Self-field suppressed CVD W-fill on PVD tungsten (W) liner

Abstract

An embodiment of a method and related apparatus for filling a feature in a substrate is provided herein.In some embodiments, a method of depositing tungsten in a feature of a substrate includes depositing a seed layer essentially made of tungsten in the feature by a physical vapor deposition (PVD) process, and depositing a bulk layer essentially made of tungsten in the feature by a chemical vapor deposition (CVD) process to fill the feature such that the deposition of the bulk layer is selective to the inside of the feature compared to the field region of the substrate, the CVD process is carried out by flowing hydrogen gas (H2) at a first flow rate and a tungsten precursor at a second flow rate, the first flow rate being less than the second flow rate.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to the processing of substrates.

Background Art

[0002] Integrated circuits are formed by a process that creates a complexly patterned layer of material on a substrate surface. Tungsten is used in the semiconductor industry as a low-resistance conductor with minimal electromigration. Tungsten may be used to fill features as contacts for transistors and also in the formation of interlayer vias in integrated devices. Tungsten may also be used for interconnects in logic and memory devices due to its stability and low resistance. However, conventional tungsten metal gap fill processes may be prone to void formation during gap fill due to early pinch-off in overhangs.

[0003] Therefore, the inventors have provided an improved process to facilitate void-free tungsten gap fill.

Summary of the Invention

[0004] Embodiments of methods and related apparatuses for filling features on a substrate are provided herein. In some embodiments, a method of depositing tungsten on a feature of a substrate includes depositing a seed layer consisting essentially of tungsten on the feature by a physical vapor deposition (PVD) process, and depositing a bulk layer consisting essentially of tungsten on the feature by a chemical vapor deposition (CVD) process to fill the feature such that the deposition of the bulk layer is selective to the interior of the feature compared to the field region of the substrate, the CVD process being performed by flowing hydrogen gas (H2) at a first flow rate and a tungsten precursor at a second flow rate, the first flow rate being less than the second flow rate, and filling.

[0005] In some embodiments, a method for depositing tungsten onto a feature on a substrate includes depositing a seed layer essentially made of tungsten onto the feature by a physical vapor deposition (PVD) process, and filling the feature by depositing a bulk layer essentially made of tungsten onto the feature by a chemical vapor deposition (CVD) process, wherein substantially all of the bulk layer deposition is within the feature relative to the field area of ​​the substrate, and the CVD process is carried out by flowing hydrogen gas (H2) at a first flow rate of about 10 to about 500 sccm, flowing a tungsten precursor at a second flow rate of about 100 to about 1000 sccm, the first flow rate being smaller than the second flow rate, and flowing argon gas at a third flow rate of about 3000 to about 7000 sccm.

[0006] In some embodiments, a computer-readable medium storing instructions for a method of depositing tungsten onto features of a substrate when executed, the method comprising: depositing a seed layer essentially made of tungsten onto the features by a physical vapor deposition (PVD) process; and filling the features by depositing a bulk layer essentially made of tungsten onto the features by a chemical vapor deposition (CVD) process such that the deposition of the bulk layer is selective to the interior of the features compared to a field area of ​​the substrate, wherein the CVD process is carried out by flowing hydrogen gas (H2) at a first flow rate and a tungsten precursor at a second flow rate, the first flow rate being less than the second flow rate, the computer-readable medium.

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

[0008] The embodiments of this disclosure, briefly summarized above and discussed in more detail below, can be understood by referring to exemplary embodiments of this disclosure shown in the accompanying drawings. However, the accompanying drawings only illustrate typical embodiments of this disclosure and should not be considered limiting in scope, as this disclosure may allow for other equally effective embodiments. [Brief explanation of the drawing]

[0009] [Figure 1] A flowchart of a method for filling features on a substrate, according to at least some embodiments of this disclosure, is shown. [Figure 2] The following is a cross-sectional view of a portion of a feature-containing substrate according to at least some embodiments of this disclosure. [Figure 3] The image shows a cross-sectional view of a portion of a substrate having a seed layer deposited on features by a physical vapor deposition (PVD) process, according to at least some embodiments of the present disclosure. [Figure 4] The image shows a cross-sectional view of a portion of a substrate after a bulk filler has been deposited on a seed layer by a chemical vapor deposition (CVD) process, according to at least some embodiments of the present disclosure. [Figure 5] The present disclosure shows a multi-chamber processing tool according to at least some embodiments. [Modes for carrying out the invention]

[0010] For ease of understanding, the same reference numerals are used to indicate the same elements common to each figure where possible. Each figure is not drawn to scale and may be simplified for clarity. Elements and features of one embodiment may be incorporated into other embodiments without further description.

[0011] The methods and apparatus described herein provide void-free or substantially void-free tungsten gap fills in a substrate. Embodiments provided herein may be used to fill features formed in a substrate, such as vias and trenches. Tungsten is widely used as a metal interconnect in logic and memory devices due to its inherent stability and low resistance. However, with technological advancements and the miniaturization of feature sizes, there is an increasing need for metal fill solutions with void-free or substantially void-free gap fills. The critical dimension (CD) of a trench or via may be in the range of approximately 1 nm to approximately 1000 nm in terms of the feature aspect ratio (AR) between approximately 1:1 and approximately 80:1.

[0012] The methods provided herein concern a superconformal chemical vapor deposition (CVD) process for bulk filling at a deposition rate that increases with depth from the front opening of a feature in the substrate (or decreases as it approaches the front opening). Thus, continuous CVD deposition on a feature fills the feature without leaving voids or pockets of low-density material, or substantially without them. Superconformal CVD deposition typically involves two or more co-reactants, the partial pressures of which are selected such that the surface coverage of the faster-diffusing co-reactants is relatively small and therefore rate-limiting near the front opening of the feature. The pressure of the slower-diffusing co-reactants decreases more rapidly with depth than the pressure of the faster-diffusing co-reactants, thereby increasing the surface coverage of the faster-diffusing co-reactants and thus increasing their growth rate; therefore, the deposition rate increases towards the depth of the feature. Thus, in superconformal CVD deposition, deposition is selective towards the interior of the feature compared to the field region of the substrate, resulting in self-suppressed CVD deposition in the field and overhang regions.

[0013] Figure 1 shows a flowchart of a method 100 for filling features in a substrate (e.g., substrate 202) according to at least some embodiments of the present disclosure. Figure 2 shows a cross-sectional view of a portion of the substrate 202 having a feature 204 according to at least some embodiments of the present disclosure. The feature 204 may be a via, trench, etc., formed in the substrate 202. The feature 204 may extend into the substrate 202 from the field area 210 or the top surface of the substrate 202. The feature 204 may include a bottom surface 212 and a side wall 206 extending from the bottom surface 212 to the field area 210.

[0014] Method 100, in 102, includes depositing a seed layer (e.g., seed layer 302) or liner made of or essentially tungsten onto a feature (e.g., feature 204) by a physical vapor deposition (PVD) process, as shown in Figure 3. For example, the seed layer or liner may be essentially pure tungsten. In some embodiments, the seed layer 302 is nitrogen-free. In some embodiments, essentially made of tungsten means that it is 95 percent or more tungsten. In some embodiments, the PVD-deposited seed layer contains approximately 100% tungsten. In some embodiments, the PVD process is carried out at a temperature of about 200 to about 500 degrees Celsius. In some embodiments, the PVD process is carried out at a chamber pressure of about 0.1 to about 10 mTorr. The seed layer 302 generally covers the bottom surface 212 and the side walls 206 of feature 204. The seed layer 302 may be deposited on the field region 210 (e.g., field layer 310) of the substrate 202, forming an overhang region 312 near the front opening 316 of the feature 204.

[0015] The method, in 104, includes filling the feature by depositing a bulk layer (e.g., bulk layer 410) consisting of or essentially tungsten by a chemical vapor deposition (CVD) process onto the feature, as shown in Figure 4. In some embodiments, essentially consisting of tungsten means that the tungsten content is 95 percent or more. In some embodiments, the tungsten concentration in the bulk layer 410 is lower than the tungsten concentration in the seed layer 302. For example, the seed layer 302 may have a tungsten concentration of 100% or approximately 100%, while the bulk layer 410 may have a tungsten concentration of 95 percent or more. The deposition of the bulk layer 410 is selective to the interior of the feature 204 compared to the field region 210 of the substrate 202, resulting in self-suppressed CVD deposition in the field region 210. Self-suppressed CVD deposition minimizes or substantially eliminates the deposition of the bulk layer 410 on the seed layer 302 in the field region 210 or overhang region 312. Therefore, feature 204 can be filled favorably without pinch-off, avoiding or substantially avoiding voids or low-density bulk filling.

[0016] The CVD process is carried out by flowing hydrogen gas (H2) at a first flow rate and a tungsten precursor at a second flow rate into the CVD chamber. The tungsten precursor may be a tungsten halide. For example, in some embodiments, the tungsten precursor may have the chemical formula WMx, where M is a halogen, such as a fluoride or chloride. In some embodiments, x may be 5 or 6. In some embodiments, the tungsten precursor is tungsten hexafluoride or tungsten pentachloride. In some embodiments, the partial pressure of the hydrogen gas (H2) is about 0.2 Torr to about 1 Torr. In some embodiments, the partial pressure of the tungsten precursor is about 0.2 Torr to about 1 Torr. In some embodiments, the CVD process is carried out at a temperature of about 200 to about 500 degrees Celsius. In some embodiments, the CVD process is carried out at a chamber pressure of about 1 to about 300 Torr.

[0017] The first flow rate is generally smaller than the second flow rate. In some embodiments, the first flow rate of hydrogen gas (H2) is about 10 to about 500 sccm. In some embodiments, the first flow rate is about 10 to about 200 sccm. In some embodiments, the first flow rate is about 25 to about 75 sccm. In some embodiments, the second flow rate of the tungsten precursor is about 100 sccm to about 1000 sccm. In some embodiments, the second flow rate is about 300 to about 800 sccm. In some embodiments, the second flow rate is about 400 to about 600 sccm. In some embodiments, the second flow rate is about 8 to about 12 times larger than the first flow rate.

[0018] In some embodiments, method 100 includes flowing an inert gas through the CVD process at a third flow rate of about 3000 sccm to about 7000 sccm. The inert gas may act as a carrier gas to help deliver the tungsten precursor into the CVD chamber and to fine-tune the CVD chamber pressure. In some embodiments, the inert gas is argon. In some embodiments, the third flow rate is about 4 to about 20 times greater than the second flow rate. In some embodiments, the third flow rate is about 15 to about 600 times greater than the first flow rate.

[0019] In some embodiments, it is advantageous that the CVD process is performed after the PVD process without an intermediate passivation process. In some embodiments, it is advantageous that the CVD process is performed after the PVD process without etching the substrate overhang region 312.

[0020] In some embodiments, the PVD process 102 and the CVD process 104 are carried out in a common multi-chamber processing tool. For example, Figure 5 shows a multi-chamber processing tool 500 according to at least some embodiments of the present disclosure. The multi-chamber processing tool 500 may be suitable for carrying out the methods of the present disclosure. The methods described herein may be carried out using other multi-chamber processing tools coupled with suitable process chambers, or in other suitable process chambers. For example, in some embodiments, the methods of the present invention discussed above may be advantageous to be carried out in a multi-chamber processing tool such that vacuum breaks between processing steps are limited or eliminated. For example, reduced vacuum breaks can limit or prevent contamination of any substrate being processed in the multi-chamber processing tool.

[0021] A multi-chamber processing tool 500 typically includes a vacuum-sealed processing platform 501, a factory interface (FI) 504, and a system controller 502. The processing platform 501 includes multiple processing chambers, e.g., 514A, 514B, 514C, and 514D, which are operably coupled to a transfer chamber 503 under vacuum. The factory interface 504 is selectively operably coupled to the transfer chamber 503 by one or more load-lock chambers, e.g., 506A and 506B shown in Figure 5.

[0022] In some embodiments, the factory interface 504 includes at least one docking station 507 and at least one factory interface robot 538 for facilitating the transfer of substrates 521, such as substrate 202. The at least one docking station 507 is configured to receive one or more front-opening unified pods (FOUPs). Four FOUPs, identified as 505A, 505B, 505C, and 505D, are shown in FIG. 5. The at least one factory interface robot 538 is configured to transfer substrates 521 from the factory interface 504 to the processing platform 501 through load lock chambers 506A, 506B. Each of the load lock chambers 506A and 506B has a first port coupled to the factory interface 504 and a second port coupled to the transfer chamber 503. The load lock chambers 506A and 506B are coupled to a pressure control system (not shown) that pumps down and evacuates the load lock chambers 506A and 506B to facilitate passage of substrates between the vacuum environment of the transfer chamber 503 and the substantially ambient (e.g., atmospheric) environment of the factory interface 504.

[0023] A vacuum robot 542 is disposed in the transfer chamber 503. The vacuum robot 542 is capable of transferring substrates 521 between the load lock chambers 506A and 506B and the processing chambers 514A, 514B, 514C, and 514D. In some embodiments, the vacuum robot 542 includes one or more upper arms 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 542 can extend and retract with respect to any of the processing chambers to which the transfer chamber 503 is coupled.

[0024] The processing chambers 514A, 514B, 514C, and 514D are coupled to the transfer chamber 503. Each of the processing chambers 514A, 514B, 514C, and 514D may 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, an etch chamber (i.e., a dry etch chamber), a pre-cleaning / annealing chamber, and the like. In some embodiments, the processing chambers 514A, 514B, 514C, and 514D include at least one PVD chamber configured to deposit the seed layer 302 and at least one CVD chamber configured to deposit the bulk layer 410.

[0025] The system controller 502 controls the operation of the multi-chamber processing tool 500 by using direct control of the process chambers 514A, 514B, 514C, and 514D or alternatively by controlling a computer (or controller) associated with the process chambers 514A, 514B, 514C, and 514D. The system controller 502 generally includes a central processing unit (CPU) 530, a memory 534, and support circuitry 532. The CPU 530 may be one of any form of general-purpose computer processor used in an industrial environment. The support circuitry 532 is conventionally coupled to the CPU 530 and may include a cache, a clock circuit, an input / output subsystem, a power supply, and the like. Software routines such as the processing methods described above may be stored in the memory 534 and may convert the CPU 530 into the system controller 502 when executed by the CPU 530. The software routines may be stored and / or executed by a second controller (not shown) located away from the multi-chamber processing tool 500.

[0026] During operation, the system controller 502 enables the collection and feedback of data from each chamber and system to optimize the performance of the multi-chamber processing tool 500, and provides instructions to the system components. For example, memory 534 may be a non-temporary computer-readable storage medium having instructions that perform the methods described herein when executed by the CPU 530 (or system controller 502).

[0027] The terms “about” or “approximately” as used herein may be within any appropriate range, for example, up to 10%. While the foregoing applies to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from its basic scope.

Claims

1. A method for depositing tungsten onto features on a substrate, A seed layer essentially consisting of tungsten is deposited on the feature by a physical vapor deposition (PVD) process, A bulk layer essentially consisting of tungsten is deposited on the feature by a chemical vapor deposition (CVD) process to fill the feature such that the deposition of the bulk layer is selective to the interior of the feature compared to the field region of the substrate, wherein the CVD process uses hydrogen gas (H 2 This is done by flowing ) at a first flow rate and the tungsten precursor at a second flow rate, wherein the first flow rate is smaller than the second flow rate, and the filling is performed A method that includes this.

2. The method according to claim 1, wherein the second flow rate is about 8 to about 12 times greater than the first flow rate.

3. The method according to claim 1, wherein the first flow rate is about 10 sccm to about 200 sccm, and the second flow rate is about 300 to about 800 sccm.

4. The method according to claim 1, further comprising flowing an inert gas through the CVD process at a third flow rate of about 3000 to about 7000 sccm.

5. The method according to claim 4, wherein the third flow rate is about 4 to about 20 times greater than the second flow rate.

6. The method according to any one of claims 1 to 5, wherein the tungsten precursor is tungsten halide.

7. The method according to any one of claims 1 to 5, wherein the seed layer does not contain nitrogen.

8. The hydrogen gas (H 2 The method according to any one of claims 1 to 5, wherein the partial pressure of is about 0.2 Torr to about 1 Torr, and the tungsten precursor has a partial pressure of about 0.2 Torr to about 1 Torr.

9. The method according to any one of claims 1 to 5, wherein the PVD process and the CVD process are carried out at a temperature of about 200 to about 500 degrees Celsius.

10. The method according to any one of claims 1 to 5, wherein the PVD process and the CVD process are performed in a common multi-chamber processing tool.

11. The method according to any one of claims 1 to 5, wherein the CVD process is performed after the PVD process without an intermediate passivation process.

12. The method according to any one of claims 1 to 5, wherein the CVD process is performed after the PVD process without etching the overhangs of the substrate.

13. The method according to any one of claims 1 to 5, wherein the PVD process is carried out at a chamber pressure of about 0.1 m to about 10 m Torr, and the CVD process is carried out at a chamber pressure of about 1 to about 300 Torr.

14. The first flow rate is approximately 10 to approximately 500 sccm. The second flow rate is approximately 100 to approximately 1000 sccm. The CVD process further includes flowing argon gas at a third flow rate of about 3000 to about 7000 sccm. The method according to claim 1.

15. The method according to claim 14, wherein the first flow rate is about 25 to about 75 sccm, and the second flow rate is about 400 to about 600 sccm.

16. A computer-readable medium storing an instruction that, when executed, causes the computer to perform the method described in any one of claims 1 to 5.

17. The computer-readable medium according to claim 16, wherein the PVD process and the CVD process are carried out at a temperature of about 200 to about 500 degrees Celsius.

18. The hydrogen gas (H 2 The computer-readable medium according to claim 16, wherein the partial pressure of the tungsten precursor is about 0.2 Torr to about 1 Torr, and the tungsten precursor has a partial pressure of about 0.2 Torr to about 1 Torr.

19. The computer-readable medium according to claim 16, wherein the seed layer is nitrogen-free.

20. The computer-readable medium according to claim 16, wherein the PVD process and the CVD process are carried out at a temperature of about 200 to about 500 degrees Celsius.

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