System and method for high aspect ratio structure atomic layer etch process and rapid in situ liner deposition

Abstract

The invention discloses a system and method for high aspect ratio structure atomic layer etching process and rapid in-situ liner deposition. The system includes a pressurized precursor buffer, and the pressurized precursor buffer is disposed proximate to the gas / precursor delivery unit. In-situ liner deposition steps may be inserted at predetermined intervals within the ALE process cycle. The system controller monitors real-time precursor pressure within the buffer to determine and release a controllable volume of precursor to the chamber. Based on the precise volume of the introduced precursor, this fast in situ liner deposition contributes to better profile control during HAR etching.

Description

[0001] Cross-references to related applications

[0002] This invention claims priority to U.S. Patent Application No. 18 / 945,487, filed on November 12, 2024. Technical Field

[0003] This invention relates to atomic layer etching (ALE) processes in semiconductor manufacturing, particularly suitable for high-aspect-ratio (HAR) structures in devices such as 3D NAND, DRAM, and logic circuits. More specifically, this invention relates to an ALE system and method that integrates rapid in-situ liner deposition technology to enhance etching profile control during cyclic etching steps and reduce sidewall bending in HAR structures. Background Technology

[0004] The continuous miniaturization of semiconductor devices has created an increasingly urgent need for high-precision etching processes, especially in the fabrication of HAR structures, such as vias in 3D NAND, capacitors in DRAM, and vertical transistor structures similar to FinFETs in logic devices. HAR structures face significant challenges in plasma etching, primarily because achieving uniform material removal at specific depths without disrupting the desired profile is difficult. Traditional ALE processes, through alternating surface modification and sputtering steps, enable precise control of material removal at the atomic scale. However, in HAR applications, these processes often lead to profile deviations and sidewall bending, consequently affecting the structural integrity and performance of the final device.

[0005] To address these issues, in-situ liner deposition steps can be added at selected intervals in the ALE cycle to protect the sidewalls of the HAR structure, thereby maintaining the desired etching profile throughout the ALE process. However, adding such steps typically increases process time and complexity significantly because conventional systems may require the delivery of precursor materials from external sources, leading to extended step transition times and potentially causing process delays.

[0006] Furthermore, existing ALE systems generally lack efficient mechanisms for storing and rapidly transporting liner deposition precursors to the process chamber. The time required to introduce these precursors can increase cycle time and impact process throughput. As device architectures continue to evolve and shrink, achieving more efficient and integrated precursor delivery and liner deposition methods in ALE processes has become crucial.

[0007] This invention addresses these limitations by introducing a pressurized precursor buffer, which is directly integrated into the ALE process system. This buffer enables rapid in-situ liner deposition and precise control of precursor delivery. This approach maintains sidewall integrity, improves etching uniformity of HAR structures, and enhances the reliability and efficiency of ALE processes in advanced semiconductor manufacturing. Summary of the Invention

[0008] In some embodiments, the present invention provides an ALE process system designed to improve profile control and sidewall protection for HAR structures such as vias in 3D NAND devices, capacitors in DRAM devices, and fins, gates, and source / drain recesses prepared for epitaxial layer growth. The system includes a pressurized precursor buffer capable of rapidly and directly delivering liner deposition precursors to the process chamber. In some embodiments, the precursor buffer is integrated with a valve system and a timing estimator that coordinates the precursor release time based on the pressure measured in the pressurized buffer and the process formulation.

[0009] In some implementations, the ALE process includes a conventional ALE cycle, namely a surface modification step (Step A) and a sputtering step (Step B), followed by an additional liner deposition step (Step C). Step C can be introduced after a predetermined number of ALE cycles and can be performed at selected intervals within the ALE cycles. A pressurized precursor buffer enables the storage of the precursor under pressure, allowing for efficient delivery during Step C without the need for lengthy external precursor supply pipelines, thereby reducing step changeover time and minimizing process overhead.

[0010] In some implementations, the pressurized precursor buffer includes a pressure sensor for monitoring internal pressure. The system controller uses this pressure information to calculate and adjust the precursor release time to ensure consistency and controllability of liner thickness and profile. The system controller may include a time estimator, a software program that determines the optimal precursor release time using process formulation and real-time pressure data, thereby improving deposition consistency.

[0011] In some implementations, a gas / precursor distribution unit within the process chamber delivers the precursor along with an inert carrier gas (such as argon), which is also used in the sputtering steps of the ALE cycle. This design allows for a continuous inert gas flow rate between the etching and liner deposition steps, maintaining plasma conditions during step transitions, thereby achieving smooth integration of the liner deposition steps while minimizing interference with the ALE process. The plasma conditions can be adjusted according to the requirements of the liner deposition process.

[0012] The liner can be made of a variety of materials, including but not limited to metals, metal oxides, metal nitrides, carbon, carbides, and metal-doped carbon or carbides. The liner can be deposited using plasma-enhanced chemical vapor deposition (PECVD), where the step coverage can be adjusted by changing the deposition conditions to remove the liner deposition at the etching front. Alternatively, the liner can be deposited using atomic layer deposition (ALD), followed by removal of the liner deposition at the etching front through an ALE step.

[0013] In some implementations, the precursor buffer can perform liner deposition at intervals in the ALE cycle, thereby maintaining sidewall integrity throughout the ALE process. After the ALE step, the liner can be consumed or removed to initiate subsequent ALE cycles.

[0014] Therefore, this invention provides an ALE system and method that integrates rapid in-situ liner deposition, improving contour control and reducing process time. This approach enhances the accuracy and efficiency of ALE processes in advanced semiconductor applications, particularly in scenarios where HAR structure fidelity is critical. Attached Figure Description

[0015] To make the description clearer, the following description will refer to the attached diagram:

[0016] Figure 1 An example is shown of an ALE process system including rapid in-situ liner deposition;

[0017] Figure 2 A schematic diagram of a pressurized precursor buffer is shown.

[0018] Figure 3 An example is shown of an ALE cycle process, which includes a surface modification step and a sputtering step, supplemented by a liner deposition step to form a HAR structure;

[0019] Figure 4 The process flow diagram of ALE with rapid in-situ liner deposition step is presented.

[0020] Figure 5 The diagram illustrates the ALE process applied to ONON etching of 3D NAND channels, which reduces profile curvature through rapid in-situ liner deposition. Detailed Implementation

[0021] To facilitate a full understanding of the invention, specific embodiments thereof will be described in detail below. While specific details are provided for ease of explanation, any modifications and variations consistent with the technical principles of the invention are considered appropriate. Certain well-known procedures and components are described selectively only to highlight the unique features of the invention.

[0022] The terminology is defined as follows:

[0023] Atomic Layer Etching (ALE): An etching technique that removes atomic layers from a material surface through cyclic processing steps. ALE typically cycles through a surface modification step (Step A) and a sputtering step (Step B) to achieve controlled material removal at the atomic level.

[0024] High aspect ratio (HAR) structures: These are structures with a high height-to-width ratio, such as vias in 3D NAND, capacitors in DRAM, and gates in logic devices. These structures face challenges during etching because ions and active materials cannot reach uniformly deep into narrow channels.

[0025] Profile Bowing: An unintended bending of the sidewalls in HAR structures during etching, primarily caused by the angular distribution of ions. This effect leads to an arched structure, affecting critical dimensions and structural integrity of semiconductor devices.

[0026] Pressurized Precursor Buffer: A storage unit designed to store precursor gas or liquid under pressure for liner deposition. The buffer is equipped with inlet, outlet, and pressure sensors to monitor and control the release of the precursor into the process chamber, and works in conjunction with the system controller.

[0027] System Controller: The central processing unit that manages and coordinates the operation of the ALE system. Its functions include controlling the timing of precursor release, regulating vacuum valves, and managing other process parameters.

[0028] Time Estimator: A software program within the system controller used to calculate the optimal duration of precursor release based on the ALE process formulation and real-time pressure data from the precursor buffer, to ensure consistency and controllability of liner deposition.

[0029] Process Chamber: The main enclosed space for substrate processing, which needs to maintain the vacuum environment required for plasma-based ALE. It is usually made of plasma-resistant material to prevent damage during processing.

[0030] Plasma Source: A device that generates plasma within a process chamber, typically implemented using inductively coupled plasma (ICP) or transformer-coupled plasma (TCP) methods. This plasma source is powered by a radio frequency generator to produce the ionized gas used in the etching or deposition process.

[0031] Gas / Precursor Distribution Unit: This component is responsible for delivering process gases or precursors to the process chamber. It can employ injectors or spray nozzles to achieve uniform gas distribution on the substrate.

[0032] Liner Deposition Step: A new step in the ALE cycle, used to deposit a protective liner on the sidewalls of the HAR structure to maintain the etching profile and prevent structural damage during subsequent etching cycles. This step is performed in situ and can be performed using PECVD or ALD methods.

[0033] Proportional-Integral-Derivative (PID) Control: A feedback mechanism used within the system controller to control chamber pressure by adjusting vacuum valves. PID control can stabilize process conditions to achieve consistent ALE results.

[0034] Oxide-Nitride-Oxide-Nitride (ONON) Stack: A multilayer structure used in 3D NAND devices, consisting of alternating oxide and nitride layers. It requires precise etching to form the vias and is a common example of a HAR structure.

[0035] Precursor: A gas or liquid stored in a pressurized precursor buffer and subsequently introduced into the process chamber for liner deposition. It can be transported together with an inert carrier gas to form a protective liner layer inside the HAR structure.

[0036] Movable Part of the Vacuum Valve: An adjustable component of the vacuum valve used to control the gas conductivity within the process chamber. Its position is regulated by PID control to maintain stable chamber pressure, especially during process transitions.

[0037] Chuck: A component used during the manufacturing process to attract and hold a substrate within the process chamber. Chucks can be electrostatic or vacuum chucks. Electrostatic chucks provide bias control to accelerate the ions required for the ALE process.

[0038] Figure 1 An ALE process system 100 is illustrated as an example. The system includes a process chamber 102, which is surrounded by a cavity structure 104. The operation of the process chamber 102 is coordinated by a system controller 106. The chamber 102 maintains a vacuum environment favorable for plasma processes. The cavity structure 104 is made of materials such as aluminum or quartz and may have an anodized layer or yttrium oxide coating inside to resist plasma damage.

[0039] For example, plasma source 120 is positioned above cavity structure 104 and separated by a sealed window 110. This window may be made of materials such as quartz or ceramic. The interior of the window may also be coated with an anti-plasma material (such as yttrium oxide). Plasma source 120 may be configured as an ICP or TCP source, employing a cylindrical or conical multi-turn coil structure with varying numbers of turns, or multiple coils may be used.

[0040] Radio frequency (RF) power generator 122 supplies power to plasma source 120 via resonator 124. Generator 122 can provide single-frequency or multi-frequency (e.g., 100 kHz, 200 kHz, 2 MHz, 13.56 MHz, 27 MHz, and 60 MHz) RF power, ranging from 50 to 5000 watts. Resonator 124 ensures impedance matching between generator 122 and the plasma load within chamber 102.

[0041] The gas / precursor distribution unit 108 is connected to the gas source 112 via a mass flow controller (MFC) 114 to deliver the process gas required for the ALE process to the chamber 102. A valve system 118 controls the flow rate between the MFC 114 and the gas / precursor distribution unit 108. The valve system 118 may include one or more valves and may be configured as a two-way valve or a three-way valve.

[0042] ALE processes typically include a surface modification step (also known as step A) and a sputtering step (also known as step B), which are repeated cyclically. For example, in a silicon ALE process, step A uses a reactive gas such as chlorine, while step B uses an inert gas such as argon. Gas source 112 may also supply purging gases to remove residual gases from chamber 102 during process gas switching.

[0043] During HAR etching, the angular distribution of ions can cause deviations from the intended straight-wall profile. To address this issue, a liner deposition step (also known as step C) is introduced to protect the sidewalls of the HAR structure and maintain the desired etching profile. Step C can be performed in an external deposition chamber or in situ within chamber 102. Since liner deposition adds additional processing time and cost, minimizing this additional overhead while improving profile quality is crucial.

[0044] This invention introduces a pressurized precursor buffer 116 for storing precursors required for liner deposition. The pressurized precursor buffer 116 is connected to a valve system 118, and a system controller 106 adjusts the duration of precursor release from the pressurized precursor buffer 116, thereby controlling the thickness of the deposited liner. The precursor in the pressurized precursor buffer 116 can be gaseous, liquid, or a combination of both. In one embodiment, the liquid precursor is mixed with a carrier gas and stored in the pressurized precursor buffer 116, vaporizing upon release and injected into the chamber 102 along with the carrier gas. In another embodiment, the carrier gas is introduced from a gas source 112 to transport the vaporized precursor to the chamber 102. In yet another embodiment, the precursor is stored in a gaseous form in the pressurized precursor buffer 116 under pressure.

[0045] In a further embodiment, the inert gas used in the sputtering step can also be used as the carrier gas for the liner deposition precursor, so that the plasma used in the sputtering step does not need to be shut off when the precursor is released. In this setup, the inert gas plasma in the sputtering step is maintained as the precursor is introduced, thereby enabling liner deposition in an existing plasma environment. Between the sputtering and liner deposition steps, the power applied to the plasma source 120 and the operating parameters of the bias unit 136 connected to the chuck 128 can be adjusted to optimize process conditions.

[0046] The ALE process described above can be used to fabricate various HAR structures, including etching channel vias formed by oxide-nitride-oxide-nitride (ONON) stacks in 3D NAND fabrication (step A can use a fluorine-containing gas, and step B can use an inert gas). Other HAR applications include vias for storage capacitors in DRAM devices, as well as fins, gates, and source / drain recess structures for epitaxial layer growth.

[0047] MFC114 regulates the gas flow rate before the gas is delivered to the gas / precursor distribution unit 108, which can be an injector or a spray head. Window 110 can also be integrated with the gas / precursor distribution unit 108, serving both as a spray head and a sealing chamber 102. Pressure gauge 126 monitors the chamber pressure, and vacuum pump 134 (e.g., a turbomolecular pump) delivers unused gas and byproducts to an external exhaust system via an exhaust line. Figure 1 (Not shown in the image).

[0048] Vacuum valve 132 works in conjunction with vacuum pump 134 to control gas conduction. The valve controller uses PID control to adjust the position of the moving parts of valve 132 to maintain the steady-state chamber pressure monitored by system controller 106.

[0049] Chamber 102 also includes a chuck 128 for supporting substrate 130. The chuck 128 can be an electrostatic chuck or a vacuum chuck, and its bias control is crucial for the ALE process. The chuck 128 is connected to a bias unit 136, which may include an additional RF power generator, a custom waveform generator, or a combination of both. The bias unit 136 applies a bias voltage to substrate 130, accelerating ions in the plasma to optimize ALE process conditions.

[0050] Figure 1 The illustration shows a single pressurization buffer, but multiple buffers can also be used. In some liner deposition processes, multiple precursors may be used, and for safety reasons, these precursors may need to be stored separately in individual buffers.

[0051] Figure 2 A schematic diagram of a pressurized precursor buffer 200 is illustrated. The buffer 200 includes a buffer structure 137 and a pressure sensor 138. A pressurized precursor 142 is stored within the buffer structure 137, and the pressure sensor 138 monitors the pressure of the pressurized precursor 142 at a predetermined frequency. The buffer structure 137 includes an inlet 144 and an outlet 146, with the outlet 146 connected to a valve system 118. A system controller 106 manages the operation of the buffer 200 and is connected to a time estimator 140. The time estimator 140 is a software program used to calculate the precursor release time based on the process formulation and the measured precursor pressure. The time estimator 140 may include models, analytical formulas, lookup tables, and neural networks.

[0052] The stored precursor can be gaseous, liquid, or a combination of both. Precursor materials used for deposition linings can include metals, metal oxides, metal nitrides, carbon, carbides, and metal-doped carbon or carbide layers.

[0053] Figure 3A schematic diagram of the ALE process 300 is shown. The ALE process includes conventional step A and step B cycles, as well as a liner deposition step (i.e., step C). Step C can be inserted into the cycles of steps A and B, depending on requirements, to maintain the sidewall integrity of the HAR structure. Steps A and B use process gases from gas source 112, while step C obtains the precursor from a pressurized precursor buffer 116. For liquid precursors, the carrier gas can either be mixed with the precursor and stored in the pressurized precursor buffer 116, or it can be supplied separately from gas source 112.

[0054] Figure 4 A flowchart of ALE process 400 is presented, illustrating the process flow including a rapid in-situ liner deposition step. Process 400 begins at step 402 and executes a predetermined number of ALE cycles (including steps A and B). Optionally, in step 404, to accelerate the transition to liner deposition step C, system controller 106 adjusts the movable part of vacuum valve 132 to a predetermined position. This position can be determined during the setup phase and stored in the storage unit of system controller 106, remaining fixed during liner deposition step C to maintain optimal process conditions.

[0055] In step 406, the precursor is released from the pressurized precursor buffer 116. The release time is precisely controlled by the system controller 106 in conjunction with the time estimator 140, and then step C is executed. In step 408, the ALE cycle counter is updated. In step 410, the system controller 106 checks whether the ALE process is complete. If complete, the process ends; if not complete, the ALE cycle including step C is repeated.

[0056] Figure 5 An example of the ALE process being applied to etch an ONON stack to form a 3D NAND device channel via is shown. Section 502 shows a schematic diagram of the structure in progress for steps A and B of the ALE process. Hard masks such as carbon layers are labeled 508, and oxide and nitride layers are labeled 510 and 512, respectively. In section 504, a protective liner 514 is deposited. In one embodiment, the liner 514 is deposited using a PECVD process. PECVD-deposited liners have specific step coverage that may not cover the etch front 516, as shown in Figure 504. In section 506, the etch front is advanced by performing an additional ALE cycle, during which the liner 514 protects the sidewalls of the structure. After the ALE cycle, the liner is removed to restart a new cycle of the ALE process, and step C is performed as needed.

[0057] In another implementation, the liner is deposited using an ALD process, followed by a pass-through step using an ALE process to remove the liner material from the etching front, thus maintaining a clean etching front for subsequent ALE processes.

Claims

1. An ALE process system, characterized in that, include: Process chambers are used to house substrates and maintain the vacuum environment required for plasma-based processes; A plasma source, which is connected to the process chamber, is used to generate plasma within the process chamber; A gas / precursor distribution unit, which is connected to a gas source, is used to deliver the process gas required for the ALE process to the process chamber; A pressurized precursor buffer, disposed adjacent to the gas / precursor distribution unit, is used for storing and releasing precursors, wherein the pressurized precursor buffer comprises: The buffer structure has an inlet and an outlet; Pressure sensor, used to monitor the internal pressure of the precursor; The pressurized precursor buffer is connected to a valve system to control the flow rate of the precursor from the pressurized precursor buffer to the process chamber. The system controller, connected to the pressurized precursor buffer, is used for: Execute an ALE cycle, wherein the ALE cycle includes a surface modification step and a sputtering step; After a predetermined number of ALE cycles, a rapid in-situ liner deposition step is initiated by releasing the precursor from the pressurized precursor buffer.

2. The system according to claim 1, characterized in that, The system controller is configured to keep the moving parts of the vacuum valve in position during the liner deposition step to reduce the time required to establish stable precursor pressure within the process chamber.

3. The system according to claim 1, characterized in that, The precursor is a liquid precursor.

4. The system according to claim 3, characterized in that, The liquid precursor is mixed and stored with the carrier gas.

5. The system according to claim 3, characterized in that, The liquid precursor vaporizes upon release from the pressurized precursor buffer and is transported to the process chamber along with the carrier gas introduced from the gas source.

6. The system according to claim 5, characterized in that, The carrier gas is the same as the process gas used in the sputtering step.

7. The system according to claim 1, characterized in that, The precursor is a gaseous precursor.

8. The system according to claim 1, characterized in that, The precursor is released from the pressurized precursor buffer into the process chamber, and the plasma in the process chamber is maintained after the sputtering step of the previous ALE cycle, wherein the liner deposition step is performed based on the plasma.

9. The system according to claim 8, characterized in that, The plasma is maintained using different operating parameters than those used in the sputtering process. These operating parameters include different power outputs from a radio frequency generator and different bias voltages provided by a bias unit connected to a chuck for supporting the substrate.

10. The system according to claim 1, characterized in that, The pressure sensor in the pressurized precursor buffer is configured to transmit real-time pressure data to the system controller in order to adaptively adjust the precursor release time according to the process formulation.

11. The system according to claim 1, characterized in that, The lining is selected from metals, metal oxides, metal nitrides, carbon, carbides, or metal-doped carbon or carbide layers.

12. The system according to claim 1, characterized in that, The ALE process is used to form a HAR structure, wherein the HAR structure includes an ONON stack for forming a 3D NAND device channel via.

13. The system according to claim 1, characterized in that, The ALE process is used to form a HAR structure, wherein the HAR structure includes holes for forming DRAM capacitors.

14. The system according to claim 1, characterized in that, The ALE process is used to form a HAR structure, wherein the HAR structure comprises one or more stacks, and the stack materials include silicon, germanium, metals, nitrides, oxides, and carbon.

15. The system according to claim 1, characterized in that, The system deposits the liner using an ALD process and performs a through-etching step to remove the deposited material at the etch front.

16. An ALE method for a HAR structure on a substrate, characterized in that, include: An ALE cycle is performed within the process chamber, wherein each ALE cycle includes a surface modification step and a sputtering step; After a predetermined number of ALE cycles, a rapid in-situ liner deposition step is initiated by releasing the precursor from a pressurized precursor buffer, wherein the pressurized precursor buffer is located adjacent to a gas / precursor distribution unit within the process chamber; and Based on the real-time pressure data from the pressure sensor inside the pressurized precursor buffer, the precursor release time is controlled to obtain a controllable lining thickness.

17. The method according to claim 16, characterized in that, The method further includes dynamically adjusting the precursor release time based on the process formulation and the real-time pressure data.

18. The method according to claim 16, characterized in that, The lining is selected from metals, metal oxides, metal nitrides, carbon, carbides, or metal-doped carbon or carbide layers, and the lining is deposited on the sidewalls of the HAR structure to form a protective layer.

19. The method according to claim 16, characterized in that, The method uses an atomic ALD process to deposit the liner and performs a through-etching step to remove the deposited material at the etch front.

20. The method according to claim 16, characterized in that, The method employs PECVD process to deposit the lining, and adjusts the step coverage of the lining by changing the deposition conditions.

Images