Enhanced stress tuning and interfacial adhesion for tungsten (w) gapfill

Abstract

Embodiments of methods and related apparatus for filling features of a substrate are provided herein.SOLUTION: In some embodiments, a method of filling a feature of a substrate includes depositing a seed layer of tungsten nitride in the feature via a physical vapor deposition (PVD) process, depositing a liner layer of tungsten on the seed layer of tungsten nitride in the feature via a PVD process, and subsequently filling the feature with a tungsten bulk fill via a chemical vapor deposition (CVD) process.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure generally relate to processing of substrates, such as semiconductor substrates. [Background technology]

[0002] Integrated circuits are formed through processes that produce intricately patterned layers of material on substrate surfaces. Tungsten is used in the semiconductor industry as a low-resistance conductor with minimal electromigration. It can be used as a contact for transistors and to fill holes in the formation of vias between layers of integrated devices. Tungsten can also be used for interconnects in logic and memory devices due to its stability and low resistivity. As technology advances, demand is created for ever lower-resistivity and lower-stress metal fill solutions. However, current tungsten fill processes that offer low resistivity and low stress result in poor adhesion for planarization processes. Current tungsten fill processes also lack adequate control over the adjustment of the stress of the tungsten fill. Summary of the Invention [Problem to be solved by the invention]

[0003] Thus, the inventors have provided an improved process for tungsten filling. [Means for solving the problem]

[0004] Embodiments of methods and associated apparatuses for filling a substrate feature are provided herein. In some embodiments, the method of filling a substrate feature includes depositing a tungsten nitride seed layer in the feature via a physical vapor deposition (PVD) process, depositing a tungsten liner layer on the tungsten nitride seed layer in the feature via the PVD process, and subsequently filling the feature with a tungsten bulk fill via a chemical vapor deposition (CVD) process.

[0005] In some embodiments, a method of filling a feature of a substrate includes depositing a tungsten nitride seed layer in the feature via a physical vapor deposition (PVD) process, depositing a tungsten liner layer on the tungsten nitride seed layer in the feature via the PVD process, performing a nitrogen radical treatment on the liner layer to provide an incubation delay for a subsequent deposition process, and subsequently filling the feature with a tungsten bulk fill via a chemical vapor deposition (CVD) process.

[0006] In some embodiments, a computer-readable medium including one or more processors that, when executed, perform a method for filling a feature of a substrate, including depositing a tungsten nitride seed layer in the feature via a physical vapor deposition (PVD) process, depositing a tungsten liner layer on the tungsten nitride seed layer in the feature via the PVD process, and subsequently filling the feature with a tungsten bulk fill via a chemical vapor deposition (CVD) process.

[0007] Other and further embodiments of the present disclosure are described below.

[0008] Embodiments of the present disclosure, briefly summarized above and discussed in more detail below, can be understood by reference to the exemplary embodiments of the present disclosure as illustrated in the accompanying drawings. However, the accompanying drawings depict only typical embodiments of the present disclosure and therefore should not be considered limiting in scope, as the present disclosure may admit of other equally effective embodiments. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a flow diagram of a method for filling features on a substrate in accordance with at least some embodiments of the present disclosure. [Figure 2A] 1 is a cross-sectional view of a high aspect ratio structure after a seed layer has been deposited via a physical vapor deposition (PVD) process, according to at least some embodiments of the present disclosure. [Figure 2B] 1 is a cross-sectional view of a high aspect ratio structure after a liner layer has been deposited on a seed layer via a PVD process, in accordance with at least some embodiments of the present disclosure. [Figure 2C] 1 is a cross-sectional view of a high aspect ratio structure after depositing a bulk fill onto a liner layer via a chemical vapor deposition (CVD) process, according to at least some embodiments of the present disclosure. [Figure 3A] 1 is a cross-sectional view of a high aspect ratio structure after a seed layer has been deposited via a physical vapor deposition (PVD) process, according to at least some embodiments of the present disclosure. [Figure 3B] 1 is a cross-sectional view of a high aspect ratio structure after a liner layer has been deposited on a seed layer via a PVD process, in accordance with at least some embodiments of the present disclosure. [Figure 3C] FIG. 2 is a cross-sectional view of a high aspect ratio structure after a nucleation layer has been deposited on a liner layer via an atomic layer deposition (ALD) process, according to at least some embodiments of the present disclosure. [Figure 3D] 1A-1C are cross-sectional views of high aspect ratio structures after bulk fill has been deposited onto a nucleation layer via a CVD process, in accordance with at least some embodiments of the present disclosure. [Figure 4] FIG. 1 illustrates a multi-chamber processing tool suitable for performing methods for processing substrates according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] For ease of understanding, the same reference numerals have been used, where possible, to designate identical elements common to the figures. The figures are not drawn to scale and may be simplified for clarity. Elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0011] The methods and apparatus described herein provide low-resistance and low-stress tungsten gap fill with enhanced interfacial adhesion. The embodiments provided herein can be used to fill structures such as vias, trenches, and the like. The critical dimension (CD) of the trench or via can be in the range of about 5 nm to about 1000 nm, and the aspect ratio (AR) of the feature can be between about 1:1 and about 15:1.

[0012] Tungsten is widely used as a metal interconnect in logic and memory devices due to its inherent stability and low resistivity. However, with technological advances, there is an increasing need for lower-resistivity and lower-stress metal fill solutions with adequate gap-filling properties that can meet the requirements of, for example, NAND flash memory structures. Conventional CVD tungsten approaches (TiN + CVD tungsten) have high tensile stress. The inventors have found that the stress of CVD tungsten can be reduced by modifying the deposition conditions, but this significantly impacts throughput and gap-filling performance. The inventors have also found that the resistance of CVD tungsten can be reduced by modifying the deposition conditions (temperature, tungsten atomic layer deposition (ALD) nucleation chemistry, etc.), but this results in limited resistive response and reduced performance (primarily throughput).

[0013] The inventors subsequently discovered an integrated approach that allows for control of tensile stress and lower resistivity of tungsten films with high throughput and improved adhesion. For example, compared to a conventional CVD tungsten approach (TiN + CVD tungsten), the integrated approach reduces the resistivity of CVD tungsten by more than 60 percent while maintaining similar throughput. The integrated approach generally involves depositing a tungsten nitride (WN) seed layer via PVD before depositing a tungsten liner layer via PVD. The seed layer advantageously adheres better to the substrate than depositing a tungsten liner layer directly on the substrate. The seed layer also promotes adhesion of the liner layer and subsequent layers to the substrate. The enhanced adhesion reduces or prevents gap-fill delamination or unplugging issues during subsequent processes, such as planarization processes such as chemical-mechanical planarization (CMP). The inventors also observed that lower resistivity is maintained even with the WN seed layer. The inventors have also observed that the tensile stress of the gap fill can be advantageously tuned to a desired stress value by controlling the concentration of nitrogen relative to tungsten in the seed layer.

[0014] FIG. 1 illustrates a flow diagram of a method 100 for filling a feature in a substrate according to at least some embodiments of the present disclosure. At 102, the method 100 includes depositing a tungsten nitride seed layer 210 within a feature 204 of a substrate 200 via a physical vapor deposition (PVD) process, as shown in FIGS. 2A and 3A. The substrate 200 may be made of a dielectric material or may consist essentially of silicon oxide. The PVD process is performed in a highly ionized process using an ambient noble gas, such as argon, krypton, or the like. The temperature during the seed layer deposition process can be from about room temperature (about 20 degrees Celsius) to about 350 degrees Celsius. While FIGS. 2A-3D illustrate the substrate 200 with one feature 204, the substrate 200 can include multiple features 204. In some embodiments, the width of each of the features 204 is between about 5 nanometers and about 65 nanometers.

[0015] The seed layer 210 will have adequate step coverage on the substrate 200. In some embodiments, the tungsten nitride seed layer 210 is between about 10 angstroms and about 60 angstroms thick. The thickness of the seed layer 210 is advantageously chosen to enhance adhesion while minimizing an increase in resistance. The concentration of nitrogen in the seed layer 210 can be tailored to provide a desired stress level, taking into account the CD of the feature 204, subsequent layers deposited on the seed layer 210, and the type of processing the substrate 200 will undergo after deposition of the seed layer 210. In some embodiments, the seed layer 210 has a nitrogen concentration between about 3 atomic percent and about 45 atomic percent. In some embodiments, the seed layer 210 has a nitrogen concentration between about 18 atomic percent and about 35 atomic percent.

[0016] At 104, method 100 includes depositing a tungsten liner layer 220 on the tungsten nitride seed layer 210 in feature 204 via a PVD process, as shown in FIGS. 2B and 3B. In some embodiments, the PVD process is a highly ionized process using an ambient noble gas, such as argon, krypton, or the like. In some embodiments, liner layer 220 is about 30 Angstroms to about 300 Angstroms thick. In some embodiments, liner layer 220 is deposited at a temperature of about 20 degrees Celsius to about 350 degrees Celsius. In some embodiments, liner layer 220 is thicker than seed layer 210.

[0017] At 106, the method 100 optionally includes depositing a nucleation layer 310 via an atomic layer deposition (ALD) process after depositing the tungsten liner layer 220, as shown in FIG. 3C. In some embodiments, the nucleation layer 310 is deposited via an atomic layer deposition (ALD) process after depositing the tungsten liner layer using a mixture of tungsten hexafluoride (WF) and silane (SiH) or diborane (BH). The nucleation layer 310 advantageously reduces void formation in a subsequent fill process. In some embodiments, the nucleation layer has a thickness of about 10 angstroms to about 60 angstroms.

[0018] At 108, the method 100 continues with filling the feature with a tungsten bulk fill 230 via a chemical vapor deposition (CVD) process, as shown in Figures 2C and 3D. In some embodiments, the tungsten bulk fill 230 is deposited on the liner layer 220. In some embodiments, the tungsten bulk fill 230 is deposited on the nucleation layer 310. In some embodiments, the CVD process is performed using tungsten hexafluoride (WF) and hydrogen (H) as precursors to fill the feature 204 with boron-free tungsten. The CVD process can be performed at a temperature of about 300 degrees Celsius to about 500 degrees Celsius and a pressure of about 5 Torr to about 300 Torr.

[0019] In some embodiments, the method 100 includes performing a nitrogen radical treatment prior to filling the feature 204 with the tungsten bulk fill 230 to provide an incubation delay for the tungsten bulk fill 230. In the nitrogen radical treatment, or nitridation process, nitrogen radicals on or near the top surface 224 of the liner layer 220 cause the subsequent deposition of the tungsten bulk fill 230 to have an incubation delay on or near the top surface 224 but normal growth near the bottom 226 and sidewalls 228 of the feature 204. The nitridation process results in bottom-up or superconformal deposition behavior of the tungsten bulk fill deposition, reducing void formation within the feature 204. In some embodiments, the nitridation process includes flowing nitrogen at a rate of about 1 sccm to about 20 sccm for a duration of about 2 seconds to about 20 seconds. A local or remote plasma source can be used.

[0020] In some embodiments, the nucleation layer 310 is applied before the nitrogen radical treatment to enhance the incubation delay on the top surface 224. The internal stress level of the subsequently deposited tungsten remains the same, but the resistance of the subsequently deposited bulk fill tungsten can increase by about 10% compared to a process without the nucleation layer 310. In some embodiments, a planarization process can be performed on the substrate 200 after filling the feature 204 with the tungsten bulk fill 230.

[0021] 4 illustrates a multi-chamber processing tool 400 suitable for performing methods for processing substrates according to some embodiments of the present disclosure. The methods described herein may also be practiced using other multi-chamber processing tools coupled with suitable process chambers or with other suitable process chambers. For example, in some embodiments, the methods of the present invention discussed above may be advantageously performed in a multi-chamber processing tool with limited or no vacuum breaks between processes. For example, reduced vacuum breaks may limit or prevent contamination of substrates being processed in the multi-chamber processing tool. Other process chambers, including those available from other manufacturers, may also be suitably used in conjunction with the teachings provided herein.

[0022] The multi-chamber processing tool 400 includes a vacuum-tight processing platform 401, a factory interface 404, and a system controller 402. The processing platform 401 includes multiple processing chambers, such as 414A, 414B, 414C, and 414D, that are operably coupled to a transfer chamber 403 that is under vacuum. The factory interface 404 is operably coupled to the transfer chamber 103 by one or more load lock chambers, such as 406A and 406B shown in FIG.

[0023] In some embodiments, the factory interface 404 includes at least one docking station 407 and at least one factory interface robot 438 to facilitate substrate transfer. The at least one docking station 407 is configured to receive one or more front-opening unified pods (FOUPs). Four FOUPs, identified as 405A, 405B, 405C, and 405D, are shown in FIG. 4. The at least one factory interface robot 438 is configured to transfer substrates from the factory interface 404 through load lock chambers 406A and 406B to the processing platform 401. Each of the load lock chambers 406A and 406B has a first port coupled to the factory interface 404 and a second port coupled to the transfer chamber 403. In some embodiments, the load lock chambers 406A and 406B are coupled to one or more service chambers (e.g., service chambers 416A and 416B). The load lock chambers 406A and 406B are coupled to a pressure control system (not shown) that pumps down and vents the load lock chambers 406A and 406B to facilitate the passage of substrates between the vacuum environment of the transfer chamber 403 and the substantially ambient (e.g., atmospheric) environment of the factory interface 404.

[0024] A vacuum robot 442 is disposed in the transfer chamber 403. The vacuum robot 442 can transfer substrates 421 between the load lock chambers 406A and 406B, the service chambers 416A and 416B, and the processing chambers 414A, 414B, 414C, and 414D. In some embodiments, the vacuum robot 442 includes one or more upper arms that are rotatable about respective shoulder axes. In some embodiments, the one or more upper arms are coupled to respective forearm and wrist members such that the vacuum robot 442 can extend into and retract from processing chambers coupled to the transfer chamber 403.

[0025] Processing chambers 414A, 414B, 414C, and 414D are coupled to transfer chamber 403 and can be configured to perform methods described herein. Each of processing chambers 414A, 414B, 414C, and 414D can include a chemical vapor deposition (CVD) chamber, an atomic layer deposition (ALD) chamber, a physical vapor deposition (PVD) chamber, a plasma-enhanced atomic layer deposition (PEALD) chamber, a pre-clean / annealing chamber, etc. For example, processing chamber 414A is a PVD chamber. In some embodiments, processing chamber 414B is a CVD process chamber.

[0026] Embodiments according to the present disclosure may be implemented in hardware, firmware, software, or any combination thereof. Embodiments may also be implemented as instructions stored using one or more computer-readable media, which may be read and executed by one or more processors. A computer-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing platform, or a "virtual machine" running on one or more computing platforms). For example, a computer-readable medium may include any suitable form of volatile or non-volatile memory. In some embodiments, a computer-readable medium may include a non-transitory computer-readable medium.

[0027] For example, the system controller 402 controls the operation of the multi-chamber processing tool 400 using direct control of the service chambers 416A and 416B and the process chambers 414A, 414B, 414C, and 414D, or alternatively, by controlling computers (or controllers) associated with the service chambers 416A and 416B and the process chambers 414A, 414B, 414C, and 414D. The system controller 402 generally includes a central processing unit (CPU) 430, memory 434, and support circuits 432. The CPU 430 may be one of any form of general-purpose computer processor that can be used in an industrial environment. The support circuits 432 are coupled to the CPU 430 in a conventional manner and may include cache, clock circuits, input / output subsystems, power supplies, etc. Software routines, such as the processing methods described above, may be stored in the memory 434 and, when executed by the CPU 430, convert the CPU 430 into the system controller 402. The software routines may also be stored and / or executed by a second controller (not shown) located remotely from the multi-chamber processing tool 400 .

[0028] During operation, the system controller 402 enables data collection and feedback from each chamber and system and provides instructions to system components to optimize performance of the multi-chamber processing tool 400. For example, the memory 434 can be a non-transitory computer-readable storage medium having instructions that, when executed by the CPU 430 (or the system controller 402), perform the methods described herein.

[0029] As used herein, the terms "about" or "approximately" can refer to any suitable range, for example, within 15%. While the foregoing relates to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof.

Claims

1. 1. A method of filling features in a substrate, comprising: depositing a seed layer of tungsten nitride within the feature via a physical vapor deposition (PVD) process; depositing a tungsten liner layer on the tungsten nitride seed layer in the feature via a PVD process; subsequently filling the feature with a tungsten bulk fill via a chemical vapor deposition (CVD) process; A method comprising:

2. The method of claim 1, wherein the tungsten nitride seed layer is between about 10 Angstroms and about 60 Angstroms thick.

3. The method of claim 1, wherein the tungsten liner layer is about 30 Angstroms to 300 Angstroms thick.

4. 10. The method of claim 1, wherein the tungsten nitride seed layer has a nitrogen concentration of about 18 atomic percent to about 35 atomic percent.

5. The method of claim 1 , further comprising performing a planarization process on the substrate after filling the feature with the tungsten bulk fill.

6. The method of claim 1 , wherein the substrate consists essentially of silicon oxide.

7. The method of any of claims 1 to 6, further comprising performing a nitrogen radical treatment prior to filling the feature with the tungsten bulk fill to provide an incubation delay for the CVD process.

8. 8. The method of claim 7, wherein the nitrogen radical treatment comprises flowing nitrogen at a rate of about 1 sccm to about 20 sccm for a period of about 2 seconds to about 20 seconds.

9. After depositing the tungsten liner layer, tungsten hexafluoride (WF) is deposited via an atomic layer deposition (ALD) process. 6 ) and silane (SiH4) or diborane (B 2 H 6 The method of any of claims 1 to 6, further comprising depositing a nucleation layer using a mixture of

10. The method of claim 9, wherein the nucleation layer has a thickness of about 10 Angstroms to about 60 Angstroms.

11. The method of any preceding claim, wherein the feature width is between about 5 nanometers and about 65 nanometers.

12. The method of any of claims 1 to 6, wherein depositing the tungsten liner layer is carried out at a temperature of about 20 degrees Celsius to about 350 degrees Celsius.

13. The method of any of claims 1 to 6, wherein the liner layer is thicker than the seed layer.

14. The tungsten bulk fill is tungsten hexafluoride (WF 6 ) and hydrogen (H 2 7. The method according to claim 1, wherein the method is carried out using as a precursor:

15. The method of any preceding claim, wherein the aspect ratio of the features is between about 1:1 and about 15:

1.

16. A non-transitory computer readable medium comprising one or more processors that, when executed, perform the method of any of claims 1-6.

17. 17. The computer-readable medium of claim 16, further comprising performing a nitrogen radical treatment prior to filling the feature with the tungsten bulk fill to provide an incubation delay for the CVD process.

18. After depositing the tungsten liner layer, tungsten hexafluoride (WF) is deposited via an atomic layer deposition (ALD) process. 6 ) and silane (SiH4) or diborane (B 2 H 6 17. The computer-readable medium of claim 16, further comprising depositing a nucleation layer using a mixture of

19. The tungsten bulk fill is tungsten hexafluoride (WF 6 ) and hydrogen (H 2 17. The computer-readable medium of claim 16, wherein the method is performed using a precursor.

20. The computer-readable medium of claim 16 , wherein the liner layer is thicker than the seed layer.

Images