DC plasma control for electron-assisted materials processing.

Abstract

A system and method are presented for material processing using precisely controlled wafer-scale waves of electrons in a DC plasma. The anode and cathode of a DC plasma chamber are connected to an adjustable DC voltage source and a DC current source, respectively. The anode potential is adjusted to shift the floating surface potential of a stage in the positive column of the DC plasma to the reference ground potential of the DC voltage / current source. A control loop can be operated throughout the various processing steps to maintain the floating surface potential of the stage at the reference ground potential. A signal generator referenced to ground potential is capacitively coupled to the stage and controls the surface potential of the stage to impart kinetic energy to the free electrons in the DC plasma.

Description

[Technical field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to U.S. Application No. 17 / 524,330, filed November 11, 2021, and entitled "DC Plasma Control for Electron Enhanced Material Processing," the contents of which are incorporated herein by reference.

[0002] The present disclosure relates generally to materials processing, and more particularly to systems and methods for generating operating conditions in a direct current plasma reaction chamber used in materials processing using precisely controlled wafer-scale waves of electrons in a direct current plasma at room temperature (or other temperatures, as desired). [Background technology]

[0003] For example, the manufacture of integrated circuits involves processing corresponding substrates in a direct current plasma reaction chamber, where electrons and / or ions are accelerated towards the substrate surface to initiate reactions that physically change the substrate surface. In some cases, and primarily due to the relatively small mass of electrons compared to ions, substrate processing via electrons may be preferred to reduce damage to the substrate surface beyond the targeted physical changes expected by the processing step itself.

[0004] In some cases, plasma processing may involve placing a substrate in a region of a direct current plasma reaction chamber such that the exact value of the surface floating potential of the substrate is not known. Thus, a bias signal externally applied to the substrate may provide a free electron energy in a region of the plasma close to the surface of the substrate that does not correlate with the electron energy threshold / level of the (atomic) material present at the surface of the substrate. The teachings of the present disclosure create operating conditions in a direct current plasma chamber that allow precise control of the energy of the free electrons to specifically target the electron energy threshold of the material present at the surface of the substrate. Summary of the Invention

[0005] Systems and methods are disclosed for material processing using precisely controlled wafer-scale waves of electrons in a DC plasma at room temperature (or other temperatures as desired). In this disclosure, such material processing, in which the kinetic energy of free electrons in the DC plasma can be precisely controlled to precisely (and selectively) target atomic energy levels at the surface of the substrate being processed, is referred to as electron enhanced material processing (EEMP).

[0006] According to one embodiment of the present disclosure, a direct-current (DC) plasma system for substrate processing is disclosed, the direct-current plasma system comprising: a DC plasma reaction chamber configured to contain a DC plasma generated between an anode and a cathode of the DC plasma reaction chamber; an adjustable DC voltage source having an output electrically coupled to the anode; a DC current source electrically coupled to the cathode; and a substrate support stage disposed in a region of the DC plasma reaction chamber containing a positive column of the DC plasma, the adjustable DC voltage source and the DC current source being electrically coupled to a reference earth; and during a substrate processing step, the adjustable DC voltage source adjusts the potential of the anode to set a floating potential at a surface of the substrate support stage to the potential of the reference earth.

[0007] According to a second embodiment of the present disclosure, a method for treating a surface of a substrate is disclosed, the method comprising the steps of: placing a substrate support stage in a region of a DC plasma reaction chamber configured to generate a positive column of DC plasma; coupling an adjustable DC voltage source and a DC current source to an anode and a cathode of the DC plasma reaction chamber, respectively, to generate a DC plasma; generating a floating potential on the surface of the substrate support stage based on the generated DC plasma; adjusting the potential of the anode via the adjustable DC voltage source while maintaining a constant DC current between the anode and the cathode via the DC current source; and setting the floating potential to a specific potential of a reference ground of the adjustable DC voltage source based on the adjusting and maintaining steps.

[0008] Further aspects of the present disclosure are set forth in the specification, drawings and claims of this application. [Brief description of the drawings]

[0009] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the present disclosure and, together with the description of the exemplary embodiments, serve to explain the principles and embodiments of the disclosure. [Figure 1A] 1 is a simplified schematic diagram of a DC plasma reaction chamber that can be used in a DC plasma processing system. [Figure 1B] 1B shows a graph representative of the change in the (electrical) potential of the plasma during operation of the DC plasma reaction chamber of FIG. 1A. [Figure 1C] 1B shows a simplified schematic diagram of a DC plasma processing system including a (substrate) stage positioned in the region of the DC plasma reaction chamber of FIG. 1A. [Figure 1D] 1D illustrates an exemplary biasing of a stage of the DC plasma processing system of FIG. 1C via an external bias signal generator. [Figure 1E] 1D shows an exemplary bias signal generated by the external bias signal generator of FIG. 1D and the corresponding potential generated at the stage surface. [Figure 1F]3 shows exemplary energy levels of atoms at the surface of the stage. [Figure 2A] 1 shows a simplified schematic diagram of a DC plasma processing system according to one embodiment of the present disclosure, including a means for controlling a surface potential of a stage. [Figure 2B] 2B is a graph representative of the control of the surface potential of a stage of the DC plasma processing apparatus of FIG. 2A. [Figure 2C] 2B shows a representative graph of adjustment of the surface potential of the stage relative to the reference ground potential of the DC plasma processing system of FIG. 2A. [Figure 3A] 1 shows a simplified schematic diagram of a DC plasma processing system according to one embodiment of the present disclosure, comprising a means for controlling a surface potential of a stage and a means for measuring the surface potential. [Figure 3B] FIG. 3B shows a simplified schematic diagram of a DC plasma processing system according to an embodiment of the present disclosure, based on the system of FIG. 3A with the addition of means for automatic control of the surface potential. [Figure 4A] FIG. 3C is a simplified schematic diagram of a DC plasma processing system according to an embodiment of the present disclosure based on the system of FIG. 3B with the addition of stage biasing means. [Figure 4B] 4B illustrates exemplary bias signals supplied to a stage of the DC plasma processing system of FIG. 4A and the corresponding potentials developed at the surface of the stage. [Figure 4C] 3 shows exemplary energy levels of atoms at the surface of the stage. [Diagram 5] 2 is a process chart illustrating various steps of a method according to one embodiment of the present disclosure for treating a surface of a substrate.

[0010] Like reference numbers and designations in the various drawings indicate like elements. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] FIG. 1A shows a simplified schematic diagram of a prior art DC plasma reaction chamber (110) that may be used in a DC plasma processing system. The bias of the DC plasma reaction chamber (110) may be provided by a DC voltage source (150) coupled between an anode A and a cathode C of the DC plasma reaction chamber (110). During operation, a glow discharge (plasma) may be formed in the chamber (110) based on the interaction of the gas with electrons of the current flowing between the anode A and the cathode D. This generates free ions and free electrons in the chamber. The operating principle of such a DC plasma reaction chamber (110) is well known to those skilled in the art, and therefore the relevant details will be omitted in this disclosure.

[0012] 1A, the glow discharge formed in the chamber (110) may include glow regions (G1, G2, G3, G4) that emit significant light and dark regions (D1, D2, D3, D4) that may not emit light. Such regions may represent different operating characteristics of the DC plasma reaction chamber (110), including, for example, temperature and electrical potential.

[0013] FIG. 1B illustrates the plasma (electrical) potential V along the axial (longitudinal) direction X of the chamber (110) during operation. PP As shown in Figure 1B, a graph representative of the change in plasma potential V PP is the value V representing the potential applied to the cathode C by the DC voltage source (150 in FIG. 1A). C , the value V represents the potential applied to the anode A by the DC voltage source (150 in FIG. 1A). A For example, as shown in FIG. 1D below, the value V A is zero volts (e.g., reference ground), and the value V C It should be noted that is negative (eg, negative for values ​​in the range of about 0 (zero) to 500 volts).

[0014] Continuing to refer to FIG. 1B, the potential V in the regions (e.g., D1, G1, D2) close to the cathode C and the region (e.g., G4) close to the anode A is PPThe rapid fluctuations in may correspond to regions of higher operating temperature in the chamber (110). The other region G3, also called the positive column, has a fairly uniform / constant potential, V PP For example, as shown in FIG. 1B, the region along the axis X of the chamber (110) is a region of low operating temperature [X G31 , X G32 Considering that the positive column region G3 includes the segment [X G31 , X G32 ] across the plasma potential V PP The variation of is minimal, in other words, the segment [X G31 , X G32 ] potential V PP can be considered to be constant. Therefore, as shown in Figure 1B, the segment [X G31 , X G32 ] plasma potential V pp is the value V G3 The lower operating temperature and constant potential value of the plasma in the positive column region G3 allows such region to be used for substrate processing, as shown in Figures 1C and 1D.

[0015] FIG. 1C shows a simplified schematic diagram of a DC plasma processing system (100C) including a (substrate) stage S located in the positive column region G3 of the DC plasma reaction chamber (110). The stage S may be designed to support a flat substrate and therefore may include a top flat / planar surface. The stage S shown in FIG. 1C is electrically isolated (not connected to an external potential) and therefore is not connected to the plasma potential V, as is well known to those skilled in the art. PP In the presence of S is generated, and the potential V S is the surface floating potential V FP This is called the (surface) floating potential V FP and the plasma potential V PP The relationship between the area [X G31 , X G32 ] at the plasma potential VPP is V G3 and the floating potential V FP is the plasma potential V G3 (plasma potential V G3 is negative with respect to

[0016] The floating potential V shown in the graph of FIG. FP can be attributed to a "plasma sheath" that develops in the presence of stage S. As known to those skilled in the art, any wall or barrier in the plasma will develop a negative potential with respect to the bulk of the plasma. As a result, an equilibrium potential drop occurs between the bulk of the plasma and the wall or barrier. Such a potential drop is confined to a small region of space adjacent to the wall or barrier due to a charge imbalance that develops between the plasma and the wall or barrier. This layer of charge imbalance has a finite thickness, characterized by the Debye Length, and is called the "plasma sheath" or "sheath." Such a layer is a few Debye lengths thick, a value that depends on various properties of the plasma. When the dimensions of the bulk plasma (e.g., chamber 110) are, for example, much larger than the Debye length, the Debye length depends on the plasma temperature and electron density. For certain DC plasma operating conditions supported by the teachings of the present disclosure (e.g., EEMP systems near to and moderately above room temperature), the Debye length is on the order of a few millimeters (e.g., less than 10 millimeters), and the potential V G3 and V FP , is on the order of a few volts (e.g., less than 10 volts). It should be noted that the plasma sheath can occur in the presence of any wall or barrier, whether conductive or not. Thus, once a substrate (whether conductive or insulating) is positioned on the stage S, it is exposed to the same floating potential V as described above with reference to FIG. 1C. FP may occur on the surface of the substrate.

[0017] FIG. 1D illustrates an example biasing of stage S of the DC plasma processing system of FIG. 1C via an external bias signal generator (180) that is capacitively coupled to stage S by a capacitor C. In the example configuration (100D) shown in FIG. 1D, a potential V A is zero volts (e.g., tied to a reference ground, Gnd). Additionally, as shown in FIG. 1D, a bias signal V applied to stage S by an external bias signal generator (180) B can be referenced to a reference ground potential Gnd. In some prior art implementations, the bias signal V B may be DC coupled to stage S, however the teachings of the present disclosure strictly prohibit such DC coupling to the stage to avoid a discharge path for DC current through any intermediate point within the chamber (110) which could significantly change the operating conditions within the chamber (110).

[0018] In the DC plasma processing system shown in FIG. 1D, the bias signal V B is the potential seen by free electrons and / or ions near the stage S, or the substrate, if present (e.g., the surface potential V S ) can be used to control the energy of the free electrons and / or ions to a level required for processing the substrate. For example, as shown in the left graph of FIG. 1E, a bias signal V generated by an external bias signal generator (e.g., 180 in FIG. 1D) can be used to control the energy of the free electrons and / or ions to a level required for processing the substrate. B starts from zero and grows to a voltage amplitude of V B1 As shown in the top right graph of FIG. 1E, during processing step (a), the voltage amplitude V B1 is applied (e.g., AC-coupled) to stage S, the voltage amplitude V B1 is the surface floating potential V FPa is added to (or subtracted if negative), and a surface potential V S However, the free electrons and / or ions are at the plasma potential V PPa Therefore, the free electrons and / or ions see a plasma potential VPPa Surface potential V exceeds S For example, as shown in the top right graph of FIG. 1E, the (kinetic) energy of free electrons and / or ions is Potential difference V KEa =(V B1 -ΔV FPa ), where: ΔV FPa , =(V PPa -V FPa ).

[0019] For example, different differential ΔV FPb , =(V PPb -V FPb ) may result in different plasma potentials V PPb , or different floating potentials V FPb Considering the process step (b) represented by the graph on the lower right side of FIG. 1E, which may have different operating conditions from those of the process step (a) including the same applied voltage amplitude V B1 , different (kinetic) energies of the free electrons and / or ions are obtained. The teachings of the present disclosure eliminate variations in the operating conditions in the chamber (e.g., 110 in FIG. 1D) and / or compensate for such variations, e.g., to allow precise control of the energy of the free electrons (and / or ions). It should be noted that variations in the operating conditions are expected when considering different types of processes (e.g., (a) and (b) in FIG. 1E) performed in the chamber (110), including, e.g., etching the substrate with different reactive gases, cleaning the substrate, or other processes that may alter and / or remove composition / material from the surface of the substrate. It should be noted that, as known to those skilled in the art, different operating conditions for performing different types of processes may further include corresponding variations and / or adjustments to any one of the DC plasma current, temperature, gas mixture, or flow rates in the chamber (110).

[0020] When the substrate is placed on the surface of the stage S, the bias signal V BThe kinetic energy of the free electrons and / or ions obtained by the application of V accelerates them towards the surface of the substrate and may cause them to collide with the substrate, releasing their kinetic energy to atoms at the surface of the substrate. However, those atoms are not able to reach the potential at which they exist, in other words the floating potential, V FP The various energy levels of such atoms for the process type (a) described above with reference to FIG. 1E are based on the energy levels E of the nuclei of the atoms at the substrate surface. n , the energy level E of the electrons bound to the nuclei of the atoms on the substrate surface B , and the energy level E of the electron in the orbital of the electron bound to the nucleus on the substrate surface e , as shown in Figure 1F.

[0021] As can be seen in Figure 1F, the nuclear energy level E n is the (negative) potential V FPa and the electron energy level E e is the (negative) electric potential (E n +E B In other words, to excite an atom to a level that breaks the bond between the electron and the nucleus, the electron must reach the energy level E e Therefore, if we consider a plasma that is processed only through free electrons, the potential difference V KEa =(V B1 -ΔV FPa ) is the bias signal V B The kinetic energy of the free electrons supplied by the application of e must be equal to or greater than . However, E e =(E n +E B ), and E n is the a priori unknown floating potential V FPa Since it is based on the energy level E e It may be impossible to precisely control the kinetic energy of the free electrons in order to target them precisely.

[0022] Floating potential (e.g., V in Figure 1F) FPa ) may be empirically and / or experimentally determined for a given process in stable operating conditions of a direct current plasma chamber, but inconsistencies and / or lack of repeatability of such operating conditions may invalidate the determined floating potential. Furthermore, since different types of processes result in essentially different floating potentials, the task of precisely controlling the kinetic energy of the free electrons to precisely target the energy levels of atoms on the substrate surface may not be feasible. As a result, in some prior art implementations, atoms on the substrate surface may be imparted with kinetic energy substantially greater than the energy levels of the targeted atoms, and thus may not be selective (since atoms of different materials / compositions having different energy levels may equally experience sufficient energy levels to break orbital bonds). Electron-assisted material processing (EEMP) according to the teachings of the present disclosure overcomes such shortcomings, thus enabling precise control of the kinetic energy of the free electrons to precisely and selectively target the energy levels of atoms on the substrate surface.

[0023] 2A shows a simplified schematic diagram of a DC plasma processing system (200A) according to one embodiment of the present disclosure, comprising means (250, 260) for controlling the surface potential of the stage S when electrically isolated. In other words, the means (250, 260) controls the floating potential V FP As shown in FIG. 2A, the means (250, 260) includes an adjustable DC voltage source (250) coupled to the anode A of the DC plasma reaction chamber (110) and a DC current source (260) coupled to the cathode C of the DC plasma reaction chamber (110). Thus, the potential VA of the anode A can be controlled to be in the range of zero volts or more (positive) with respect to a reference earth (Gnd at zero volts), and the (drain) current Ip flowing between the anode A and the cathode C through the reaction chamber (110) can be set by the DC current source (260). Thus, the potential V of the cathode C can be controlled to be in the range of zero volts or more (positive) with respect to a reference earth (Gnd at zero volts), and the (drain) current Ip flowing between the anode A and the cathode C through the reaction chamber (110) can be set by the DC current source (260). Cis not forced by an external DC voltage source (e.g., 150 in FIG. 1D), but rather (floats) to the adjustable potential V of anode A. A and settles to a (negative) voltage based on the set current Ip. Such a configuration allows the floating potential V to be increased while maintaining the set current Ip through the reaction chamber (110) constant in order to establish and maintain a higher level of process stability and optimization. FP This allows the user to control / adjust the

[0024] FIG. 2B illustrates the surface potential V of the stage S of the DC plasma processing system (200A) described above with reference to FIG. 2A. FP In particular, FIG. 2B shows two graphs, differentiated by the use of solid or dashed lines, each graph showing two different voltages (V A1 , V A2 ) across the longitudinal extension X of the chamber (110) relative to the plasma potential V PP As can be seen in Figure 2B, the voltage V A1 to voltage V A2 A positive step increase in the anode potential to +ΔV 12 For floating potential (V FP1 , V FP2 ) and cathode potential (V C1 , V C2 ) is the same positive step, +ΔV 12 In fact, as shown in Figure 2B, the plasma potential V PP For the whole of 12 In other words, the range [X C , X A For any longitudinal coordinate X in PP (X) is the step increase, +ΔV 12 A similar behavior applies to the negative step variation applied to anode A by the adjustable DC voltage source (250). In other words, the control of the potential of anode A by the adjustable DC voltage source follows the plasma potential V PP and therefore the floating potential VFP and the voltage V at the top of stage S S As will be described later in this disclosure, such linearity is important while operating a DC plasma chamber for different types of material processing, as well as the floating potential V FP This can be used in an EEMP system in accordance with the present teachings to implement a closed-loop control subsystem that automatically controls the value of to a preset value (e.g., zero volts).

[0025] Figure 2C shows the anode voltage V A1 FIG. 2B shows two graphs similar to the one described above with reference to FIG. 2B, including the special case where V is equal to zero volts (solid line). As can be seen in FIG. 2B, the floating potential voltage in such a case is a negative value V FP1 and therefore the plasma potential V PP Furthermore, as can be seen in FIG. 2C, a positive step increase in the anode potential, +ΔV 13 =(V A1 -V FP1 ), the floating potential is equal to zero volts, V FP3 According to one embodiment of the present disclosure, the floating potential V FP Such zeroing of may allow for precise control of the kinetic energy of free electrons in a DC plasma to precisely (and selectively) target the energy levels of atoms at the surface of the substrate (whether conductive or insulating) being processed. In other words, referring back to FIG. 1F, the energy level E of the nuclei of the atoms targeted / selected for processing may be n The a priori unknown floating potential that determines the floating potential V FP On the other hand, as shown in FIG. 4B below, this causes the energy level E e , the kinetic energy level of free electrons in a DC plasma (e.g., V in Fig. 1F) KEa ), and the bias voltage V applied to stage S B allows all of the power supplies to be referenced to the same known and fixed reference, the zero volt potential Gnd.

[0026] FIG. 3A shows a means for controlling the surface potential of the stage S (250, 260 in FIG. 2A) and a surface potential V S (For example, floating potential, V FP ) measuring means (R, 311, V in FIG. 3A) R 3 shows a simplified schematic diagram of a direct current plasma processing system (300A) according to an embodiment of the present disclosure, comprising a surface potential V S Means for measuring (R, 311, V R ), or in other words, the floating (surface) potential above the stage V FP Means for measuring (R, 311, V R ) represents an improvement over the system (200A) described above with reference to FIG. 2A. FP By enabling such measurement, adjustment of the DC voltage source (250) as described above with reference to FIGS. 2A-2C can be made to the surface potential V FP This may be done while monitoring / measuring the floating potential V, including for example setting such potential to zero (VFP=0 volts). FP This allows for precise control of the amount of heat generated.

[0027] With continued reference to FIG. 3A, the means (R, 311, V R ) includes a reference plate R that is located in the DC plasma chamber (110) in the same (longitudinal coordinate) segment [XG31, XG32] as the stage S. The reference plate R may be made of any conductive material that can withstand the (internal) operating conditions of the chamber (110) and may have any planar shape, including, for example, planar shapes according to a square, rectangle, circle, pentagon, trapezoid or others. The reference plate R is located in the same area as the plate S and therefore has the same approximately constant plasma potential V PP Since the reference plate R is located in the region of FP In other words, the (surface) potential V on the reference plate R R By measuring the potential V, the floating potential at stage S can be determined. An insulated conductive wire (311) attached to reference plate R is connected to a potential VR to measurement electronics (e.g., transducers) located outside of the chamber (110). It should be noted that such measurement electronics should not provide a DC current path to the plasma through plate R.

[0028] With continued reference to FIG. 3A, the location of the reference plate R may be any longitudinal extension of the chamber (110) within the segments [XG31, XG32] that is technically feasible and practical. The chamber S may include an access door adjacent to the stage S on one side of the chamber (110), and in some exemplary embodiments, the reference plate R may be located against or near a wall of the chamber (110) opposite the access door and the stage S. Furthermore, according to exemplary embodiments, the center of the reference plate R and the center of the stage S (e.g., the intersection of the two segments of the stage T as shown in the figure) may be included in a line perpendicular to the axial direction (e.g., centerline, direction of longitudinal extension) of the chamber (110). Applicants of the present disclosure have proposed a method for tracking the floating potential of the stage S using a means (R, 311, V R ) was confirmed to be highly accurate.

[0029] FIG. 3B illustrates the surface potential V on stage S based on the system (300A) of FIG. FP 1 shows a simplified schematic diagram of a DC plasma processing system (300B) according to an embodiment of the present disclosure, with the addition of a means (320, CT) for automatic control of the floating potential V at stage S while operating the DC plasma chamber for different types of processes. FP The control electronics (320) is configured to incorporate a closed-loop control system that automatically controls the value of V to a preset value (e.g., zero volts). In particular, as shown in FIG. 3B, the control electronics (320) controls the (surface) potential V of the reference plate R via the coupling provided by the insulated conductive wire (311). R is taken as an input, and the voltage V supplied to the anode A is A, and thus generates a control (error) signal CT to regulate the floating potential V in stage S, as described above with reference to FIGS. 2A-2C. FP The control (error) signal CT is connected to a floating potential V, e.g. zero volts. FP The control electronics (320) may be generated with respect to a desired target / preset value of V. Those skilled in the art are familiar with design techniques for implementing control electronics (320), which are outside the scope of this disclosure. In particular, those skilled in the art are familiar with the use of operational amplifiers or error amplifiers in such control electronics (320), the input of which is connected to a potential V R , and the floating potential V FP to a desired target / preset value (e.g., zero volts) and generate an error signal (e.g., CT) based on the difference in the inputs.

[0030] FIG. 4A shows a biasing means (C S FIG. 4 shows a simplified schematic diagram of a direct current plasma processing system (400A) according to one embodiment of the present disclosure based on the system of FIG. 3B with the addition of bias means (C , 480). S , 480) is a capacitor C S In other words, the bias signal V generated at the output of the bias signal generator (480) is B is the capacitor C S The bias signal generator (480) capacitively couples the bias signal V to the stage S via a bias voltage VV, as previously described in this disclosure. As previously described in this disclosure, such capacitive coupling allows for the elimination of any direct current paths to or from the DC plasma chamber (110), thereby preventing any undesired perturbation of the operating conditions of the chamber (110). The bias signal generator (480) adjusts the bias signal V according to desired characteristics including, for example, amplitude, frequency, duty cycle, and / or rising / falling edges / slope. B It should be noted that the stage S may include a programmable waveform generator configured to output a waveform of a bias signal V Bto the stage S. S 3), and a second portion of the stage (e.g., a horizontal support plate), which may include conductive and / or insulating materials.

[0031] FIG. 4B illustrates an exemplary bias signal V applied to stage S of the DC plasma processing system (400A) of FIG. 4A. B1 , and the corresponding surface potential V generated on the surface of the stage S. S As will be clearly understood by those skilled in the art, the graph shown in FIG. FP 1E )。 Therefore, in view of (or in contrast to) the above description with reference to FIG. 1E, the (kinetic) energy of free electrons and / or ions attracted to the surface of the stage S or a substrate thereon is determined by the potential difference V KE =(V B1 -ΔV FP ) and ΔV FP =(V PP -V FP ) Therefore, in practical substrate processing applications using a DC plasma chamber, ΔV FP The value of V KE (e.g., the energy level E of the target electron in FIG. 4C) e Since the approximate value V KE =V B1 is believed to be reasonable, which in turn provides a bias signal V provided to stage S for performing electron-enhanced material processing (EEMP) according to the teachings of the present disclosure that precisely and selectively targets the energy levels of atoms (e.g., bound electrons) at the surface of the substrate. B1 This allows for simple and easy generation of

[0032] With further reference to FIGS. 4A and 4B, the excitation of the energy levels of atoms at the surface of the stage S or at the surface of a substrate disposed on the stage S is primarily due to the surface potential V SNote that the excitation of the energy levels may be based on the instantaneous change in the bias voltage V. B1 This can be achieved immediately at the end of the transition to , in other words, at the end of the ramp shown in FIG. 4B.

[0033] 4C illustrates exemplary energy levels of atoms at the surface of stage S of the DC plasma processing system (400A) of FIG. 4A. FIG. 4C illustrates the floating potential V, according to the description above with reference to FIGS. 2A-2C, further based on a reference plate R according to the description above with reference to FIG. 3A, further based on an (optional) closed loop control system provided by the control electronics (320) according to the description above with reference to FIG. 3B, and further based on capacitive coupling of a bias signal VB provided by the bias signal generator (480) according to the description above with reference to FIG. 4A. FP Based on the zeroing of KE This application highlights the advantages of electron-enhanced materials processing (EEMP) according to the teachings of the present disclosure, which allows for precise and selective targeted adjustment of the surface area of ​​a material.

[0034] 5 is a process chart (500) illustrating various steps of a method according to an embodiment of the present disclosure for treating a surface of a substrate. As shown in FIG. 5, such steps include: placing a substrate support stage in a region of a DC plasma reaction chamber configured to generate a positive column of DC plasma according to step (510); generating DC plasma by coupling an adjustable DC voltage source and a DC current source to an anode and a cathode of the DC plasma reaction chamber, respectively, according to step (520); generating a floating potential on the surface of the substrate support stage based on the generating step according to step (530); adjusting the potential of the anode via the adjustable DC voltage source while maintaining the DC current between the anode and the cathode constant via the DC current source according to step (540); and setting the floating potential to the potential of the reference ground of the adjustable DC voltage source based on the adjusting and maintaining step according to step (550).

[0035] A number of embodiments of the present disclosure have been described. Nevertheless, it will be understood that various modifications can be made without departing from the spirit and scope of the disclosure. Accordingly, other embodiments are within the scope of the following claims.

[0036] The above examples are provided to those of ordinary skill in the art as a complete disclosure and description of how to make and use the embodiments of the present disclosure, and are not intended to limit the scope of what the inventors regard as their disclosure.

[0037] Modifications of the above-described modes for implementing the methods and systems disclosed herein that are obvious to one skilled in the art are intended to be within the scope of the following claims. All patents and publications mentioned in this specification are indicative of the level of skill of those skilled in the art to which this disclosure pertains. All references cited in this disclosure are incorporated by reference to the same extent as if each reference was individually incorporated by reference in its entirety.

[0038] It is to be understood that the present disclosure is not limited to a particular method or system, as such may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting. As used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the content clearly dictates otherwise. The term "plurality" includes two or more references unless the content clearly dictates otherwise. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

Claims

1. 1. A direct current (DC) plasma system for processing a substrate, comprising: a DC plasma reaction chamber configured to contain a DC plasma generated between an anode and a cathode of the DC plasma reaction chamber; an adjustable DC voltage source having an output electrically coupled to the anode; a direct current source electrically coupled to the cathode; and a substrate support stage disposed in a region of the DC plasma reaction chamber that contains a positive column of the DC plasma; Equipped with the adjustable DC voltage source and the DC current source are electrically coupled to a reference ground; and A DC plasma system, wherein the adjustable DC voltage source is configured to adjust the potential of the anode during processing of the substrate to set a floating potential on a surface of the substrate support stage to a reference earth potential.

2. 2. The DC plasma system of claim 1 , wherein the DC current source is configured to set a constant DC current flowing between the anode and the cathode during processing of the substrate, the constant DC current being configured to generate the DC plasma.

3. 3. The DC plasma system of claim 2, wherein the combined anode potential and the constant DC current establish a cathode potential.

4. 3. The DC plasma system of claim 2, wherein the potential of the anode is adjustable independently of the constant DC current.

5. 5. The DC plasma system according to claim 1, further comprising a reference plate made of a conductive material, the reference plate being positioned in the DC plasma reaction chamber in a region including the positive column such that a surface potential of the reference plate is equal to a floating potential.

6. 6. The DC plasma system of claim 5, wherein the substrate support stage and the reference plate are disposed in a segment along a longitudinal extension of the DC plasma reaction chamber.

7. 7. The DC plasma system of claim 6, wherein a center of the substrate support stage and a center of the reference plate are contained within a line perpendicular to a direction of the longitudinal extension.

8. 6. The DC plasma system of claim 5, further comprising control electronics electrically coupled to the reference plate via an insulated conductive wire and configured to generate an error signal based on a difference between a surface potential of the reference plate and a potential of the reference ground.

9. 9. The DC plasma system of claim 8, wherein the control electronics includes an operational amplifier or an error amplifier.

10. 9. The DC plasma system of claim 8, wherein the adjustable DC voltage source is configured to receive the error signal and adjust the potential of the anode based on a value of the error signal.

11. 11. The DC plasma system of claim 10, wherein the adjustable DC voltage source, the reference plate, and the control electronics are configured to provide a closed loop control system that maintains the floating potential at the potential of the reference earth.

12. 5. The DC plasma system of claim 1, further comprising a bias signal generator capacitively coupled to the substrate support stage; the bias signal generator generating a bias signal having a voltage level referenced to a potential of the reference ground and capacitively coupled to the substrate support stage; and The bias signal is configured to control a surface potential of the substrate support stage.

13. 13. The DC plasma system of claim 12, A DC plasma system, wherein the bias signal generator is configured to control a waveform characteristic of the bias signal, the waveform characteristics including the voltage level, frequency, duty cycle, rising edge, or falling edge.

14. 13. The DC plasma system of claim 12, A DC plasma system, wherein when the voltage level of the bias signal is zero volts, the surface potential of the substrate support stage is zero volts, the energy level of free electrons in the DC plasma is zero volts, and the energy level of atomic nuclei at the surface of the substrate is zero volts.

15. 15. The DC plasma system of claim 14, wherein increasing the voltage level of the bias signal by a positive voltage step increases the surface potential of the substrate support stage by the same positive voltage step and the energy level of the free electrons increases in proportion to the positive voltage step.

16. 16. The DC plasma system of claim 15, A direct current plasma system, wherein the positive voltage step is selectable to raise the energy level of the free electrons to the energy level of electrons bound to the atomic nuclei during processing of the substrate.

17. A method for processing a surface of a substrate, comprising treating the substrate through a direct current (DC) plasma system according to any one of claims 1 to 4.

18. A method for processing a surface of a substrate, comprising the steps of: positioning a substrate support stage within a region of a direct current plasma reaction chamber configured to generate a positive column of a direct current plasma; generating a DC plasma by coupling an adjustable DC voltage source and a DC current source to an anode and a cathode of a DC plasma reaction chamber, respectively; generating a floating potential on a surface of the substrate support stage based on the step of generating the DC plasma; adjusting the potential of the anode with the adjustable DC voltage source while maintaining a constant DC current between the anode and the cathode with the DC current source; and setting the floating potential to a particular potential of a reference ground of the adjustable DC voltage source based on the adjusting and maintaining steps; A method comprising:

19. 20. The method of claim 18 further comprising: placing a substrate on the substrate support stage; capacitively coupling a bias signal to the substrate support stage to energize free electrons in the DC plasma; accelerating the free electrons to a surface of the substrate based on the energy applying step; and colliding the free electrons with atoms on the surface of the substrate based on the accelerating step, thereby breaking energy bonds between the electrons and atomic nuclei; Equipped with A method wherein the voltage level of the bias signal is selected to target a particular energy level of the electrons of atoms that make up a particular material.

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