Substrate processing system with positively-biased substrate and method thereof

Abstract

To provide a method for applying positively biased DC voltage to a substrate to reduce ion damage during substrate processing and a substrate processing system using the method.SOLUTION: For reducing ion damage from an ion bombardment, a substrate processing system may comprise: a reaction chamber comprising a susceptor and a substrate process space, where the susceptor comprises a heater; and a direct current (DC) bias unit comprising a DC supply configured to generate a triangular-pulsed DC voltage signal and a switch disposed between the DC supply and the susceptor, the switch being configured to open or close a line from the DC supply to the susceptor, where the triangular-pulsed DC voltage signal has a first crest and a first frequency.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a substrate processing system, and more particularly to a substrate processing system in which a substrate susceptor and substrate are positively biased with a direct current (DC) voltage signal. The positively biased substrate (and susceptor) can reflect and / or deflect high-energy ion bombardment, preventing any ion damage that may be caused on the surface of the substrate. [Background technology]

[0002] In some CCP (Capacitively Coupled Plasma) semiconductor processing applications, substrates can be damaged by high-energy ions, and the same problem can occur in systems using ICP (Inductively Coupled Plasma).

[0003] Ion filters may be used to reduce ion damage, but they may also reduce the radicals necessary for treatment of the substrate, not just the ions.

[0004] A pulsed positive DC bias may be used to reduce ion energy, but a typical pulsed DC bias may require polarity switching during which a negative voltage may cause the ions to have higher energy, which may increase ion damage on the substrate.

[0005] Therefore, to overcome the above-mentioned drawbacks, the present disclosure presents a method for applying a positively biased DC voltage to a substrate to reduce ion damage, and a substrate processing system with the same capability. Summary of the Invention

[0006] This Summary is provided to introduce a selection of concepts in a simplified form that are described in more detail below in the Detailed Description of Example Embodiments of this Disclosure. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0007] According to one embodiment, there may be provided a substrate processing system using plasma, the substrate processing system comprising: a reaction chamber including a susceptor having a heater and a substrate process space; a direct current (DC) bias unit including a DC supply configured to generate a triangular pulse DC voltage signal; and a switch disposed between the DC supply and the susceptor, the switch configured to open or close a line from the DC supply to the susceptor, wherein the triangular pulse DC voltage signal has a first peak and a first frequency.

[0008] In at least one embodiment, the system further comprises a measurement unit disposed between the switch and the susceptor, the measurement unit configured to measure the line voltage and current and further configured to measure the capacitance of a heater in the susceptor; and a controller disposed between the measurement unit and the DC supply and connected to the switch, the controller configured to monitor the measured voltage, current, and capacitance and further configured to control the DC supply to change the first peak and / or first frequency of the DC voltage signal to a second peak and / or second frequency.

[0009] In at least one embodiment, the controller is further configured to calculate a positive biased voltage on the substrate according to Equation 1 below:

[0010]

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[0011] In at least one embodiment, the controller is further configured to switch off the triangular pulse DC voltage signal at the top of the triangular pulse DC voltage signal until the start of the next cycle of the triangular pulse DC voltage signal.

[0012] In at least one embodiment, the controller is further configured to monitor whether V(Substrate) is above a first threshold voltage or below a second threshold voltage.

[0013] In at least one embodiment, the controller is further configured to control the DC supply to increase the amplitude of the triangular pulse DC voltage signal when V(Substrate) is below a second threshold voltage and to decrease the amplitude of the triangular pulse DC voltage signal when V(Substrate) is above the first threshold voltage.

[0014] In at least one embodiment, the biased positive voltage on the substrate is strong enough to reflect ions from the plasma so that the substrate is not damaged from ion bombardment.

[0015] According to another embodiment, there may be provided a method of applying a positively biased DC voltage to a substrate to reduce ion damage during substrate processing, the method comprising: generating a triangular pulse DC voltage signal; applying the generated triangular pulse DC voltage signal to a substrate support to maintain a positive DC bias on a surface of the substrate; and periodically switching off the triangular pulse DC voltage signal when the triangular pulse DC voltage signal reaches a crest of the triangular pulse DC voltage signal in each cycle, wherein the generated triangular pulse DC voltage signal has a first crest and a first frequency.

[0016] In at least one embodiment, the method further comprises measuring and calculating the parameters.

[0017] In at least one embodiment, the parameters include the biased positive voltage induced on the substrate (V(substrate)), the voltage generated from the DC supply (V(bias)), the current flowing from the plasma to the heater (I(plasma)), the capacitance value of the heater (C(heater)), and the initial voltage at the substrate [V0].

[0018] In at least one embodiment, the positive bias voltage on the substrate is calculated according to Equation 2 below:

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[0019] It should be understood that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of the illustrated embodiments of the present disclosure. [Brief explanation of the drawings]

[0020] [Figure 1] 1 shows a schematic diagram of a substrate processing system according to an embodiment of the present disclosure. [Figure 2(a)] 1 illustrates a voltage signal provided by a DC supply and its amplitude change (increase) with the amount of "A" according to an embodiment of the present disclosure. [Figure 2(b)]10 shows a positively biased substrate (or susceptor) when the bias falls below V2 (second threshold) at time t2, according to an embodiment of the present disclosure. [Figure 3(a)] 1 illustrates a voltage signal provided by a DC supply and its amplitude change (decrease) with the amount "B" according to an embodiment of the present disclosure. [Figure 3(b)] 1 shows a positively biased substrate (or susceptor) when the bias exceeds V1 (first threshold) at time t2, according to an embodiment of the present disclosure. [Figure 4(a)] 10 illustrates bias variation with voltage signal from a DC supply without switching it off, according to an embodiment of the present disclosure. [Figure 4(b)] 10 illustrates bias change due to voltage signal from DC supply with switching off according to an embodiment of the present disclosure. [Figure 5(a)] FIG. 1 shows a diagram illustrating radicals and ions bombarding a substrate without any positive bias on the substrate according to an embodiment of the present disclosure. [Figure 5(b)] FIG. 1 shows a diagram illustrating radicals and ions impacting on a substrate, where the radicals are unaffected while the ions are reflected and / or deflected by a positive bias, according to an embodiment of the present disclosure. [Figure 6] 10 shows a flowchart illustrating a flow of a method for positive biasing according to another embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0021] DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS While certain specific embodiments and examples are disclosed below, it will be understood by those skilled in the art that the invention extends beyond the specifically disclosed embodiments and / or uses of the invention, and obvious variations and equivalents thereof. It is therefore not intended that the scope of the disclosed invention should be limited by the specific disclosed embodiments described below.

[0022] As used in this disclosure, the term "substrate" may refer to any single or multiple underlying materials, such as any single or multiple underlying materials that may be modified or upon which a device, circuit, or film may be formed. A "substrate" may be continuous or discontinuous, rigid or flexible, solid or porous, and combinations thereof. The substrate may be in any form, such as a powder, a plate, or a workpiece. Substrates in plate form may include wafers of various shapes and sizes. The substrate may be made of semiconductor materials, such as, for example, silicon, silicon germanium, silicon oxide, gallium arsenide, gallium nitride, and silicon carbide.

[0023] For example, the substrate in powder form may have applications in pharmaceutical manufacturing. The porous substrate may comprise a polymer. Examples of workpieces may include medical devices (e.g., stents and syringes), jewelry, tooling devices, components for battery manufacturing (e.g., anodes, cathodes, or separators), or components of photovoltaic cells, etc.

[0024] The continuous substrate may extend beyond the boundaries of the process chamber in which the deposition process occurs. In some processes, the continuous substrate may move through the process chamber, allowing the process to continue until the end of the substrate is reached. The continuous substrate may be supplied from a continuous substrate supply system to enable the manufacture and production of the continuous substrate in any suitable form.

[0025] Non-limiting examples of continuous substrates may include sheets, nonwoven films, rolls, foils, webs, flexible materials, bundles of continuous filaments or fibers (e.g., ceramic or polymeric fibers). Continuous substrates may also include carriers or sheets onto which discontinuous substrates are placed.

[0026] The examples presented in this disclosure are not intended to be actual representations of any particular materials, structures, or devices, but are merely idealized representations used to describe embodiments of the present disclosure.

[0027] The specific embodiments shown and described are illustrative of the present invention and its best mode and are not intended to otherwise limit the scope of the present application. Also, for purposes of brevity, conventional manufacturing, association, preparation, and other functional aspects of the present system may not be described in detail. Furthermore, connecting lines shown in the various figures are intended to represent example functional relationships and / or physical couplings between the various elements. Many alternative or additional functional relationships or physical connections may be present in an actual system and / or may not be present in some embodiments.

[0028] It should be understood that the configurations and / or approaches described in this disclosure are exemplary in nature, and that these specific embodiments or examples are not to be construed in a limiting sense, as numerous variations are possible. The specific routines or methods described in this disclosure may represent one or more of any number of processing strategies. As such, various illustrated operations may be performed in the order illustrated, in other orders, or omitted in some cases.

[0029] The subject matter of the present disclosure includes all novel and non-obvious combinations and subcombinations of the various processes, systems, and configurations, and other features, functions, operations and / or properties disclosed herein, as well as all equivalents thereof.

[0030] FIG. 1 shows a schematic diagram of a substrate processing system according to an embodiment of the present disclosure.

[0031] The substrate processing system 100 may include a reaction chamber 101 having a substrate process space 102 and a susceptor 110 having a heater 113. A substrate 111 may be disposed on the susceptor 110. A direct current (DC) bias unit 150 may be disposed below the susceptor 110.

[0032] The DC bias unit 150 may include a DC supply 120 that can generate and supply a triangular pulse DC voltage signal (described below) to the susceptor 110. The DC bias unit 150 may also include a switch 141 disposed between the DC supply 120 and the susceptor 110, a measurement unit 121 disposed between the switch 141 and the susceptor 110, and a controller 122 disposed between the measurement unit 121 and the DC supply 120. The controller 122 may be connected to the switch 141.

[0033] DC supply 120 may generate a triangular pulse DC voltage signal, which may be shown in Figures 2(a) (200) and 3(a) (300). In Figure 2(a), the similarity of signal 200 and triangle 202 may explain why the pulses generated by DC supply 120 may be referred to as "triangular pulses."

[0034] Among the radicals and ions generated in the plasma environment, ion bombardment can cause ion damage to the substrate surface, and therefore, the ions may need to be removed. Ions are positively charged, and therefore, if the substrate and a susceptor on which the substrate may be placed can be positively charged, the ions can be reflected and / or deflected from the substrate so that ion damage can be reduced.

[0035] A measurement unit 121 may be disposed between the switch 141 and the susceptor 110. The measurement unit 121 may measure parameters such as voltage and current as well as capacitance. It may measure the voltage from the DC supply 120, shown as V (bias), the current 132 flowing from the plasma in the substrate process space 102 into the susceptor region, shown as I (plasma), and the capacitance formed in the heater 113, shown as C (heater).

[0036] Switch 141 may turn off (open circuit) signal 140 from DC supply 120 and may periodically turn on (close circuit) signal 140 to susceptor 110. In FIG. 2(a), triangular pulse DC voltage signal 200 may have repeating cycles, each cycle having increasing phases (A-phase and C-phase) and decreasing and recovery phases (B-phase and D-phase). When signal 200 reaches its apex at point 201, switch 141 may turn off (open circuit) at time (t2) during decreasing phase 202 and recovery phase 203 until time (t3) so that the negative voltage of phases 202 and 203 may not affect the voltage at the substrate, as in the negative drop shown in "X-phase" in FIG. 2(b). When the signal 200 restarts at time t3, the switch 141 may be switched on (closed circuit) to allow the generated signal 200 to flow into the susceptor 110.

[0037] A controller 122 may monitor and control units 120, 141, 121. The positive bias on the substrate 111 (and / or susceptor 110 and heater 113), denoted as V(substrate), may be calculated from the measured parameters using the following formula EQ:

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[0038] FIG. 2(b) illustrates the calculated bias voltage 131, V(Substrate), on the substrate without switching it off. The voltage 210 may be stabilized or may oscillate, with an allowed oscillation gap from a second threshold voltage (V2) to a first threshold voltage (V1). If the calculated bias voltage, V(Substrate), falls below V2 (211) in "Phase W," the controller 122 may increase the amplitude of the signal generated in the next cycle beginning at time t3. In FIG. 2(a), the amount of amplitude increase may be shown as "A," and this increase may be sufficient to keep the calculated bias voltage, V(Substrate), as flat as that shown in "Phase Y" of FIG. 2(b).

[0039] When the DC supply 120 generates and supplies a triangular pulse DC voltage signal 140, the substrate 111 (and / or the susceptor 110 and heater 113) may be positively biased 131, but the bias may be gradually ramped down to zero and released without the continuous supply of the signal 140 and for substrate uniformity and protection from ion damage. The positive bias 131 may need to be maintained uniformly throughout the processing period by supplying a gradually increasing voltage signal such as a "triangle pulse" 200. However, because the signal 200 cannot increase indefinitely, there may be a ramp-down phase 202 and a recovery phase 203, which are switched off (disconnected or open) as described above.

[0040] FIG. 3(b) illustrates the calculated bias voltage 131, V(Substrate), on the substrate without switching it off. The voltage 310 may be stabilized or may oscillate, with an allowed oscillation gap from a second threshold voltage (V2) to a first threshold voltage (V1). If the calculated bias voltage, V(Substrate) exceeds V1 (311) in "Phase W," the controller 122 may reduce the amplitude of the signal generated in the next cycle beginning at time t3. In FIG. 3(a), the amount of amplitude reduction may be shown as "B," and this reduction may be sufficient to keep the calculated bias voltage, V(Substrate), as flat as that shown in "Phase Y" of FIG. 3(b).

[0041] 4(a) shows that without the switch off, the calculated bias voltage, V(substrate) 410, can drop very quickly below zero in phases X1 and Z1. With a negative bias on the substrate, positive ions will gain more energy and cause more damage on the substrate.

[0042] To avoid this adverse effect, the controller 122 may be configured to switch off the switch 141 when the generated triangular pulse signal 200, 300 reaches its apex (201, 301) at time t2 (in Figures 2(a) and 3(a)). By turning off the switch, the calculated signal will gradually (e.g., exponentially) decrease towards zero in phases X2 and Z2.

[0043] The bias voltage, V(substrate), calculated on the substrate during phases X2 and Z2 in Figure 4(b) when switched off compared to when not switched off will be higher than zero and will remain flatter than when not switched off during phases X1 and Z1 in Figure 4(a). This means that the protection effect from the positive bias may be maintained during the entire cycle and will remain flatter so that it may also increase uniformity.

[0044] 5(a) shows a diagram illustrating radicals 550, 553 and ions 551, 552 bombarding a substrate 511 placed on a susceptor 510 without any positive bias on the substrate 511. In this case, the ions 551, 552 may cause ionic damage to the substrate 511.

[0045] FIG. 5(b) shows a diagram illustrating radicals 560, 563 and ions 561, 562 impacting a substrate 513 disposed on a susceptor 512, where the radicals 560, 563 may be unaffected while the ions 561, 562 may be reflected and / or deflected (570) by a positive bias 531.

[0046] FIG. 6 shows a flowchart illustrating a flow of a method for positive biasing according to an embodiment of the present disclosure.

[0047] In step 610 of the method, the DC supply 120 may generate a triangular pulse DC voltage signal (200, 300), which may be applied to the heater in step 620.

[0048] Then, in step 630, periodically, when the signal reaches its apex, switch 141 may be switched off so that the generated signal does not have to flow into the heater.

[0049] If desired, parameters such as the voltage from the DC supply 120, shown as V(bias), the current 132 flowing from the plasma in the substrate process space 102 into the susceptor region, shown as I(plasma), and the capacitance formed in the heater 113, shown as C(heater), may be measured, and the bias voltage on the substrate, shown as V(substrate), may be measured and calculated in step 640 by the controller and measurement unit.

[0050] The bias voltage on the substrate, V(substrate), may be calculated by the mathematical formula EQ disclosed above.

[0051] Then, in step 650, the controller may determine that the calculated V(Substrate) is above a first threshold voltage or below a second threshold voltage, and the controller may change the amplitude (height of the peaks of the signal) of the next restarting cycle of the triangular pulse DC voltage signal in step 660. More specifically, the controller may increase the amplitude of the triangular pulse DC voltage signal if V(Substrate) is below the second threshold voltage, and decrease the amplitude of the triangular pulse DC voltage signal if V(Substrate) is above the first threshold voltage.

[0052] The above-described arrangements of apparatus and method are merely illustrative of the application of the principles of the present invention, and numerous other embodiments and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims. The scope of the invention should, therefore, be determined not with reference to the above description, but should instead be determined with reference to the appended claims along with their full scope of equivalents.

Claims

1. 1. A substrate processing system using plasma, comprising: a reaction chamber comprising a susceptor and a substrate process space, the susceptor comprising a heater; A DC bias unit, a DC supply configured to generate a triangular pulse DC voltage signal; a DC bias unit comprising: a switch disposed between the DC supply and the susceptor, the switch configured to open or close a line from the DC supply to the susceptor; The triangular pulse DC voltage signal has a first peak and a first frequency.

2. a measurement unit disposed between the switch and the susceptor, the measurement unit configured to measure the voltage and current of the line and further configured to measure the capacitance of the heater in the susceptor; 2. The system of claim 1, further comprising: a controller disposed between the measurement unit and the DC supply and connected to the switch, the controller configured to monitor the voltage, the current, and the capacitance, and further configured to control the DC supply to vary a first crest and / or a first frequency of the triangular pulse DC voltage signal to a second crest and / or a second frequency.

3. The controller is further configured to calculate a biased positive voltage on the substrate according to Equation 1: [Equation 1] In Equation 1, V(substrate) is the biased positive voltage induced on the substrate; V(bias) is the voltage generated from the DC supply; I(plasma) is the current flowing from the plasma to the heater; C(heater) is the capacitance of the heater; The system of claim 2 , wherein V0 is an initial voltage of the substrate.

4. 3. The system of claim 2, wherein the controller is further configured to switch off the triangular pulse DC voltage signal at a peak of the triangular pulse DC voltage signal until a next cycle of the triangular pulse DC voltage signal begins.

5. 4. The system of claim 3, wherein the controller is further configured to monitor whether V(Substrate) is above a first threshold voltage or below a second threshold voltage.

6. 6. The system of claim 5, wherein the controller is further configured to control the DC supply to increase an amplitude of the triangular pulse DC voltage signal when V(Substrate) is below the second threshold voltage and to decrease the amplitude of the triangular pulse DC voltage signal when V(Substrate) is above the first threshold voltage.

7. The system of claim 3 , wherein the biased positive voltage on the substrate is strong enough to reflect ions from the plasma so that the substrate is not damaged from ion bombardment.

8. 1. A method for reducing ion damage during substrate processing by applying a positively biased DC voltage to a substrate, comprising: generating a triangular pulse DC voltage signal; applying the generated triangular pulse DC voltage signal to a substrate support to maintain a positive DC bias on a surface of the substrate; periodically switching off the triangular pulse DC voltage signal when the triangular pulse DC voltage signal reaches a peak of the triangular pulse DC voltage signal in each cycle; The generated triangular pulse DC voltage signal has a first peak and a first frequency.

9. The method of claim 8 further comprising measuring and calculating a plurality of parameters.

10. 10. The method of claim 9, wherein the plurality of parameters comprises a biased positive voltage induced on the substrate (V(substrate)), a voltage generated from a DC supply (V(bias)), a current flowing from the plasma to the heater (I(plasma)), a capacitance value of the heater (C(heater)), and an initial voltage of the substrate (VO).

11. The positive bias voltage on the substrate is calculated by the following equation: [Equation 2] The method of claim 10.

12. determining whether the calculated voltage (V(substrate)) is above a first threshold voltage or below a second threshold voltage; 12. The method of claim 11, further comprising: increasing an amplitude of the triangular pulse DC voltage signal when the calculated voltage (V(Substrate)) is below the second threshold voltage; and decreasing the amplitude of the triangular pulse DC voltage signal when the calculated voltage (V(Substrate)) is above the first threshold voltage.

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