Low temperature plasma pre-clean for selective gap fill

Abstract

Methods for pre-cleaning a substrate having metal and dielectric surfaces are described. A temperature of a pedestal comprising a cooling feature is set to be less than or equal to 100 °C, with a substrate positioned on the pedestal. The substrate is exposed to a plasma treatment to remove chemical residues and / or impurities from features of the substrate including a metal bottom, a dielectric sidewall, and / or a dielectric field, and / or to repair surface defects in the dielectric sidewall and / or the dielectric field. The plasma treatment can be an oxygen plasma, for example, a direct oxygen plasma. Processing tools and computer readable media for implementing the methods are also described.

Description

Technical Field

[0001] Embodiments of this disclosure generally relate to methods for filling gaps in semiconductors. More specifically, embodiments of this disclosure relate to methods for pre-cleaning substrates to improve metal deposition selectivity. Background Technology

[0002] Interconnect metallization is widely used in logic and memory devices. Typically, a substrate film and a subsequent bulk-deposited CVD / PVD film are used for via / trench gap filling applications. However, as feature sizes shrink, via / trench structures become smaller, and the volume ratio of the substrate film increases, making it difficult to achieve defect-free and low-resistivity metal gap filling.

[0003] Selective deposition processes utilize the incubation difference between one surface material and another during deposition. This incubation delay can be used to achieve bottom-up gap filling without gaps / voids and substrate films. However, several challenges hinder the wider adoption of this technique. For example, impurities at the bottom of vias and on dielectric surfaces can reduce the selectivity of metal growth on the metal surface relative to the dielectric field. Existing processes that use heated plasmas (e.g., H2 or O2 plasmas) to clean surface contaminants (e.g., oxygen, carbon, fluorine, chlorine) result in unstable wafer temperatures, increasing them by orders of magnitude from 30°C to 100°C. Conversely, metal oxidation and challenges in subsequent processing and deposition processes also increase.

[0004] Generally speaking, efficiently cleaning metal surfaces while maintaining no or minimal growth on the field is a major challenge preventing widespread use. Furthermore, different surface structures with varying etching residues or contaminants may require different pre-cleaning processes to achieve selective growth.

[0005] Therefore, there is a continuous need in the art for improved methods and equipment to pre-clean substrate surfaces for selective deposition. Summary of the Invention

[0006] One or more embodiments of this disclosure relate to a pre-cleaning method. A substrate comprising a surface structure is situated on a pedestal having a metal base, dielectric sidewalls, and a dielectric field, the pedestal including cooling features. The temperature of the pedestal is set to less than or equal to 100°C. The substrate is exposed to plasma treatment to remove chemical residues and / or impurities from the metal base, dielectric sidewalls, and / or dielectric field, and / or repair surface defects in the dielectric sidewalls and / or dielectric field.

[0007] Additional embodiments of this disclosure relate to a method for pre-cleaning a substrate comprising a surface structure having a metal base, dielectric sidewalls, and a dielectric field. The substrate is placed on a pedestal within a processing chamber, the pedestal comprising radio frequency (RF) capability and cooling features. The temperature of the pedestal is set to less than or equal to 100°C. The substrate is exposed to a plasma treatment within the processing chamber to remove chemical residues and / or impurities from the metal base, dielectric sidewalls, and / or dielectric field, and / or to repair surface defects in the dielectric sidewalls and / or dielectric field, wherein the plasma treatment comprises hydrogen plasma and oxygen plasma.

[0008] Further embodiments of this disclosure relate to a non-transitory computer-readable medium including instructions that, when executed by a controller of a processing chamber, cause the processing chamber to perform the following operations: placing a substrate on a base in a first processing chamber, the base including cooling features; exposing the substrate to plasma processing in the first processing chamber; and setting the temperature of the base to less than or equal to 100°C. Attached Figure Description

[0009] Therefore, the above-described features of this disclosure can be understood in detail by referring to the embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings only show typical embodiments of this disclosure and should therefore not be considered as limiting its scope, as this disclosure allows for other equally effective embodiments.

[0010] Figure 1 Schematic representative diagrams showing substrate structures according to one or more embodiments of the present disclosure; and

[0011] Figure 2 A flowchart illustrating one or more embodiments of a method according to this disclosure is provided. Detailed Implementation

[0012] Before describing several exemplary embodiments of this disclosure, it should be understood that this disclosure is not limited to the details of the construction or process steps set forth in the following description. This disclosure can have other embodiments and can be implemented or performed in various ways.

[0013] As used in this specification and the appended claims, the term "substrate" refers to a surface, or a portion of a surface, on which the process is performed. Those skilled in the art will also understand that, unless the context clearly indicates otherwise, reference to a substrate may refer only to a portion of a substrate. Furthermore, reference to deposition on a substrate may refer to both a bare substrate and a substrate having one or more films or features deposited or formed thereon.

[0014] As used herein, "substrate" refers to any substrate or material surface formed on a substrate, on which a film treatment is performed during a manufacturing process. For example, depending on the application, substrate surfaces on which treatment can be performed may include materials such as silicon, silicon oxide, strained silicon, silicon-on-insulator (SOI), carbon-doped silicon oxide, amorphous silicon, doped silicon, germanium, gallium arsenide, glass, sapphire, and any other materials (such as metals, metal nitrides, metal alloys, and other conductive materials). Substrates may include, but are not limited to, semiconductor wafers. Substrates may be exposed to pretreatment processes such as polishing, etching, reduction, oxidation, hydroxylation, annealing, UV curing, electron beam curing, and / or baking of the substrate surface. In addition to performing film treatments directly on the surface of the substrate itself, any of the film treatment steps disclosed herein (as disclosed in more detail below) may also be performed on an underlayer formed on the substrate, and the term "substrate surface" is intended to include such an underlayer as referred to in the context. Therefore, for example, when a film / layer or part of a film / layer has been deposited onto the substrate surface, the exposed surface of the newly deposited film / layer becomes the substrate surface.

[0015] To accommodate a wider range of structural types and selectivity windows, one or more embodiments of this disclosure advantageously provide methods for pre-cleaning substrates. Some embodiments advantageously provide cryogenic processing using a cryogenic plasma substrate, which can provide a stable temperature window from room temperature to sub-zero temperatures during pre-cleaning in the presence of plasma. Using the process described herein can advantageously improve dielectric selectivity and maintain impurity removal capabilities while suppressing metal oxidation (not preferred). Subsequently, the selectivity of metal deposition is improved. In one or more embodiments, the selectivity of tungsten (W) deposition can be improved after cryogenic pre-cleaning in the presence of any oxygen plasma (particularly direct oxygen plasma).

[0016] Some embodiments of this disclosure provide methods for selective metal deposition processes at the bottom of contacts or vias, which require clean surfaces to begin with minimal formation. In some embodiments, removal of chemical residues and / or impurities, including but not limited to metal oxides / metal nitrides / metal carbides, etc., can hinder the selective deposition process and cause significant formation delays. Some embodiments effectively clean metal contaminants while maintaining a contact / via structure that is optimal for selective processes.

[0017] The process described in this disclosure uses a cooled substrate. The substrate includes cooling features that dissipate heat generated by the plasma, thereby maintaining a stable substrate temperature below a desired temperature. In one or more embodiments, the cooling feature of the substrate may be a heat exchange channel (not illustrated) through which a heat exchange fluid passes to control the substrate temperature. Example heat exchange fluids are ethylene glycol or water. In one or more embodiments, the substrate includes radio frequency (RF) capability.

[0018] In one or more embodiments, the temperature of the substrate is set to less than or equal to 100°C, including values ​​and sub-ranges ranging from greater than or equal to -20°C to less than or equal to 85°C, less than or equal to 60°C, less than or equal to 40°C, less than or equal to 35°C, and in between. In one or more embodiments, the cooled substrate has radio frequency (RF) capability. During the process, the substrate is exposed to plasma treatment to remove chemical residues and / or impurities from the metal bottom, dielectric sidewalls, and / or dielectric field, and / or repair surface defects in the dielectric sidewalls and / or dielectric field. In one or more embodiments, the plasma treatment comprises oxygen plasma. In one or more embodiments, the oxygen plasma is direct plasma. In one or more embodiments, the plasma treatment further comprises hydrogen plasma, for example, direct hydrogen plasma.

[0019] In a non-limiting embodiment of the example, the cleaning process sequence includes: (1) setting and maintaining the temperature of the radio frequency (RF)-enabled substrate in the processing chamber within a range of -20°C to 100°C; (2) performing a direct plasma treatment of the substrate in the processing chamber, wherein the plasma contains hydrogen. The hydrogen plasma is used to reduce the primary metal contaminants—i.e., metal oxides and metal nitrides—to pure metals; and (3) performing a direct plasma treatment of the substrate in the processing chamber, wherein the plasma contains oxygen. In this step, the oxidation process can convert residual metal nitrides into oxides, which can be reduced to pure metals in a subsequent step, and / or oxidize sidewall and top field dielectric materials (oxides and nitrides) that may have been damaged during the initial hydrogen plasma process. In some embodiments, the oxidation process repairs the dielectric surface with strong oxidation, maintaining high selectivity for selective metal deposition. Oxygen treatment can also reduce contamination from carbon / organic residues. During oxygen plasma exposure, a bias voltage between 0 watts and 1000 watts is applied to the substrate, including all values ​​and ranges in between, including 200 watts and 600 watts. One advantage of this process is that it provides strong dielectric recovery and weak metal oxidation for high-power, low-temperature O2 treatment.

[0020] In one or more embodiments, a substrate on a cooled pedestal is exposed to plasma treatment to process or clean the substrate. In one or more embodiments, the substrate includes at least one feature. The at least one feature may include any feature known to those skilled in the art, including but not limited to trenches, vias, or peaks. In embodiments where the substrate is exposed to remote plasma and / or direct plasma to process or clean the substrate, the processing or cleaning removes, for example, one or more residues from previous processing and / or native oxides.

[0021] Experiments show that, regardless of temperature, strong dielectric recovery occurs at high power (e.g., 200 W to 600 W during low-temperature oxygen plasma treatment). Experiments also show that, regardless of power, weak metal oxidation occurs at low temperatures (e.g., 100 °C, 60 °C, or 35 °C during oxygen plasma treatment).

[0022] Figure 1 The diagram illustrates the contact structure used according to one or more embodiments. Figure 1The substrate 100 illustrated includes a structure 130 bounded by a first material 102 and a second material 104. In the illustrated embodiment, the structure 130, including a bottom 132 and a side 134, is a through-hole or trench. The structure is bounded by the first material 102 at the bottom 132 and by the second material 104 at the side 134, the second material 104 being different from the first material 102. In some embodiments, the first material 102 includes a metal 110, which forms a metallic bottom 115 of the structure. The metal 110 can be any suitable metal, including but not limited to tungsten (W), cobalt (Co), and / or ruthenium (Ru). In some embodiments, the first material 102 and the bottom 132 of the structure 130 include non-metals. Suitable non-metals include, but are not limited to, metal nitrides (e.g., titanium nitride (TiN)), metal silicides (e.g., titanium silicide (TiSi)), or silicon (Si). As used in this specification and appended claims, unless otherwise specified by subscript, chemical formulas are representations of elemental identification and are not intended to imply any particular stoichiometric ratio. For example, a titanium nitride (TiN) film can be any suitable combination of titanium and nitrogen atoms, and is not limited to a single relationship.

[0023] In some embodiments, the second material 104 comprises a dielectric 120. The sidewalls 122 of the dielectric 120 form the sidewalls 134 of the structure 130. The top surface 106 of the second material 104 is also referred to as a field. In some embodiments, the second material 104 comprises a dielectric 120 having sidewalls 122 and a field 124. The dielectric 120 can be any suitable material, including but not limited to silicon oxide (SiO), silicon dioxide (SiO2), silicon nitride (SiN), silicon oxynitride (SiON), aluminum nitride (AlN), aluminum oxide (AlO), or high-k dielectric materials. In some embodiments, the second material 104 comprises a hard mask material (e.g., carbon (C)).

[0024] Figure 2 A method 200 for pre-cleaning a substrate prior to selective deposition, according to one or more embodiments, is illustrated. Surface contaminants in some embodiments include one or more of the following: oxygen, nitrogen, carbon, or halogens (e.g., fluorine, chlorine, bromine, or iodine). In some embodiments, the contaminants include organic compounds.

[0025] In operation 202, the substrate is placed on a base within the processing chamber, as appropriate. In operation 204, the base, including cooling features, is cooled. One or more embodiments of the base include radio frequency (RF) capability. The temperature of the base is maintained below 100°C, including less than or equal to 85°C, 60°C, and 35°C. In operation 206, the substrate is exposed to plasma processing. The plasma processing includes oxygen plasma, for example, direct oxygen plasma. Depending on the situation, the plasma processing may further include hydrogen plasma, for example, direct hydrogen plasma.

[0026] In one or more embodiments, the substrate can be maintained at a temperature range of -20°C to 100°C during exposure to oxygen plasma.

[0027] In some embodiments, the oxygen plasma is a capacitively coupled plasma (CCP). In some embodiments, the oxygen (O2) plasma is a high-density, high-energy plasma. In some embodiments, the low-energy plasma has a power of greater than or equal to 100 watts to less than or equal to 600 watts.

[0028] In some implementations, the oxygen plasma has a pressure in the range of 1 Torr to 30 Torr.

[0029] In some embodiments, the hydrogen (H2) plasma is a capacitively coupled plasma (CCP). In some embodiments, the H2 plasma is a low-energy plasma.

[0030] In one or more embodiments, the hydrogen plasma has a pressure in the range of 1 Torr to 30 Torr.

[0031] Following operation 206, the substrate can be further processed for selective metal deposition. In one or more embodiments, after a cleaning process, the substrate is exposed to at least one metal precursor to selectively form a metal film on the substrate. In one or more embodiments, the method further includes exposing the substrate to at least one precursor to deposit a film on the substrate via a plasma-enhanced chemical vapor deposition (PECVD) process or a plasma-enhanced atomic layer deposition (PEALD) process. Any suitable precursor known to those skilled in the art can be used to form a film on the substrate.

[0032] In some implementations... Figure 2 The pre-cleaning method illustrated in the diagram effectively removes residues and enhances the selectivity of subsequent deposition processes.

[0033] Method 200 can be implemented using various hardware arrangements. In some embodiments, for surface cleaning, one or two chambers can be used to perform multiple processes. The chambers can be used for O2 / H2 plasma treatment of different gas types. In some embodiments, H2 and O2 treatment are performed in one chamber.

[0034] Additional embodiments of this disclosure relate to processing systems for performing the methods described herein.

[0035] Typically, clustering tools are modular systems comprising multiple chambers performing various functions, including substrate centering and orientation, degassing, annealing, deposition, and / or etching. According to one or more embodiments, a clustering tool includes at least a first chamber and a central transfer chamber. The central transfer chamber houses a robot that can transfer substrates between a processing chamber and a loading and locking chamber. The transfer chamber is typically maintained under vacuum conditions and provides an intermediate stage for transferring substrates from one chamber to another, and / or to a loading and locking chamber located at the front end of the clustering tool. Two well-known clustering tools suitable for application in this disclosure are... and Both are available from Applied Materials, Inc., Santa Clara, California, USA. However, the actual setup and combination of chambers can be modified to perform specific steps of the process described herein. Other processing chambers that can be used include, but are not limited to, circulating layer deposition (CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), etching, pre-cleaning, chemical cleaning, thermal treatment (such as RTP), plasma nitriding, degassing, orientation, hydroxylation, and other substrate processes. By performing the process in a chamber on a cluster tool, surface contamination of the substrate by atmospheric impurities is avoided by eliminating the need for oxidation prior to the deposition of subsequent films.

[0036] At least one controller may be coupled to one or both of the first chamber and the central transfer chamber. In some embodiments, more than one controller is connected to individual chambers or stations, and a main control processor is coupled to each individual processor to control the system. The controller may be any type of general-purpose computer processor, microcontroller, microprocessor, etc., which can be used in industrial settings to control individual chambers and subprocessors.

[0037] At least one controller may have a processor, a memory coupled to the processor, input / output devices coupled to the processor, and supporting circuitry for communication between different electronic components. The memory may include one or more of temporary memory (e.g., random access memory) and non-temporary memory (e.g., storage).

[0038] The processor's memory or computer-readable medium can be one or more readily available memories, such as random access memory (RAM), read-only memory (ROM), floppy disk, hard disk, or any other form of local or remote digital storage. The memory may hold an instruction set that can be operated by the processor 952 to control system parameters and components. Supporting circuitry is coupled to the processor to support it in a conventional manner. This circuitry may include, for example, caches, power supplies, clock circuits, input / output circuitry systems, subsystems, etc.

[0039] Typically, the process can be stored in memory as a software routine, which, when executed by a processor, causes the processing chamber to perform the process of this disclosure. The software routine can also be stored and / or executed by a remote second processor (not shown) located in processor-controlled hardware. Some or all of the methods of this disclosure can also be executed in hardware. Thus, the process can be implemented as software and executed using a computer system, implemented as hardware (e.g., an application-specific integrated circuit or other type of hardware implementation), or implemented as a combination of software and hardware. When executed by a processor, the software routine transforms a general-purpose computer into a dedicated computer (controller) that controls the operation of the processing chamber to perform the processing.

[0040] In some implementations, the controller has one or more configurations to perform individual processes or sub-processes to perform the method. The controller may be connected to and configured to operate intermediate components to perform the functions of the method. For example, the controller may be connected to and configured to control one or more of a gas valve, actuator, motor, slit valve, vacuum control, etc.

[0041] Some implementations of the controller have one or more configurations selected from: a configuration for moving a substrate on a robot between multiple processing chambers and metering stations; a configuration for loading and / or unloading a substrate from the system; and a configuration for moving a substrate between a central transfer station and a processing chamber.

[0042] One or more embodiments relate to a non-transitory computer-readable medium including instructions that, when executed by a controller of a processing chamber, cause the processing chamber to perform the following operations: placing a substrate on a base in a first processing chamber, the base including cooling features; exposing the substrate to plasma processing in the first processing chamber; and setting the temperature of the base to less than or equal to 100°C. In one or more embodiments, the non-transitory computer-readable medium includes instructions that, when executed by a controller of the processing chamber, cause the processing chamber to perform the following operations: exposing the substrate to at least one precursor to form a film on the substrate.

[0043] Throughout this specification, references to "one embodiment," "some embodiments," "one or more embodiments," or "an embodiment" mean that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of this disclosure. Therefore, the use of terms such as "in one or more embodiments," "in some embodiments," "in one embodiment," or "in one embodiment" throughout this specification does not necessarily refer to the same embodiment of this disclosure. Furthermore, in one or more embodiments, specific features, structures, materials, or characteristics can be combined in any manner.

[0044] Although the disclosure herein has been described with reference to specific embodiments, those skilled in the art will understand that these embodiments are merely illustrative of the principles and applications of the disclosure. It will be apparent to those skilled in the art that various modifications and variations can be made to the methods and apparatus of this disclosure without departing from the spirit and scope of the disclosure. Therefore, this disclosure is intended to include modifications and variations within the scope of the appended claims and their equivalents.

Claims

1. A pre-cleaning method, the method comprising the following steps: A substrate on a base is exposed to plasma treatment containing oxygen plasma. The substrate includes a surface structure having a metal base, dielectric sidewalls, and a dielectric field. The metal base comprises one or more of tungsten (W), cobalt (Co), or ruthenium (Ru) to remove chemical residues and / or impurities from the metal base, the dielectric sidewalls, and / or the dielectric field, and / or to repair surface defects in the dielectric sidewalls and / or the dielectric field. The temperature of the base, which includes cooling features, is set to be greater than or equal to -20°C and less than or equal to 60°C, wherein the pre-cleaning effectively improves the selectivity of subsequent metal deposition processes.

2. The method of claim 1, wherein the base includes radio frequency (RF) capability.

3. The method of claim 1, wherein the oxygen plasma is a direct plasma.

4. The method of claim 1, wherein the plasma treatment further comprises hydrogen plasma.

5. The method of claim 1, wherein during plasma exposure, a bias voltage in the range of 0 watts or less than or equal to 1000 watts is applied to the substrate.

6. The method of claim 1, wherein during the plasma exposure, the base is maintained at a temperature in the range of greater than or equal to -20°C to less than or equal to 40°C.

7. The method of claim 1, wherein the dielectric comprises one or more of the following: silicon nitride (SiN), silicon oxide (SiO), silicon oxynitride (SiON), or a high-k dielectric.

8. A processing method comprising the following steps: The temperature of the base in the processing chamber is set to be greater than or equal to -20°C and less than or equal to 60°C, and the base includes radio frequency (RF) capability and cooling features; A substrate on a base is exposed to plasma treatment in the processing chamber. The substrate includes a surface structure having a metal bottom, dielectric sidewalls, and a dielectric field. The metal bottom comprises one or more of tungsten (W), cobalt (Co), or ruthenium (Ru) to remove chemical residues and / or impurities from the metal bottom, the dielectric sidewalls, and / or the dielectric field, and / or repair surface defects in the dielectric sidewalls and / or the dielectric field. The plasma treatment comprises oxygen plasma. and The substrate is exposed to at least one precursor of the metal to selectively form a metal film on the substrate.

9. The method of claim 8, wherein the oxygen plasma is a direct plasma.

10. The method of claim 8, wherein during the plasma exposure, a bias voltage in the range of 0 watts or less than or equal to 1000 watts is applied to the substrate.

11. The method of claim 8, wherein during the plasma exposure, the base is maintained at a temperature in the range of greater than or equal to -20°C to less than or equal to 40°C.

12. The method of claim 8, wherein the dielectric comprises one or more of the following: silicon nitride (SiN), silicon oxide (SiO), silicon oxynitride (SiON), or a high-k dielectric.

13. A non-transitory computer-readable medium comprising instructions that, when executed by a controller of a processing chamber, cause the processing chamber to perform the following operations: A substrate on a base containing cooling features in a first processing chamber is exposed to plasma processing containing oxygen plasma within the first processing chamber. The substrate includes a surface structure having a metallic base, dielectric sidewalls, and a dielectric field. The metallic base comprises one or more of tungsten (W), cobalt (Co), or ruthenium (Ru). The temperature of the base is set to be greater than or equal to -20°C and less than or equal to 60°C to repair surface defects in the dielectric sidewalls and / or the dielectric field and to improve the selectivity of subsequent metal deposition processes.

14. The non-transitory computer-readable medium of claim 13, wherein the base includes radio frequency (RF) capability.

15. The non-transitory computer-readable medium of claim 13, further comprising instructions that, when executed by a controller of the processing chamber, cause the processing chamber to perform the following operation: expose the substrate to hydrogen plasma.

16. The non-transitory computer-readable medium of claim 13, wherein the oxygen plasma is a direct plasma.

17. The non-transitory computer-readable medium of claim 13, further comprising instructions that, when executed by a controller of a processing chamber, cause the processing chamber to perform the following operations: during the plasma exposure, applying a bias voltage in the range of 0 watts or greater and 1000 watts or less to the substrate.

18. The non-transitory computer-readable medium of claim 13, further comprising instructions that, when executed by a controller of the processing chamber, cause the processing chamber to perform the following operations: maintaining the pedestal at a temperature in the range of greater than or equal to -20°C to less than 40°C during the plasma exposure.

19. The non-transitory computer-readable medium of claim 13, wherein the dielectric comprises one or more of the following: silicon nitride (SiN), silicon oxide (SiO), silicon oxynitride (SiON), or a high-k dielectric.

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