WO2025006215A1

WO2025006215A1 - Thermal generation of radical species for selective etching of silicon germanium or silicon nitride relative to silicon

Info

Publication number: WO2025006215A1
Application number: PCT/US2024/033999
Authority: WO
Inventors: Madeleine Parker GORDON; Ji Zhu; Mark Kawaguchi; Nathan Musselwhite
Original assignee: Lam Research Corp
Current assignee: Lam Research Corp
Priority date: 2023-06-27
Filing date: 2024-06-14
Publication date: 2025-01-02
Anticipated expiration: 2025-12-27
Also published as: CN121400119A; TW202516580A

Abstract

A method for etching at least one first material relative to at least one second material, includes arranging a substrate on a substrate support in a processing chamber, and supplying a carrier gas, at least one thermal etchant gas, and at least one radical generating gas to the processing chamber to etch the at least one first material relative to the at least one second material. Other example methods and systems are also disclosed.

Description

THERMAL GENERATION OF RADICAL SPECIES FOR SELECTIVE ETCHING OF SILICON GERMANIUM OR SILICON NITRIDE RELATIVE TO SILICON

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63/523,631 , filed on June 27, 2023. The entire disclosure of the application referenced above is incorporated herein by reference.

FIELD

[0002] The present disclosure relates to substrate processing systems, and more particularly to substrate processing systems for selective etching of silicon germanium or silicon nitride relative to silicon.

BACKGROUND

[0003] The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

[0004] Substrate processing systems may be used to treat substrates such as semiconductor wafers. The substrate treatments may include deposition, etching, cleaning, and/or other treatments. During processing, a substrate may be arranged on a substrate support in a processing chamber of the substrate processing system. Gas mixtures are introduced into the processing chamber using a gas delivery device. In some processes, plasma may be used to initiate chemical reactions.

[0005] The use of gate-all-around (GAA) technology is expanding to a variety of logic and memory applications. Silicon germanium (SiGe) plays an important role in GAA technology. During processing, SiGe is selectively etched relative to one or more other exposed materials such as Si. SiGe etching may be performed using a plasma-based approach or thermal molecular etching (without plasma). The plasma processes typically lack sufficient selectivity between SiGe and Si, which is important for GAA applications. While thermal molecular etching is highly selective, it is overly sensitive to variations in Ge concentration and/or impurities in the SiGe material. SUMMARY

[0006] A method for etching at least one first material relative to at least one second material, includes arranging a substrate on a substrate support in a processing chamber, and supplying a carrier gas, at least one thermal etchant gas, and at least one radical generating gas to the processing chamber to etch the at least one first material relative to the at least one second material.

[0007] In other features, the method further includes modulating a ratio of the thermal etchant gas and the radical generating gas.

[0008] In other features, supplying the carrier gas, the thermal etchant gas, and the radical generating gas to the processing chamber includes supplying the thermal etchant gas and the radical generating gas to the processing chamber at the ratio.

[0009] In other features, the ratio is a predetermined ratio between the thermal etchant gas and the radical generating gas.

[0010] In other features, modulating the ratio of the thermal etchant gas and the radical generating gas includes modulating the ratio so that an amount of the thermal etchant gas is greater than an amount of the radical generating gas to selectively etch the at least one first material relative to the at least one second material.

[0011] In other features, modulating the ratio of the thermal etchant gas and the radical generating gas includes modulating the ratio so that an amount of the radical generating gas is greater than an amount of the thermal etchant gas to radically etch the at least one first material relative to the at least one second material.

[0012] In other features, the at least one first material is silicon germanium (SiGe) and the at least one second material is silicon (Si).

[0013] In other features, the method further includes adjusting a pressure within the processing chamber to a predetermined pressure value.

[0014] In other features, the predetermined pressure value is in a range from 10OmT to 10 Torr.

[0015] In other features, the method further includes adjusting a temperature within the processing chamber to a predetermined temperature value.

[0016] In other features, the predetermined temperature value is in a range from -40 ^QC to 500 ^QC. [0017] In other features, supplying the carrier gas, the thermal etchant gas, and the radical generating gas to the processing chamber includes supplying the thermal etchant gas to the processing chamber separately from the radical generating gas.

[0018] In other features, supplying the carrier gas, the thermal etchant gas, and the radical generating gas to the processing chamber includes supplying the thermal etchant gas to the processing chamber together with the radical generating gas.

[0019] In other features, the method further includes supplying at least one chemical additive gas to the processing chamber to enable tunable control of etching the at least one first material relative to the at least one second material.

[0020] In other features, supplying the at least one chemical additive gas to the processing chamber includes supplying the chemical additive gas to the processing chamber separately from the at least one thermal etchant gas and the at least one radical generating gas.

[0021] In other features, supplying the at least one chemical additive gas to the processing chamber includes supplying the chemical additive gas to the processing chamber together with the at least one thermal etchant gas and the at least one radical generating gas.

[0022] In other features, the at least one chemical additive gas is selected from a group consisting of ammonia (NH3), molecular hydrogen (H2), methane (CH4), fluoromethane (CH3F), difluoromethane (CH2F2), water or steam (H2O), molecular oxygen (O2), hydrogen fluoride (HF), and sulfur hexafluoride (SFe).

[0023] In other features, the at least one thermal etchant gas includes a molecular etchant selected from a group consisting of molecular fluorine (F2), chlorine trifluoride (CIF3), xenon difluoride (XeF2), nitrogen trifluoride (NF3), and hydrogen fluoride (HF).

[0024] In other features, the at least one radical generating gas is selected from a group consisting of nitric oxide (NO), nitrogen dioxide (NO2), ozone (O3), chlorine dioxide (CIO2), hypochlorous acid (HOCI), hydrogen peroxide (H2O2), carbon monoxide (CO), nitrous oxide (N2O), hypobromous acid (HOBr), chloride trifluoride (CIF3), and tert-butyl hydroperoxide (TBHP).

[0025] A system includes a processing chamber including a substrate support configured to support a substrate, at least one gas delivery system configured to output one or more gases to the processing chamber, and a controller in communication with the at least one gas delivery system. The controller is configured to control the at least one gas delivery system to supply a carrier gas, at least one thermal etchant gas, and at least one radical generating gas to the processing chamber to etch at least one first material of the substrate relative to at least one second material of the substrate.

[0026] In other features, the controller is configured to control the at least one gas delivery system to supply at least one chemical additive gas to the processing chamber to enable tunable control of etching the at least one first material relative to the at least one second material.

[0027] In other features, the at least one gas delivery system is a first gas delivery system, the system further comprises a second gas delivery system configured to output one or more gases to the processing chamber, and the controller is configured to control the second gas delivery system to supply at least one chemical additive gas to the processing chamber to enable tunable control of etching the at least one first material relative to the at least one second material.

[0028] In other features, the controller is configured to set a ratio of the thermal etchant gas and the radical generating gas and control the at least one gas delivery system to supply the at least one thermal etchant gas and the at least one radical generating gas to the processing chamber at the ratio.

[0029] In other features, the ratio of the thermal etchant gas and the radical generating gas includes an amount of the thermal etchant gas being greater than an amount of the radical generating gas to selectively etch the at least one first material relative to the at least one second material.

[0030] In other features, the ratio of the thermal etchant gas and the radical generating gas includes an amount of the radical generating gas is greater than an amount of the thermal etchant gas to radically etch the at least one first material relative to the at least one second material.

[0031] In other features, the at least one first material is silicon germanium (SiGe) and the at least one second material is silicon (Si).

[0032] In other features, the system further includes a pump and a valve coupled to the processing chamber. The controller is configured to control the at least of the pump and the valve to adjust a pressure within the processing chamber to a predetermined pressure value. [0033] In other features, the controller is configured to control adjust a temperature within the processing chamber to a predetermined temperature value.

[0034] Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:

[0036] FIG. 1A is a functional block diagram of an example of a substrate processing system for selective thermal etchant using thermally generated radicals according to the present disclosure;

[0037] FIG. 1 B is a functional block diagram of another example of a substrate processing system for selective thermal and radical etching according to the present disclosure;

[0038] FIG. 2 is a flowchart of an example of a method for selective thermal and radical etching according to the present disclosure;

[0039] FIG. 3 is a graph illustrating an example of energetic differences of radicals generated via a thermal process versus a plasma process;

[0040] FIG. 4 is a graph selectivity versus thermal etch regimes according to the present disclosure according to the present disclosure;

[0041] FIG. 5 illustrates an example of etching of a substrate when the etch is more radical in nature according to the present disclosure;

[0042] FIG. 6 illustrates an example of etching of a substrate when the etch is a tunable mixture of thermal radical and thermal molecular etch according to the present disclosure;

[0043] FIG. 7 is a graph illustrating etch rate as a function of germanium concentration for a non-selective case according to the present disclosure;

[0044] FIG. 8 is a graph illustrating etch rate as a function of germanium concentration for a selective case according to the present disclosure; and [0045] FIG. 9 is a graph illustrating etch rate as a function of germanium concentration for a tuned case according to the present disclosure.

[0046] In the drawings, reference numbers may be reused to identify similar and/or identical elements.

DETAILED DESCRIPTION

[0047] During processing of GAA structures, SiGe is selectively etched relative to Si. SiGe etching is typically performed using a plasma-based approach or thermal etchant (without plasma) to selectively etch SiGe relative to Si. For example, remote plasma including nitrogen trifluoride (NF3) may be used for plasma based SiGe removal. This approach utilizes low energy radical etching that has poor sensitivity and selectivity relative to other exposed materials such as Si. To attempt to overcome this challenge, higher pressure and/or lower temperature conditions may be used to improve selectivity. However, using higher pressures and lower temperatures also reduces throughput, which increases cost.

[0048] Thermal molecular etching is highly selective. However, the high degree of selectivity can be a hinderance when small changes in the incoming SiGe materials occur. For example, the SiGe may have variations in Ge percentage in SiGe or the SiGe may include carbon (C), oxygen (O), nitrogen (N), and/or other impurities. These variations may cause large changes in etching behavior that create etch profile nonuniformities.

[0049] The present disclosure relates to a method for selectively etching SiGe, silicon nitride (SiN), or other materials relative to one or more other exposed materials such as Si, silicon dioxide (SiO2), or silicon oxycarbonitride (SiOCN). The selective etching method includes supplying a carrier gas (e.g., an inert gas), a thermal etchant gas (e.g., molecular fluorine (F2) and argon (Ar)), and a radical generating gas (e.g., nitric oxide (NO), nitrogen dioxide (NO2), ozone (O3), etc.) to a processing chamber. In some examples, a chemical additive (e.g., ammonia (NH3)) is used to generate thermal radicals for tunable selective SiGe etching.

[0050] In some examples, the thermal etchant gas may include one or more halogen containing gasses. For example, the thermal etchant gas may include a molecular etchant selected from a group consisting of chlorine (CI2), molecular fluorine (F2), chlorine trifluoride (CIF3), xenon difluoride (XeF2), interhalogens, nitrogen trifluoride (NF3), hydrogen fluoride (HF), and/or other suitable thermal etchant gases.

[0051] In some examples, the radical generating gas may include one or more oxidizing gasses. For example, the radical generating gas may be selected from a group consisting of nitric acid (HNO3), chlorine (CI2), molecular fluorine (F2), nitric oxide (NO), nitrogen dioxide (NO2), dioxygen (O2), ozone (O3), chlorine dioxide (CIO2), hypochlorous acid (HOCI), hydrogen peroxide (H2O2), carbon monoxide (CO), nitrous oxide (N2O), hypobromous acid (HOBr), chloride trifluoride (CIF3), tert-butyl hydroperoxide (TBHP), interhalogens (different than the interhalogen used for the thermal etchant (if used)), polymer initiators, and/or liquid/vapor phase free radicals.

[0052] In some examples, the chemical additive gas may include one or more halogen containing gasses, hydrocarbon gasses, and/or nitrogen containing gasses. For example, the chemical additive gas may be selected from a group consisting of ammonia (NH3), chlorine (CI2), boron trichloride (BCh), boron trifluoride (BF3), molecular hydrogen (H2), methane (CH4), fluoromethane (CH3F), difluoromethane (CH2F2), water or steam (H2O), molecular oxygen (O2), hydrogen fluoride (HF), sulfur hexafluoride (SFe), or other suitable gases. In some examples, the chemical additive gas is delivered together with or separately from the thermal etchant and the radical generating gas. The chemical additive gas provides one or more functions including radical quenching, modifying the degree of etch radical character, surface passivation, and/or etch front control.

[0053] The etch process according to the present disclosure leverages the benefits of both a radical process and a thermal process to provide tunable selectivity across different SiGe % concentrations. Radical characteristics can be tuned by modulating ratios of the thermal etchant gas, the radical generating gas, and the optional chemical additive gas to enable tunable control of etch selectivity of SiGe (or silicon nitride (SiN)) relative to Si. In such examples, the ratios may be predetermined ratios.

[0054] This selective etching process enables the generation of radicals without a traditional radical chamber hardware configuration and enables potential use on either the Sells® or Prevos® processing chambers available from Lam Research Corporation. The Selis® processing chamber is shown and described in FIG. 1 B below. The Prevos® processing chamber uses light emitting diodes to heat the substrate during thermal molecular etching. The Prevos® processing chamber is shown and described in U.S. Patent Publication No. 20230131233, which is hereby incorporated by reference in its entirety. If the process is performed in the Prevos® processing chamber, single chamber processing can be performed for oxide breakthrough (BT) and main etch (ME). If the process is performed in the Sells® processing chamber, it would be possible to pair this thermal radical approach with a traditional plasma radical process. Enabling the convenience of switching back and forth with ease when necessary. This selective etching process creates the potential for a radical based clean step to be used without the need for traditional plasma hardware. In other words, the radicals that are created clean the processing chamber during selective etching of the substrate and/or in a separate step after the substrate is removed.

[0055] While examples of specific substrate processing chambers are shown and described below, the methods described herein may be implemented on other types of substrate processing systems. Examples of suitable processing chambers are shown in FIGS. 1 A to 1 B below and in commonly assigned US Patent Publication No. 20230131233 (using LED heating for thermal molecular etching). In some examples, the processing chambers shown below include RF plasma generators and/or RF bias generators that can be used for other types of substrate processing. However, the selective etching according to the present disclosure is performed without the use of RF plasma and the RF bias generators.

[0056] Referring now to FIG. 1 A, a substrate processing system 100 includes a processing chamber 102. The processing chamber 102 includes a gas distribution device 104 and a substrate support 106. In some examples, the substrate support 106 includes an electrostatic chuck (ESC). During operation, a substrate 108 is arranged on the substrate support 106. The gas distribution device 104 introduces and distributes process gases. For example only, the gas distribution device 104 may include a showerhead 109. The showerhead 109 may include a stem portion including one end connected to a top surface of the processing chamber 102. A base portion is generally cylindrical, includes a gas plenum and extends radially outwardly from an opposite end of the stem portion at a location that is spaced from the top surface of the processing chamber 102. A substratefacing surface or faceplate of the base portion of the showerhead 109 includes holes through which process gas or purge gas flows. In some examples, the chemical additive gas can be supplied in the same way or via another gas delivery device (e.g., to prevent unwanted chemical interactions in gas lines). [0057] The substrate support 106 includes a baseplate 1 10. The baseplate 1 10 supports a top plate 1 12, which may be formed of ceramic. In some examples, the top plate 1 12 may include one or more heating layers, such as a ceramic multi-zone heating plate. The one or more heating layers may include one or more heating elements, such as conductive traces. A bond layer 1 14 is disposed between and bonds the top plate 1 12 to the baseplate 1 10. The baseplate 110 may include one or more coolant channels 1 16 for flowing coolant through the baseplate 1 10.

[0058] A gas delivery system 130 includes one or more gas sources 132-1 , 132-2, ..., and 132-N (referred to collectively as gas sources 132), where N is an integer greater than zero. The gas sources 132 supply one or more gas mixtures including carrier gas, thermal etchant gas, radical generating gas, and/or chemical additive gas. The gas sources 132 are connected by valves 134-1 , 134-2, ... , and 134-N (referred to collectively as valves 134) and mass flow controllers 136-1 , 136-2, ..., and 136-N (referred to collectively as mass flow controllers 136) to a manifold 140. In this example, ratios (e.g., predetermined ratios, etc.) of the thermal etchant gas, the radical generating gas, and/or the optional chemical additive gas may be controlled (e.g., modulated) by, for example, the mass flow controllers 136. A second set of valves (not shown) may be arranged between the mass flow controllers 136 and the manifold 140. An output of the manifold 140 is fed to the processing chamber 102. For example only, the output of the manifold 140 is fed to the showerhead 109.

[0059] In the example of FIG. 1 A, the gases (e.g., the thermal etchant gas, the radical generating gas, and/or the chemical additive gas) are generally provided to the processing chamber 102 via one or more gas lines between the manifold 140 and the processing chamber 102. For example, in some embodiments, all of the gases (e.g., the thermal etchant gas, radical generating gas, and/or the chemical additive gas) may be provided together via one gas line. In such examples, mixing of the gases generally occurs in the gas line. In other examples, each gas may be separately provided via its own gas line such that mixing of the gases occurs in the processing chamber 102.

[0060] A temperature controller 142 may be connected to heating elements, such as thermal control elements (TCEs) 144 arranged in the top plate 1 12. For example, the heating elements may include, but are not limited to, macro heating elements corresponding to respective zones in a multi-zone heating plate and/or an array of micro heating elements disposed across multiple zones of a multi-zone heating plate. The temperature controller 142 may be used to control the heating elements to control a temperature of the substrate support 106 and the substrate 108.

[0061] The temperature controller 142 may communicate with a coolant assembly 146 to control coolant flow through the coolant channels 116. For example, the coolant assembly 146 may include a coolant pump and reservoir. The temperature controller 142 operates the coolant assembly 146 to selectively flow the coolant through the coolant channels 1 16 to cool the substrate support 106.

[0062] A valve 150 and pump 152 are connected to a gas line 148 (e.g., an exhaust gas line or another gas line) and are used to control pressure within the processing chamber 102 and/or to evacuate reactants from the processing chamber 102. A controller 160 may be used to control components of the substrate processing system 100, such as the gas delivery system 130, the valve 150, the pump 152, etc. as shown in FIG. 1 A. One or more robots 161 may be used to deliver substrates onto, and remove substrates from, the substrate support 106.

[0063] In some examples, a vapor delivery system 170 includes one or more vapor delivery sources that supply vapor and include an ampoule 174, a vaporizer 176, and a flow metering device 178.

[0064] Referring now to FIG. 1 B, another example of a substrate processing system 200 for selectively etching a substrate according to the present disclosure is shown. In some examples, the substrate processing system 200 includes a processing chamber 201 that corresponds to a Sells® processing chamber available from Lam Research Corporation.

[0065] The processing chamber 201 includes a lower chamber region 202 and an upper chamber region 204. The lower chamber region 202 is defined by chamber sidewall surfaces 208, a chamber bottom surface 210 and a lower surface of a gas distribution device 214. In some examples, the gas distribution device 214 is omitted.

[0066] The upper chamber region 204 is defined by an upper surface of the gas distribution device 214 and an inner surface of an upper chamber wall 218 (for example a dome-shaped chamber). In some examples, the upper chamber wall 218 rests on a first annular support 221 . In some examples, the first annular support 221 includes one or more gas flow channels and/or holes 223 for delivering process gas to the upper chamber region 204, as will be described further below. The gas flow channels and/or holes 223 may be uniformly spaced around a periphery of the upper chamber region 204. In some examples, the process gas is delivered by the one or more gas flow channels and/or holes 223 in an upward direction at an acute angle relative to a plane including the gas distribution device 214, although other angles/directions may be used. In some examples, a plenum 234 in the first annular support 221 supplies gas to and/or holes 223 and/or one or more spaced gas flow channels or injectors 236, which direct the gas upward (indicated by arrow 238) to mix with gas and/or plasma in the upper chamber region 204.

[0067] The first annular support 221 may rest on a second annular support 225 that defines one or more gas flow channels and/or holes 227 for delivering process gas to the lower chamber region 202. In some examples, holes 231 in the gas distribution device 214 align with the gas flow channels and/or holes 227. In other examples, the gas distribution device 214 has a smaller diameter and the holes 231 are not needed. In some examples, the process gas is delivered by the one or more spaced gas flow channels and/or holes 227 in a downward direction towards the substrate at an acute angle relative to the plane including the gas distribution device 214, although other angles/directions may be used.

[0068] In other examples, the upper chamber region 204 is cylindrical with a flat top surface and one or more flat inductive coils may be used. In still other examples, a single chamber may be used with a spacer located between a showerhead and the substrate support.

[0069] A substrate support 222 is arranged in the lower chamber region 204. In some examples, the substrate support 222 includes an electrostatic chuck (ESC), although other types of substrate supports can be used. A substrate 226 is arranged on an upper surface of the substrate support 222 during etching. In some examples, a temperature of the substrate 226 may be controlled by a heater plate 241 , an optional cooling plate with fluid channels and one or more sensors (not shown); although any other suitable substrate support temperature control system may be used. In some examples, a temperature controller 243 may be used to control heating and cooling of the substrate support 222. Heating may be performed by the heater plate 241 and cooling may be performed by the cooling plate with fluid channels 245.

[0070] A temperature controller 247 may be used to control a temperature of the gas distribution device 214 by supplying heating/cooling fluid to a plenum in the gas distribution device 214. The temperature controllers 243 and/or 247 may further include a source of fluid, a pump, control valves and a temperature sensor (all not shown).

[0071] In some examples, the gas distribution device 214 includes a showerhead (for example, a plate 228 having a plurality of spaced holes 229). The plurality of spaced holes 229 extend from the upper surface of the plate 228 to the lower surface of the plate 228.

[0072] One or more inductive coils 240 are arranged around an outer portion of the upper chamber wall 218. When energized, the one or more inductive coils 240 create an electromagnetic field inside of the upper chamber wall 218. In some examples, an upper coil and a lower coil are used. A gas injector 242 injects one or more gas mixtures from a gas delivery system 250-1 into the upper chamber region 204.

[0073] In some examples, the gas delivery system 250-1 includes one or more gas sources 252, one or more valves 254, one or more mass flow controllers 256, and a mixing manifold 258, although other types of gas delivery systems may be used. A gas splitter (not shown) may be used to vary flow rates of a gas mixture. In various embodiments, the gas sources 252 may supply one or more gas mixtures including carrier gas, thermal etchant gas, radical generating gas, and/or chemical additive gas. In some embodiments, another gas delivery system 250-2 may be used to supply the chemical additive or other gas mixtures to the gas flow channels and/or holes 223 and/or 227 (in addition to or instead of etch gas from the gas injector 242). In this example, ratios (e.g., predetermined ratios, etc.) of the thermal etchant gas, the radical generating gas, and/or the optional chemical additive gas may be controlled by, for example, the mass flow controllers 256 in the gas delivery system 250-1 and/or one or more mass flow controllers (not shown) in the gas delivery system 250-2.

[0074] In the example of FIG. 1 B, the gases (e.g., the thermal etchant gas, the radical generating gas and/or the chemical additive gas) are generally provided to the processing chamber 201 via one or more gas lines between the mixing manifold 258 and the processing chamber 201 . For example, in some embodiments, all of the gases (e.g., the thermal etchant gas, the radical generating gas and/or the chemical additive gas) may be provided together via one gas line such that mixing of the gases generally occurs in the gas line. In other examples, each gas may be separately provided via its own gas line such that mixing of the gases occurs in the processing chamber 201 . [0075] In some examples, the gas injector 242 includes a center injection location that directs gas in a downward direction and one or more side injection locations that inject gas at an angle with respect to the downward direction.

[0076] A plasma generator 270 may be used to generate RF power that is output to the one or more inductive coils 240. Plasma 290 is generated in the upper chamber region 204. In some examples, the plasma generator 270 includes an RF generator 272 and a matching network 274. The matching network 274 matches an impedance of the RF generator 272 to the impedance of the one or more inductive coils 240. In some examples, the gas distribution device 214 is connected to a reference potential such as ground. A valve 278 and a pump 280 may be used to control pressure inside of the lower and upper chamber regions 202, 204 and to evacuate reactants.

[0077] A controller 276 communicates with the gas delivery systems 250-1 and 250-2, the valve 278, the pump 280, and/or the plasma generator 270 to control flow of process gas, purge gas, tuning gas, RF plasma and chamber pressure. In some examples, plasma is sustained inside the upper chamber wall 218 by the one or more inductive coils 240. One or more gas mixtures are introduced from a top portion of the chamber using the gas injector 242 (and/or gas flow channels and/or holes 223) and plasma is confined within the upper chamber wall 218 using the gas distribution device 214.

[0078] In other examples, an RF bias generator 284 is provided and includes an RF generator 286 and a matching network 288. The RF bias can be used to create plasma between the gas distribution device 214 and the substrate support or to create a self-bias on the substrate 226 to attract ions. The controller 276 may be used to control the RF bias.

[0079] During selective etching according to the present disclosure, a gas mixture including the thermal etchant gas and the radical generating gas are supplied together or separately with the optional chemical additive gas and mixed in a substrate processing chamber (e.g., in the processing chamber 102 of FIG. 1A, in the upper chamber region 204 of the processing chamber 201 of FIG. 1 B, etc.). In other examples, the optional chemical additive gas is supplied to the processing chamber separately from the thermal etchant gas and the radical generating gas. For example, when ammonia is used as the chemical additive, it can be supplied separately to prevent chemical interactions in gas supply lines. In some examples, the RF generator and/or RF bias generator and related structures are omitted. [0080] Referring now to FIG. 2, a method for selectively etching SiGe (or SiN) relative to Si is shown. At 210, the substrate is arranged on a substrate support in a processing chamber. At 214, pressure is adjusted in the processing to a predetermined pressure. In some examples, the predetermined pressure is in a range from 100mT to 10 Torr. In some examples, the predetermined pressure is in a range from 200mT to 7 Torr.

[0081] At 218, the substrate is heated by the substrate support to a predetermined temperature. In some examples, the predetermined temperature is in a range from -40 ^QC to 500 ^QC. In some examples, the predetermined temperature is in a range from -10 ^QC to 120 ^QC. As can be appreciated, higher temperatures above about 120 ^QC can be used when LED heating is performed.

[0082] At 222, carrier gas, etchant gas, radical generating gas, and/or optional chemical additive gas are supplied to the processing chamber. At 226, the method determines whether the etch period is over. If 226 is false, the method returns to 222. In other examples, the method may alternatively return to 214, as shown by the dashed line. In such examples, the pressure may be adjusted again (e.g., to another predetermined pressure) at 214 and/or the temperature may be adjusted again (e.g., to another predetermined temperature) at 218. If the pressure and/or the temperature are adjusted again, the supply of gases, such as the etchant gas, the radical generating gas, and the optional chemical additive gas may be temporarily paused until the pressure is stabilized at the new pressure value and/or the temperature is stabilized at the new temperature value. If 226 is true, the method ends. For example, the processing chamber is evacuated and the substrate is removed from the processing chamber.

[0083] Referring now to FIG. 3, the energetic differences between thermal radicals and plasma radicals is demonstrated. In this example, a solid line 302 represents the thermal radicals and a dashed line 304 represents the plasma radicals. A line 306 represents a cutoff for the thermal radicals. When plasma radical etching is employed, a larger energy distribution occurs (exemplified as a high energy tail in FIG. 3) causing aggressive etching with decreased selectivity. Due to the narrower energy distribution expected for thermal radicals, the process is expected to be superior to traditional plasma generated radicals due to it being more controllable.

[0084] Referring now to FIGS. 4 to 9, examples of etch selectivity are shown for SiGe relative to Si. In FIG. 4, a graph defines different etch behavior regimes (e.g., a radical regime, a mixture or tunable regime, and a molecular regime) corresponding to different ratios of etchant and radicalizer to ultimately show how selectivity changes. For example, when the supply or amount of radicalizer (the radical generating gas) exceeds the supply or amount of etchant (thermal etchant gas), etching may be in the radical regime to radically etch at least one material (e.g. SiGe) relative to another material (e.g., Si). When the supply of etchant exceeds the supply of radicalizer, etching may be in the molecular regime to selectively etch at least one material (e.g. SiGe) relative to another material (e.g., Si). The radical generating gas reacts with F2 spontaneously to generate F-radicals. There is the potential to widen selectivity control down to 1 :1 or less than 1 :1 SiGe:Si with a narrower energy distribution. The chemical additive can be added to help modulate radical etch behavior.

[0085] In FIG. 5, an example of etching of a substrate when the radicalizer supply is greater than the etchant supply is shown. When the etch is in the radical regime, both SiGe layers 414-1 , 414-2, ..., and 414-P (having different Ge%) relative to Si layers 416- 1 , 416-2, ..., and 416-R of a GAA substrate (where R and P are integers greater than one) are aggressively etched. This process is more well suited for cases where etching with near 1 :1 (SiGe:Si) selectivity is preferred. In FIG. 6, an example of etching of a substrate when the etch is in the tunable regime is shown. When this is the case, the SiGe layers 414-1 , 414-2, ..., and 414-P are etched selectively relative to the Si.

[0086] Referring now to FIGS. 7 to 9, various graphs show various knobs for controlling selectivity. In the examples of FIGS. 7 to 9, the percentage of germanium (Ge) in SiGe varies. For example, FIG. 7 depicts a graph showing an etch rate as a function of Ge concentration for a non-selective etching process (e.g., in the radical regime shown in FIG. 4), FIG. 8 depicts a graph showing an etch rate as a function of Ge concentration for a selective etching process (e.g., in the molecular regime shown in FIG. 4), and FIG. 9 depicts a graph showing an etch rate as a function of Ge concentration for a tunable etching process (e.g., in the mixture or tunable regime shown in FIG. 4). In the examples of FIGS. 7 to 9, a ratio of radical generating gas and thermal etchant gas is adjustable.

[0087] By modulating different conditions (e.g., etchant to radical generator ratio, pressure, temperature, flow, etc.), the nature of the etch is modulated. The non-selective process creates an etch process that is mostly radical in nature. Lowering pressure and modifying etchant to radical generator ratio enables highly selective etching behavior. Alternatively, moving to higher temperatures can create more tunable selectivity where all SiGe materials are etched close to 1 :1 , but remain highly selective to Si. [0088] The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. Further, although each of the embodiments is described above as having certain features, any one or more of those features described with respect to any embodiment of the disclosure can be implemented in and/or combined with features of any of the other embodiments, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with one another remain within the scope of this disclosure.

[0089] Spatial and functional relationships between elements (for example, between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including “connected,” “engaged,” “coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and “disposed.” Unless explicitly described as being “direct,” when a relationship between first and second elements is described in the above disclosure, that relationship can be a direct relationship where no other intervening elements are present between the first and second elements, but can also be an indirect relationship where one or more intervening elements are present (either spatially or functionally) between the first and second elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.”

[0090] In some implementations, a controller is part of a system, which may be part of the above-described examples. Such systems can comprise semiconductor processing equipment, including a processing tool or tools, chamber or chambers, a platform or platforms for processing, and/or specific processing components (a wafer pedestal, a gas flow system, etc.). These systems may be integrated with electronics for controlling their operation before, during, and after processing of a semiconductor wafer or substrate. The electronics may be referred to as the “controller,” which may control various components or subparts of the system or systems. The controller, depending on the processing requirements and/or the type of system, may be programmed to control any of the processes disclosed herein, including the delivery of processing gases, temperature settings (e.g., heating and/or cooling), pressure settings, vacuum settings, power settings, radio frequency (RF) generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, positional and operation settings, wafer transfers into and out of a tool and other transfer tools and/or load locks connected to or interfaced with a specific system.

[0091] Broadly speaking, the controller may be defined as electronics having various integrated circuits, logic, memory, and/or software that receive instructions, issue instructions, control operation, enable cleaning operations, enable endpoint measurements, and the like. The integrated circuits may include chips in the form of firmware that store program instructions, digital signal processors (DSPs), chips defined as application specific integrated circuits (ASICs), and/or one or more microprocessors, or microcontrollers that execute program instructions (e.g., software). Program instructions may be instructions communicated to the controller in the form of various individual settings (or program files), defining operational parameters for carrying out a particular process on or for a semiconductor wafer or to a system. The operational parameters may, in some embodiments, be part of a recipe defined by process engineers to accomplish one or more processing steps during the fabrication of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and/or dies of a wafer.

[0092] The controller, in some implementations, may be a part of or coupled to a computer that is integrated with the system, coupled to the system, otherwise networked to the system, or a combination thereof. For example, the controller may be in the “cloud” or all or a part of a fab host computer system, which can allow for remote access of the wafer processing. The computer may enable remote access to the system to monitor current progress of fabrication operations, examine a history of past fabrication operations, examine trends or performance metrics from a plurality of fabrication operations, to change parameters of current processing, to set processing steps to follow a current processing, or to start a new process. In some examples, a remote computer (e.g. a server) can provide process recipes to a system over a network, which may include a local network or the Internet. The remote computer may include a user interface that enables entry or programming of parameters and/or settings, which are then communicated to the system from the remote computer. In some examples, the controller receives instructions in the form of data, which specify parameters for each of the processing steps to be performed during one or more operations. It should be understood that the parameters may be specific to the type of process to be performed and the type of tool that the controller is configured to interface with or control. Thus as described above, the controller may be distributed, such as by comprising one or more discrete controllers that are networked together and working towards a common purpose, such as the processes and controls described herein. An example of a distributed controller for such purposes would be one or more integrated circuits on a chamber in communication with one or more integrated circuits located remotely (such as at the platform level or as part of a remote computer) that combine to control a process on the chamber.

[0093] Without limitation, example systems may include a plasma etch chamber or module, a deposition chamber or module, a spin-rinse chamber or module, a metal plating chamber or module, a clean chamber or module, a bevel edge etch chamber or module, a physical vapor deposition (PVD) chamber or module, a chemical vapor deposition (CVD) chamber or module, an atomic layer deposition (ALD) chamber or module, an atomic layer etch (ALE) chamber or module, an ion implantation chamber or module, a track chamber or module, and any other semiconductor processing systems that may be associated or used in the fabrication and/or manufacturing of semiconductor wafers.

[0094] As noted above, depending on the process step or steps to be performed by the tool, the controller might communicate with one or more of other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, neighboring tools, tools located throughout a factory, a main computer, another controller, or tools used in material transport that bring containers of wafers to and from tool locations and/or load ports in a semiconductor manufacturing factory.

Claims

CLAIMS What is claimed is:

1 . A method for etching at least one first material relative to at least one second material, the method comprising: arranging a substrate on a substrate support in a processing chamber; and supplying a carrier gas, at least one thermal etchant gas, and at least one radical generating gas to the processing chamber to etch the at least one first material relative to the at least one second material.

2. The method of claim 1 , wherein: the method further comprises modulating a ratio of the thermal etchant gas and the radical generating gas; and supplying the carrier gas, the thermal etchant gas, and the radical generating gas to the processing chamber includes supplying the thermal etchant gas and the radical generating gas to the processing chamber at the ratio.

3. The method of claim 2, wherein the ratio is a predetermined ratio between the thermal etchant gas and the radical generating gas.

4. The method of claim 2, wherein modulating the ratio of the thermal etchant gas and the radical generating gas includes modulating the ratio so that an amount of the thermal etchant gas is greater than an amount of the radical generating gas to selectively etch the at least one first material relative to the at least one second material.

5. The method of claim 2, wherein modulating the ratio of the thermal etchant gas and the radical generating gas includes modulating the ratio so that an amount of the radical generating gas is greater than an amount of the thermal etchant gas to radically etch the at least one first material relative to the at least one second material.

6. The method of claim 2, wherein the at least one first material is silicon germanium (SiGe) and the at least one second material is silicon (Si).

7. The method of claim 2, further comprising adjusting a pressure within the processing chamber to a predetermined pressure value.

8. The method of claim 7, wherein the predetermined pressure value is in a range from l OOmT to 10 Torr.

9. The method of claim 2, further comprising adjusting a temperature within the processing chamber to a predetermined temperature value.

10. The method of claim 9, wherein the predetermined temperature value is in a range from -40 ^QC to 500 ^QC.

1 1 . The method of claim 1 , wherein supplying the carrier gas, the thermal etchant gas, and the radical generating gas to the processing chamber includes supplying the thermal etchant gas to the processing chamber separately from the radical generating gas.

12. The method of claim 1 , wherein supplying the carrier gas, the thermal etchant gas, and the radical generating gas to the processing chamber includes supplying the thermal etchant gas to the processing chamber together with the radical generating gas.

13. The method of claim 1 , further comprising supplying at least one chemical additive gas to the processing chamber to enable tunable control of etching the at least one first material relative to the at least one second material.

14. The method of claim 13, wherein supplying the at least one chemical additive gas to the processing chamber includes supplying the chemical additive gas to the processing chamber separately from the at least one thermal etchant gas and the at least one radical generating gas.

15. The method of claim 13, wherein supplying the at least one chemical additive gas to the processing chamber includes supplying the chemical additive gas to the processing chamber together with the at least one thermal etchant gas and the at least one radical generating gas.

16. The method of claim 13, wherein the at least one chemical additive gas is selected from a group consisting of ammonia (NH3), molecular hydrogen (H2), methane (CH4), fluoromethane (CH3F), difluoromethane (CH2F2), water or steam (H2O), molecular oxygen (O2), hydrogen fluoride (HF), and sulfur hexafluoride (SFe).

17. The method of claim 1 , wherein the at least one thermal etchant gas includes a molecular etchant selected from a group consisting of molecular fluorine (F2), chlorine trifluoride (CIF3), xenon difluoride (XeF2), nitrogen trifluoride (NF3), and hydrogen fluoride (HF).

18. The method of claim 1 , wherein the at least one radical generating gas is selected from a group consisting of nitric oxide (NO), nitrogen dioxide (NO2), ozone (O3), chlorine dioxide (CIO2), hypochlorous acid (HOCI), hydrogen peroxide (H2O2), carbon monoxide (CO), nitrous oxide (N2O), hypobromous acid (HOBr), chloride trifluoride (CIF3), and tertbutyl hydroperoxide (TBHP).

19. A system comprising: a processing chamber including a substrate support configured to support a substrate; at least one gas delivery system configured to output one or more gases to the processing chamber; and a controller in communication with the at least one gas delivery system, the controller configured to control the at least one gas delivery system to supply a carrier gas, at least one thermal etchant gas, and at least one radical generating gas to the processing chamber to etch at least one first material of the substrate relative to at least one second material of the substrate.

20. The system of claim 19, wherein the controller is configured to control the at least one gas delivery system to supply at least one chemical additive gas to the processing chamber to enable tunable control of etching the at least one first material relative to the at least one second material.

21 . The system of claim 19, wherein: the at least one gas delivery system is a first gas delivery system; the system further comprises a second gas delivery system configured to output one or more gases to the processing chamber; and the controller is configured to control the second gas delivery system to supply at least one chemical additive gas to the processing chamber to enable tunable control of etching the at least one first material relative to the at least one second material.

22. The system of claim 20, wherein the controller is configured to: set a ratio of the thermal etchant gas and the radical generating gas; and control the at least one gas delivery system to supply the at least one thermal etchant gas and the at least one radical generating gas to the processing chamber at the ratio.

23. The system of claim 22, wherein the ratio of the thermal etchant gas and the radical generating gas includes an amount of the thermal etchant gas being greater than an amount of the radical generating gas to selectively etch the at least one first material relative to the at least one second material.

24. The system of claim 22, wherein the ratio of the thermal etchant gas and the radical generating gas includes an amount of the radical generating gas is greater than an amount of the thermal etchant gas to radically etch the at least one first material relative to the at least one second material.

25. The system of claim 19, wherein the at least one first material is silicon germanium (SiGe) and the at least one second material is silicon (Si).

26. The system of claim 19, further comprising: a pump and a valve coupled to the processing chamber, wherein the controller configured to control the at least of the pump and the valve to adjust a pressure within the processing chamber to a predetermined pressure value.

27. The system of claim 19, wherein the controller is configured to control adjust a temperature within the processing chamber to a predetermined temperature value.