SUBSTRATE SUPPORT WITH MULTIPLE EMBEDDED ELECTRODES

Abstract

A method and apparatus for biasing regions of a substrate in a plasma-assisted processing chamber are provided. Biasing of the substrate, or regions thereof, increases the potential difference between the substrate and a plasma formed in the processing chamber thereby accelerating ions from the plasma towards the active surfaces of the substrate regions. A plurality of bias electrodes herein are spatially arranged across the substrate support in a pattern that is advantageous for managing uniformity of processing results across the substrate.

Description

BACKGROUND

Field

Embodiments described herein generally relate to processing chambers used in semiconductor device manufacturing, in particular, to processing chambers having a substrate support assembly configured to bias a substrate and methods of biasing the substrate.

Description of the Related Art

Reliably producing high aspect ratio features is one of the key technology challenges for the next generation of very large-scale integration (VLSI) and ultra large scale integration (ULSI) of semiconductor devices. One method of forming high aspect ratio features uses a plasma-assisted etching process to form high aspect ratio openings in a material layer, such as a dielectric layer, of a substrate. In a typical plasma-assisted etching process, a plasma is formed in the processing chamber, and ions from the plasma are accelerated towards the substrate, and openings formed in a mask thereon, to form openings in a material layer beneath the mask surface. Typically, the ions are accelerated towards the substrate by coupling a low-frequency RF power in the range of 400 kHz to 2 MHz to the substrate, thereby creating a bias voltage thereon. However, coupling an RF power to the substrate does not apply a single voltage to the substrate relative to the plasma. In commonly used configurations, the potential difference between the substrate and the plasma oscillates from a near-zero value to a maximum negative value at the frequency of the RF power. The lack of a single potential, accelerating ions from the plasma to the substrate, results in a large range of ion energies at the substrate surface and in the openings (features) being formed in the material layers thereof. In addition, the disparate ion trajectories that result from RF biasing produce large angular distributions of the ions relative to the substrate surface. Large ranges of ion energies are undesirable when etching the openings of high aspect ratio features as the ions do not reach the bottom of the features with sufficiently high energies to maintain desirable etch rates. Large angular distributions of ions relative to the substrate surface are undesirable as they lead to deformations of the feature profiles, such as necking and bowing in the vertical sidewalls thereof.

Accordingly, there is a need in the art for the ability to provide narrow ranges of high-energy ions with low angular distributions at the material surface of a substrate during a plasma-assisted etching process.

SUMMARY

The present disclosure generally relates to plasma-assisted or plasma-enhanced processing chambers. More specifically, embodiments herein relate to electrostatic chucking (ESC) substrate supports configured to provide individual pulsed (cyclic) DC voltages to regions of a substrate during plasma-assisted or plasma-enhanced semiconductor manufacturing processes and methods of biasing regions of the substrate.

In one embodiment, a substrate support assembly is provided that includes a substrate support, comprising a plurality of first electrodes within the substrate support, each electrode of the plurality of first electrodes electrically isolated from, and coplanar with, every other electrode of the plurality of first electrodes, wherein each electrode of the plurality of first electrodes is configured to provide a pulsed DC power to a region of a substrate through capacitive coupling therewith, and a second electrode disposed within the substrate support, and electrically isolated from the plurality of first electrodes, for electrically clamping the substrate to the substrate support.

Other embodiments provide a processing chamber comprising one or more sidewalls and a bottom defining a processing volume and a substrate support. The substrate support comprises a plurality of first electrodes within the substrate support, each electrode of the plurality of first electrodes electrically isolated from, and coplanar with, every other electrode of the plurality of first electrodes, wherein each electrode of the plurality of first electrodes is configured to provide a pulsed DC bias to a region of a substrate through capacitive coupling therewith, and a second electrode disposed within the substrate support, and electrically isolated from the plurality of first electrodes, for electrically clamping the substrate to the substrate support.

In another embodiment, a method of biasing a substrate with a plurality of cyclic DC voltages is provided. The method includes flowing a processing gas into the processing chamber, forming a plasma from the processing gas, electrically clamping the substrate to a substrate support disposed in a processing chamber, and biasing the substrate across a plurality of regions. Biasing the substrate across a plurality of regions comprises capacitively coupling a plurality of cyclic DC voltages, provided to a plurality of bias electrodes disposed in the substrate support through a switching system, to respective regions of the substrate through the capacitance of a first dielectric layer of the substrate support. The plurality of cyclic DC voltages herein includes a range of frequencies and/or multiple polarities.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

FIG. 1 is a schematic sectional view of a processing chamber with an electrostatic chucking (ESC) substrate support assembly disposed therein, according to one embodiment.

FIG. 2A is a close-up sectional view of a portion of the substrate support assembly used in the processing chamber of FIG. 1.

FIG. 2B is top-down view of the substrate support assembly shown in FIG. 2A.

FIG. 3 is a flow diagram illustrating a method of biasing regions of a substrate during plasma-assisted processing, according to embodiments described herein.

DETAILED DESCRIPTION

Embodiments of the present disclosure generally relate to plasma processing chambers, such as plasma-assisted or plasma-enhanced processing chambers. More specifically, embodiments herein relate to electrostatic chucking (ESC) substrate supports configured to provide capacitively coupled pulsed DC voltage to a substrate disposed thereon during plasma-assisted or plasma-enhanced semiconductor manufacturing processing. Capacitive coupling of the substrate to a cyclic DC power source (placing a pulsed DC bias on the substrate) increases the potential difference between the substrate and a plasma formed in the processing chamber thereby accelerating ions from the plasma towards the active surface of the substrate. In contrast to RF biasing, pulsed DC biasing provides a single potential for ions to accelerate from the plasma to the substrate. The substrate supports herein include a plurality of bias electrodes each independently coupled to portions of a pulsed DC power supply switching system and each configured to provide tunable biasing of a region of the substrate by capacitive coupling therewith. The plurality of bias electrodes herein are spatially arranged across the substrate support in patterns that are advantageous for managing uniformity of processing results across the substrate.

FIG. 1 is a schematic sectional view of a processing chamber 100 with an electrostatic chucking (ESC) substrate support assembly 200 disposed therein, according to one embodiment. In this embodiment, the processing chamber 100 is a plasma processing chamber, such as a plasma etch chamber, a plasma-enhanced deposition chamber, for example, a plasma-enhanced chemical vapor deposition (PECVD) chamber or a plasma-enhanced atomic layer deposition (PEALD) chamber, or a plasma-based ion implant chamber, for example, a plasma doping (PLAD) chamber.

The processing chamber 100 features a chamber lid 103, one or more sidewalls 102, and a chamber bottom 104, which define a processing volume 120. A showerhead 112, having a plurality of openings 118 disposed therethrough, is disposed in the chamber lid 103 and is used to uniformly distribute processing gases from a gas inlet 114 into the processing volume 120. The showerhead 112 is coupled to an RF power supply 142, or in some embodiments a VHF power supply, which forms a plasma 135 from the processing gases through capacitive coupling therewith. The processing volume 120 is fluidly coupled to a vacuum, such as to one or more dedicated vacuum pumps, through a vacuum outlet 152, which maintains the processing volume 120 at sub-atmospheric conditions and evacuates processing, and other gases, therefrom. A substrate support assembly 200, disposed in the processing volume 120, is disposed on a support shaft 124 sealingly extending through the chamber bottom 104. The support shaft 124 is coupled to a controller 140 that raises and lowers the support shaft 124, and the substrate support assembly 200 disposed thereon, to facilitate processing of the substrate 115 and transfer of the substrate 115 to and from the processing chamber 100. Typically, when the substrate support assembly 200 is in a raised or processing position, the substrate 115 is spaced apart from the showerhead 112 between about 0.75 inches and 1.75 inches, such as about 1.25 inches.

The substrate 115 is loaded into the processing volume 120 through an opening 126 in one of the one or more sidewalls 102, which is conventionally sealed with a door or a valve (not shown) during substrate 115 processing. A plurality of lift pins 136 disposed above a lift pin hoop 134 are movably disposed through the substrate support assembly 200 to facilitate transferring of the substrate 115 thereto and therefrom. The lift pin hoop 134 is coupled to a lift hoop shaft 131 sealingly extending through the chamber bottom 104, which raises and lowers the lift pin hoop 134 by means of an actuator 130. The substrate support assembly 200 has a substrate support 227 on which a substrate is disposed for processing. When the lift pin hoop 134 is in a raised position, the plurality of lift pins 136 extend above the surface of the substrate support 227 lifting the substrate 115 therefrom and enabling access to the substrate 115 by a robot handler (not shown). When the lift pin hoop 134 is in a lowered position, the plurality of lift pins 136 are flush with, or below, the surface of the substrate support 227, and the substrate 115 rests directly thereon for processing.

The substrate support assembly 200 herein includes a cooling base 125. The substrate support 227 is thermally coupled to, and disposed on, the cooling base 125. The cooling base 125 of the substrate support assembly 200 is used to regulate the temperature of the substrate support 227, and thereby the substrate 115 disposed on the substrate support surface 203, during processing. Herein, the cooling base 125 may include one or more fluid conduits 137 disposed therein that are fluidly coupled to, and in fluid communication with, a coolant source 133, such as a refrigerant source or water source. Typically, the cooling base 125 is formed of a corrosion-resistant thermally conductive material, such as a corrosion-resistant metal, for example, aluminum, an aluminum alloy, or stainless steel, and is thermally coupled to the substrate support 227 with an adhesive or by mechanical means.

During processing, ion bombardment of the substrate 115 will heat the substrate 115 to potentially undesirable high temperatures as the low pressure of the processing volume 120 results in poor thermal conduction between the substrate 115 and the substrate support surface 203. Therefore, in embodiments herein, a backside gas is provided between the substrate 115 and the substrate support surface 203 during processing, where the backside gas thermally couples the substrate 115 to the substrate support surface 203 and increases the heat transfer therebetween. Typically, the substrate support surface 203 includes a plurality of protrusions 228 extending therefrom that enable the backside side gas to flow or occupy space between the substrate 115 and the substrate support surface 203 when the substrate 115 is disposed thereon. The backside gas flows to the substrate support surface 203 through one or more gas conduits 147 disposed through the substrate support 227. Herein, the one or more gas conduits 147 are coupled to thermally conductive inert backside gas source 146, such as a Helium gas source.

FIG. 2A is a close-up sectional view of a portion of the substrate support assembly 200 used in the processing chamber 100 of FIG. 1. FIG. 2B is top-down view of the substrate support assembly 200 shown in FIG. 1. Herein, the substrate support 227 includes a first layer 227A and a second layer 227B where each layer 227AB is formed from a dielectric material comprising a metal oxide or metal nitride, or a dielectric layer comprising a mixture of metal oxides or metal nitrides, such as Al₂O₃, AlN, Y₂O₃, or combinations thereof. In some embodiments, the first layer 227A is formed of a dielectric material having a breakdown voltage of between about 20 V/μm and about 200 V/μm, such as between about 100 V/μm and about 200V/μm or between about 20 V/μm and about 100 V/μm. In one embodiment, the first layer 227A is formed of 99.5% alumina having a breakdown voltage of about 9 kV at about 160 μm. In some embodiments, the substrate support 227 is formed by bonding a bulk dielectric material to the second layer 227B and a plurality of electrodes disposed therein or thereon before grinding the bulk dielectric material to a desired thickness D to form the first layer 227A. Typically, the thickness D of the first layer 227A is between about 5 μm and about 300 μm, such as between about 100 μm and about 300 μm, for example, about 160 μm. In other embodiments, the first layer 227A is formed using any suitable coating method, such as CVD, PECVD, ALD, PEALD, evaporation, sputtering, plasma arc coating, aerosol coating, or combinations thereof.

A plurality of electrodes disposed and/or embedded in the substrate support herein includes a plurality of bias electrodes 238A-C and a unitary ESC electrode 222. Each electrode of the plurality of bias electrodes is electrically isolated from every other electrode of the plurality of bias electrodes and from the unitary ESC electrode 222. Each electrode of the plurality of bias electrodes 238A-C herein is configured to provide one or more independent pulsed DC biases to respective regions of the substrate 115 through capacitive coupling therewith. The unitary ESC electrode 222 provides a clamping force between the substrate 115 and the substrate support surface 203 by providing a potential therebetween. Typically, the ESC electrode is coupled to a static DC power supply 158, which, herein, provides a voltage between about −5000 V and about 5000 V, such as between about 100 V and about 4000 V, such as between about 1000 V and about 3000 V, for example about 2000V.

In embodiments herein, the substrate support 227 may be configured to support a 300 mm diameter substrate and may include between 2 and 20 bias electrodes, such as the three bias electrodes 238A-C shown. However, larger substrate supports for processing larger substrates and/or substrates of different shapes may include any number of bias electrodes. The plurality of bias electrodes 238A-C are each formed of one or more electrically conductive material parts, such as a metal mesh, foil, plate, or combinations thereof. In some embodiments, each of the plurality of bias electrodes 238A-C are formed of more than one discontinuous electrically conductive material parts, such as a plurality of metal meshes, foils, plates, or combinations thereof, that are electrically coupled with one or more connectors (not shown) disposed in the substrate support 227 so that the electrically coupled discontinuous material parts comprise a single electrode, such as the center bias electrode 238A, the intermediate bias electrode 238B, or the outer bias electrode 238C.

The plurality of bias electrodes 238A-C are spatially arranged across the substrate support 227 in a pattern that is advantageous for managing uniformity of processing results across the substrate 115. In the embodiment shown in FIG. 2A, the circular plate of the center bias electrode 238A and the discontinuous annuluses of the bias electrodes 238B-C define a plurality of concentric zones. Other spatial arrangements, including spoke patterns, grid patterns, line patterns, spiral patterns, interdigitated patterns, random patterns, or combinations thereof, may be used. Each electrode of the plurality of bias electrodes 238A-C herein is coplanar with every other electrode of the plurality of bias electrodes and with the unitary ESC electrode 222. The unitary ESC electrode 222 is planarly disposed within the substrate support 227 and parallel to the substrate support surface 203. Each electrode of the plurality of bias electrodes 238A-C is electrically isolated from the unitary ESC electrode 222 by openings formed in the unitary ESC electrode 222 and by the dielectric material of the substrate support 227 disposed therebetween. In other embodiments, each electrode of the plurality of bias electrodes-238A-C, or a portion thereof, is coplanar with at least a portion of every other electrode of the plurality of bias electrodes, and the plurality of bias electrodes 238A-C is closer to the substrate support surface 203 than the unitary ESC electrode 222.

Herein, each of the plurality of bias electrodes 238A-C is independently electrically coupled to portions of a DC power supply switching system 150 comprising a plurality of solid state pulser/switchers, herein a plurality of first switches S1, S3, S5 and a plurality of second switches S2, S4, S6, are capable of converting a high voltage (HV) DC power to a cyclic DC voltage having a frequency between about 10 Hz, or lower, and about 100 kHZ. The plurality of first switches S1, S3, S5 and the plurality of second switches S2, S4, S6, are further capable of converting a high voltage (HV) DC power to a cyclic DC voltage having a duty cycle in the range 2% to 98%. The switches S1-S6 are operated cyclically at a frequency or are operated as needed according to any pattern, or no pattern. Each of the plurality of bias electrodes is electrically coupled to one of the plurality of first switches S1, S3, S5, and one of the plurality of second switches S2, S4, S6.

Herein, the plurality of first switches S1, S3, S5 are electrically coupled to a first DC voltage source 1566, which may be, for example, a positive (+ve) voltage source, and the plurality of second switches S2, S4, S6 are electrically coupled to a second DC voltage source 156A, which may be, for example, a negative (−ve) voltage source. In other embodiments, the two voltage sources 156A and 1566 may both be positive, or both be negative, sources of different voltages. The first and second DC voltage sources 1566 and 156A herein provide a DC bias, positive or negative, of between about 0V and about 10 kV in their respective voltage magnitudes.

Each set of switches, such as S1 and S2, S3 and S4, or S5 and S6, operates independently, providing individual frequencies, patterns, or operation of cyclic DC voltages of positive or negative polarity to respective bias electrodes 238A-C of the substrate support 227 and, through capacitive coupling therewith, providing an individual pulsed DC bias to respective regions of the substrate 115 disposed on the substrate support 227. Typically, coupling a negative DC pulse to a substrate region will increase the potential difference between the substrate region and the plasma 135, wherein the substrate region is at a more negative potential than the plasma during the pulse. In this case of negative DC bias, positively charged species in the plasma will accelerate towards the substrate region's surface, affecting a processing of the substrate region. Coupling a positive DC pulse to a substrate region will increase the potential difference between the substrate region and the plasma 135, wherein the substrate region is at a more positive potential than the plasma during the pulse. In this case of positive DC bias, negatively charged species in the plasma will accelerate towards the substrate region's surface, affecting a processing of the substrate region. The ability to adjust the frequency, duty cycle, and/or duration of the cyclic DC voltages, for both positive and negative DC bias conditions, provided to different substrate regions, allow for tuning of across-substrate processing uniformity and improvement thereof. Among other useful attributes, the ability to apply both positive and negative DC bias pulses provides for charge neutralization of the substrate regions, wherein the surface of the substrate region can be periodically brought to a neutral charge state.

FIG. 3 is a flow diagram illustrating a method 300 of biasing regions of a substrate during plasma-assisted processing, according to embodiments described herein. At activity 310, the method 300 includes flowing a processing gas into the processing chamber, and at activity 320 the method includes forming a plasma from the processing gas.

At activity 330, the method 300 includes electrically clamping a substrate to a substrate support disposed in a processing chamber using a chucking electrode disposed in the substrate support, the substrate support comprising a first dielectric layer and a second dielectric layer.

At activity 340, the method 300 includes providing a plurality of cyclic DC voltages to a plurality of bias electrodes disposed in the substrate support, wherein each respective cyclic DC voltage provides an individual pulsed DC bias to a region of the substrate through capacitive coupling therewith. In some embodiments, the plurality of cyclic DC voltages comprises more than one polarity, more than one frequency, more than one duty cycle, and/or more than one duration. The pulsed DC bias causes ions in the plasma formed at 330 to accelerate toward the substrate to perform a material process, such as deposition or removal, on the substrate. It should be noted that the plasma may also be formed after activity 320, after activity 330, or after activity 340.

The substrate support assembly and methods described herein enable capacitively coupled pulsed DC biasing of individual substrate regions during plasma-assisted processing that is compatible with the use of an electrostatic clamping force. Pulsed DC biasing allows for increased control of ion energy and angular distribution at the substrate surface and/or regions thereof and in feature openings formed therein. This increased control is desirable at least in forming high aspect ratio features and/or features requiring a square etch profile, such as silicon etch for shallow trench isolation (STI) applications or for silicon fins used in FinFET technologies. The ability to apply DC pulses of varying frequency, duty cycle, polarity, and/or duration to different regions of the substrate enables tuning of across-substrate processing uniformity and improvement thereof.

While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. A substrate processing system comprising a substrate support assembly, the substrate support assembly comprising: a metal base having a substrate support disposed thereon, the substrate support comprising a plurality of electrodes, wherein each of the plurality of electrodes is spaced apart from a substrate supporting surface of the substrate support by a first layer of dielectric material,the plurality of electrodes are spaced apart from the metal base by a second layer of dielectric material,each of the plurality of electrodes is isolated from a different one of the plurality of electrodes by a portion of dielectric material,a first electrode and a second electrode of the plurality of electrodes are each electrically coupled to a voltage source of a pulsed DC bias system,the pulsed DC bias system is configured to simultaneously deliver a first pulsed DC voltage to the first electrode and a second pulsed DC voltage to the second electrode,the second electrode of the plurality of electrodes is disposed radially outward from and at least partially surrounds the first electrode, andone of the plurality of electrodes is coupled to a chucking power supply for electrically clamping a substrate to the substrate supporting surface of the substrate support.

2. The substrate processing system of claim 1, wherein the pulsed DC bias system is configured to adjust one or more characteristics of the first pulsed DC voltage relative to one or more characteristics of the second pulsed DC voltage.

3. The substrate processing system of claim 2, wherein the one or more characteristics of the first and second pulsed DC voltages include pulse frequency, duty cycle, polarity, pulse duration, or a combination thereof.

4. The substrate processing system of claim 2, further comprising an RF power supply for forming a capacitively coupled plasma in a processing volume of the substrate processing system.

5. The substrate processing system of claim 1, wherein the first layer of dielectric material has a thickness between about 5 μm and about 300 μm.

6. The substrate processing system of claim 1, wherein the one of the plurality of electrodes that is coupled to the chucking power supply comprises a metal mesh.

7. The substrate processing system of claim 1, wherein the first electrode and the second electrode are concentrically disposed about a center of the substrate supporting surface of the substrate support.

8. The substrate processing system of claim 7, wherein the first electrode has a substantially circular shape in a plane parallel to the substrate supporting surface.

9. The substrate processing system of claim 7, wherein the second electrode is disposed proximate to a circumferential edge of the substrate support.

10. The substrate processing system of claim 7, wherein the substrate supporting surface comprises a plurality of protrusions, andone or more gas conduits formed through the substrate support are in fluid communication with a space at the substrate supporting surface that is formed between plurality of protrusions.

11. The substrate processing system of claim 10, wherein the one or more gas conduits are fluidly coupled to an inert gas source.

12. The substrate processing system of claim 11, wherein one or more fluid conduits formed in the metal base are fluidly coupled to a coolant source.

13. The substrate processing system of claim 12, wherein the substrate support is thermally coupled to the metal base by an adhesive layer interposed therebetween.

14. The substrate processing system of claim 1, wherein the voltage source comprises a high voltage DC power supply and one or more first switches for converting a static DC voltage from the high voltage DC power supply to the first pulsed DC voltage.

15. A method for processing a substrate, comprising: (a) positioning the substrate on a substrate support disposed in a processing volume, the substrate support comprising a plurality of electrodes, wherein the substrate support is disposed on a metal base,each of the plurality of electrodes is spaced apart from a substrate supporting surface of the substrate support by a first layer of dielectric material,the plurality of electrodes are spaced apart from the metal base by a second layer of dielectric material,a first electrode and a second electrode of the plurality of electrodes are each electrically coupled to a voltage source of a pulsed DC bias system, andthe second electrode of the plurality of electrodes at least partially surrounds a portion of the first electrode;(b) forming a plasma within the processing volume;(c) applying a chucking voltage to one of the plurality of electrodes to electrically clamp the substrate to the substrate support; and(d) applying, by use of the pulsed DC bias system, a first pulsed DC voltage to the first electrode and a second pulsed DC voltage to the second electrode.

16. The method of claim 15, further comprising: (e) adjusting one or more characteristics of the first pulsed DC voltage relative to one or more characteristics of the second pulsed DC voltage.

17. The method of claim 16, wherein (e) adjusting one or more characteristics of the first pulsed DC voltage relative to the one or more characteristics of the second pulsed DC voltage comprises changing one or more of a pulse frequency, duty cycle, polarity, or a pulse duration of the first pulsed DC voltage, the second pulsed DC voltage, or both.

18. The method of claim 15, wherein the plasma is formed through capacitively coupling an RF power to a processing gas disposed in the processing volume.

19. The method of claim 15, wherein the first electrode and the second electrode are concentrically disposed about a center of the substrate supporting surface.

20. The method of claim 19, wherein the second electrode is disposed proximate to a circumferential edge of the substrate support.