllers 2433 and 2435 can be coupled to communicate with each other and share processing resources.

  FIG. 25 illustrates a further embodiment of a plasma processing system 2500. The illustrated embodiment includes a switch mode power supply 2530 that produces an AC waveform that may have a DC offset provided by a DC power supply (not shown). The switch mode power supply can be controlled via an optional controller 2535, including voltage and current controllers 2537, 2539. The switch mode power supply 2530 can include a controllable voltage source 2538 having a voltage output controlled by a voltage controller 2537 and a controllable current source 2540 having a current output controlled by a current controller 2539. . The controllable voltage and current sources 2538, 2540 can be in a parallel arrangement. Controllable current source 2540 is configured to compensate for ion current between plasma 2504 and substrate 2506.

  Voltage and current controllers 2537, 2539 can be coupled to and communicate with each other. The voltage controller 2537 can also control the switchable output 2539 of the controllable voltage source 2538. Switchable output 2539 can include two switches in parallel, as shown, or any output that converts the output of controllable voltage source 2538 to the desired AC waveform (eg, non-sinusoidal). Circuitry can be included. Via two switches, the controlled voltage or AC waveform from controllable voltage source 2538 is combined with the controlled current output of controllable current source 2540 to generate the AC waveform output of switch mode power supply 2530. can do.

  Although controllable voltage source 2538 is illustrated as having a given polarity, those skilled in the art will recognize that the opposite polarity also corresponds to that illustrated. Optionally, the controllable voltage and current sources 2538, 2540 can be part of an AC power source 2536 with a switchable output 2539, the AC power source 2536 being a DC that is inside or outside the switch mode power supply 2530. It can be arranged in series with a power source (not shown).

  FIG. 26 illustrates yet another embodiment of the plasma processing system 2600. In the illustrated embodiment, the switch mode power supply 2630 provides the electrostatic chuck 2611 with an AC waveform having a DC offset. The AC component of the waveform is generated through a parallel combination of a controllable voltage source 2638 and a controllable current source 2640 that are connected together through a switchable output 2639. The DC offset is generated by a DC power source 2634 that is coupled in series between ground and a controllable voltage source 2638. In some embodiments, the DC power source 2634 can be floating rather than grounded. Similarly, the switch mode power supply 2630 can be floating or grounded.

  System 2600 can include one or more controllers for controlling the output of switch mode power supply 2630. For example, the first controller 2632 can control the output of the switch mode power supply unit 2630 via the second controller 2633 and the third controller 2635. The second controller 2633 can control the DC offset of the switch mode power supply 2630 as generated by the DC power source 2634. The third controller 2635 can control the AC waveform of the switch mode power supply 2630 by controlling the controllable voltage source 2638 and the controllable current source 2640. In some embodiments, voltage controller 2637 controls the voltage output of controllable voltage source 2638 and current controller 2639 controls the current of controllable current source 2640. The voltage and current controllers 2637, 2639 can communicate with each other and can be part of the third controller 2635.

  Those skilled in the art will appreciate the various configurations of the controller for power supplies 2634, 2638, 2640, and the foregoing embodiments are not limiting, and various other configurations may also be implemented without departing from this disclosure. You will recognize that you can. For example, the third controller 2635 or voltage controller 2637 can control a switchable output 2639 between a controllable voltage source 2638 and a controllable current source 2640. As another example, the second and third controllers 2633, 2635 can communicate with each other (not shown as such). It should also be understood that the polarities of controllable voltage and current sources 2638, 2640 are illustrative only and are not meant to be limiting.

  Switchable output 2639 can operate by alternately switching two parallel switches to shape an AC waveform. The switchable output 2639 can include any of a variety of switches including, but not limited to, MOSFETs and BJTs. In one variation, the DC power source 2634 can be arranged between the controllable current source 2640 and the electrostatic chuck 2611 (in other words, the DC power source 2634 can float) and switch mode power supply. Part 2630 can be grounded.

  FIG. 27 illustrates another embodiment of a plasma processing system 2700. In this variation, the switch mode power supply 2734 is again grounded, but instead of being integrated into the switch mode power supply 2730, here the DC power source 2734 is a separate component and the switch mode power supply 2734 is The DC offset is provided not only to the components in the power supply unit 2730 but also to the entire switch mode power supply unit 2730.

  FIG. 28 illustrates a method 2800 according to an embodiment of the present disclosure. The method 2800 includes an operation 2802 of placing a substrate in a plasma chamber. The method 2800 further includes an operation 2804 of forming a plasma in the plasma chamber. Such a plasma can be formed in situ or via a remote projection source. Method 2800 also includes switch power operation 2806. Switched power operation 2806 involves controllably switching power to the substrate to apply a periodic voltage function to the substrate. The periodic voltage function is considered a pulsed waveform (eg, a square wave) or an AC waveform, and may include a DC offset generated by a DC power supply in series with the switch mode power supply. In certain embodiments, the DC power source is incorporated into the switch mode power supply and can therefore be in series with the AC power of the switch mode power supply. The DC offset creates a potential difference between the upper surface of the electrostatic chuck and the reference layer in the substrate, and this potential difference is referred to as the chucking potential. The chucking potential between the electrostatic chuck and the substrate holds the substrate to the electrostatic chuck and thus prevents the substrate from moving during processing. Method 2800 further includes a modulating operation 2808 in which the periodic voltage function is modulated over a plurality of cycles. The modulation is responsive to a desired (or defined) ion energy distribution at the surface of the substrate to provide a desired (or defined) ion energy distribution based on a time average.

  FIG. 29 illustrates another method 2900 according to an embodiment of the present disclosure. The method 2900 includes an act 2902 of placing a substrate in a plasma chamber. The method 2900 further includes an operation 2904 of forming a plasma in the plasma chamber. Such a plasma can be formed in situ or via a remote projection source. The method 2900 also includes an operation 2906 that receives at least one ion energy distribution setting. The settings received in receive operation 2906 may indicate one or more ion energies at the surface of the substrate. The method 2900 is further controllable such that the power to the substrate provides (1) a desired (or defined) distribution of ion energy based on the time average, and (2) a desired chucking potential based on the time average. Switch power operation 2908, which is switched to The power can have an AC waveform and a DC offset.

  In conclusion, the present invention provides, among other things, a method and apparatus for selectively generating desired (or defined) ion energy using a switch mode power supply. Those skilled in the art will recognize that the present invention, its use, and its construction have many variations and permutations so as to achieve substantially the same results as those achieved by the embodiments described herein. It can be easily recognized what can be done. Accordingly, there is no intention to limit the invention to the disclosed exemplary forms. Many variations, modifications, and alternative constructions fall within the scope and spirit of the disclosed invention.

Claims (42)

An apparatus for providing a modified periodic voltage function to an electrical node, wherein the electrical node is configured to couple to a substrate support of a plasma processing chamber, the apparatus comprising:
A power supply for providing a periodic voltage function to the electrical node, wherein the periodic voltage function comprises a pulse and a portion between the pulses;
An ion current compensation component that modifies the slope of the portion between the pulses by providing ion current compensation, thereby forming a modified periodic voltage function;
A communicable controller and the power supply and the ion current compensation component,
Wherein the controller,
Identifying a value of the ion current compensation that, when provided to the electrical node, will result in a defined ion energy distribution function of ions reaching the surface of the substrate ;
Receiving a user selection of ion energy;
Setting an initial power supply voltage;
Measuring a voltage step of the modified periodic voltage function at the electrical node;
Calculating a current ion energy based on the voltage step;
If the current ion energy is not equal to the user selection of ion energy, setting a new power supply voltage;
Configured to do the device.   The apparatus according to claim 1, wherein the power supply unit is a switch mode power supply unit.   The apparatus of claim 2, wherein the switch mode power supply includes one or more switching components. The system of claim 1, wherein the controller samples two or more voltages from the modified periodic voltage function and calculates a slope dV ₀ / dt of the two or more voltages. 5. The slope dV ₀ / dt is calculated based on two or more voltages sampled from a portion of the modified periodic voltage function between pulses of the modified periodic voltage function. The system described. It said controller, in order to establish an average ion energy of the first set of ions reaching the surface of the substrate, is configured to regulate the voltage of the power supply unit, according to claim 5 system. It said controller, in order to establish an average ion energy of the second set of ions reaching the surface of the substrate, is configured to further adjust the voltage of the power supply unit, according to claim 6 System. The power supply is configured to adjust a voltage step of the modified periodic voltage function to establish the average ion energy of the first set of ions reaching the surface of the substrate. The system of claim 5. The power supply is configured to adjust a peak-to-peak voltage of the modified periodic voltage function to establish the average ion energy of the first set of ions that reach the surface of the substrate. 6. The system of claim 5, wherein:   Switching of the one or more switching components is timed to affect the slope of the portion of the modified periodic voltage function between the pulses of the modified periodic voltage function. The system according to claim 5.   The apparatus of claim 1, wherein the controller adjusts an amplitude of the ion current compensation until the defined ion energy distribution function of ions reaching the surface of the substrate is achieved. A method of providing a modified periodic voltage function to an electrical node, wherein the electrical node is configured to be electrically coupled to a substrate support of a plasma processing chamber, the method comprising:
Providing a ion current compensation I _C to the electrical node,
The method comprising: providing a periodic voltage function to the electrical node, the periodic voltage function is modified by the ion current compensation I _C, to form the modified periodic voltage function, and that,
Providing the modified periodic voltage function to the electrical node, the modified periodic voltage function comprising a pulse and a portion between the pulses;
Accessing at least an effective capacitance value C ₁ representing the capacitance of the substrate support;
Determining a slope dV ₀ / dt of the portion between the pulses of the modified periodic voltage function;
Identifying a value of the ion current compensation Ic that will result in a defined ion energy distribution function of ions arriving at the surface of the substrate, the identifying comprising identifying the effective capacitance C ₁ and the Is a function of the slope dV ₀ / dt of the portion between pulses ;
Receiving a user selection of ion energy;
Setting an initial power supply voltage;
Measuring a voltage step of the modified periodic voltage function at the electrical node;
Calculating a current ion energy based on the voltage step;
Setting a new power supply voltage if the current ion energy is not equal to the user selection of ion energy .   The method of claim 12, wherein the defined ion energy distribution is a narrow ion energy distribution. The value of the ion current compensation Ic that will result in the defined ion energy distribution function of ions reaching the surface of the substrate is a value that satisfies the function f as follows:
The method of claim 12. Setting the ion current compensation Ic to a first value;
Determining the sign of the function f;
15. The method of claim 14, further comprising: increasing the ion current compensation Ic if the sign of the function f is positive and decreasing the ion current compensation Ic if the sign of the function f is negative. the method of.   The method of claim 12, wherein the identifying comprises sampling the voltage of the portion between the pulses of the modified periodic voltage function at two or more times. The method of claim 16, wherein the identifying comprises calculating the slope dV ₀ / dt from the voltages sampled at the two or more times. The identifying includes calculating the slope dV ₀ / dt for two or more cycles of the modified periodic voltage function, each of the two or more cycles comprising the ion current compensation The method of claim 17, wherein the method is associated with different values of Ic. The identifying includes sampling a voltage of the portion between the pulses of the modified periodic voltage function during a first cycle and a second cycle, and at least from these sampled voltages The method of claim 16, comprising calculating the slope dV ₀ / dt. The method of claim 12, wherein the ion current compensation Ic is linearly related to an ion current I _I across a plasma sheath of plasma formed in the plasma processing chamber. The ion current compensation Ic is linearly related to the ion current I _I according to the following equation:
The method of claim 10, wherein C ₁ is an effective volume of the plasma chamber and C _strain is a cumulative stray volume of the plasma chamber. The method of claim 21, wherein the effective capacity C ₁ varies with time.   The method of claim 21, wherein the ion current compensation Ic varies with time.   The method of claim 12, further comprising providing the modified periodic voltage function to the electrical node such that ions reach the surface of the substrate with a first ion energy.   25. The method of claim 24, wherein the modified periodic voltage function comprises a first voltage step corresponding to the first ion energy.   26. The method of claim 25, further comprising: providing the modified periodic voltage function with a second value of the ion current compensation Ic to the electrical node to expand the ion energy distribution function.   26. The method of claim 25, wherein the first voltage step and the second voltage step are provided in adjacent cycles of the modified periodic voltage function.   25. The method of claim 24, wherein the providing has a negligible effect on the density of the plasma. Applying a modified periodic voltage function to an electrical node, the modified periodic voltage function comprising a periodic voltage function modified by ion current compensation, wherein the electrical node comprises a plasma processing chamber Configured to couple to a substrate support coupled to an inner substrate; and
Sampling at least one cycle of the modified periodic voltage function to generate voltage data points;
Estimating a value of a first ion energy of ions reaching the surface of the substrate, wherein the estimating is based on the voltage data points;
Adjusting the modified periodic voltage function until the first ion energy is equal to a defined ion energy ;
Receiving a user selection of ion energy;
Setting an initial power supply voltage;
Measuring a voltage step of the modified periodic voltage function at the electrical node;
Calculating a current ion energy based on the voltage step;
Setting a new power supply voltage if the current ion energy is not equal to the user selection of ion energy .   30. The method of claim 29, further comprising sampling at least one cycle of the modified periodic voltage function after each voltage increment of the adjustment to estimate the value of the first ion energy. .   30. The method of claim 29, wherein the estimating is a function of ion current.   32. The method of claim 31, wherein the ion current is a function of the ion current compensation. The following equation is used in estimating the value of the first ion energy:
ΔV is the voltage step of each cycle of the modified periodic voltage function, C ₁ is the effective capacity of the chamber, C _sheath is the sheath capacity of the plasma sheath, and C _sheath is the ion 35. The method of claim 32, wherein the method is dependent on current.   34. The adjusting of claim 33, wherein the adjusting comprises adjusting the step voltage ΔV of the modified periodic voltage function until the first ion energy is equal to the defined ion energy. Method.   30. The method of claim 29, further comprising changing the first value of the ion current compensation to a second value to expand the width of the ion energy distribution.   30. The method of claim 29, wherein the adjusting comprises adjusting a bias supply voltage until the first ion energy is equal to the defined ion energy. Providing a modified periodic voltage function to an electrical node, wherein the electrical node is configured to couple to a substrate support of a plasma processing chamber;
Sampling at least two voltages from the modified periodic voltage function at a first time and a second time;
Calculating the slope of the at least two voltages as dV / dt;
Comparing the slope to a reference slope known to correspond to the ion energy distribution function width;
Adjusting the modified periodic voltage function such that the slope approaches the reference slope ;
Receiving a user selection of ion energy;
Setting an initial power supply voltage;
Measuring a voltage step of the modified periodic voltage function at the electrical node;
Calculating a current ion energy based on the voltage step;
Setting a new power supply voltage if the current ion energy is not equal to the user selection of ion energy .   The first time occurs during a first cycle of the modified periodic voltage function and the second time occurs during a second cycle of the modified periodic voltage function; 38. The method of claim 37.   38. The method of claim 37, wherein the first and second times occur during the same cycle of the modified periodic voltage function.   38. The method of claim 37, wherein the sampling is performed at a sampling rate of at least 400 kHz. A non-transitory tangible computer-readable storage medium encoded with processor readable instructions for performing a method for identifying a defined ionic current compensation I _C, the method comprising:
And sampling said ion current compensation I modified periodic voltage function given _C having a first value,
And sampling said ion current compensation I modified periodic voltage function given _C having a second value,
Accessing the effective capacity value C ₁ of the plasma processing chamber;
Determining a slope dV ₀ / dt of the modified periodic voltage function based on the first and second samplings;
Calculating a third value of the ion current compensation I _C that makes the following equation true :
Receiving a user selection of ion energy;
Setting an initial power supply voltage;
Measuring a voltage step of the modified periodic voltage function;
Calculating a current ion energy based on the voltage step;
A non-transitory tangible computer readable storage medium comprising setting a new power supply voltage if the current ion energy is not equal to the user selection of ion energy . 42. The non-transitory tangible computer readable storage medium of claim 41, further comprising calculating a sheath voltage across a plasma sheath of plasma in the plasma processing chamber.