WO2023277920A1

WO2023277920A1 - System and method for delivering precursor to a process chamber

Info

Publication number: WO2023277920A1
Application number: PCT/US2021/040118
Authority: WO
Inventors: Guangwei Sun; Jeffrey A. Kho; Lai ZHAO; Zhelin SUN; Mehran Behdjat; Ming Xu; Kenric T. Choi; Kwang Soo Huh
Original assignee: Applied Materials, Inc.
Priority date: 2021-07-01
Filing date: 2021-07-01
Publication date: 2023-01-05
Also published as: KR20240024266A; CN117730167A; TW202315961A; JP2024524401A

Abstract

The present disclosure is directed to a precursor delivery system is provided having a vaporizer and a reservoir. The reservoir includes an upstream end in fluid communication with the vaporizer. A reservoir valve is in fluid communication with a downstream end of the reservoir and a final valve is disposed downstream of the reservoir valve. A buffer zone is defined between the reservoir valve and the final valve. A first gas inlet is coupled to the buffer zone. The first gas inlet is coupled to a buffer valve.

Description

SYSTEM AND METHOD FOR DELIVERING PRECURSOR TO A PROCESS

CHAMBER

BACKGROUND

Field

[0001] Embodiments of the present disclosure generally relate to methods of delivering process gases for processing substrates.

Description of the Related Art

[0002] Thin film technology has moved toward thinner deposition layers, better uniformity over increasingly larger area substrates, such as substrate sizes for flat panel technology. Thin film technology has also moved towards larger production yields and higher productivity. Various processes are used for depositing thin films over substrates, including sputter or physical vapor deposition (PVD), chemical vapor deposition (CVD), and atomic layer deposition (ALD) methods.

[0003] Forming and growing thin films by ALD includes formation of a saturated monolayer of reactive precursor molecules by chemisorption at the deposition surface of the substrate. In ALD, reactive gaseous precursors are alternately pulsed or injected into a process chamber. Each pulse or injection of a reactive precursor is separated by an inert gas purge. The precursor injections react on the surface of the substrate to form a new atomic layer with each full cycle of the process. Delivering precursors to the process chamber uses flow timing control. In order to maintain good flow timing control, precursor is released from a vaporizer continuously to maintain a steady state condition. Continuous flow of precursor vapor from the vaporizer is exhausted when flow into the chamber is not required according to the process recipe. Although diverting or exhausting the precursor vapor to a chamber foreline results in good process uniformity, the amount of precursor vapor used is high. Additionally, pulsing the precursor from the vaporizer or continuously releasing the precursor vapor from the vaporizer results in pressure drops along the conduit to the process chamber. The pressure drop presents risks of condensation. [0004] Thus, there is a need in the art for a precursor vapor delivery system that reduces precursor vapor use during processing, manages risk of condensation, while maintaining flow control to the process chamber.

SUMMARY

[0005] In some embodiments, a precursor delivery system is provided having a vaporizer and a reservoir. The reservoir includes an upstream end in fluid communication with the vaporizer. A reservoir valve is in fluid communication with a downstream end of the reservoir and a final valve is disposed downstream of the reservoir valve. A buffer zone is defined between the reservoir valve and the final valve. A first gas inlet is coupled to the buffer zone. The first gas inlet is coupled to a buffer valve.

[0006] In some embodiments, a method of supplying precursors to a process volume of a process chamber is provided. The method includes supplying a precursor to a reservoir until the reservoir reaches a first pressure. The precursor is supplied from the reservoir to a buffer zone through a reservoir valve situated in an open state. The buffer zone is defined between the reservoir valve and a final valve. The precursor is supplied from the buffer zone to the process volume through the final valve situated in an open state. Each of the reservoir valve and the final valve is switched to a closed state. A buffer gas is supplied to the buffer zone through a buffer valve situated in an open state. The buffer gas is diverted to a foreline through a divert valve situated in an open state. The divert valve is switched to a closed state and the reservoir valve is switched to a closed state.

[0007] In some embodiments, a substrate processing system is provided having a process chamber with a process volume for processing a substrate. The process chamber includes a gas inlet and a gas distribution assembly fluidly coupled to the gas inlet. The gas distribution assembly includes a vaporizer, a reservoir with an upstream end in fluid communication with the vaporizer, and a reservoir valve in fluid communication with a downstream end of the reservoir. A final valve is disposed downstream of the reservoir valve. A buffer zone is defined between the reservoir valve and the final valve, and a buffer gas inlet is coupled to the buffer zone. The buffer gas inlet is coupled to a buffer valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, and may admit to other equally effective embodiments.

[0009] FIG. 1 depicts a schematic representation of a precursor delivery system in accordance with embodiments of the present disclosure;

[0010] FIG. 2 depicts a flow diagram of a method for delivering precursors in accordance with embodiments of the present disclosure;

[0011] FIGs. 3A-3D depict a schematic representation of a precursor delivery system at various stages of a method for distributing gases in accordance with embodiments of the present disclosure; and

[0012] FIG. 4 depicts a graphical representation of pressures along a precursor delivery system at various stages of a method for delivering precursors in accordance with embodiments of the present disclosure.

[0013] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

DETAILED DESCRIPTION

[0014] Embodiments of the present disclosure provide a precursor delivery system having stable precursor delivery from a vaporizer to a process chamber. The delivery system enhances throughput, improves processing efficiency, reduces waste of precursor, and reduces condensation along a precursor delivery line. One or more embodiments of the present disclosure are described with respect to an atomic layer deposition chamber. Flowever, the precursor delivery system is useful in other types of process chambers, such as plasma etch chambers, chemical vapor deposition chambers, implant chambers, or other chambers. In particular, the precursor delivery system described herein provides accurate flow timing control, and reduced condensation resulting in pressure drops along a delivery line, such that flows may be pulsed quickly in a manner that have little to no flow rate settling time resulting in very stable precursor delivery that promotes process uniformity and reduction of defects. The precursor delivery system does not rely on dumping precursors into a foreline as contemplated in other gas delivery systems resulting in less precursor waste.

[0015] FIG. 1 depicts a schematic representation of a precursor delivery system 100. The system 100 includes a vaporizer 102. Liquid precursor is supplied to the vaporizer 102 through a liquid flow controller (LFC) 120. In some embodiments, other fluids are supplied to the vaporizer 102, such as carrier gas via gas source 121. A reservoir 104 is in fluid communication with the vaporizer 102, such that the reservoir 104 is coupled to a downstream end of the vaporizer 102. In some embodiments, a refill valve 122 is disposed at the upstream end of the reservoir 104. Alternatively, precursor is supplied to the reservoir 104 directly from the vaporizer 102 without a refill valve 122. Other delivery systems do not use reservoirs to deliver precursors. It has been discovered that systems that do not use reservoirs rely on pulsing precursors directly from vaporizers, however, response time of the vaporizer without a reservoir is not fast enough to keep up with pulsing precursors for certain processes which results in inaccurate flow timing control. It has also been discovered that it is possible to pulse the precursor by quickly switching precursor flow between the process chamber and a foreline. Diverting the precursor wastes the precursor. Adding a reservoir addresses certain challenges, however, during operation, the reservoir builds up in pressure, and when open to a lower pressure downstream gas line at low pressure, the temperature of the precursor drops and risks condensation within the line. Without being bound by theory, it is believed arranging flow control valves and timing sequential opening and closing of the valves reduces pressure differentials and temperature drops along the gas line, thus reducing risks of condensation.

[0016] A reservoir valve 126 is disposed downstream of the reservoir 104. In some embodiments, a first pressure gauge 152 is disposed at the downstream end of the reservoir 104 and upstream of the reservoir valve 126. In some embodiments, a second pressure gauge 154 is disposed downstream of the reservoir valve 126. A bypass line having a bypass valve 124 disposed thereon fluidly couples the gas line upstream of refill valve 122 and downstream of the reservoir valve 126, such as downstream of the second pressure gauge 154 (not shown) or upstream of the second pressure gauge 154. The bypass line enables precursor to be conveyed to the process chamber 106 bypassing the reservoir 104. A buffer zone 130 is defined between the reservoir valve 126 and a final valve 128. In some embodiments, the second pressure gauge 154 is coupled to the buffer zone 130. A first gas inlet 140 is coupled to the buffer zone 130 and a buffer valve 132. The first gas inlet 140 is capable of delivering buffer gases such as nitrogen gas, argon gas, or other non reactive gases.

[0017] In some embodiments, the buffer valve 132 is a three way valve coupled to an exhaust. Alternatively, a foreline 138 is coupled to an exhaust valve 136 and configured to exhaust precursor from the buffer zone 130 to the foreline 138 when the vacuum valve is in an open position. The final valve 128 is coupled to the gas line 101 downstream of the exhaust valve 136 and is fluidly coupled to the process chamber 106.

[0018] Additional gas inlets with valves along the gas line is also contemplated such gas line 144 with valve 146 and gas line 142 with valve 148. Each gas line 142, 144 is capable of delivery process gases such as nitrous oxide (N2O), oxygen (O2), argon, or other process gases, including nonreactive gases. In some embodiments, a filter 129 is coupled to the gas line 101 downstream of the final valve 128. Alternatively, the filter 129 disposed between the vaporizer 102 and the reservoir 104. In some embodiments, the final valve 128 is a three-way valve operable to divert precursor to a foreline 150. In some embodiments, foreline 150 is used instead of foreline 138 to exhaust precursor. In some embodiments, the final valve 128 is a two- way valve and is not coupled to a foreline 150. The gas line 101 is coupled to the process chamber 106 at inlet 109. The precursor is distributed over a substrate 112 disposed on a substrate support 108 within a process volume 114 of the process chamber 106. In some embodiments, the precursor is distributed using a gas delivery assembly 110. [0019] The precursor delivery system 100 depicted in FIG. 1 is useful for delivering precursors to the process chamber 106 in accordance to methods such as method 200 described with reference to FIG. 2. Certain operations of method 200 are depicted with reference to FIGs. 3A-3D. In operation 202, a precursor is supplied to a reservoir 104 until the reservoir 104 reaches a first pressure. In the some embodiments the first pressure is measured by a first pressure gauge 152 disposed a downstream end of the reservoir 104. In some embodiments, a buffer pressure as measured by the second pressure gauge 154 is slightly lower than the reservoir pressure as measured by the first pressure gauge 152. In some embodiments, the precursor is supplied to the buffer zone when the second pressure is substantially the same or about 10% lower, such as 1 % to about 10% lower than the first pressure of the reservoir. The precursor is supplied from a vaporizer 102 through a refill valve 122 disposed at an upstream end of the reservoir 104. In some embodiments, the precursor is supplied from the vaporizer 102 directly to the reservoir 104 either without a refill valve 122, or with refill valve 122 at a constant open state. In some embodiments, supplying the precursor to the reservoir include positioning a liquid flow controller (LFC) in an open state, the LFC disposed upstream of the reservoir, such as upstream of the vaporizer 102.

[0020] In operation 204, the precursor is supplied from the reservoir 104 to a buffer zone through reservoir valve 126 situated in an open state, as shown in FIG. 3A. The buffer zone is defined between the reservoir valve and a final valve. The buffer valve 132 and the divert valve 136 each remain in a closed state. In some embodiments, the final valve 128 is situated in a closed state. In operation 206, the precursor is supplied from the buffer zone to the process volume through the final valve situated in an open state, as shown in FIG. 3A. In some embodiments, the final valve 128 is switched from a closed state to an open state substantially simultaneously with switching the reservoir valve 126 from a closed state to an open state, such that operations 204 and 206 occur substantially simultaneously with one another. Without being bound by theory, it is believed that the buffer gas is discharged to low pressure and draws precursor to flow with reduced pressure drop. Operations 204 and 206 occur for about 100 msec to about 2 sec, such as about 300 msec to 5 msec, depending on process recipe. The buffer gas is any non-reactive gas, such as a nitrogen containing gas, such as nitrogen gas (N2). In some embodiments, the buffer gas includes argon gas.

[0021] In operation 208, each of the reservoir valve 126 and final valve 128 are switched to a closed state, as shown in FIG. 3B. The reservoir valve 126 and the final valve 128 are both closed at substantially the same time in order to stop precursor flow. In operation 210, a buffer gas is supplied to the buffer zone through a buffer valve 132 situated in an open state, also shown in FIG. 3B. In operation 212, the buffer gas is diverted to a foreline through a divert valve 136 situated in an open state, shown in FIG. 3B. In some embodiments, operations 208, 210, and 212 occur substantially simultaneously with one another. The residual precursor in the buffer zone is diverted to exhaust. In some embodiments, the reservoir valve 126 and the final valve 128 are in a closed state for about 0.5 sec, to about 3 sec, such as about 1 sec to about 2 sec in operation 208. In some embodiments, the buffer gas is supplied to the buffer zone through the buffer valve 132 and diverted through the divert valve 136 for about 50 msec to about 550 msec, such as about 100 msec to about 500 msec, in operations 210 and 212. Operations 210 and 212 occur entirely simultaneously with one another, or at least partially simultaneously with one another. In some embodiments, operation 214 begins when the buffer zone is substantially free of precursor. In some embodiments, the reservoir pressure increases when the reservoir valve is closed. In some embodiments, a pressure within the reservoir is controlled using the refill valve 122 disposed upstream of the reservoir 104. For example, a refill valve 122 is switched to a closed state when the pressure of the reservoir exceeds a predetermined pressure. In some embodiments, the refill valve 122 is switched to an open state when the pressure of the reservoir drops below a predetermined pressure. In some embodiments, the refill valve 122 and the LFC 120 are switched to an open state so that precursor refills the reservoir, such as during operation 212. The refill valve 122 is used to control the reservoir pressure. Without being bound by theory, it is believed that for processes with fast gas exchange, an LFC may have long relative response time that causes cycle-to-cycle pressure variation in the reservoir. Using the refill valve 122 reduces the pressure variation in the reservoir, and instead the pressure variation remains within the vaporizer 102. Alternatively, a refill valve 122 is not used, and the LFC 129 is always in an open state and the vaporizer 102 continuously charges the reservoir 104. In some embodiments, the refill valve 122 is in an open state during all operations 202 to 212. In some embodiments, the buffer zone pressure is maintained during operations 208, 210, and 212.

[0022] In operation 214, the divert valve 136 is switched to a closed state, as shown in FIG. 3C. In some embodiments, the divert valve 136 is switched to a closed state once the residual precursor is evacuated from the buffer zone. In some embodiments, the buffer valve 132 remains in an open state to pressurize the buffer zone 130. In some embodiments, operation 214 occurs for about 0.5 sec to about 2.5 sec, such as about 0.9 sec to about 1.9 sec, such as about 1.2 sec to 1.7 sec depending on process recipe.

[0023] In operation 216, the buffer valve 132 is switched to a closed state as shown in FIG. 3D. In some embodiments, the buffer valve 132 is switched to a closed state when the buffer zone reaches a predetermined pressure, such as a max design pressure. Condensation, is thus reduced since transient pressure drop is minimized at the reservoir outlet. In some embodiments, one or more additional gases are supplied through a downstream inlet fluidly coupled to an outlet of the final valve.

[0024] Operations 202 to 216 are repeated cyclically. In some embodiments, a cycle time from operations 202 to 215 is about 1 .5 sec to about 5 sec, such as about 2 sec to about 3 sec.

Example

[0025] FIG. 4 depicts a graphical representation of pressures along a precursor delivery system at various stages of a method, such as method 200, for delivering precursors in accordance with embodiments of the present disclosure. Curve PG1 represents a pressure of the reservoir 104 at the first pressure gauge 152 over time. Curve PG2 represents a pressure of the buffer zone 130 at the second pressure gauge 154 over time. Curve 402 represents a state of the reservoir valve 126, including a closed state 412 with the reservoir valve is situated in an closed position over time and an open state 422 when the reservoir valve is situated in an open position over time. Curve 404 represents a state of the buffer valve 132, including a closed state 414 and an open state 424. Curve 406 represents a state of the final valve 128, including a closed state 416 and an open state 426. Curve 408 represents a state of the divert valve 136, including a closed state 418 and an open state 428.

[0026] The times to, ti, t2, t3, and t4, correspond to process operations described in method 200. In particular, prior to to, each of the reservoir, buffer, and final valves are in a closed position, such as in operation 202. At to, the reservoir pressure (PG1) reaches a design pressure of about 30 torr. Other design pressures are also contemplated based on a size of a reservoir and a precursor type, such as pressures of about 20 torr to about 50 torr. In some embodiments, at to, the reservoir pressure and the buffer zone pressure is substantially equal, such as within 10% of one another. The reservoir valve and the final valve are each positioned to an open state while the buffer valve and the divert valve each remain in a closed state as described in operations 204 and 206. As can be seen between to and ti , a pressure of the reservoir and the pressure of the buffer zone are reduced. At ti, the reservoir valve and the final valve are each switched to a closed state while the buffer valve and the divert valve are each switched to an open state as described in operations 208, 210, and 212. This results in a rise in reservoir pressure PG1 while the buffer zone pressure PG2 is substantially maintained between ti and t2. At t2, the divert valve is switched to a closed state as described in operation 214. The reservoir pressure continues to increase and the buffer zone pressure increases between t2 and t3. At t3, the buffer valve is switched to a closed state as described in operation 216. At t4, the operations are repeated from to when the pressure of the buffer zone PG2 is substantially equal to or slightly lower than the pressure of the reservoir PG1. As can be seen from to and t4, the reservoir outlet pressure PG1 and the buffer zone pressures PG2 are at all times maintained within 20% of one another, such as within 10%, such as within 5% of one another.

[0027] In summation a precursor delivery system is provided having stable precursor delivery from a vaporizer to a process chamber. The delivery system enhances throughput, improves processing efficiency, reduces waste of precursor, and reduces condensation along a precursor delivery line. The precursor delivery system described herein provides accurate flow timing control, and reduced condensation caused by pressure drops along a delivery line, such that flows may be pulsed quickly in a manner that have little to no flow rate settling time resulting in very stable precursor delivery that promotes process uniformity and reduction of defects. The precursor delivery system does not rely on dumping precursors into a foreline as contemplated in other gas delivery systems resulting in less precursor waste. In particular, using a reservoir and a plurality of valves disposed along the gas line enables enhanced process control by maintaining reservoir and buffer zone pressures each within a predetermined pressure range and, more importantly, within a predetermined pressure range relative to one another. Thus, when the reservoir pressure is high, the valves are switched between open and closed states. Certain areas of the gas line (e.g., buffer zone) are pressurized using buffer gas, such as prior to opening the reservoir to the gas line, which reduces pressure drop from the reservoir to the gas line at various stages of processing. The switching of each valve from an open state to a closed state is timed based on process recipe, or are automatically switched based on pressure gauge readings within the buffer zone. Precursor flow timing control is greatly enhanced and pressure differential across the gas line is also enhanced, reducing condensation associated with pressure drops.

[0028] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the scope thereof, and the scope thereof is determined by the claims that follow.

Claims

What is claimed is:

1. A precursor delivery system, comprising: a vaporizer; a reservoir comprising an upstream end in fluid communication with the vaporizer; a reservoir valve in fluid communication with a downstream end of the reservoir; a final valve disposed downstream of the reservoir valve; a buffer zone defined between the reservoir valve and the final valve; and a first gas inlet coupled to the buffer zone, wherein the first gas inlet is coupled to a buffer valve.

2. The system of claim 1 , further comprising a liquid flow controller (LFC) coupled to the upstream end of the vaporizer.

3. The system of claim 1 , further comprising a first pressure gauge proximate to the downstream end of the reservoir.

4. The system of claim 3, further comprising a second pressure gauge coupled to the buffer zone.

5. The system of claim 1 , further comprising an exhaust valve coupled to the buffer zone.

6. The system of claim 1 , wherein the buffer valve is a three-way valve, the buffer valve operable to divert to a foreline.

7. The system of claim 1 , wherein the final valve is a three-way valve, the final valve operable to divert to a foreline.

8. The system of claim 1 , wherein the final valve is communicatively coupled to a process chamber.

9. The system of claim 1, further comprising a bypass line, the bypass line fluidly couples the vaporizer with the buffer zone, wherein the bypass line comprises a bypass valve.

10. A method of supplying precursors to a process volume of a process chamber, the method comprising: supplying a precursor to a reservoir until the reservoir reaches a first pressure; supplying the precursor from the reservoir to a buffer zone through a reservoir valve situated in an open state, wherein the buffer zone is defined between the reservoir valve and a final valve; supplying the precursor from the buffer zone to the process volume through the final valve situated in an open state; switching each of the reservoir valve and the final valve to a closed state; supplying a buffer gas to the buffer zone through a buffer valve situated in an open state; diverting the buffer gas to a foreline through a divert valve situated in an open state; switching the divert valve to a closed state; and switching the reservoir valve to a closed state.

11. The method of claim 10, wherein supplying the precursor to the reservoir comprises supplying gas through a refill valve disposed at an upstream end of the reservoir.

12. The method of claim 11 , wherein supplying the precursor to the reservoir further comprises positioning a liquid flow controller (LFC) in an open state, the LFC disposed upstream of the reservoir.

13. The method of claim 12, wherein the LFC is disposed upstream of a vaporizer, the vaporizer disposed upstream of the reservoir.

14. The method of claim 10, wherein the reservoir valve and the downstream valve are situated to an open state simultaneously.

15. The method of claim 10, wherein the buffer zone comprises a second pressure, wherein the precursor is supplied to the buffer zone when the second pressure is substantially same as or less than 10% lower than the first pressure of the reservoir.

16. The method of claim 10, wherein the buffer gas is a nitrogen containing gas.

17. The method of claim 10, wherein switching the divert valve to a closed state increases a pressure of the buffer zone.

18. The method of claim 10, further comprising introducing one or more additional gases through a downstream inlet fluidly coupled to an outlet of the final valve.

19. A substrate processing system, comprising: a process chamber comprising a process volume for processing a substrate, the process chamber having a gas inlet; and a gas distribution assembly fluidly coupled to the gas inlet, the gas distribution assembly comprising: a vaporizer; a reservoir comprising an upstream end in fluid communication with the vaporizer; a reservoir valve in fluid communication with a downstream end of the reservoir; a final valve disposed downstream of the reservoir valve; a buffer zone defined between the reservoir valve and the final valve; and a buffer gas inlet coupled to the buffer zone, wherein the buffer gas inlet is coupled to a buffer valve.

20. The substrate processing system of claim 19, further comprising a downstream gas inlet fluidly coupled to the gas inlet, the downstream gas inlet configured to deliver additional process gases to the process volume.